// Copyright 2006 The Closure Library Authors. All Rights Reserved.
//
// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
//      http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS-IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

/**
 * @fileoverview Bootstrap for the Google JS Library (Closure).
 *
 * In uncompiled mode base.js will write out Closure's deps file, unless the
 * global <code>CLOSURE_NO_DEPS</code> is set to true.  This allows projects to
 * include their own deps file(s) from different locations.
 *
 * @author arv@google.com (Erik Arvidsson)
 *
 * @provideGoog
 */


/**
 * @define {boolean} Overridden to true by the compiler when
 *     --process_closure_primitives is specified.
 */
var COMPILED = false;


/**
 * Base namespace for the Closure library.  Checks to see goog is already
 * defined in the current scope before assigning to prevent clobbering if
 * base.js is loaded more than once.
 *
 * @const
 */
var goog = goog || {};


/**
 * Reference to the global context.  In most cases this will be 'window'.
 */
goog.global = this;


/**
 * A hook for overriding the define values in uncompiled mode.
 *
 * In uncompiled mode, {@code CLOSURE_UNCOMPILED_DEFINES} may be defined before
 * loading base.js.  If a key is defined in {@code CLOSURE_UNCOMPILED_DEFINES},
 * {@code goog.define} will use the value instead of the default value.  This
 * allows flags to be overwritten without compilation (this is normally
 * accomplished with the compiler's "define" flag).
 *
 * Example:
 * <pre>
 *   var CLOSURE_UNCOMPILED_DEFINES = {'goog.DEBUG': false};
 * </pre>
 *
 * @type {Object<string, (string|number|boolean)>|undefined}
 */
goog.global.CLOSURE_UNCOMPILED_DEFINES;


/**
 * A hook for overriding the define values in uncompiled or compiled mode,
 * like CLOSURE_UNCOMPILED_DEFINES but effective in compiled code.  In
 * uncompiled code CLOSURE_UNCOMPILED_DEFINES takes precedence.
 *
 * Also unlike CLOSURE_UNCOMPILED_DEFINES the values must be number, boolean or
 * string literals or the compiler will emit an error.
 *
 * While any @define value may be set, only those set with goog.define will be
 * effective for uncompiled code.
 *
 * Example:
 * <pre>
 *   var CLOSURE_DEFINES = {'goog.DEBUG': false} ;
 * </pre>
 *
 * @type {Object<string, (string|number|boolean)>|undefined}
 */
goog.global.CLOSURE_DEFINES;


/**
 * Returns true if the specified value is not undefined.
 * WARNING: Do not use this to test if an object has a property. Use the in
 * operator instead.
 *
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is defined.
 */
goog.isDef = function(val) {
  // void 0 always evaluates to undefined and hence we do not need to depend on
  // the definition of the global variable named 'undefined'.
  return val !== void 0;
};


/**
 * Builds an object structure for the provided namespace path, ensuring that
 * names that already exist are not overwritten. For example:
 * "a.b.c" -> a = {};a.b={};a.b.c={};
 * Used by goog.provide and goog.exportSymbol.
 * @param {string} name name of the object that this file defines.
 * @param {*=} opt_object the object to expose at the end of the path.
 * @param {Object=} opt_objectToExportTo The object to add the path to; default
 *     is |goog.global|.
 * @private
 */
goog.exportPath_ = function(name, opt_object, opt_objectToExportTo) {
  var parts = name.split('.');
  var cur = opt_objectToExportTo || goog.global;

  // Internet Explorer exhibits strange behavior when throwing errors from
  // methods externed in this manner.  See the testExportSymbolExceptions in
  // base_test.html for an example.
  if (!(parts[0] in cur) && cur.execScript) {
    cur.execScript('var ' + parts[0]);
  }

  // Certain browsers cannot parse code in the form for((a in b); c;);
  // This pattern is produced by the JSCompiler when it collapses the
  // statement above into the conditional loop below. To prevent this from
  // happening, use a for-loop and reserve the init logic as below.

  // Parentheses added to eliminate strict JS warning in Firefox.
  for (var part; parts.length && (part = parts.shift());) {
    if (!parts.length && goog.isDef(opt_object)) {
      // last part and we have an object; use it
      cur[part] = opt_object;
    } else if (cur[part]) {
      cur = cur[part];
    } else {
      cur = cur[part] = {};
    }
  }
};


/**
 * Defines a named value. In uncompiled mode, the value is retrieved from
 * CLOSURE_DEFINES or CLOSURE_UNCOMPILED_DEFINES if the object is defined and
 * has the property specified, and otherwise used the defined defaultValue.
 * When compiled the default can be overridden using the compiler
 * options or the value set in the CLOSURE_DEFINES object.
 *
 * @param {string} name The distinguished name to provide.
 * @param {string|number|boolean} defaultValue
 */
goog.define = function(name, defaultValue) {
  var value = defaultValue;
  if (!COMPILED) {
    if (goog.global.CLOSURE_UNCOMPILED_DEFINES &&
        Object.prototype.hasOwnProperty.call(
            goog.global.CLOSURE_UNCOMPILED_DEFINES, name)) {
      value = goog.global.CLOSURE_UNCOMPILED_DEFINES[name];
    } else if (
        goog.global.CLOSURE_DEFINES &&
        Object.prototype.hasOwnProperty.call(
            goog.global.CLOSURE_DEFINES, name)) {
      value = goog.global.CLOSURE_DEFINES[name];
    }
  }
  goog.exportPath_(name, value);
};


/**
 * @define {boolean} DEBUG is provided as a convenience so that debugging code
 * that should not be included in a production js_binary can be easily stripped
 * by specifying --define goog.DEBUG=false to the JSCompiler. For example, most
 * toString() methods should be declared inside an "if (goog.DEBUG)" conditional
 * because they are generally used for debugging purposes and it is difficult
 * for the JSCompiler to statically determine whether they are used.
 */
goog.define('goog.DEBUG', true);


/**
 * @define {string} LOCALE defines the locale being used for compilation. It is
 * used to select locale specific data to be compiled in js binary. BUILD rule
 * can specify this value by "--define goog.LOCALE=<locale_name>" as JSCompiler
 * option.
 *
 * Take into account that the locale code format is important. You should use
 * the canonical Unicode format with hyphen as a delimiter. Language must be
 * lowercase, Language Script - Capitalized, Region - UPPERCASE.
 * There are few examples: pt-BR, en, en-US, sr-Latin-BO, zh-Hans-CN.
 *
 * See more info about locale codes here:
 * http://www.unicode.org/reports/tr35/#Unicode_Language_and_Locale_Identifiers
 *
 * For language codes you should use values defined by ISO 693-1. See it here
 * http://www.w3.org/WAI/ER/IG/ert/iso639.htm. There is only one exception from
 * this rule: the Hebrew language. For legacy reasons the old code (iw) should
 * be used instead of the new code (he), see http://wiki/Main/IIISynonyms.
 */
goog.define('goog.LOCALE', 'en');  // default to en


/**
 * @define {boolean} Whether this code is running on trusted sites.
 *
 * On untrusted sites, several native functions can be defined or overridden by
 * external libraries like Prototype, Datejs, and JQuery and setting this flag
 * to false forces closure to use its own implementations when possible.
 *
 * If your JavaScript can be loaded by a third party site and you are wary about
 * relying on non-standard implementations, specify
 * "--define goog.TRUSTED_SITE=false" to the JSCompiler.
 */
goog.define('goog.TRUSTED_SITE', true);


/**
 * @define {boolean} Whether a project is expected to be running in strict mode.
 *
 * This define can be used to trigger alternate implementations compatible with
 * running in EcmaScript Strict mode or warn about unavailable functionality.
 * @see https://goo.gl/g5EoHI
 *
 */
goog.define('goog.STRICT_MODE_COMPATIBLE', false);


/**
 * @define {boolean} Whether code that calls {@link goog.setTestOnly} should
 *     be disallowed in the compilation unit.
 */
goog.define('goog.DISALLOW_TEST_ONLY_CODE', COMPILED && !goog.DEBUG);


/**
 * @define {boolean} Whether to use a Chrome app CSP-compliant method for
 *     loading scripts via goog.require. @see appendScriptSrcNode_.
 */
goog.define('goog.ENABLE_CHROME_APP_SAFE_SCRIPT_LOADING', false);


/**
 * Defines a namespace in Closure.
 *
 * A namespace may only be defined once in a codebase. It may be defined using
 * goog.provide() or goog.module().
 *
 * The presence of one or more goog.provide() calls in a file indicates
 * that the file defines the given objects/namespaces.
 * Provided symbols must not be null or undefined.
 *
 * In addition, goog.provide() creates the object stubs for a namespace
 * (for example, goog.provide("goog.foo.bar") will create the object
 * goog.foo.bar if it does not already exist).
 *
 * Build tools also scan for provide/require/module statements
 * to discern dependencies, build dependency files (see deps.js), etc.
 *
 * @see goog.require
 * @see goog.module
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part".
 */
goog.provide = function(name) {
  if (goog.isInModuleLoader_()) {
    throw Error('goog.provide can not be used within a goog.module.');
  }
  if (!COMPILED) {
    // Ensure that the same namespace isn't provided twice.
    // A goog.module/goog.provide maps a goog.require to a specific file
    if (goog.isProvided_(name)) {
      throw Error('Namespace "' + name + '" already declared.');
    }
  }

  goog.constructNamespace_(name);
};


/**
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part".
 * @param {Object=} opt_obj The object to embed in the namespace.
 * @private
 */
goog.constructNamespace_ = function(name, opt_obj) {
  if (!COMPILED) {
    delete goog.implicitNamespaces_[name];

    var namespace = name;
    while ((namespace = namespace.substring(0, namespace.lastIndexOf('.')))) {
      if (goog.getObjectByName(namespace)) {
        break;
      }
      goog.implicitNamespaces_[namespace] = true;
    }
  }

  goog.exportPath_(name, opt_obj);
};


