/**
 * Copyright 2015 Google Inc. 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.
 */

// jshint node: true
'use strict';


let fs = require('fs');
let path = require('path');
let ResourceList = require('./listresources');

/**
 * Map of file extension to request type.
 * See https://fetch.spec.whatwg.org/#concept-request-type
 * @const
 */
const EXTENSION_TO_TYPE = {
  '.css': 'style',
  '.gif': 'image',
  '.html': 'document',
  '.png': 'image',
  '.jpg': 'image',
  '.js': 'script',
  '.json': 'script',
  '.svg': 'image',
  '.webp': 'image',
  '.woff': 'font',
  '.woff2': 'font'
};

/**
 * JSON manifest for push resources.
 * @class
 */
class PushManifest {

  // Single file format:
  // {
  //   "/style.css": {
  //     "type": "style",
  //     "weight": 50
  //   },
  //   "/path/to/app.js": {
  //     "type": "script",
  //     "weight": 10
  //   }
  // }
  //
  // The multi-file format is a superset of the single case:

  // Multi-file format:
  // {
  //   "/index.html": {
  //     "/style.css": {
  //       "type": "style",
  //       "weight": 50
  //     },
  //     "/path/to/app.js"; {
  //       "type": "script",
  //       "weight": 10
  //     }
  //   },
  //   "/page.html": {
  //     ...
  //   }
  // }

  // TODO: node 4.1.2 doesn't support default function args yet.
  constructor(opts) {
    opts = opts || {};

    this.name = opts.name || this.DEFAULT_MANIFEST_NAME;
    this.basePath = opts.basePath;
    this.inputPath = opts.inputPath;

    if (this.basePath && this.inputPath) {
      this.resourceList = new ResourceList(opts);
    }
  }

  get DEFAULT_MANIFEST_NAME() {
    return 'push_manifest.json';
  }

  get PUSH_PRIORITY() {
    return 1; // TODO: this gives every resource priority 1.
  }

  /**
   * Generates the JSON format listing the inputs resources.
   *
   * @return {Promise({urls, fileContent}) The list of urls and generated JSON.
   */
  generate() {
    if (!this.resourceList) {
      console.warn('Cannot generate resources. You did not provide an inputPath/basePath.');
    }

    return this.resourceList.list().then(urls => {
      console.log(`Found ${urls.length} resource URLs in ${this.inputPath}:`);

      /* jshint ignore:start */
      for (let i = 0, url; url = urls[i]; ++i) {
        console.log('  ', url);
      }
      /* jshint ignore:end */

      let priorityMapping = {};

      urls.map((url, i) => {
        priorityMapping[url] = {
          weight: this.PUSH_PRIORITY
        };
        var type = EXTENSION_TO_TYPE[path.extname(url)];
        priorityMapping[url].type = type ? type : '';
      });

      this.fileContent = priorityMapping;

      // TODO: node 4.2.1 doesnt support ... spread operator.
      return {urls: urls, file: this.fileContent};
    });
  }

  /**
   * Writes the manifest.
   *
   * @param {Promise} Optional file content to write. By default, the content
   * from calling generate() is used.
   */
  write(opt_fileContent) {
    let fileContent = opt_fileContent || this.fileContent;
    fs.writeFile(this.name, JSON.stringify(fileContent, null, 2), err => {
      if (err) {
        return console.log(err);
      }
    });
  }

}

module.exports = PushManifest;