MBOILE-2838 site: Batch WS calls to reduce the number of HTTP requests

src/classes/site.ts

@@ -26,7 +26,7 @@ import { CoreDomUtilsProvider } from '@providers/utils/dom';
 import { CoreTextUtilsProvider } from '@providers/utils/text';
 import { CoreTimeUtilsProvider } from '@providers/utils/time';
 import { CoreUrlUtilsProvider } from '@providers/utils/url';
-import { CoreUtilsProvider } from '@providers/utils/utils';
+import { CoreUtilsProvider, PromiseDefer } from '@providers/utils/utils';
 import { CoreConstants } from '@core/constants';
 import { CoreConfigConstants } from '../configconstants';
 import { Md5 } from 'ts-md5/dist/md5';
@@ -113,6 +113,17 @@ export interface CoreSiteWSPreSets {
      * @type {string}
      */
     typeExpected?: string;
+
+    /**
+     * Wehther a pending request in the queue matching the same function and arguments can be reused instead of adding
+     * a new request to the queue. Defaults to true for read requests.
+     */
+    reusePending?: boolean;
+
+    /**
+     * Whether the request will be be sent immediately as a single request. Defaults to false.
+     */
+    skipQueue?: boolean;
 }
 
 /**
@@ -144,6 +155,18 @@ export interface LocalMobileResponse {
     coreSupported?: boolean;
 }
 
+/**
+ * Info of a request waiting in the queue.
+ */
+interface RequestQueueItem {
+    cacheId: string;
+    method: string;
+    data: any;
+    preSets: CoreSiteWSPreSets;
+    wsPreSets: CoreWSPreSets;
+    deferred: PromiseDefer;
+}
+
 /**
  * Class that represents a site (combination of site + user).
  * It will have all the site data and provide utility functions regarding a site.
@@ -151,6 +174,9 @@ export interface LocalMobileResponse {
  * the tables are created in all the sites, not just the current one.
  */
 export class CoreSite {
+    static REQUEST_QUEUE_DELAY = 50; // Maximum number of miliseconds to wait before processing the queue.
+    static REQUEST_QUEUE_LIMIT = 10; // Maximum number of requests allowed in the queue.
+
     // List of injected services. This class isn't injectable, so it cannot use DI.
     protected appProvider: CoreAppProvider;
     protected dbProvider: CoreDbProvider;
@@ -186,6 +212,8 @@ export class CoreSite {
     protected lastAutoLogin = 0;
     protected offlineDisabled = false;
     protected ongoingRequests: { [cacheId: string]: Promise<any> } = {};
+    protected requestQueue: RequestQueueItem[] = [];
+    protected requestQueueTimeout = null;
 
     /**
      * Create a site.
@@ -476,6 +504,9 @@ export class CoreSite {
         if (typeof preSets.saveToCache == 'undefined') {
             preSets.saveToCache = true;
         }
+        if (typeof preSets.reusePending == 'undefined') {
+            preSets.reusePending = true;
+        }
 
         return this.request(method, data, preSets);
     }
@@ -592,7 +623,7 @@ export class CoreSite {
 
         const promise = this.getFromCache(method, data, preSets, false, originalData).catch(() => {
             // Do not pass those options to the core WS factory.
-            return this.wsProvider.call(method, data, wsPreSets).then((response) => {
+            return this.callOrEnqueueRequest(method, data, preSets, wsPreSets).then((response) => {
                 if (preSets.saveToCache) {
                     this.saveToCache(method, data, response, preSets);
                 }
@@ -707,6 +738,146 @@ export class CoreSite {
         });
     }
 