/**
 * Module identifier validation regexp.
 * Note: This is a conservative check, it is very possible to be more lenient,
 *   the primary exclusion here is "/" and "\" and a leading ".", these
 *   restrictions are intended to leave the door open for using goog.require
 *   with relative file paths rather than module identifiers.
 * @private
 */
goog.VALID_MODULE_RE_ = /^[a-zA-Z_$][a-zA-Z0-9._$]*$/;


/**
 * Defines a module in Closure.
 *
 * Marks that this file must be loaded as a module and claims the namespace.
 *
 * A namespace may only be defined once in a codebase. It may be defined using
 * goog.provide() or goog.module().
 *
 * goog.module() has three requirements:
 * - goog.module may not be used in the same file as goog.provide.
 * - goog.module must be the first statement in the file.
 * - only one goog.module is allowed per file.
 *
 * When a goog.module annotated file is loaded, it is enclosed in
 * a strict function closure. This means that:
 * - any variables declared in a goog.module file are private to the file
 * (not global), though the compiler is expected to inline the module.
 * - The code must obey all the rules of "strict" JavaScript.
 * - the file will be marked as "use strict"
 *
 * NOTE: unlike goog.provide, goog.module does not declare any symbols by
 * itself. If declared symbols are desired, use
 * goog.module.declareLegacyNamespace().
 *
 *
 * See the public goog.module proposal: http://goo.gl/Va1hin
 *
 * @param {string} name Namespace provided by this file in the form
 *     "goog.package.part", is expected but not required.
 */
goog.module = function(name) {
  if (!goog.isString(name) || !name ||
      name.search(goog.VALID_MODULE_RE_) == -1) {
    throw Error('Invalid module identifier');
  }
  if (!goog.isInModuleLoader_()) {
    throw Error('Module ' + name + ' has been loaded incorrectly.');
  }
  if (goog.moduleLoaderState_.moduleName) {
    throw Error('goog.module may only be called once per module.');
  }

  // Store the module name for the loader.
  goog.moduleLoaderState_.moduleName = name;
  if (!COMPILED) {
    // Ensure that the same namespace isn't provided twice.
    // A goog.module/goog.provide maps a goog.require to a specific file
    if (goog.isProvided_(name)) {
      throw Error('Namespace "' + name + '" already declared.');
    }
    delete goog.implicitNamespaces_[name];
  }
};


/**
 * @param {string} name The module identifier.
 * @return {?} The module exports for an already loaded module or null.
 *
 * Note: This is not an alternative to goog.require, it does not
 * indicate a hard dependency, instead it is used to indicate
 * an optional dependency or to access the exports of a module
 * that has already been loaded.
 * @suppress {missingProvide}
 */
goog.module.get = function(name) {
  return goog.module.getInternal_(name);
};


/**
 * @param {string} name The module identifier.
 * @return {?} The module exports for an already loaded module or null.
 * @private
 */
goog.module.getInternal_ = function(name) {
  if (!COMPILED) {
    if (goog.isProvided_(name)) {
      // goog.require only return a value with-in goog.module files.
      return name in goog.loadedModules_ ? goog.loadedModules_[name] :
                                           goog.getObjectByName(name);
    } else {
      return null;
    }
  }
};


/**
 * @private {?{moduleName: (string|undefined), declareLegacyNamespace:boolean}}
 */
goog.moduleLoaderState_ = null;


/**
 * @private
 * @return {boolean} Whether a goog.module is currently being initialized.
 */
goog.isInModuleLoader_ = function() {
  return goog.moduleLoaderState_ != null;
};


/**
 * Provide the module's exports as a globally accessible object under the
 * module's declared name.  This is intended to ease migration to goog.module
 * for files that have existing usages.
 * @suppress {missingProvide}
 */
goog.module.declareLegacyNamespace = function() {
  if (!COMPILED && !goog.isInModuleLoader_()) {
    throw new Error(
        'goog.module.declareLegacyNamespace must be called from ' +
        'within a goog.module');
  }
  if (!COMPILED && !goog.moduleLoaderState_.moduleName) {
    throw Error(
        'goog.module must be called prior to ' +
        'goog.module.declareLegacyNamespace.');
  }
  goog.moduleLoaderState_.declareLegacyNamespace = true;
};


/**
 * Marks that the current file should only be used for testing, and never for
 * live code in production.
 *
 * In the case of unit tests, the message may optionally be an exact namespace
 * for the test (e.g. 'goog.stringTest'). The linter will then ignore the extra
 * provide (if not explicitly defined in the code).
 *
 * @param {string=} opt_message Optional message to add to the error that's
 *     raised when used in production code.
 */
goog.setTestOnly = function(opt_message) {
  if (goog.DISALLOW_TEST_ONLY_CODE) {
    opt_message = opt_message || '';
    throw Error(
        'Importing test-only code into non-debug environment' +
        (opt_message ? ': ' + opt_message : '.'));
  }
};


/**
 * Forward declares a symbol. This is an indication to the compiler that the
 * symbol may be used in the source yet is not required and may not be provided
 * in compilation.
 *
 * The most common usage of forward declaration is code that takes a type as a
 * function parameter but does not need to require it. By forward declaring
 * instead of requiring, no hard dependency is made, and (if not required
 * elsewhere) the namespace may never be required and thus, not be pulled
 * into the JavaScript binary. If it is required elsewhere, it will be type
 * checked as normal.
 *
 *
 * @param {string} name The namespace to forward declare in the form of
 *     "goog.package.part".
 */
goog.forwardDeclare = function(name) {};


/**
 * Forward declare type information. Used to assign types to goog.global
 * referenced object that would otherwise result in unknown type references
 * and thus block property disambiguation.
 */
goog.forwardDeclare('Document');
goog.forwardDeclare('HTMLScriptElement');
goog.forwardDeclare('XMLHttpRequest');


if (!COMPILED) {
  /**
   * Check if the given name has been goog.provided. This will return false for
   * names that are available only as implicit namespaces.
   * @param {string} name name of the object to look for.
   * @return {boolean} Whether the name has been provided.
   * @private
   */
  goog.isProvided_ = function(name) {
    return (name in goog.loadedModules_) ||
        (!goog.implicitNamespaces_[name] &&
         goog.isDefAndNotNull(goog.getObjectByName(name)));
  };

  /**
   * Namespaces implicitly defined by goog.provide. For example,
   * goog.provide('goog.events.Event') implicitly declares that 'goog' and
   * 'goog.events' must be namespaces.
   *
   * @type {!Object<string, (boolean|undefined)>}
   * @private
   */
  goog.implicitNamespaces_ = {'goog.module': true};

  // NOTE: We add goog.module as an implicit namespace as goog.module is defined
  // here and because the existing module package has not been moved yet out of
  // the goog.module namespace. This satisifies both the debug loader and
  // ahead-of-time dependency management.
}


/**
 * Returns an object based on its fully qualified external name.  The object
 * is not found if null or undefined.  If you are using a compilation pass that
 * renames property names beware that using this function will not find renamed
 * properties.
 *
 * @param {string} name The fully qualified name.
 * @param {Object=} opt_obj The object within which to look; default is
 *     |goog.global|.
 * @return {?} The value (object or primitive) or, if not found, null.
 */
goog.getObjectByName = function(name, opt_obj) {
  var parts = name.split('.');
  var cur = opt_obj || goog.global;
  for (var part; part = parts.shift();) {
    if (goog.isDefAndNotNull(cur[part])) {
      cur = cur[part];
    } else {
      return null;
    }
  }
  return cur;
};


/**
 * Globalizes a whole namespace, such as goog or goog.lang.
 *
 * @param {!Object} obj The namespace to globalize.
 * @param {Object=} opt_global The object to add the properties to.
 * @deprecated Properties may be explicitly exported to the global scope, but
 *     this should no longer be done in bulk.
 */
goog.globalize = function(obj, opt_global) {
  var global = opt_global || goog.global;
  for (var x in obj) {
    global[x] = obj[x];
  }
};


/**
 * Adds a dependency from a file to the files it requires.
 * @param {string} relPath The path to the js file.
 * @param {!Array<string>} provides An array of strings with
 *     the names of the objects this file provides.
 * @param {!Array<string>} requires An array of strings with
 *     the names of the objects this file requires.
 * @param {boolean|!Object<string>=} opt_loadFlags Parameters indicating
 *     how the file must be loaded.  The boolean 'true' is equivalent
 *     to {'module': 'goog'} for backwards-compatibility.  Valid properties
 *     and values include {'module': 'goog'} and {'lang': 'es6'}.
 */
goog.addDependency = function(relPath, provides, requires, opt_loadFlags) {
  if (goog.DEPENDENCIES_ENABLED) {
    var provide, require;
    var path = relPath.replace(/\\/g, '/');
    var deps = goog.dependencies_;
    if (!opt_loadFlags || typeof opt_loadFlags === 'boolean') {
      opt_loadFlags = opt_loadFlags ? {'module': 'goog'} : {};
    }
    for (var i = 0; provide = provides[i]; i++) {
      deps.nameToPath[provide] = path;
      deps.pathIsModule[path] = opt_loadFlags['module'] == 'goog';
    }
    for (var j = 0; require = requires[j]; j++) {
      if (!(path in deps.requires)) {
        deps.requires[path] = {};
      }
      deps.requires[path][require] = true;
    }
  }
};




// NOTE(nnaze): The debug DOM loader was included in base.js as an original way
// to do "debug-mode" development.  The dependency system can sometimes be
// confusing, as can the debug DOM loader's asynchronous nature.
//
// With the DOM loader, a call to goog.require() is not blocking -- the script
// will not load until some point after the current script.  If a namespace is
// needed at runtime, it needs to be defined in a previous script, or loaded via
// require() with its registered dependencies.
//
// User-defined namespaces may need their own deps file. For a reference on
// creating a deps file, see:
// Externally: https://developers.google.com/closure/library/docs/depswriter
//
// Because of legacy clients, the DOM loader can't be easily removed from
// base.js.  Work is being done to make it disableable or replaceable for
// different environments (DOM-less JavaScript interpreters like Rhino or V8,
// for example). See bootstrap/ for more information.


