116 lines
2.8 KiB
JavaScript
116 lines
2.8 KiB
JavaScript
/**
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* Used to run asynchronous tasks sequentially (ajax mainly)
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* An asynchronous task must be created with:
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* - a required run() function that may call success(), error() or retry()
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* - an optional onSuccess() function
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* - an optional onError() function
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* - an optional timeout field (default is 30000)
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*/
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define(["underscore"], function() {
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var asyncTaskRunner = {};
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// Dependencies
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var core = undefined;
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var asyncTaskQueue = [];
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var currentTask = undefined;
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var currentTaskRunning = false;
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var currentTaskStartTime = 0;
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// Run the next task in the queue if any and no other is running
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function runTask() {
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// If there is a task currently running
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if(currentTaskRunning === true) {
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// If the current task takes too long
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var timeout = currentTask.timeout || ASYNC_TASK_DEFAULT_TIMEOUT;
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if(currentTaskStartTime + timeout < core.currentTime) {
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currentTask.error();
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}
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return;
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}
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if(currentTask === undefined) {
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// If no task in the queue
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if(asyncTaskQueue.length === 0) {
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return;
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}
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// Dequeue an enqueued task
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currentTask = asyncTaskQueue.shift();
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currentTaskStartTime = core.currentTime;
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core.showWorkingIndicator(true);
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// Set task attributes and functions
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currentTask.finished = false;
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currentTask.retryCounter = 0;
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currentTask.success = function() {
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runSafe(this.onSuccess);
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};
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currentTask.error = function() {
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runSafe(this.onError);
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};
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currentTask.retry = function() {
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if(this.finished === true) {
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return;
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}
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if(currentTask.retryCounter === 5) {
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this.error();
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return;
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}
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// Implement an exponential backoff
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var delay = Math.pow(2, currentTask.retryCounter++) * 1000;
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currentTaskStartTime = core.currentTime + delay;
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currentTaskRunning = false;
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asyncTaskRunner.runTask();
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};
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}
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// Run the task
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if(currentTaskStartTime <= core.currentTime) {
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currentTaskRunning = true;
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currentTask.run();
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}
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}
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asyncTaskRunner.runTask = function() {
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// Use defer to avoid stack overflow
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_.defer(runTask);
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};
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function runSafe(func) {
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if(currentTask === undefined || currentTask.finished === true) {
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return;
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}
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try {
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if(func) {
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func();
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}
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} finally {
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currentTask.finished = true;
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currentTask = undefined;
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currentTaskRunning = false;
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if(asyncTaskQueue.length === 0) {
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core.showWorkingIndicator(false);
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}
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else {
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asyncTaskRunner.runTask();
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}
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}
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}
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// Add a task into the queue
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asyncTaskRunner.addTask = function(asyncTask) {
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asyncTaskQueue.push(asyncTask);
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asyncTaskRunner.runTask();
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};
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asyncTaskRunner.init = function(coreModule) {
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core = coreModule;
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};
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return asyncTaskRunner;
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});
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