import { EventEmitter } from "eventemitter3";
import logger from "./logger";

export class EncodingQueue extends EventEmitter {
	readonly fileReader: FileReader = new FileReader();

	private _queue: Blob[] = [];
	private _processing: boolean = false;

	constructor() {
		super();

		this.fileReader.onload = (evt) => {
			this._processing = false;

			if (evt.target) {
				this.emit("done", evt.target.result as ArrayBuffer);
			}

			this.doNextTask();
		};

		this.fileReader.onerror = (evt) => {
			logger.error(`EncodingQueue error:`, evt);
			this._processing = false;
			this.destroy();
			this.emit("error", evt);
		};
	}

	get queue(): Blob[] {
		return this._queue;
	}

	get size(): number {
		return this.queue.length;
	}

	get processing(): boolean {
		return this._processing;
	}

	enque(blob: Blob): void {
		this.queue.push(blob);

		if (this.processing) return;

		this.doNextTask();
	}

	destroy(): void {
		this.fileReader.abort();
		this._queue = [];
	}

	private doNextTask(): void {
		if (this.size === 0) return;
		if (this.processing) return;

		this._processing = true;

		this.fileReader.readAsArrayBuffer(this.queue.shift());
	}
}