/**
 * @define {boolean} Whether to enable the debug loader.
 *
 * If enabled, a call to goog.require() will attempt to load the namespace by
 * appending a script tag to the DOM (if the namespace has been registered).
 *
 * If disabled, goog.require() will simply assert that the namespace has been
 * provided (and depend on the fact that some outside tool correctly ordered
 * the script).
 */
goog.define('goog.ENABLE_DEBUG_LOADER', true);


/**
 * @param {string} msg
 * @private
 */
goog.logToConsole_ = function(msg) {
  if (goog.global.console) {
    goog.global.console['error'](msg);
  }
};


/**
 * Implements a system for the dynamic resolution of dependencies that works in
 * parallel with the BUILD system. Note that all calls to goog.require will be
 * stripped by the JSCompiler when the --process_closure_primitives option is
 * used.
 * @see goog.provide
 * @param {string} name Namespace to include (as was given in goog.provide()) in
 *     the form "goog.package.part".
 * @return {?} If called within a goog.module file, the associated namespace or
 *     module otherwise null.
 */
goog.require = function(name) {
  // If the object already exists we do not need do do anything.
  if (!COMPILED) {
    if (goog.ENABLE_DEBUG_LOADER && goog.IS_OLD_IE_) {
      goog.maybeProcessDeferredDep_(name);
    }

    if (goog.isProvided_(name)) {
      if (goog.isInModuleLoader_()) {
        return goog.module.getInternal_(name);
      } else {
        return null;
      }
    }

    if (goog.ENABLE_DEBUG_LOADER) {
      var path = goog.getPathFromDeps_(name);
      if (path) {
        goog.writeScripts_(path);
        return null;
      }
    }

    var errorMessage = 'goog.require could not find: ' + name;
    goog.logToConsole_(errorMessage);

    throw Error(errorMessage);
  }
};


/**
 * Path for included scripts.
 * @type {string}
 */
goog.basePath = '';


/**
 * A hook for overriding the base path.
 * @type {string|undefined}
 */
goog.global.CLOSURE_BASE_PATH;


/**
 * Whether to write out Closure's deps file. By default, the deps are written.
 * @type {boolean|undefined}
 */
goog.global.CLOSURE_NO_DEPS;


/**
 * A function to import a single script. This is meant to be overridden when
 * Closure is being run in non-HTML contexts, such as web workers. It's defined
 * in the global scope so that it can be set before base.js is loaded, which
 * allows deps.js to be imported properly.
 *
 * The function is passed the script source, which is a relative URI. It should
 * return true if the script was imported, false otherwise.
 * @type {(function(string): boolean)|undefined}
 */
goog.global.CLOSURE_IMPORT_SCRIPT;


/**
 * Null function used for default values of callbacks, etc.
 * @return {void} Nothing.
 */
goog.nullFunction = function() {};


/**
 * When defining a class Foo with an abstract method bar(), you can do:
 * Foo.prototype.bar = goog.abstractMethod
 *
 * Now if a subclass of Foo fails to override bar(), an error will be thrown
 * when bar() is invoked.
 *
 * Note: This does not take the name of the function to override as an argument
 * because that would make it more difficult to obfuscate our JavaScript code.
 *
 * @type {!Function}
 * @throws {Error} when invoked to indicate the method should be overridden.
 */
goog.abstractMethod = function() {
  throw Error('unimplemented abstract method');
};


/**
 * Adds a {@code getInstance} static method that always returns the same
 * instance object.
 * @param {!Function} ctor The constructor for the class to add the static
 *     method to.
 */
goog.addSingletonGetter = function(ctor) {
  ctor.getInstance = function() {
    if (ctor.instance_) {
      return ctor.instance_;
    }
    if (goog.DEBUG) {
      // NOTE: JSCompiler can't optimize away Array#push.
      goog.instantiatedSingletons_[goog.instantiatedSingletons_.length] = ctor;
    }
    return ctor.instance_ = new ctor;
  };
};


/**
 * All singleton classes that have been instantiated, for testing. Don't read
 * it directly, use the {@code goog.testing.singleton} module. The compiler
 * removes this variable if unused.
 * @type {!Array<!Function>}
 * @private
 */
goog.instantiatedSingletons_ = [];


/**
 * @define {boolean} Whether to load goog.modules using {@code eval} when using
 * the debug loader.  This provides a better debugging experience as the
 * source is unmodified and can be edited using Chrome Workspaces or similar.
 * However in some environments the use of {@code eval} is banned
 * so we provide an alternative.
 */
goog.define('goog.LOAD_MODULE_USING_EVAL', true);


/**
 * @define {boolean} Whether the exports of goog.modules should be sealed when
 * possible.
 */
goog.define('goog.SEAL_MODULE_EXPORTS', goog.DEBUG);


/**
 * The registry of initialized modules:
 * the module identifier to module exports map.
 * @private @const {!Object<string, ?>}
 */
goog.loadedModules_ = {};


/**
 * True if goog.dependencies_ is available.
 * @const {boolean}
 */
goog.DEPENDENCIES_ENABLED = !COMPILED && goog.ENABLE_DEBUG_LOADER;


if (goog.DEPENDENCIES_ENABLED) {
  /**
   * This object is used to keep track of dependencies and other data that is
   * used for loading scripts.
   * @private
   * @type {{
   *   pathIsModule: !Object<string, boolean>,
   *   nameToPath: !Object<string, string>,
   *   requires: !Object<string, !Object<string, boolean>>,
   *   visited: !Object<string, boolean>,
   *   written: !Object<string, boolean>,
   *   deferred: !Object<string, string>
   * }}
   */
  goog.dependencies_ = {
    pathIsModule: {},  // 1 to 1

    nameToPath: {},  // 1 to 1

    requires: {},  // 1 to many

    // Used when resolving dependencies to prevent us from visiting file twice.
    visited: {},

    written: {},  // Used to keep track of script files we have written.

    deferred: {}  // Used to track deferred module evaluations in old IEs
  };


  /**
   * Tries to detect whether is in the context of an HTML document.
   * @return {boolean} True if it looks like HTML document.
   * @private
   */
  goog.inHtmlDocument_ = function() {
    /** @type {Document} */
    var doc = goog.global.document;
    return doc != null && 'write' in doc;  // XULDocument misses write.
  };


  /**
   * Tries to detect the base path of base.js script that bootstraps Closure.
   * @private
   */
  goog.findBasePath_ = function() {
    if (goog.isDef(goog.global.CLOSURE_BASE_PATH)) {
      goog.basePath = goog.global.CLOSURE_BASE_PATH;
      return;
    } else if (!goog.inHtmlDocument_()) {
      return;
    }
    /** @type {Document} */
    var doc = goog.global.document;
    var scripts = doc.getElementsByTagName('SCRIPT');
    // Search backwards since the current script is in almost all cases the one
    // that has base.js.
    for (var i = scripts.length - 1; i >= 0; --i) {
      var script = /** @type {!HTMLScriptElement} */ (scripts[i]);
      var src = script.src;
      var qmark = src.lastIndexOf('?');
      var l = qmark == -1 ? src.length : qmark;
      if (src.substr(l - 7, 7) == 'base.js') {
        goog.basePath = src.substr(0, l - 7);
        return;
      }
    }
  };


  /**
   * Imports a script if, and only if, that script hasn't already been imported.
   * (Must be called at execution time)
   * @param {string} src Script source.
   * @param {string=} opt_sourceText The optionally source text to evaluate
   * @private
   */
  goog.importScript_ = function(src, opt_sourceText) {
    var importScript =
        goog.global.CLOSURE_IMPORT_SCRIPT || goog.writeScriptTag_;
    if (importScript(src, opt_sourceText)) {
      goog.dependencies_.written[src] = true;
    }
  };


  /** @const @private {boolean} */
  goog.IS_OLD_IE_ =
      !!(!goog.global.atob && goog.global.document && goog.global.document.all);


  /**
   * Given a URL initiate retrieval and execution of the module.
   * @param {string} src Script source URL.
   * @private
   */
  goog.importModule_ = function(src) {
    // In an attempt to keep browsers from timing out loading scripts using
    // synchronous XHRs, put each load in its own script block.
    var bootstrap = 'goog.retrieveAndExecModule_("' + src + '");';

    goog.importScript_('', bootstrap);
  };


  /** @private {!Array<string>} */
  goog.queuedModules_ = [];


  /**
   * Return an appropriate module text. Suitable to insert into
   * a script tag (that is unescaped).
   * @param {string} srcUrl
   * @param {string} scriptText
   * @return {string}
   * @private
   */
  goog.wrapModule_ = function(srcUrl, scriptText) {
    if (!goog.LOAD_MODULE_USING_EVAL || !goog.isDef(goog.global.JSON)) {
      return '' +
          'goog.loadModule(function(exports) {' +
          '"use strict";' + scriptText +
          '\n' +  // terminate any trailing single line comment.
          ';return exports' +
          '});' +
          '\n//# sourceURL=' + srcUrl + '\n';
    } else {
      return '' +
          'goog.loadModule(' +
          goog.global.JSON.stringify(
              scriptText + '\n//# sourceURL=' + srcUrl + '\n') +
          ');';
    }
  };

  // On IE9 and earlier, it is necessary to handle
  // deferred module loads. In later browsers, the
  // code to be evaluated is simply inserted as a script
  // block in the correct order. To eval deferred
  // code at the right time, we piggy back on goog.require to call
  // goog.maybeProcessDeferredDep_.
  //
  // The goog.requires are used both to bootstrap
  // the loading process (when no deps are available) and
  // declare that they should be available.
  //
  // Here we eval the sources, if all the deps are available
  // either already eval'd or goog.require'd.  This will
  // be the case when all the dependencies have already
  // been loaded, and the dependent module is loaded.
  //
  // But this alone isn't sufficient because it is also
  // necessary to handle the case where there is no root
  // that is not deferred.  For that there we register for an event
  // and trigger goog.loadQueuedModules_ handle any remaining deferred
  // evaluations.

