'use strict';

var utils = require('../utils.js');
var AxiosError = require('../core/AxiosError.js');
var form_data = require('../../../form-data/lib/form_data.js');

/**
 * Determines if the given thing is a array or js object.
 *
 * @param {string} thing - The object or array to be visited.
 *
 * @returns {boolean}
 */
function isVisitable(thing) {
  return utils.isPlainObject(thing) || utils.isArray(thing);
}

/**
 * It removes the brackets from the end of a string
 *
 * @param {string} key - The key of the parameter.
 *
 * @returns {string} the key without the brackets.
 */
function removeBrackets(key) {
  return utils.endsWith(key, '[]') ? key.slice(0, -2) : key;
}

/**
 * It takes a path, a key, and a boolean, and returns a string
 *
 * @param {string} path - The path to the current key.
 * @param {string} key - The key of the current object being iterated over.
 * @param {string} dots - If true, the key will be rendered with dots instead of brackets.
 *
 * @returns {string} The path to the current key.
 */
function renderKey(path, key, dots) {
  if (!path) return key;
  return path.concat(key).map(function each(token, i) {
    // eslint-disable-next-line no-param-reassign
    token = removeBrackets(token);
    return !dots && i ? '[' + token + ']' : token;
  }).join(dots ? '.' : '');
}

/**
 * If the array is an array and none of its elements are visitable, then it's a flat array.
 *
 * @param {Array<any>} arr - The array to check
 *
 * @returns {boolean}
 */
function isFlatArray(arr) {
  return utils.isArray(arr) && !arr.some(isVisitable);
}

const predicates = utils.toFlatObject(utils, {}, null, function filter(prop) {
  return /^is[A-Z]/.test(prop);
});

/**
 * Convert a data object to FormData
 *
 * @param {Object} obj
 * @param {?Object} [formData]
 * @param {?Object} [options]
 * @param {Function} [options.visitor]
 * @param {Boolean} [options.metaTokens = true]
 * @param {Boolean} [options.dots = false]
 * @param {?Boolean} [options.indexes = false]
 *
 * @returns {Object}
 **/

/**
 * It converts an object into a FormData object
 *
 * @param {Object<any, any>} obj - The object to convert to form data.
 * @param {string} formData - The FormData object to append to.
 * @param {Object<string, any>} options
 *
 * @returns
 */
function toFormData(obj, formData, options) {
  if (!utils.isObject(obj)) {
    throw new TypeError('target must be an object');
  }

  // eslint-disable-next-line no-param-reassign
  formData = formData || new (form_data || FormData)();

  // eslint-disable-next-line no-param-reassign
  options = utils.toFlatObject(options, {
    metaTokens: true,
    dots: false,
    indexes: false
  }, false, function defined(option, source) {
    // eslint-disable-next-line no-eq-null,eqeqeq
    return !utils.isUndefined(source[option]);
  });

  const metaTokens = options.metaTokens;
  // eslint-disable-next-line no-use-before-define
  const visitor = options.visitor || defaultVisitor;
  const dots = options.dots;
  const indexes = options.indexes;
  const _Blob = options.Blob || typeof Blob !== 'undefined' && Blob;
  const useBlob = _Blob && utils.isSpecCompliantForm(formData);

  if (!utils.isFunction(visitor)) {
    throw new TypeError('visitor must be a function');
  }

  function convertValue(value) {
    if (value === null) return '';

    if (utils.isDate(value)) {
      return value.toISOString();
    }

    if (!useBlob && utils.isBlob(value)) {
      throw new AxiosError('Blob is not supported. Use a Buffer instead.');
    }

    if (utils.isArrayBuffer(value) || utils.isTypedArray(value)) {
      return useBlob && typeof Blob === 'function' ? new Blob([value]) : Buffer.from(value);
    }

    return value;
  }

  /**
   * Default visitor.
   *
   * @param {*} value
   * @param {String|Number} key
   * @param {Array<String|Number>} path
   * @this {FormData}
   *
   * @returns {boolean} return true to visit the each prop of the value recursively
   */
  function defaultVisitor(value, key, path) {
    let arr = value;

    if (value && !path && typeof value === 'object') {
      if (utils.endsWith(key, '{}')) {
        // eslint-disable-next-line no-param-reassign
        key = metaTokens ? key : key.slice(0, -2);
        // eslint-disable-next-line no-param-reassign
        value = JSON.stringify(value);
      } else if (
        (utils.isArray(value) && isFlatArray(value)) ||
        ((utils.isFileList(value) || utils.endsWith(key, '[]')) && (arr = utils.toArray(value))
        )) {
        // eslint-disable-next-line no-param-reassign
        key = removeBrackets(key);

        arr.forEach(function each(el, index) {
          !(utils.isUndefined(el) || el === null) && formData.append(
            // eslint-disable-next-line no-nested-ternary
            indexes === true ? renderKey([key], index, dots) : (indexes === null ? key : key + '[]'),
            convertValue(el)
          );
        });
        return false;
      }
    }

    if (isVisitable(value)) {
      return true;
    }

    formData.append(renderKey(path, key, dots), convertValue(value));

    return false;
  }

  const stack = [];

  const exposedHelpers = Object.assign(predicates, {
    defaultVisitor,
    convertValue,
    isVisitable
  });

  function build(value, path) {
    if (utils.isUndefined(value)) return;

    if (stack.indexOf(value) !== -1) {
      throw Error('Circular reference detected in ' + path.join('.'));
    }

    stack.push(value);

    utils.forEach(value, function each(el, key) {
      const result = !(utils.isUndefined(el) || el === null) && visitor.call(
        formData, el, utils.isString(key) ? key.trim() : key, path, exposedHelpers
      );

      if (result === true) {
        build(el, path ? path.concat(key) : [key]);
      }
    });

    stack.pop();
  }

  if (!utils.isObject(obj)) {
    throw new TypeError('data must be an object');
  }

  build(obj);

  return formData;
}

module.exports = toFormData;
