var Q = require("q");
  var URL = require("url2");
  var Negotiation = require("./negotiate");
  var HtmlApps = require("./html");
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `301`
   * @returns {App}
   */
  exports.PermanentRedirect = function (location, status, tree) {
      return function (request, response) {
          return exports.permanentRedirect(request, location, status, tree);
      };
  };
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `301`
   * @returns {App}
   */
  exports.PermanentRedirectTree = function (location, status) {
      return function (request, response) {
          return exports.permanentRedirect(request, location, status, true);
      };
  };
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `307`
   * @returns {App}
   */
  exports.TemporaryRedirect = function (location, status, tree) {
      return function (request, response) {
          return exports.temporaryRedirect(request, location, status, tree);
      };
  };
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `307`
   * @returns {App}
   */
  exports.TemporaryRedirectTree = function (location, status) {
      return function (request, response) {
          return exports.temporaryRedirect(request, location, status, true);
      };
  };
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `307`
   * @returns {App}
   */
  exports.Redirect = function (location, status, tree) {
      return function (request, response) {
          return exports.redirect(request, location, status, tree);
      };
  };
  
  /**
   * @param {String} path
   * @param {Number} status (optional) default is `307`
   * @returns {App}
   */
  exports.RedirectTree = function (location, status) {
      return function (request, response) {
          return exports.redirect(request, location, status, true);
      };
  };
  
  exports.permanentRedirect = function (request, location, status) {
      return exports.redirect(request, location, status || 301);
  };
  
  exports.permanentRedirectTree = function (request, location, status) {
      return exports.redirect(request, location, status || 301, true);
  };
  
  exports.temporaryRedirect = function (request, location, status) {
      return exports.redirect(request, location, status || 307);
  };
  
  exports.temporaryRedirectTree = function (request, location, status) {
      return exports.redirect(request, location, status || 307, true);
  };
  
  exports.redirectTree = function (request, location, status) {
      return exports.redirect(request, location, status, true);
  };
  
  /**
   * @param {String} location
   * @param {Number} status (optional) default is `301`
   * @returns {Response}
   */
  exports.redirect = function (request, location, status, tree) {
  
      // request.permanent gets set by Permanent middleware
      status = status || (request.permanent ? 301 : 307);
  
      // ascertain that the location is absolute, per spec
      location = URL.resolve(request.url, location);
  
      // redirect into a subtree with the remaining unrouted
      // portion of the path, if so configured
      if (tree) {
          location = URL.resolve(
              location,
              request.pathInfo.replace(/^\//, "")
          );
      }
  
      var handlers = {};
      handlers["text/plain"] = exports.redirectText;
      if (request.handleHtmlFragmentResponse) {
          handlers["text/html"] = exports.redirectHtml;
      }
      var handler = Negotiation.negotiate(request, handlers) || exports.redirectText;
      return handler(request, location, status);
  
  };
  
  exports.redirectText = function (request, location, status) {
      var content = (
          (request.permanent ? "Permanent redirect\n" : "Temporary redirect\n") +
          "See: " + location + "\n"
      );
      var contentLength = content.length;
      return {
          status: status,
          headers: {
              location: location,
              "content-type": "text/plain"
          },
          body: [content]
      };
  };
  
  exports.redirectHtml = function (request, location, status) {
      var title = request.permanent ? "Permanent redirect" : "Temporary redirect";
      return {
          status: status,
          headers: {
              location: location,
              "content-type": "text/html"
          },
          htmlTitle: title,
          htmlFragment: {
              forEach: function (write) {
                  write("<h1>" + HtmlApps.escapeHtml(title) + "</h1>\n");
                  write(
                      "<p>See: <a href=\"" + HtmlApps.escapeHtml(location) + "\">" +
                      HtmlApps.escapeHtml(location) +
                      "</a></p>\n"
                  );
              }
          }
      };
  };
  
  exports.RedirectTrap = function (app, maxRedirects) {
      maxRedirects = maxRedirects || 20;
      return function (request, response) {
          var remaining = maxRedirects;
          var deferred = Q.defer();
          var self = this;
          var args = arguments;
  
          request = HTTP.normalizeRequest(request);
  
          // try redirect loop
          function next() {
              Q.fcall(function () {
                  return app(request, response);
              })
              .then(function (response) {
                  if (exports.isRedirect(response)) {
                      if (remaining--) {
                          request.url = response.headers.location;
                          next();
                      } else {
                          throw new Error("Maximum redirects.");
                      }
                  } else {
                      deferred.resolve(response);
                  }
              })
              .fail(deferred.reject)
          }
          next();
  
          return deferred.promise;
      };
  };
  
  exports.isRedirect = function (response) {
      return isRedirect[response.status] || false;
  };
  
  var isRedirect = {
      301: true,
      302: true,
      303: true,
      307: true
  };