  /**
   * Handle any remaining deferred goog.module evals.
   * @private
   */
  goog.loadQueuedModules_ = function() {
    var count = goog.queuedModules_.length;
    if (count > 0) {
      var queue = goog.queuedModules_;
      goog.queuedModules_ = [];
      for (var i = 0; i < count; i++) {
        var path = queue[i];
        goog.maybeProcessDeferredPath_(path);
      }
    }
  };


  /**
   * Eval the named module if its dependencies are
   * available.
   * @param {string} name The module to load.
   * @private
   */
  goog.maybeProcessDeferredDep_ = function(name) {
    if (goog.isDeferredModule_(name) && goog.allDepsAreAvailable_(name)) {
      var path = goog.getPathFromDeps_(name);
      goog.maybeProcessDeferredPath_(goog.basePath + path);
    }
  };

  /**
   * @param {string} name The module to check.
   * @return {boolean} Whether the name represents a
   *     module whose evaluation has been deferred.
   * @private
   */
  goog.isDeferredModule_ = function(name) {
    var path = goog.getPathFromDeps_(name);
    if (path && goog.dependencies_.pathIsModule[path]) {
      var abspath = goog.basePath + path;
      return (abspath) in goog.dependencies_.deferred;
    }
    return false;
  };

  /**
   * @param {string} name The module to check.
   * @return {boolean} Whether the name represents a
   *     module whose declared dependencies have all been loaded
   *     (eval'd or a deferred module load)
   * @private
   */
  goog.allDepsAreAvailable_ = function(name) {
    var path = goog.getPathFromDeps_(name);
    if (path && (path in goog.dependencies_.requires)) {
      for (var requireName in goog.dependencies_.requires[path]) {
        if (!goog.isProvided_(requireName) &&
            !goog.isDeferredModule_(requireName)) {
          return false;
        }
      }
    }
    return true;
  };


  /**
   * @param {string} abspath
   * @private
   */
  goog.maybeProcessDeferredPath_ = function(abspath) {
    if (abspath in goog.dependencies_.deferred) {
      var src = goog.dependencies_.deferred[abspath];
      delete goog.dependencies_.deferred[abspath];
      goog.globalEval(src);
    }
  };


  /**
   * Load a goog.module from the provided URL.  This is not a general purpose
   * code loader and does not support late loading code, that is it should only
   * be used during page load. This method exists to support unit tests and
   * "debug" loaders that would otherwise have inserted script tags. Under the
   * hood this needs to use a synchronous XHR and is not recommeneded for
   * production code.
   *
   * The module's goog.requires must have already been satisified; an exception
   * will be thrown if this is not the case. This assumption is that no
   * "deps.js" file exists, so there is no way to discover and locate the
   * module-to-be-loaded's dependencies and no attempt is made to do so.
   *
   * There should only be one attempt to load a module.  If
   * "goog.loadModuleFromUrl" is called for an already loaded module, an
   * exception will be throw.
   *
   * @param {string} url The URL from which to attempt to load the goog.module.
   */
  goog.loadModuleFromUrl = function(url) {
    // Because this executes synchronously, we don't need to do any additional
    // bookkeeping. When "goog.loadModule" the namespace will be marked as
    // having been provided which is sufficient.
    goog.retrieveAndExecModule_(url);
  };


  /**
   * @param {function(?):?|string} moduleDef The module definition.
   */
  goog.loadModule = function(moduleDef) {
    // NOTE: we allow function definitions to be either in the from
    // of a string to eval (which keeps the original source intact) or
    // in a eval forbidden environment (CSP) we allow a function definition
    // which in its body must call {@code goog.module}, and return the exports
    // of the module.
    var previousState = goog.moduleLoaderState_;
    try {
      goog.moduleLoaderState_ = {
        moduleName: undefined,
        declareLegacyNamespace: false
      };
      var exports;
      if (goog.isFunction(moduleDef)) {
        exports = moduleDef.call(goog.global, {});
      } else if (goog.isString(moduleDef)) {
        exports = goog.loadModuleFromSource_.call(goog.global, moduleDef);
      } else {
        throw Error('Invalid module definition');
      }

      var moduleName = goog.moduleLoaderState_.moduleName;
      if (!goog.isString(moduleName) || !moduleName) {
        throw Error('Invalid module name \"' + moduleName + '\"');
      }

      // Don't seal legacy namespaces as they may be uses as a parent of
      // another namespace
      if (goog.moduleLoaderState_.declareLegacyNamespace) {
        goog.constructNamespace_(moduleName, exports);
      } else if (goog.SEAL_MODULE_EXPORTS && Object.seal) {
        Object.seal(exports);
      }

      goog.loadedModules_[moduleName] = exports;
    } finally {
      goog.moduleLoaderState_ = previousState;
    }
  };


  /**
   * @private @const {function(string):?}
   *
   * The new type inference warns because this function has no formal
   * parameters, but its jsdoc says that it takes one argument.
   * (The argument is used via arguments[0], but NTI does not detect this.)
   * @suppress {newCheckTypes}
   */
  goog.loadModuleFromSource_ = function() {
    // NOTE: we avoid declaring parameters or local variables here to avoid
    // masking globals or leaking values into the module definition.
    'use strict';
    var exports = {};
    eval(arguments[0]);
    return exports;
  };


  /**
   * Writes a new script pointing to {@code src} directly into the DOM.
   *
   * NOTE: This method is not CSP-compliant. @see goog.appendScriptSrcNode_ for
   * the fallback mechanism.
   *
   * @param {string} src The script URL.
   * @private
   */
  goog.writeScriptSrcNode_ = function(src) {
    goog.global.document.write(
        '<script type="text/javascript" src="' + src + '"></' +
        'script>');
  };


  /**
   * Appends a new script node to the DOM using a CSP-compliant mechanism. This
   * method exists as a fallback for document.write (which is not allowed in a
   * strict CSP context, e.g., Chrome apps).
   *
   * NOTE: This method is not analogous to using document.write to insert a
   * <script> tag; specifically, the user agent will execute a script added by
   * document.write immediately after the current script block finishes
   * executing, whereas the DOM-appended script node will not be executed until
   * the entire document is parsed and executed. That is to say, this script is
   * added to the end of the script execution queue.
   *
   * The page must not attempt to call goog.required entities until after the
   * document has loaded, e.g., in or after the window.onload callback.
   *
   * @param {string} src The script URL.
   * @private
   */
  goog.appendScriptSrcNode_ = function(src) {
    /** @type {Document} */
    var doc = goog.global.document;
    var scriptEl =
        /** @type {HTMLScriptElement} */ (doc.createElement('script'));
    scriptEl.type = 'text/javascript';
    scriptEl.src = src;
    scriptEl.defer = false;
    scriptEl.async = false;
    doc.head.appendChild(scriptEl);
  };


  /**
   * The default implementation of the import function. Writes a script tag to
   * import the script.
   *
   * @param {string} src The script url.
   * @param {string=} opt_sourceText The optionally source text to evaluate
   * @return {boolean} True if the script was imported, false otherwise.
   * @private
   */
  goog.writeScriptTag_ = function(src, opt_sourceText) {
    if (goog.inHtmlDocument_()) {
      /** @type {!HTMLDocument} */
      var doc = goog.global.document;

      // If the user tries to require a new symbol after document load,
      // something has gone terribly wrong. Doing a document.write would
      // wipe out the page. This does not apply to the CSP-compliant method
      // of writing script tags.
      if (!goog.ENABLE_CHROME_APP_SAFE_SCRIPT_LOADING &&
          doc.readyState == 'complete') {
        // Certain test frameworks load base.js multiple times, which tries
        // to write deps.js each time. If that happens, just fail silently.
        // These frameworks wipe the page between each load of base.js, so this
        // is OK.
        var isDeps = /\bdeps.js$/.test(src);
        if (isDeps) {
          return false;
        } else {
          throw Error('Cannot write "' + src + '" after document load');
        }
      }

      var isOldIE = goog.IS_OLD_IE_;

      if (opt_sourceText === undefined) {
        if (!isOldIE) {
          if (goog.ENABLE_CHROME_APP_SAFE_SCRIPT_LOADING) {
            goog.appendScriptSrcNode_(src);
          } else {
            goog.writeScriptSrcNode_(src);
          }
        } else {
          var state = " onreadystatechange='goog.onScriptLoad_(this, " +
              ++goog.lastNonModuleScriptIndex_ + ")' ";
          doc.write(
              '<script type="text/javascript" src="' + src + '"' + state +
              '></' +
              'script>');
        }
      } else {
        doc.write(
            '<script type="text/javascript">' + opt_sourceText + '</' +
            'script>');
      }
      return true;
    } else {
      return false;
    }
  };


  /** @private {number} */
  goog.lastNonModuleScriptIndex_ = 0;


  /**
   * A readystatechange handler for legacy IE
   * @param {!HTMLScriptElement} script
   * @param {number} scriptIndex
   * @return {boolean}
   * @private
   */
  goog.onScriptLoad_ = function(script, scriptIndex) {
    // for now load the modules when we reach the last script,
    // later allow more inter-mingling.
    if (script.readyState == 'complete' &&
        goog.lastNonModuleScriptIndex_ == scriptIndex) {
      goog.loadQueuedModules_();
    }
    return true;
  };

  /**
   * Resolves dependencies based on the dependencies added using addDependency
   * and calls importScript_ in the correct order.
   * @param {string} pathToLoad The path from which to start discovering
   *     dependencies.
   * @private
   */
  goog.writeScripts_ = function(pathToLoad) {
    /** @type {!Array<string>} The scripts we need to write this time. */
    var scripts = [];
    var seenScript = {};
    var deps = goog.dependencies_;

    /** @param {string} path */
    function visitNode(path) {
      if (path in deps.written) {
        return;
      }

      // We have already visited this one. We can get here if we have cyclic
      // dependencies.
      if (path in deps.visited) {
        return;
      }

      deps.visited[path] = true;

      if (path in deps.requires) {
        for (var requireName in deps.requires[path]) {
          // If the required name is defined, we assume that it was already
          // bootstrapped by other means.
          if (!goog.isProvided_(requireName)) {
            if (requireName in deps.nameToPath) {
              visitNode(deps.nameToPath[requireName]);
            } else {
              throw Error('Undefined nameToPath for ' + requireName);
            }
          }
        }
      }

      if (!(path in seenScript)) {
        seenScript[path] = true;
        scripts.push(path);
      }
    }

    visitNode(pathToLoad);

