/*
  Copyright 2018 Google LLC

  Use of this source code is governed by an MIT-style
  license that can be found in the LICENSE file or at
  https://opensource.org/licenses/MIT.
*/

import {BackgroundSyncPlugin} from 'workbox-background-sync/BackgroundSyncPlugin.js';
import {Queue} from 'workbox-background-sync/Queue.js';
import {cacheNames} from 'workbox-core/_private/cacheNames.js';
import {getFriendlyURL} from 'workbox-core/_private/getFriendlyURL.js';
import {logger} from 'workbox-core/_private/logger.js';
import {RouteMatchCallbackOptions} from 'workbox-core/types.js';
import {Route} from 'workbox-routing/Route.js';
import {Router} from 'workbox-routing/Router.js';
import {NetworkFirst} from 'workbox-strategies/NetworkFirst.js';
import {NetworkOnly} from 'workbox-strategies/NetworkOnly.js';
import {
  QUEUE_NAME,
  MAX_RETENTION_TIME,
  GOOGLE_ANALYTICS_HOST,
  GTM_HOST,
  ANALYTICS_JS_PATH,
  GTAG_JS_PATH,
  GTM_JS_PATH,
  COLLECT_PATHS_REGEX,
} from './utils/constants.js';
import './_version.js';


interface GoogleAnalyticsInitializeOptions {
  cacheName?: string;
  parameterOverrides?: {[paramName: string]: string};
  hitFilter?: (params: URLSearchParams) => void;
}

/**
 * Creates the requestWillDequeue callback to be used with the background
 * sync plugin. The callback takes the failed request and adds the
 * `qt` param based on the current time, as well as applies any other
 * user-defined hit modifications.
 *
 * @param {Object} config See {@link module:workbox-google-analytics.initialize}.
 * @return {Function} The requestWillDequeue callback function.
 *
 * @private
 */
const createOnSyncCallback = (config: GoogleAnalyticsInitializeOptions) => {
  return async ({queue}: {queue: Queue}) => {
    let entry;
    while (entry = await queue.shiftRequest()) {
      const {request, timestamp} = entry;
      const url = new URL(request.url);

      try {
        // Measurement protocol requests can set their payload parameters in
        // either the URL query string (for GET requests) or the POST body.
        const params = request.method === 'POST' ?
            new URLSearchParams(await request.clone().text()) :
            url.searchParams;

        // Calculate the qt param, accounting for the fact that an existing
        // qt param may be present and should be updated rather than replaced.
        const originalHitTime = timestamp! - (Number(params.get('qt')) || 0);
        const queueTime = Date.now() - originalHitTime;

        // Set the qt param prior to applying hitFilter or parameterOverrides.
        params.set('qt', String(queueTime));

        // Apply `parameterOverrides`, if set.
        if (config.parameterOverrides) {
          for (const param of Object.keys(config.parameterOverrides)) {
            const value = config.parameterOverrides[param];
            params.set(param, value);
          }
        }

        // Apply `hitFilter`, if set.
        if (typeof config.hitFilter === 'function') {
          config.hitFilter.call(null, params);
        }

        // Retry the fetch. Ignore URL search params from the URL as they're
        // now in the post body.
        await fetch(new Request(url.origin + url.pathname, {
          body: params.toString(),
          method: 'POST',
          mode: 'cors',
          credentials: 'omit',
          headers: {'Content-Type': 'text/plain'},
        }));


        if (process.env.NODE_ENV !== 'production') {
          logger.log(`Request for '${getFriendlyURL(url.href)}'` +
             `has been replayed`);
        }
      } catch (err) {
        await queue.unshiftRequest(entry);

        if (process.env.NODE_ENV !== 'production') {
          logger.log(`Request for '${getFriendlyURL(url.href)}'` +
             `failed to replay, putting it back in the queue.`);
        }
        throw err;
      }
    }
    if (process.env.NODE_ENV !== 'production') {
      logger.log(`All Google Analytics request successfully replayed; ` +
          `the queue is now empty!`);
    }
  };
};

