All: Created ResourceFetcher class to handle resource downloads

ReactNativeClient/lib/services/ResourceFetcher.js

@@ -0,0 +1,116 @@
+const Resource = require('lib/models/Resource');
+const BaseService = require('lib/services/BaseService');
+const BaseSyncTarget = require('lib/BaseSyncTarget');
+const { Logger } = require('lib/logger.js');
+
+class ResourceFetcher extends BaseService {
+
+	constructor(fileApi) {
+		super();
+
+		if (typeof fileApi !== 'function') throw new Error('fileApi must be a function that returns the API');
+		
+		this.logger_ = new Logger();
+		this.fileApi_ = fileApi;
+		this.queue_ = [];
+		this.fetchingItems_ = {};
+		this.resourceDirName_ = BaseSyncTarget.resourceDirName();
+		this.queueMutex_ = new Mutex();
+		this.maxDownloads_ = 3;
+	}
+
+	setLogger(logger) {
+		this.logger_ = logger;
+	}
+
+	logger() {
+		return this.logger_;
+	}
+
+	fileApi() {
+		return this.fileApi_();
+	}
+
+	queuedItemIndex_(resourceId) {
+		for (let i = 0; i < this.fetchingItems_.length; i++) {
+			const item = this.fetchingItems_[i];
+			if (item.id === resourceId) return i;
+		}
+		return -1;
+	}
+
+	queueDownload(resourceId, priority = null) {
+		if (priority === null) priority = 'normal';
+
+		const index = this.queuedItemIndex_(resourceId);
+		if (index >= 0) return;
+
+		const item = { id: resourceId };
+
+		if (priority === 'high') {
+			this.queue_.splice(0, 0, item);
+		} else {
+			this.queue_.push(item);
+		}
+
+		this.scheduleQueueProcess_();
+	}
+
+	async startDownload_(resourceId) {
+		if (this.fetchingItems_[resourceId]) return;
+		this.fetchingItems_[resourceId] = true;
+
+		const resource = await Resource.load(resourceId);
+
+		this.fetchingItems_[resourceId] = resource;
+
+		const localResourceContentPath = Resource.fullPath(resource);
+		const remoteResourceContentPath = this.resourceDirName_ + "/" + resource.id;
+
+		await Resource.save({ id: resource.id, fetch_status: Resource.FETCH_STATUS_STARTED });
+
+		this.fileApi().get(remoteResourceContentPath, { path: localResourceContentPath, target: "file" }).then(async () => {
+			delete this.fetchingItems_[resource.id];
+			await Resource.save({ id: resource.id, fetch_status: Resource.FETCH_STATUS_DONE });
+			this.scheduleQueueProcess_();
+		}).catch(async (error) => {
+			delete this.fetchingItems_[resource.id];
+			await Resource.save({ id: resource.id, fetch_status: Resource.FETCH_STATUS_ERROR, fetch_error: error.message });
+			this.scheduleQueueProcess_();
+		});
+	}
+
+	processQueue_() {
+		while (Object.getOwnPropertyNames(this.fetchingItems_).length < this.maxDownloads_) {
+			if (!this.queue_.length) return;
+			const item = this.queue_.splice(0, 1)[0];
+			this.startDownload_(item.id);
+		}
+	}
+
+	async waitForAllFinished() {
+		return new Promise((resolve, reject) => {
+			const iid = setInterval(() => {
+				if (!this.queue_.length && !Object.getOwnPropertyNames(this.fetchingItems_).length) {
+					clearInterval(iid);
+					resolve();
+				}
+			}, 100);
+		});
+	}
+
+	scheduleQueueProcess_() {
+		if (this.scheduleQueueProcessIID_) {
+			clearTimeout(this.scheduleQueueProcessIID_);
+			this.scheduleQueueProcessIID_ = null;
+		}
+
+		this.scheduleQueueProcessIID_ = setTimeout(() => {
+			this.processQueue_();
+			this.scheduleQueueProcessIID_ = null;
+		}, 100);
+	}
+
+}
+
+module.exports = ResourceFetcher;