    // record that we are going to load all these scripts.
    for (var i = 0; i < scripts.length; i++) {
      var path = scripts[i];
      goog.dependencies_.written[path] = true;
    }

    // If a module is loaded synchronously then we need to
    // clear the current inModuleLoader value, and restore it when we are
    // done loading the current "requires".
    var moduleState = goog.moduleLoaderState_;
    goog.moduleLoaderState_ = null;

    for (var i = 0; i < scripts.length; i++) {
      var path = scripts[i];
      if (path) {
        if (!deps.pathIsModule[path]) {
          goog.importScript_(goog.basePath + path);
        } else {
          goog.importModule_(goog.basePath + path);
        }
      } else {
        goog.moduleLoaderState_ = moduleState;
        throw Error('Undefined script input');
      }
    }

    // restore the current "module loading state"
    goog.moduleLoaderState_ = moduleState;
  };


  /**
   * Looks at the dependency rules and tries to determine the script file that
   * fulfills a particular rule.
   * @param {string} rule In the form goog.namespace.Class or project.script.
   * @return {?string} Url corresponding to the rule, or null.
   * @private
   */
  goog.getPathFromDeps_ = function(rule) {
    if (rule in goog.dependencies_.nameToPath) {
      return goog.dependencies_.nameToPath[rule];
    } else {
      return null;
    }
  };

  goog.findBasePath_();

  // Allow projects to manage the deps files themselves.
  if (!goog.global.CLOSURE_NO_DEPS) {
    goog.importScript_(goog.basePath + 'deps.js');
  }
}


/**
 * Normalize a file path by removing redundant ".." and extraneous "." file
 * path components.
 * @param {string} path
 * @return {string}
 * @private
 */
goog.normalizePath_ = function(path) {
  var components = path.split('/');
  var i = 0;
  while (i < components.length) {
    if (components[i] == '.') {
      components.splice(i, 1);
    } else if (
        i && components[i] == '..' && components[i - 1] &&
        components[i - 1] != '..') {
      components.splice(--i, 2);
    } else {
      i++;
    }
  }
  return components.join('/');
};


/**
 * Loads file by synchronous XHR. Should not be used in production environments.
 * @param {string} src Source URL.
 * @return {string} File contents.
 * @private
 */
goog.loadFileSync_ = function(src) {
  if (goog.global.CLOSURE_LOAD_FILE_SYNC) {
    return goog.global.CLOSURE_LOAD_FILE_SYNC(src);
  } else {
    /** @type {XMLHttpRequest} */
    var xhr = new goog.global['XMLHttpRequest']();
    xhr.open('get', src, false);
    xhr.send();
    return xhr.responseText;
  }
};


/**
 * Retrieve and execute a module.
 * @param {string} src Script source URL.
 * @private
 */
goog.retrieveAndExecModule_ = function(src) {
  if (!COMPILED) {
    // The full but non-canonicalized URL for later use.
    var originalPath = src;
    // Canonicalize the path, removing any /./ or /../ since Chrome's debugging
    // console doesn't auto-canonicalize XHR loads as it does <script> srcs.
    src = goog.normalizePath_(src);

    var importScript =
        goog.global.CLOSURE_IMPORT_SCRIPT || goog.writeScriptTag_;

    var scriptText = goog.loadFileSync_(src);

    if (scriptText != null) {
      var execModuleScript = goog.wrapModule_(src, scriptText);
      var isOldIE = goog.IS_OLD_IE_;
      if (isOldIE) {
        goog.dependencies_.deferred[originalPath] = execModuleScript;
        goog.queuedModules_.push(originalPath);
      } else {
        importScript(src, execModuleScript);
      }
    } else {
      throw new Error('load of ' + src + 'failed');
    }
  }
};


//==============================================================================
// Language Enhancements
//==============================================================================


/**
 * This is a "fixed" version of the typeof operator.  It differs from the typeof
 * operator in such a way that null returns 'null' and arrays return 'array'.
 * @param {?} value The value to get the type of.
 * @return {string} The name of the type.
 */
goog.typeOf = function(value) {
  var s = typeof value;
  if (s == 'object') {
    if (value) {
      // Check these first, so we can avoid calling Object.prototype.toString if
      // possible.
      //
      // IE improperly marshals typeof across execution contexts, but a
      // cross-context object will still return false for "instanceof Object".
      if (value instanceof Array) {
        return 'array';
      } else if (value instanceof Object) {
        return s;
      }

      // HACK: In order to use an Object prototype method on the arbitrary
      //   value, the compiler requires the value be cast to type Object,
      //   even though the ECMA spec explicitly allows it.
      var className = Object.prototype.toString.call(
          /** @type {!Object} */ (value));
      // In Firefox 3.6, attempting to access iframe window objects' length
      // property throws an NS_ERROR_FAILURE, so we need to special-case it
      // here.
      if (className == '[object Window]') {
        return 'object';
      }

      // We cannot always use constructor == Array or instanceof Array because
      // different frames have different Array objects. In IE6, if the iframe
      // where the array was created is destroyed, the array loses its
      // prototype. Then dereferencing val.splice here throws an exception, so
      // we can't use goog.isFunction. Calling typeof directly returns 'unknown'
      // so that will work. In this case, this function will return false and
      // most array functions will still work because the array is still
      // array-like (supports length and []) even though it has lost its
      // prototype.
      // Mark Miller noticed that Object.prototype.toString
      // allows access to the unforgeable [[Class]] property.
      //  15.2.4.2 Object.prototype.toString ( )
      //  When the toString method is called, the following steps are taken:
      //      1. Get the [[Class]] property of this object.
      //      2. Compute a string value by concatenating the three strings
      //         "[object ", Result(1), and "]".
      //      3. Return Result(2).
      // and this behavior survives the destruction of the execution context.
      if ((className == '[object Array]' ||
           // In IE all non value types are wrapped as objects across window
           // boundaries (not iframe though) so we have to do object detection
           // for this edge case.
           typeof value.length == 'number' &&
               typeof value.splice != 'undefined' &&
               typeof value.propertyIsEnumerable != 'undefined' &&
               !value.propertyIsEnumerable('splice')

               )) {
        return 'array';
      }
      // HACK: There is still an array case that fails.
      //     function ArrayImpostor() {}
      //     ArrayImpostor.prototype = [];
      //     var impostor = new ArrayImpostor;
      // this can be fixed by getting rid of the fast path
      // (value instanceof Array) and solely relying on
      // (value && Object.prototype.toString.vall(value) === '[object Array]')
      // but that would require many more function calls and is not warranted
      // unless closure code is receiving objects from untrusted sources.

      // IE in cross-window calls does not correctly marshal the function type
      // (it appears just as an object) so we cannot use just typeof val ==
      // 'function'. However, if the object has a call property, it is a
      // function.
      if ((className == '[object Function]' ||
           typeof value.call != 'undefined' &&
               typeof value.propertyIsEnumerable != 'undefined' &&
               !value.propertyIsEnumerable('call'))) {
        return 'function';
      }

    } else {
      return 'null';
    }

  } else if (s == 'function' && typeof value.call == 'undefined') {
    // In Safari typeof nodeList returns 'function', and on Firefox typeof
    // behaves similarly for HTML{Applet,Embed,Object}, Elements and RegExps. We
    // would like to return object for those and we can detect an invalid
    // function by making sure that the function object has a call method.
    return 'object';
  }
  return s;
};


/**
 * Returns true if the specified value is null.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is null.
 */
goog.isNull = function(val) {
  return val === null;
};


/**
 * Returns true if the specified value is defined and not null.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is defined and not null.
 */
goog.isDefAndNotNull = function(val) {
  // Note that undefined == null.
  return val != null;
};


/**
 * Returns true if the specified value is an array.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is an array.
 */
goog.isArray = function(val) {
  return goog.typeOf(val) == 'array';
};


/**
 * Returns true if the object looks like an array. To qualify as array like
 * the value needs to be either a NodeList or an object with a Number length
 * property. As a special case, a function value is not array like, because its
 * length property is fixed to correspond to the number of expected arguments.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is an array.
 */
goog.isArrayLike = function(val) {
  var type = goog.typeOf(val);
  // We do not use goog.isObject here in order to exclude function values.
  return type == 'array' || type == 'object' && typeof val.length == 'number';
};


/**
 * Returns true if the object looks like a Date. To qualify as Date-like the
 * value needs to be an object and have a getFullYear() function.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a like a Date.
 */
goog.isDateLike = function(val) {
  return goog.isObject(val) && typeof val.getFullYear == 'function';
};


/**
 * Returns true if the specified value is a string.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a string.
 */
goog.isString = function(val) {
  return typeof val == 'string';
};


/**
 * Returns true if the specified value is a boolean.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is boolean.
 */
goog.isBoolean = function(val) {
  return typeof val == 'boolean';
};


/**
 * Returns true if the specified value is a number.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a number.
 */
goog.isNumber = function(val) {
  return typeof val == 'number';
};


/**
 * Returns true if the specified value is a function.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is a function.
 */
goog.isFunction = function(val) {
  return goog.typeOf(val) == 'function';
};


/**
 * Returns true if the specified value is an object.  This includes arrays and
 * functions.
 * @param {?} val Variable to test.
 * @return {boolean} Whether variable is an object.
 */
goog.isObject = function(val) {
  var type = typeof val;
  return type == 'object' && val != null || type == 'function';
  // return Object(val) === val also works, but is slower, especially if val is
  // not an object.
};


/**
 * Gets a unique ID for an object. This mutates the object so that further calls
 * with the same object as a parameter returns the same value. The unique ID is
 * guaranteed to be unique across the current session amongst objects that are
 * passed into {@code getUid}. There is no guarantee that the ID is unique or
 * consistent across sessions. It is unsafe to generate unique ID for function
 * prototypes.
 *
 * @param {Object} obj The object to get the unique ID for.
 * @return {number} The unique ID for the object.
 */
goog.getUid = function(obj) {
  // TODO(arv): Make the type stricter, do not accept null.