/**
 * Creates GET and POST routes to catch failed Measurement Protocol hits.
 *
 * @param {BackgroundSyncPlugin} bgSyncPlugin
 * @return {Array<Route>} The created routes.
 *
 * @private
 */
const createCollectRoutes = (bgSyncPlugin: BackgroundSyncPlugin) => {
  const match = ({url}: RouteMatchCallbackOptions) =>
      url.hostname === GOOGLE_ANALYTICS_HOST &&
      COLLECT_PATHS_REGEX.test(url.pathname);

  const handler = new NetworkOnly({
    plugins: [bgSyncPlugin],
  });

  return [
    new Route(match, handler, 'GET'),
    new Route(match, handler, 'POST'),
  ];
};

/**
 * Creates a route with a network first strategy for the analytics.js script.
 *
 * @param {string} cacheName
 * @return {Route} The created route.
 *
 * @private
 */
const createAnalyticsJsRoute = (cacheName: string) => {
  const match = ({url}: RouteMatchCallbackOptions) =>
      url.hostname === GOOGLE_ANALYTICS_HOST &&
      url.pathname === ANALYTICS_JS_PATH;

  const handler = new NetworkFirst({cacheName});

  return new Route(match, handler, 'GET');
};

/**
 * Creates a route with a network first strategy for the gtag.js script.
 *
 * @param {string} cacheName
 * @return {Route} The created route.
 *
 * @private
 */
const createGtagJsRoute = (cacheName: string) => {
  const match = ({url}: RouteMatchCallbackOptions) =>
      url.hostname === GTM_HOST &&
      url.pathname === GTAG_JS_PATH;

  const handler = new NetworkFirst({cacheName});

  return new Route(match, handler, 'GET');
};

/**
 * Creates a route with a network first strategy for the gtm.js script.
 *
 * @param {string} cacheName
 * @return {Route} The created route.
 *
 * @private
 */
const createGtmJsRoute = (cacheName: string) => {
  const match = ({url}: RouteMatchCallbackOptions) =>
      url.hostname === GTM_HOST &&
      url.pathname === GTM_JS_PATH;

  const handler = new NetworkFirst({cacheName});

  return new Route(match, handler, 'GET');
};

/**
 * @param {Object=} [options]
 * @param {Object} [options.cacheName] The cache name to store and retrieve
 *     analytics.js. Defaults to the cache names provided by `workbox-core`.
 * @param {Object} [options.parameterOverrides]
 *     [Measurement Protocol parameters](https://developers.google.com/analytics/devguides/collection/protocol/v1/parameters),
 *     expressed as key/value pairs, to be added to replayed Google Analytics
 *     requests. This can be used to, e.g., set a custom dimension indicating
 *     that the request was replayed.
 * @param {Function} [options.hitFilter] A function that allows you to modify
 *     the hit parameters prior to replaying
 *     the hit. The function is invoked with the original hit's URLSearchParams
 *     object as its only argument.
 *
 * @memberof module:workbox-google-analytics
 */
const initialize = (options: GoogleAnalyticsInitializeOptions = {}) => {
  const cacheName = cacheNames.getGoogleAnalyticsName(options.cacheName);

  const bgSyncPlugin = new BackgroundSyncPlugin(QUEUE_NAME, {
    maxRetentionTime: MAX_RETENTION_TIME,
    onSync: createOnSyncCallback(options),
  });

  const routes = [
    createGtmJsRoute(cacheName),
    createAnalyticsJsRoute(cacheName),
    createGtagJsRoute(cacheName),
    ...createCollectRoutes(bgSyncPlugin),
  ];

  const router = new Router();
  for (const route of routes) {
    router.registerRoute(route);
  }

  router.addFetchListener();
};

export {
  initialize,
};