headers-parser-behavior.html

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@license
Copyright 2016 The Advanced REST client authors <arc@mulesoft.com>

Licensed under the Apache License, Version 2.0 (the "License"); you may not
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<link rel="import" href="../polymer/polymer.html">
<link rel="import" href="../arc-polyfills/arc-polyfills.html">
<link rel="import" href="../fetch-polyfill/fetch-polyfill.html">
<script>
(function(global) {
  'use strict';

  var ERROR_MESSAGES = {
    CONTENT_TYPE_MISSING: 'Content-Type header is not defined',
    HEADER_NAME_EMPTY: 'Header name can\'t be empty',
    HEADER_NAME_WHITESPACES: 'Header name should not contain whitespaces',
    HEADER_VALUE_EMPTY: 'Header value should not be empty'
  };

  global.ArcBehaviors = global.ArcBehaviors || {};
  /**
   * Headers parser behavior to be impplemented with elements that needs to parse headers data.
   *
   * In most cases function defined in this behavior can work with the headers defined as a string,
   * array of objects (name, value keys) or as Header object.
   *
   * To calculate errors properly, set `isPayload` property when current request can carry a
   * payload.
   *
   * @polymerBehavior ArcBehaviors.HeadersParserBehavior
   */
  global.ArcBehaviors.HeadersParserBehavior = {
    properties: {
      /**
       * Set to true when the request can carry a payload.
       * It's required for calculating headers errors.
       */
      isPayload: Boolean
    },
    /**
     * Filter array of headers and return not duplicated array of the same headers.
     * Duplicated headers should be appended to already found one using coma separator.
     *
     * @param {Array} headers
     *                Headers array to filter. All objects in headers array must have "name"
     *                and "value" keys.
     * @return {Array} An array of filtered headers.
     */
    filterHeaders: function(headers) {
      var _tmp = {};
      headers.forEach(function(header) {
        if (header.name in _tmp) {
          if (!!header.value) {
            _tmp[header.name] += ', ' + header.value;
          }
        } else {
          _tmp[header.name] = header.value;
        }
      });
      var result = [];
      for (var _key in _tmp) {
        result[result.length] = {
          'name': _key,
          'value': _tmp[_key]
        };
      }
      return result;
    },

    /**
     * Parse headers array to Raw HTTP headers string.
     *
     * @param {Array|String|Headers} headersArray List of objects with "name" and "value"
     * properties.
     * @returns {String} A HTTP representation of the headers.
     */
    headersToString: function(headersArray) {
      if (typeof headersArray === 'string') {
        return headersArray;
      }
      if (!(headersArray instanceof Array)) {
        headersArray = this.headersToJSON(headersArray);
      }
      if (headersArray.length === 0) {
        return '';
      }
      headersArray = this.filterHeaders(headersArray);
      var result = '';
      headersArray.forEach(function(header) {
        if (result !== '') {
          result += '\n';
        }
        var key = header.name;
        var value = header.value;
        if (key && key.trim() !== '') {
          result += key + ': ';
          if (value && value.trim() !== '') {
            result += value;
          }
        }
      });
      return result;
    },
    /**
     * Parse HTTP headers input from string to array of objects containing `name` and `value`
     * properties.
     *
     * @param {String|Headers} headers Raw HTTP headers input or Headers object
     * @returns {Array<Object>} The array of objects where properties are `name` as a header
     * name and `value` as a header content.
     */
    headersToJSON: function(headers) {
      if (typeof headers === 'string') {
        return this._headersStringToJSON(headers);
      } else {
        return this._hedersToJSON(headers);
      }
    },
    /**
     * Parse headers string to array of objects.
     * See `#toJSON` for more info.
     */
    _headersStringToJSON: function(headersString) {
      if (!headersString || headersString.trim() === '') {
        return [];
      }
      if (typeof headersString !== 'string') {
        throw new Error('Headers must be an instance of String.');
      }
      var result = [];
      var headers = headersString.split(/\n(?=[^ \t]+)/gim);

      for (var i = 0, len = headers.length; i < len; i++) {
        var line = headers[i].trim();
        if (line === '') {
          continue;
        }
        var sepPosition = line.indexOf(':');
        if (sepPosition === -1) {
          result[result.length] = {
            name: line,
            value: ''
          };
          continue;
        }
        var name = line.substr(0, sepPosition);
        var value = line.substr(sepPosition + 1).trim();
        var obj = {
          name: name,
          value: value
        };
        result.push(obj);
      }
      return result;
    },