  // In Opera window.hasOwnProperty exists but always returns false so we avoid
  // using it. As a consequence the unique ID generated for BaseClass.prototype
  // and SubClass.prototype will be the same.
  return obj[goog.UID_PROPERTY_] ||
      (obj[goog.UID_PROPERTY_] = ++goog.uidCounter_);
};


/**
 * Whether the given object is already assigned a unique ID.
 *
 * This does not modify the object.
 *
 * @param {!Object} obj The object to check.
 * @return {boolean} Whether there is an assigned unique id for the object.
 */
goog.hasUid = function(obj) {
  return !!obj[goog.UID_PROPERTY_];
};


/**
 * Removes the unique ID from an object. This is useful if the object was
 * previously mutated using {@code goog.getUid} in which case the mutation is
 * undone.
 * @param {Object} obj The object to remove the unique ID field from.
 */
goog.removeUid = function(obj) {
  // TODO(arv): Make the type stricter, do not accept null.

  // In IE, DOM nodes are not instances of Object and throw an exception if we
  // try to delete.  Instead we try to use removeAttribute.
  if (obj !== null && 'removeAttribute' in obj) {
    obj.removeAttribute(goog.UID_PROPERTY_);
  }
  /** @preserveTry */
  try {
    delete obj[goog.UID_PROPERTY_];
  } catch (ex) {
  }
};


/**
 * Name for unique ID property. Initialized in a way to help avoid collisions
 * with other closure JavaScript on the same page.
 * @type {string}
 * @private
 */
goog.UID_PROPERTY_ = 'closure_uid_' + ((Math.random() * 1e9) >>> 0);


/**
 * Counter for UID.
 * @type {number}
 * @private
 */
goog.uidCounter_ = 0;


/**
 * Adds a hash code field to an object. The hash code is unique for the
 * given object.
 * @param {Object} obj The object to get the hash code for.
 * @return {number} The hash code for the object.
 * @deprecated Use goog.getUid instead.
 */
goog.getHashCode = goog.getUid;


/**
 * Removes the hash code field from an object.
 * @param {Object} obj The object to remove the field from.
 * @deprecated Use goog.removeUid instead.
 */
goog.removeHashCode = goog.removeUid;


/**
 * Clones a value. The input may be an Object, Array, or basic type. Objects and
 * arrays will be cloned recursively.
 *
 * WARNINGS:
 * <code>goog.cloneObject</code> does not detect reference loops. Objects that
 * refer to themselves will cause infinite recursion.
 *
 * <code>goog.cloneObject</code> is unaware of unique identifiers, and copies
 * UIDs created by <code>getUid</code> into cloned results.
 *
 * @param {*} obj The value to clone.
 * @return {*} A clone of the input value.
 * @deprecated goog.cloneObject is unsafe. Prefer the goog.object methods.
 */
goog.cloneObject = function(obj) {
  var type = goog.typeOf(obj);
  if (type == 'object' || type == 'array') {
    if (obj.clone) {
      return obj.clone();
    }
    var clone = type == 'array' ? [] : {};
    for (var key in obj) {
      clone[key] = goog.cloneObject(obj[key]);
    }
    return clone;
  }

  return obj;
};


/**
 * A native implementation of goog.bind.
 * @param {Function} fn A function to partially apply.
 * @param {Object|undefined} selfObj Specifies the object which this should
 *     point to when the function is run.
 * @param {...*} var_args Additional arguments that are partially applied to the
 *     function.
 * @return {!Function} A partially-applied form of the function bind() was
 *     invoked as a method of.
 * @private
 * @suppress {deprecated} The compiler thinks that Function.prototype.bind is
 *     deprecated because some people have declared a pure-JS version.
 *     Only the pure-JS version is truly deprecated.
 */
goog.bindNative_ = function(fn, selfObj, var_args) {
  return /** @type {!Function} */ (fn.call.apply(fn.bind, arguments));
};


/**
 * A pure-JS implementation of goog.bind.
 * @param {Function} fn A function to partially apply.
 * @param {Object|undefined} selfObj Specifies the object which this should
 *     point to when the function is run.
 * @param {...*} var_args Additional arguments that are partially applied to the
 *     function.
 * @return {!Function} A partially-applied form of the function bind() was
 *     invoked as a method of.
 * @private
 */
goog.bindJs_ = function(fn, selfObj, var_args) {
  if (!fn) {
    throw new Error();
  }

  if (arguments.length > 2) {
    var boundArgs = Array.prototype.slice.call(arguments, 2);
    return function() {
      // Prepend the bound arguments to the current arguments.
      var newArgs = Array.prototype.slice.call(arguments);
      Array.prototype.unshift.apply(newArgs, boundArgs);
      return fn.apply(selfObj, newArgs);
    };

  } else {
    return function() { return fn.apply(selfObj, arguments); };
  }
};


/**
 * Partially applies this function to a particular 'this object' and zero or
 * more arguments. The result is a new function with some arguments of the first
 * function pre-filled and the value of this 'pre-specified'.
 *
 * Remaining arguments specified at call-time are appended to the pre-specified
 * ones.
 *
 * Also see: {@link #partial}.
 *
 * Usage:
 * <pre>var barMethBound = goog.bind(myFunction, myObj, 'arg1', 'arg2');
 * barMethBound('arg3', 'arg4');</pre>
 *
 * @param {?function(this:T, ...)} fn A function to partially apply.
 * @param {T} selfObj Specifies the object which this should point to when the
 *     function is run.
 * @param {...*} var_args Additional arguments that are partially applied to the
 *     function.
 * @return {!Function} A partially-applied form of the function goog.bind() was
 *     invoked as a method of.
 * @template T
 * @suppress {deprecated} See above.
 */
goog.bind = function(fn, selfObj, var_args) {
  // TODO(nicksantos): narrow the type signature.
  if (Function.prototype.bind &&
      // NOTE(nicksantos): Somebody pulled base.js into the default Chrome
      // extension environment. This means that for Chrome extensions, they get
      // the implementation of Function.prototype.bind that calls goog.bind
      // instead of the native one. Even worse, we don't want to introduce a
      // circular dependency between goog.bind and Function.prototype.bind, so
      // we have to hack this to make sure it works correctly.
      Function.prototype.bind.toString().indexOf('native code') != -1) {
    goog.bind = goog.bindNative_;
  } else {
    goog.bind = goog.bindJs_;
  }
  return goog.bind.apply(null, arguments);
};


/**
 * Like goog.bind(), except that a 'this object' is not required. Useful when
 * the target function is already bound.
 *
 * Usage:
 * var g = goog.partial(f, arg1, arg2);
 * g(arg3, arg4);
 *
 * @param {Function} fn A function to partially apply.
 * @param {...*} var_args Additional arguments that are partially applied to fn.
 * @return {!Function} A partially-applied form of the function goog.partial()
 *     was invoked as a method of.
 */
goog.partial = function(fn, var_args) {
  var args = Array.prototype.slice.call(arguments, 1);
  return function() {
    // Clone the array (with slice()) and append additional arguments
    // to the existing arguments.
    var newArgs = args.slice();
    newArgs.push.apply(newArgs, arguments);
    return fn.apply(this, newArgs);
  };
};


/**
 * Copies all the members of a source object to a target object. This method
 * does not work on all browsers for all objects that contain keys such as
 * toString or hasOwnProperty. Use goog.object.extend for this purpose.
 * @param {Object} target Target.
 * @param {Object} source Source.
 */
goog.mixin = function(target, source) {
  for (var x in source) {
    target[x] = source[x];
  }

  // For IE7 or lower, the for-in-loop does not contain any properties that are
  // not enumerable on the prototype object (for example, isPrototypeOf from
  // Object.prototype) but also it will not include 'replace' on objects that
  // extend String and change 'replace' (not that it is common for anyone to
  // extend anything except Object).
};


/**
 * @return {number} An integer value representing the number of milliseconds
 *     between midnight, January 1, 1970 and the current time.
 */
goog.now = (goog.TRUSTED_SITE && Date.now) || (function() {
             // Unary plus operator converts its operand to a number which in
             // the case of
             // a date is done by calling getTime().
             return +new Date();
           });


/**
 * Evals JavaScript in the global scope.  In IE this uses execScript, other
 * browsers use goog.global.eval. If goog.global.eval does not evaluate in the
 * global scope (for example, in Safari), appends a script tag instead.
 * Throws an exception if neither execScript or eval is defined.
 * @param {string} script JavaScript string.
 */
goog.globalEval = function(script) {
  if (goog.global.execScript) {
    goog.global.execScript(script, 'JavaScript');
  } else if (goog.global.eval) {
    // Test to see if eval works
    if (goog.evalWorksForGlobals_ == null) {
      goog.global.eval('var _evalTest_ = 1;');
      if (typeof goog.global['_evalTest_'] != 'undefined') {
        try {
          delete goog.global['_evalTest_'];
        } catch (ignore) {
          // Microsoft edge fails the deletion above in strict mode.
        }
        goog.evalWorksForGlobals_ = true;
      } else {
        goog.evalWorksForGlobals_ = false;
      }
    }

    if (goog.evalWorksForGlobals_) {
      goog.global.eval(script);
    } else {
      /** @type {Document} */
      var doc = goog.global.document;
      var scriptElt =
          /** @type {!HTMLScriptElement} */ (doc.createElement('SCRIPT'));
      scriptElt.type = 'text/javascript';
      scriptElt.defer = false;
      // Note(user): can't use .innerHTML since "t('<test>')" will fail and
      // .text doesn't work in Safari 2.  Therefore we append a text node.
      scriptElt.appendChild(doc.createTextNode(script));
      doc.body.appendChild(scriptElt);
      doc.body.removeChild(scriptElt);
    }
  } else {
    throw Error('goog.globalEval not available');
  }
};


