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import {bindAll, isWorker, isSafari} from './util';
import window from './window';
import {serialize, deserialize} from './web_worker_transfer';
import ThrottledInvoker from './throttled_invoker';
import type {Transferable} from '../types/transferable';
import type {Cancelable} from '../types/cancelable';
/**
* An implementation of the [Actor design pattern](http://en.wikipedia.org/wiki/Actor_model)
* that maintains the relationship between asynchronous tasks and the objects
* that spin them off - in this case, tasks like parsing parts of styles,
* owned by the styles
*
* @param {WebWorker} target
* @param {WebWorker} parent
* @param {string|number} mapId A unique identifier for the Map instance using this Actor.
* @private
*/
class Actor {
target: any;
parent: any;
mapId: ?number;
callbacks: { number: any };
name: string;
tasks: { number: any };
taskQueue: Array<number>;
cancelCallbacks: { number: Cancelable };
invoker: ThrottledInvoker;
globalScope: any;
constructor(target: any, parent: any, mapId: ?number) {
this.target = target;
this.parent = parent;
this.mapId = mapId;
this.callbacks = {};
this.tasks = {};
this.taskQueue = [];
this.cancelCallbacks = {};
bindAll(['receive', 'process'], this);
this.invoker = new ThrottledInvoker(this.process);
this.target.addEventListener('message', this.receive, false);
this.globalScope = isWorker() ? target : window;
}
/**
* Sends a message from a main-thread map to a Worker or from a Worker back to
* a main-thread map instance.
*
* @param type The name of the target method to invoke or '[source-type].[source-name].name' for a method on a WorkerSource.
* @param targetMapId A particular mapId to which to send this message.
* @private
*/
send(type: string, data: mixed, callback: ?Function, targetMapId: ?string, mustQueue: boolean = false): ?Cancelable {
// We're using a string ID instead of numbers because they are being used as object keys
// anyway, and thus stringified implicitly. We use random IDs because an actor may receive
// message from multiple other actors which could run in different execution context. A
// linearly increasing ID could produce collisions.
const id = Math.round((Math.random() * 1e18)).toString(36).substring(0, 10);
if (callback) {
this.callbacks[id] = callback;
}
const buffers: ?Array<Transferable> = isSafari(this.globalScope) ? undefined : [];
this.target.postMessage({
id,
type,
hasCallback: !!callback,
targetMapId,
mustQueue,
sourceMapId: this.mapId,
data: serialize(data, buffers)
}, buffers);
return {
cancel: () => {
if (callback) {
// Set the callback to null so that it never fires after the request is aborted.
delete this.callbacks[id];
}
this.target.postMessage({
id,
type: '<cancel>',
targetMapId,
sourceMapId: this.mapId
});
}
};
}
receive(message: Object) {
const data = message.data,
id = data.id;
if (!id) {
return;
}
if (data.targetMapId && this.mapId !== data.targetMapId) {
return;
}
if (data.type === '<cancel>') {
// Remove the original request from the queue. This is only possible if it
// hasn't been kicked off yet. The id will remain in the queue, but because
// there is no associated task, it will be dropped once it's time to execute it.
delete this.tasks[id];
const cancel = this.cancelCallbacks[id];
delete this.cancelCallbacks[id];
if (cancel) {
cancel();
}
} else {
if (isWorker() || data.mustQueue) {
// In workers, store the tasks that we need to process before actually processing them. This
// is necessary because we want to keep receiving messages, and in particular,
// <cancel> messages. Some tasks may take a while in the worker thread, so before
// executing the next task in our queue, postMessage preempts this and <cancel>
// messages can be processed. We're using a MessageChannel object to get throttle the
// process() flow to one at a time.
this.tasks[id] = data;
this.taskQueue.push(id);
this.invoker.trigger();
} else {
// In the main thread, process messages immediately so that other work does not slip in
// between getting partial data back from workers.
this.processTask(id, data);
}
}
}
process() {
if (!this.taskQueue.length) {
return;
}
const id = this.taskQueue.shift();
const task = this.tasks[id];
delete this.tasks[id];
// Schedule another process call if we know there's more to process _before_ invoking the
// current task. This is necessary so that processing continues even if the current task
// doesn't execute successfully.
if (this.taskQueue.length) {
this.invoker.trigger();
}
if (!task) {
// If the task ID doesn't have associated task data anymore, it was canceled.
return;
}
this.processTask(id, task);
}
processTask(id: number, task: any) {
if (task.type === '<response>') {
// The done() function in the counterpart has been called, and we are now
// firing the callback in the originating actor, if there is one.
const callback = this.callbacks[id];
delete this.callbacks[id];
if (callback) {
// If we get a response, but don't have a callback, the request was canceled.
if (task.error) {
callback(deserialize(task.error));
} else {
callback(null, deserialize(task.data));
}
}
} else {
let completed = false;
const buffers: ?Array<Transferable> = isSafari(this.globalScope) ? undefined : [];
const done = task.hasCallback ? (err, data) => {
completed = true;
delete this.cancelCallbacks[id];
this.target.postMessage({
id,
type: '<response>',
sourceMapId: this.mapId,
error: err ? serialize(err) : null,
data: serialize(data, buffers)
}, buffers);
} : (_) => {
completed = true;
};
let callback = null;
const params = (deserialize(task.data): any);
if (this.parent[task.type]) {
// task.type == 'loadTile', 'removeTile', etc.
callback = this.parent[task.type](task.sourceMapId, params, done);
} else if (this.parent.getWorkerSource) {
// task.type == sourcetype.method
const keys = task.type.split('.');
const scope = (this.parent: any).getWorkerSource(task.sourceMapId, keys[0], params.source);
callback = scope[keys[1]](params, done);
} else {
// No function was found.
done(new Error(`Could not find function ${task.type}`));
}
if (!completed && callback && callback.cancel) {
// Allows canceling the task as long as it hasn't been completed yet.
this.cancelCallbacks[id] = callback.cancel;
}
}
}
remove() {
this.invoker.remove();
this.target.removeEventListener('message', this.receive, false);
}
}
export default Actor;
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