    /**
     * Parse Headers object to array of objects.
     * See `#toJSON` for more info.
     */
    _hedersToJSON: function(headers) {
      var result = [];
      if (!headers) {
        return result;
      }
      var _tmp = {};
      headers.forEach(function(value, name) {
        if (_tmp[name]) {
          _tmp[name] += ', ' + value;
        } else {
          _tmp[name] = value;
        }
      });
      return Object.keys(_tmp).map(function(key) {
        var value = _tmp[key];
        if (value && value.indexOf(',') !== -1) {
          value = value.split(',').map(function(part) {
            return part.trim();
          }).join(', ');
        }
        return {
          name: key,
          value: value
        };
      });
    },

    /**
     * Helper method for old system: combine headers list with encoding value.
     * Note that this function will update the original array.
     *
     * @param {Array} headers An array of headers
     * @param {String} encoding An encoding string from the old request.
     * @return {Boolean} True if encoding has been added to the array.
     */
    _oldCombine: function(headers, encoding) {
      if (!(headers instanceof Array)) {
        throw new Error('Headers must be an array');
      }
      encoding = String(encoding);
      var ct = headers.filter(function(item) {
        return item.name.toLowerCase() === 'content-type';
      });
      if (ct.length === 0) {
        headers.push({
          'name': 'Content-Type',
          'value': encoding.trim()
        });
        return true;
      }
      return false;
    },

    /**
     * Get the Content-Type value from the headers.
     *
     * @param {Array|String} headers Either HTTP headers string or list of headers.
     * @return {String|null} A content-type header value or null if not found
     */
    getContentType: function(headers) {
      if (typeof headers !== 'string') {
        headers = this.headersToString(headers);
      }
      headers = headers.trim();
      if (headers === '') {
        return null;
      }
      var re = /^content-type:\s?(.*)$/im;
      var match = headers.match(re);
      if (!match) {
        return null;
      }
      var ct = match[1].trim();
      if (ct.indexOf('multipart') === -1) {
        var index = ct.indexOf('; ');
        if (index > 0) {
          ct = ct.substr(0, index);
        }
      }
      return ct;
    },

    /**
     * Replace value for given header in the headers list.
     *
     * @param {Array|String|Object} headers A headers object. Can be string, array of objects or
     * Headers object.
     * @param {String} name Header name to be replaced.
     * @param {String} value Header value to be repleced.
     * @return {Array} Updated headers.
     */
    replaceHeaderValue: function(headers, name, value) {
      var origType = 'headers';
      if (headers instanceof Array) {
        origType = 'array';
      } else if (typeof headers === 'string') {
        origType = 'string';
      }
      if (origType !== 'array') {
        headers = this.headersToJSON(headers);
      }
      var _name = name.toLowerCase();
      var found = false;
      headers.forEach(function(header) {
        if (header.name.toLowerCase() === _name) {
          header.value = value;
          found = true;
        }
      });
      if (!found) {
        headers.push({
          name: name,
          value: value
        });
      }
      if (origType === 'array') {
        return headers;
      } else if (origType === 'string') {
        return this.headersToString(headers);
      }
      var obj = {};
      headers.forEach(function(header) {
        obj[header.name] = header.value;
      });
      return new Headers(obj);
    },

    /**
     * Get error message for given header string.
     * @param {Header|Array|String} input A headers to check.
     * @return {?String} An error message or null if the headers are valid.
     */
    getHeaderError: function(input) {
      if (!input) {
        if (this.isPayload) {
          return ERROR_MESSAGES.CONTENT_TYPE_MISSING;
        }
        return null;
      }
      if (!(input instanceof Array)) {
        input = this.headersToJSON(input);
      }
      var msg = [];
      var hasContentType = false;
      for (var i = 0, len = input.length; i < len; i++) {
        var name = input[i].name;
        var value = input[i].value;
        if (name.toLowerCase() === 'content-type') {
          hasContentType = true;
        }
        if (!name || !name.trim()) {
          msg[msg.length] = ERROR_MESSAGES.HEADER_NAME_EMPTY;
        } else if (/\s/.test(name)) {
          msg[msg.length] = ERROR_MESSAGES.HEADER_NAME_WHITESPACES;
        }
        if (!value || !value.trim()) {
          msg[msg.length] = ERROR_MESSAGES.HEADER_VALUE_EMPTY;
        }
      }
      if (this.isPayload && !hasContentType) {
        msg[msg.length] = ERROR_MESSAGES.CONTENT_TYPE_MISSING;
      }
      if (msg.length > 0) {
        return msg.join('\n');
      }
      return null;
    }
  };
})(window);
</script>