/**
 * Indicates whether or not we can call 'eval' directly to eval code in the
 * global scope. Set to a Boolean by the first call to goog.globalEval (which
 * empirically tests whether eval works for globals). @see goog.globalEval
 * @type {?boolean}
 * @private
 */
goog.evalWorksForGlobals_ = null;


/**
 * Optional map of CSS class names to obfuscated names used with
 * goog.getCssName().
 * @private {!Object<string, string>|undefined}
 * @see goog.setCssNameMapping
 */
goog.cssNameMapping_;


/**
 * Optional obfuscation style for CSS class names. Should be set to either
 * 'BY_WHOLE' or 'BY_PART' if defined.
 * @type {string|undefined}
 * @private
 * @see goog.setCssNameMapping
 */
goog.cssNameMappingStyle_;


/**
 * Handles strings that are intended to be used as CSS class names.
 *
 * This function works in tandem with @see goog.setCssNameMapping.
 *
 * Without any mapping set, the arguments are simple joined with a hyphen and
 * passed through unaltered.
 *
 * When there is a mapping, there are two possible styles in which these
 * mappings are used. In the BY_PART style, each part (i.e. in between hyphens)
 * of the passed in css name is rewritten according to the map. In the BY_WHOLE
 * style, the full css name is looked up in the map directly. If a rewrite is
 * not specified by the map, the compiler will output a warning.
 *
 * When the mapping is passed to the compiler, it will replace calls to
 * goog.getCssName with the strings from the mapping, e.g.
 *     var x = goog.getCssName('foo');
 *     var y = goog.getCssName(this.baseClass, 'active');
 *  becomes:
 *     var x = 'foo';
 *     var y = this.baseClass + '-active';
 *
 * If one argument is passed it will be processed, if two are passed only the
 * modifier will be processed, as it is assumed the first argument was generated
 * as a result of calling goog.getCssName.
 *
 * @param {string} className The class name.
 * @param {string=} opt_modifier A modifier to be appended to the class name.
 * @return {string} The class name or the concatenation of the class name and
 *     the modifier.
 */
goog.getCssName = function(className, opt_modifier) {
  var getMapping = function(cssName) {
    return goog.cssNameMapping_[cssName] || cssName;
  };

  var renameByParts = function(cssName) {
    // Remap all the parts individually.
    var parts = cssName.split('-');
    var mapped = [];
    for (var i = 0; i < parts.length; i++) {
      mapped.push(getMapping(parts[i]));
    }
    return mapped.join('-');
  };

  var rename;
  if (goog.cssNameMapping_) {
    rename =
        goog.cssNameMappingStyle_ == 'BY_WHOLE' ? getMapping : renameByParts;
  } else {
    rename = function(a) { return a; };
  }

  if (opt_modifier) {
    return className + '-' + rename(opt_modifier);
  } else {
    return rename(className);
  }
};


/**
 * Sets the map to check when returning a value from goog.getCssName(). Example:
 * <pre>
 * goog.setCssNameMapping({
 *   "goog": "a",
 *   "disabled": "b",
 * });
 *
 * var x = goog.getCssName('goog');
 * // The following evaluates to: "a a-b".
 * goog.getCssName('goog') + ' ' + goog.getCssName(x, 'disabled')
 * </pre>
 * When declared as a map of string literals to string literals, the JSCompiler
 * will replace all calls to goog.getCssName() using the supplied map if the
 * --process_closure_primitives flag is set.
 *
 * @param {!Object} mapping A map of strings to strings where keys are possible
 *     arguments to goog.getCssName() and values are the corresponding values
 *     that should be returned.
 * @param {string=} opt_style The style of css name mapping. There are two valid
 *     options: 'BY_PART', and 'BY_WHOLE'.
 * @see goog.getCssName for a description.
 */
goog.setCssNameMapping = function(mapping, opt_style) {
  goog.cssNameMapping_ = mapping;
  goog.cssNameMappingStyle_ = opt_style;
};


/**
 * To use CSS renaming in compiled mode, one of the input files should have a
 * call to goog.setCssNameMapping() with an object literal that the JSCompiler
 * can extract and use to replace all calls to goog.getCssName(). In uncompiled
 * mode, JavaScript code should be loaded before this base.js file that declares
 * a global variable, CLOSURE_CSS_NAME_MAPPING, which is used below. This is
 * to ensure that the mapping is loaded before any calls to goog.getCssName()
 * are made in uncompiled mode.
 *
 * A hook for overriding the CSS name mapping.
 * @type {!Object<string, string>|undefined}
 */
goog.global.CLOSURE_CSS_NAME_MAPPING;


if (!COMPILED && goog.global.CLOSURE_CSS_NAME_MAPPING) {
  // This does not call goog.setCssNameMapping() because the JSCompiler
  // requires that goog.setCssNameMapping() be called with an object literal.
  goog.cssNameMapping_ = goog.global.CLOSURE_CSS_NAME_MAPPING;
}


/**
 * Gets a localized message.
 *
 * This function is a compiler primitive. If you give the compiler a localized
 * message bundle, it will replace the string at compile-time with a localized
 * version, and expand goog.getMsg call to a concatenated string.
 *
 * Messages must be initialized in the form:
 * <code>
 * var MSG_NAME = goog.getMsg('Hello {$placeholder}', {'placeholder': 'world'});
 * </code>
 *
 * This function produces a string which should be treated as plain text. Use
 * {@link goog.html.SafeHtmlFormatter} in conjunction with goog.getMsg to
 * produce SafeHtml.
 *
 * @param {string} str Translatable string, places holders in the form {$foo}.
 * @param {Object<string, string>=} opt_values Maps place holder name to value.
 * @return {string} message with placeholders filled.
 */
goog.getMsg = function(str, opt_values) {
  if (opt_values) {
    str = str.replace(/\{\$([^}]+)}/g, function(match, key) {
      return (opt_values != null && key in opt_values) ? opt_values[key] :
                                                         match;
    });
  }
  return str;
};


/**
 * Gets a localized message. If the message does not have a translation, gives a
 * fallback message.
 *
 * This is useful when introducing a new message that has not yet been
 * translated into all languages.
 *
 * This function is a compiler primitive. Must be used in the form:
 * <code>var x = goog.getMsgWithFallback(MSG_A, MSG_B);</code>
 * where MSG_A and MSG_B were initialized with goog.getMsg.
 *
 * @param {string} a The preferred message.
 * @param {string} b The fallback message.
 * @return {string} The best translated message.
 */
goog.getMsgWithFallback = function(a, b) {
  return a;
};


/**
 * Exposes an unobfuscated global namespace path for the given object.
 * Note that fields of the exported object *will* be obfuscated, unless they are
 * exported in turn via this function or goog.exportProperty.
 *
 * Also handy for making public items that are defined in anonymous closures.
 *
 * ex. goog.exportSymbol('public.path.Foo', Foo);
 *
 * ex. goog.exportSymbol('public.path.Foo.staticFunction', Foo.staticFunction);
 *     public.path.Foo.staticFunction();
 *
 * ex. goog.exportSymbol('public.path.Foo.prototype.myMethod',
 *                       Foo.prototype.myMethod);
 *     new public.path.Foo().myMethod();
 *
 * @param {string} publicPath Unobfuscated name to export.
 * @param {*} object Object the name should point to.
 * @param {Object=} opt_objectToExportTo The object to add the path to; default
 *     is goog.global.
 */
goog.exportSymbol = function(publicPath, object, opt_objectToExportTo) {
  goog.exportPath_(publicPath, object, opt_objectToExportTo);
};


/**
 * Exports a property unobfuscated into the object's namespace.
 * ex. goog.exportProperty(Foo, 'staticFunction', Foo.staticFunction);
 * ex. goog.exportProperty(Foo.prototype, 'myMethod', Foo.prototype.myMethod);
 * @param {Object} object Object whose static property is being exported.
 * @param {string} publicName Unobfuscated name to export.
 * @param {*} symbol Object the name should point to.
 */
goog.exportProperty = function(object, publicName, symbol) {
  object[publicName] = symbol;
};


/**
 * Inherit the prototype methods from one constructor into another.
 *
 * Usage:
 * <pre>
 * function ParentClass(a, b) { }
 * ParentClass.prototype.foo = function(a) { };
 *
 * function ChildClass(a, b, c) {
 *   ChildClass.base(this, 'constructor', a, b);
 * }
 * goog.inherits(ChildClass, ParentClass);
 *
 * var child = new ChildClass('a', 'b', 'see');
 * child.foo(); // This works.
 * </pre>
 *
 * @param {!Function} childCtor Child class.
 * @param {!Function} parentCtor Parent class.
 */
goog.inherits = function(childCtor, parentCtor) {
  /** @constructor */
  function tempCtor() {}
  tempCtor.prototype = parentCtor.prototype;
  childCtor.superClass_ = parentCtor.prototype;
  childCtor.prototype = new tempCtor();
  /** @override */
  childCtor.prototype.constructor = childCtor;

  /**
   * Calls superclass constructor/method.
   *
   * This function is only available if you use goog.inherits to
   * express inheritance relationships between classes.
   *
   * NOTE: This is a replacement for goog.base and for superClass_
   * property defined in childCtor.
   *
   * @param {!Object} me Should always be "this".
   * @param {string} methodName The method name to call. Calling
   *     superclass constructor can be done with the special string
   *     'constructor'.
   * @param {...*} var_args The arguments to pass to superclass
   *     method/constructor.
   * @return {*} The return value of the superclass method/constructor.
   */
  childCtor.base = function(me, methodName, var_args) {
    // Copying using loop to avoid deop due to passing arguments object to
    // function. This is faster in many JS engines as of late 2014.
    var args = new Array(arguments.length - 2);
    for (var i = 2; i < arguments.length; i++) {
      args[i - 2] = arguments[i];
    }
    return parentCtor.prototype[methodName].apply(me, args);
  };
};


