/*
  Copyright 2017 Google Inc.

  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

      https://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.
*/

const ol = require('common-tags').oneLine;

const errors = require('./errors');
const stringifyWithoutComments = require('./stringify-without-comments');

/**
 * Given a set of options that configures `sw-toolbox`'s behavior, convert it
 * into a string that would configure equivalent `workbox-sw` behavior.
 *
 * @param {Object} options See
 *        https://googlechrome.github.io/sw-toolbox/api.html#options
 * @return {string} A JSON string representing the equivalent options.
 *
 * @private
 */
function getOptionsString(options = {}) {
  let plugins = [];
  if (options.plugins) {
    // Using libs because JSON.stringify won't handle functions.
    plugins = options.plugins.map(stringifyWithoutComments);
    delete options.plugins;
  }

  // Pull handler-specific config from the options object, since they are
  // not directly used to construct a Plugin instance. If set, need to be
  // passed as options to the handler constructor instead.
  const handlerOptionKeys =
      ['cacheName', 'networkTimeoutSeconds', 'fetchOptions', 'matchOptions'];
  const handlerOptions = {};
  for (const key of handlerOptionKeys) {
    if (key in options) {
      handlerOptions[key] = options[key];
      delete options[key];
    }
  }

  const pluginsMapping = {
    backgroundSync: 'workbox.backgroundSync.Plugin',
    broadcastUpdate: 'workbox.broadcastUpdate.Plugin',
    expiration: 'workbox.expiration.Plugin',
    cacheableResponse: 'workbox.cacheableResponse.Plugin',
  };

  for (const [pluginName, pluginConfig] of Object.entries(options)) {
    // Ensure that we have some valid configuration to pass to Plugin().
    if (Object.keys(pluginConfig).length === 0) {
      continue;
    }

    const pluginString = pluginsMapping[pluginName];
    if (!pluginString) {
      throw new Error(`${errors['bad-runtime-caching-config']} ${pluginName}`);
    }

    let pluginCode;
    switch (pluginName) {
      // Special case logic for plugins that have a required parameter, and then
      // an additional optional config parameter.
      case 'backgroundSync': {
        const name = pluginConfig.name;
        pluginCode = `new ${pluginString}(${JSON.stringify(name)}`;
        if ('options' in pluginConfig) {
          pluginCode += `, ${JSON.stringify(pluginConfig.options)}`;
        }
        pluginCode += `)`;

        break;
      }

      case 'broadcastUpdate': {
        const channelName = pluginConfig.channelName;
        pluginCode = `new ${pluginString}(${JSON.stringify(channelName)}`;
        if ('options' in pluginConfig) {
          pluginCode += `, ${JSON.stringify(pluginConfig.options)}`;
        }
        pluginCode += `)`;

        break;
      }

      // For plugins that just pass in an Object to the constructor, like
      // expiration and cacheableResponse
      default: {
        pluginCode = `new ${pluginString}(${JSON.stringify(pluginConfig)})`;
      }
    }

    plugins.push(pluginCode);
  }

  if (Object.keys(handlerOptions).length > 0 || plugins.length > 0) {
    const optionsString = JSON.stringify(handlerOptions).slice(1, -1);
    return ol`{
      ${optionsString ? optionsString + ',' : ''}
      plugins: [${plugins.join(', ')}]
    }`;
  } else {
    return '';
  }
}

module.exports = (runtimeCaching = []) => {
  return runtimeCaching.map((entry) => {
    const method = entry.method || 'GET';

    if (!entry.urlPattern) {
      throw new Error(errors['urlPattern-is-required']);
    }

    if (!entry.handler) {
      throw new Error(errors['handler-is-required']);
    }

    // This validation logic is a bit too gnarly for joi, so it's manually
    // implemented here.
    if (entry.options && entry.options.networkTimeoutSeconds &&
        entry.handler !== 'networkFirst') {
      throw new Error(errors['invalid-network-timeout-seconds']);
    }

    // urlPattern might be either a string or a RegExp object.
    // If it's a string, it needs to be quoted. If it's a RegExp, it should
    // be used as-is.
    const matcher = typeof entry.urlPattern === 'string' ?
      JSON.stringify(entry.urlPattern) :
      entry.urlPattern;

    if (typeof entry.handler === 'string') {
      const optionsString = getOptionsString(entry.options || {});

      const strategyString =
        `workbox.strategies.${entry.handler}(${optionsString})`;

      return `workbox.routing.registerRoute(` +
        `${matcher}, ${strategyString}, '${method}');\n`;
    } else if (typeof entry.handler === 'function') {
      return `workbox.routing.registerRoute(` +
        `${matcher}, ${entry.handler}, '${method}');\n`;
    }
  }).filter((entry) => Boolean(entry)); // Remove undefined map() return values.
};