/// <reference path="../../../dist/preview release/babylon.d.ts" />

module BABYLON {
    interface WorkerInfo {
        worker: Worker;
        active: boolean;
    }

    /**
     * Helper class to push actions to a pool of workers.
     */
    export class WorkerPool implements IDisposable {
        private _workerInfos: Array<WorkerInfo>;
        private _pendingActions = new Array<(worker: Worker, onComplete: () => void) => void>();

        /**
         * Constructor
         * @param workers Array of workers to use for actions
         */
        constructor(workers: Array<Worker>) {
            this._workerInfos = workers.map(worker => ({
                worker: worker,
                active: false
            }));
        }

        /**
         * Terminates all workers and clears any pending actions.
         */
        public dispose(): void {
            for (const workerInfo of this._workerInfos) {
                workerInfo.worker.terminate();
            }

            delete this._workerInfos;
            delete this._pendingActions;
        }

        /**
         * Pushes an action to the worker pool. If all the workers are active, the action will be
         * pended until a worker has completed its action.
         * @param action The action to perform. Call onComplete when the action is complete.
         */
        public push(action: (worker: Worker, onComplete: () => void) => void): void {
            for (const workerInfo of this._workerInfos) {
                if (!workerInfo.active) {
                    this._execute(workerInfo, action);
                    return;
                }
            }

            this._pendingActions.push(action);
        }

        private _execute(workerInfo: WorkerInfo, action: (worker: Worker, onComplete: () => void) => void): void {
            workerInfo.active = true;
            action(workerInfo.worker, () => {
                workerInfo.active = false;
                const nextAction = this._pendingActions.shift();
                if (nextAction) {
                    this._execute(workerInfo, nextAction);
                }
            });
        }
    }
}