/**
 * Call up to the superclass.
 *
 * If this is called from a constructor, then this calls the superclass
 * constructor with arguments 1-N.
 *
 * If this is called from a prototype method, then you must pass the name of the
 * method as the second argument to this function. If you do not, you will get a
 * runtime error. This calls the superclass' method with arguments 2-N.
 *
 * This function only works if you use goog.inherits to express inheritance
 * relationships between your classes.
 *
 * This function is a compiler primitive. At compile-time, the compiler will do
 * macro expansion to remove a lot of the extra overhead that this function
 * introduces. The compiler will also enforce a lot of the assumptions that this
 * function makes, and treat it as a compiler error if you break them.
 *
 * @param {!Object} me Should always be "this".
 * @param {*=} opt_methodName The method name if calling a super method.
 * @param {...*} var_args The rest of the arguments.
 * @return {*} The return value of the superclass method.
 * @suppress {es5Strict} This method can not be used in strict mode, but
 *     all Closure Library consumers must depend on this file.
 */
goog.base = function(me, opt_methodName, var_args) {
  var caller = arguments.callee.caller;

  if (goog.STRICT_MODE_COMPATIBLE || (goog.DEBUG && !caller)) {
    throw Error(
        'arguments.caller not defined.  goog.base() cannot be used ' +
        'with strict mode code. See ' +
        'http://www.ecma-international.org/ecma-262/5.1/#sec-C');
  }

  if (caller.superClass_) {
    // Copying using loop to avoid deop due to passing arguments object to
    // function. This is faster in many JS engines as of late 2014.
    var ctorArgs = new Array(arguments.length - 1);
    for (var i = 1; i < arguments.length; i++) {
      ctorArgs[i - 1] = arguments[i];
    }
    // This is a constructor. Call the superclass constructor.
    return caller.superClass_.constructor.apply(me, ctorArgs);
  }

  // Copying using loop to avoid deop due to passing arguments object to
  // function. This is faster in many JS engines as of late 2014.
  var args = new Array(arguments.length - 2);
  for (var i = 2; i < arguments.length; i++) {
    args[i - 2] = arguments[i];
  }
  var foundCaller = false;
  for (var ctor = me.constructor; ctor;
       ctor = ctor.superClass_ && ctor.superClass_.constructor) {
    if (ctor.prototype[opt_methodName] === caller) {
      foundCaller = true;
    } else if (foundCaller) {
      return ctor.prototype[opt_methodName].apply(me, args);
    }
  }

  // If we did not find the caller in the prototype chain, then one of two
  // things happened:
  // 1) The caller is an instance method.
  // 2) This method was not called by the right caller.
  if (me[opt_methodName] === caller) {
    return me.constructor.prototype[opt_methodName].apply(me, args);
  } else {
    throw Error(
        'goog.base called from a method of one name ' +
        'to a method of a different name');
  }
};


/**
 * Allow for aliasing within scope functions.  This function exists for
 * uncompiled code - in compiled code the calls will be inlined and the aliases
 * applied.  In uncompiled code the function is simply run since the aliases as
 * written are valid JavaScript.
 *
 *
 * @param {function()} fn Function to call.  This function can contain aliases
 *     to namespaces (e.g. "var dom = goog.dom") or classes
 *     (e.g. "var Timer = goog.Timer").
 */
goog.scope = function(fn) {
  if (goog.isInModuleLoader_()) {
    throw Error('goog.scope is not supported within a goog.module.');
  }
  fn.call(goog.global);
};


/*
 * To support uncompiled, strict mode bundles that use eval to divide source
 * like so:
 *    eval('someSource;//# sourceUrl sourcefile.js');
 * We need to export the globally defined symbols "goog" and "COMPILED".
 * Exporting "goog" breaks the compiler optimizations, so we required that
 * be defined externally.
 * NOTE: We don't use goog.exportSymbol here because we don't want to trigger
 * extern generation when that compiler option is enabled.
 */
if (!COMPILED) {
  goog.global['COMPILED'] = COMPILED;
}


//==============================================================================
// goog.defineClass implementation
//==============================================================================


/**
 * Creates a restricted form of a Closure "class":
 *   - from the compiler's perspective, the instance returned from the
 *     constructor is sealed (no new properties may be added).  This enables
 *     better checks.
 *   - the compiler will rewrite this definition to a form that is optimal
 *     for type checking and optimization (initially this will be a more
 *     traditional form).
 *
 * @param {Function} superClass The superclass, Object or null.
 * @param {goog.defineClass.ClassDescriptor} def
 *     An object literal describing
 *     the class.  It may have the following properties:
 *     "constructor": the constructor function
 *     "statics": an object literal containing methods to add to the constructor
 *        as "static" methods or a function that will receive the constructor
 *        function as its only parameter to which static properties can
 *        be added.
 *     all other properties are added to the prototype.
 * @return {!Function} The class constructor.
 */
goog.defineClass = function(superClass, def) {
  // TODO(johnlenz): consider making the superClass an optional parameter.
  var constructor = def.constructor;
  var statics = def.statics;
  // Wrap the constructor prior to setting up the prototype and static methods.
  if (!constructor || constructor == Object.prototype.constructor) {
    constructor = function() {
      throw Error('cannot instantiate an interface (no constructor defined).');
    };
  }

  var cls = goog.defineClass.createSealingConstructor_(constructor, superClass);
  if (superClass) {
    goog.inherits(cls, superClass);
  }

  // Remove all the properties that should not be copied to the prototype.
  delete def.constructor;
  delete def.statics;

  goog.defineClass.applyProperties_(cls.prototype, def);
  if (statics != null) {
    if (statics instanceof Function) {
      statics(cls);
    } else {
      goog.defineClass.applyProperties_(cls, statics);
    }
  }

  return cls;
};


/**
 * @typedef {{
 *   constructor: (!Function|undefined),
 *   statics: (Object|undefined|function(Function):void)
 * }}
 * @suppress {missingProvide}
 */
goog.defineClass.ClassDescriptor;


/**
 * @define {boolean} Whether the instances returned by goog.defineClass should
 *     be sealed when possible.
 *
 * When sealing is disabled the constructor function will not be wrapped by
 * goog.defineClass, making it incompatible with ES6 class methods.
 */
goog.define('goog.defineClass.SEAL_CLASS_INSTANCES', goog.DEBUG);


/**
 * If goog.defineClass.SEAL_CLASS_INSTANCES is enabled and Object.seal is
 * defined, this function will wrap the constructor in a function that seals the
 * results of the provided constructor function.
 *
 * @param {!Function} ctr The constructor whose results maybe be sealed.
 * @param {Function} superClass The superclass constructor.
 * @return {!Function} The replacement constructor.
 * @private
 */
goog.defineClass.createSealingConstructor_ = function(ctr, superClass) {
  if (!goog.defineClass.SEAL_CLASS_INSTANCES) {
    // Do now wrap the constructor when sealing is disabled. Angular code
    // depends on this for injection to work properly.
    return ctr;
  }

  // Compute whether the constructor is sealable at definition time, rather
  // than when the instance is being constructed.
  var superclassSealable = !goog.defineClass.isUnsealable_(superClass);

  /**
   * @this {Object}
   * @return {?}
   */
  var wrappedCtr = function() {
    // Don't seal an instance of a subclass when it calls the constructor of
    // its super class as there is most likely still setup to do.
    var instance = ctr.apply(this, arguments) || this;
    instance[goog.UID_PROPERTY_] = instance[goog.UID_PROPERTY_];

    if (this.constructor === wrappedCtr && superclassSealable &&
        Object.seal instanceof Function) {
      Object.seal(instance);
    }
    return instance;
  };

  return wrappedCtr;
};


/**
 * @param {Function} ctr The constructor to test.
 * @returns {boolean} Whether the constructor has been tagged as unsealable
 *     using goog.tagUnsealableClass.
 * @private
 */
goog.defineClass.isUnsealable_ = function(ctr) {
  return ctr && ctr.prototype &&
      ctr.prototype[goog.UNSEALABLE_CONSTRUCTOR_PROPERTY_];
};


// TODO(johnlenz): share these values with the goog.object
/**
 * The names of the fields that are defined on Object.prototype.
 * @type {!Array<string>}
 * @private
 * @const
 */
goog.defineClass.OBJECT_PROTOTYPE_FIELDS_ = [
  'constructor', 'hasOwnProperty', 'isPrototypeOf', 'propertyIsEnumerable',
  'toLocaleString', 'toString', 'valueOf'
];


// TODO(johnlenz): share this function with the goog.object
/**
 * @param {!Object} target The object to add properties to.
 * @param {!Object} source The object to copy properties from.
 * @private
 */
goog.defineClass.applyProperties_ = function(target, source) {
  // TODO(johnlenz): update this to support ES5 getters/setters

  var key;
  for (key in source) {
    if (Object.prototype.hasOwnProperty.call(source, key)) {
      target[key] = source[key];
    }
  }

  // For IE the for-in-loop does not contain any properties that are not
  // enumerable on the prototype object (for example isPrototypeOf from
  // Object.prototype) and it will also not include 'replace' on objects that
  // extend String and change 'replace' (not that it is common for anyone to
  // extend anything except Object).
  for (var i = 0; i < goog.defineClass.OBJECT_PROTOTYPE_FIELDS_.length; i++) {
    key = goog.defineClass.OBJECT_PROTOTYPE_FIELDS_[i];
    if (Object.prototype.hasOwnProperty.call(source, key)) {
      target[key] = source[key];
    }
  }
};


/**
 * Sealing classes breaks the older idiom of assigning properties on the
 * prototype rather than in the constructor. As such, goog.defineClass
 * must not seal subclasses of these old-style classes until they are fixed.
 * Until then, this marks a class as "broken", instructing defineClass
 * not to seal subclasses.
 * @param {!Function} ctr The legacy constructor to tag as unsealable.
 */
goog.tagUnsealableClass = function(ctr) {
  if (!COMPILED && goog.defineClass.SEAL_CLASS_INSTANCES) {
    ctr.prototype[goog.UNSEALABLE_CONSTRUCTOR_PROPERTY_] = true;
  }
};


/**
 * Name for unsealable tag property.
 * @const @private {string}
 */
goog.UNSEALABLE_CONSTRUCTOR_PROPERTY_ = 'goog_defineClass_legacy_unsealable';