+    /**
+     * Adds a request to the queue or calls it immediately when not using the queue.
+     *
+     * @param {string} method The WebService method to be called.
+     * @param {any} data Arguments to pass to the method.
+     * @param {CoreSiteWSPreSets} preSets Extra options related to the site.
+     * @param {CoreWSPreSets} wsPreSets Extra options related to the WS call.
+     * @returns {Promise<any>} Promise resolved with the response when the WS is called.
+     */
+    protected callOrEnqueueRequest(method: string, data: any, preSets: CoreSiteWSPreSets, wsPreSets: CoreWSPreSets): Promise<any> {
+        if (preSets.skipQueue || !this.wsAvailable('tool_mobile_call_external_functions')) {
+            return this.wsProvider.call(method, data, wsPreSets);
+        }
+
+        const cacheId = this.getCacheId(method, data);
+
+        // Check if there is an identical request waiting in the queue (read requests only by default).
+        if (preSets.reusePending) {
+            const request = this.requestQueue.find((request) => request.cacheId == cacheId);
+            if (request) {
+                return request.deferred.promise;
+            }
+        }
+
+        const request: RequestQueueItem = {
+            cacheId,
+            method,
+            data,
+            preSets,
+            wsPreSets,
+            deferred: {}
+        };
+
+        request.deferred.promise = new Promise((resolve, reject): void => {
+            request.deferred.resolve = resolve;
+            request.deferred.reject = reject;
+        });
+
+        this.requestQueue.push(request);
+
+        if (this.requestQueue.length >= CoreSite.REQUEST_QUEUE_LIMIT) {
+            this.processRequestQueue();
+        } else if (!this.requestQueueTimeout) {
+            this.requestQueueTimeout = setTimeout(this.processRequestQueue.bind(this), CoreSite.REQUEST_QUEUE_DELAY);
+        }
+
+        return request.deferred.promise;
+    }
+
+    /**
+     * Call the enqueued web service requests.
+     */
+    protected processRequestQueue(): void {
+        this.logger.debug(`Processing request queue (${this.requestQueue.length} requests)`);
+
+        // Clear timeout if set.
+        if (this.requestQueueTimeout) {
+            clearTimeout(this.requestQueueTimeout);
+            this.requestQueueTimeout = null;
+        }
+
+        // Extract all requests from the queue.
+        const requests = this.requestQueue;
+        this.requestQueue = [];
+
+        if (requests.length == 1) {
+            // Only one request, do a regular web service call.
+            this.wsProvider.call(requests[0].method, requests[0].data, requests[0].wsPreSets).then((data) => {
+                requests[0].deferred.resolve(data);
+            }).catch((error) => {
+                requests[0].deferred.reject(error);
+            });
+
+            return;
+        }
+
+        const data = {
+            requests: requests.map((request) => {
+                const args = {};
+                const settings = {};
+
+                // Separate WS settings from function arguments.
+                Object.keys(request.data).forEach((key) => {
+                    let value = request.data[key];
+                    const match = /^moodlews(setting.*)$/.exec(key);
+                    if (match) {
+                        if (match[1] == 'settingfilter' || match[1] == 'settingfileurl') {
+                            // Undo special treatment of these settings in CoreWSProvider.convertValuesToString.
+                            value = (value == 'true' ? '1' : '0');
+                        }
+                        settings[match[1]] = value;
+                    } else {
+                        args[key] = value;
+                    }
+                });
+
+                return {
+                    function: request.method,
+                    arguments: JSON.stringify(args),
+                    ...settings
+                };
+            })
+        };
+
+        const wsPresets: CoreWSPreSets = {
+            siteUrl: this.siteUrl,
+            wsToken: this.token,
+        };
+
+        this.wsProvider.call('tool_mobile_call_external_functions', data, wsPresets).then((data) => {
+            if (!data || !data.responses) {
+                return Promise.reject(null);
+            }
+
+            requests.forEach((request, i) => {
+                const response = data.responses[i];
+
+                if (!response) {
+                    // Request not executed, enqueue again.
+                    this.callOrEnqueueRequest(request.method, request.data, request.preSets, request.wsPreSets);
+                } else if (response.error) {
+                    request.deferred.reject(this.textUtils.parseJSON(response.exception));
+                } else {
+                    let responseData = this.textUtils.parseJSON(response.data);
+                    // Match the behaviour of CoreWSProvider.call when no response is expected.
+                    if (!responseData && (typeof wsPresets.responseExpected == 'undefined' || wsPresets.responseExpected)) {
+                        responseData = {};
+                    }
+                    request.deferred.resolve(responseData);
+                }
+            });
+
+        }).catch((error) => {
+            // Error not specific to a single request, reject all promises.
+            requests.forEach((request) => {
+                request.deferred.reject(error);
+            });
+        });
+    }
+
     /**
      * Check if a WS is available in this site.
      *