"use strict";

import Config from './ClientConfig.mjs';

class WorkerWrapper {
	constructor() {
		this.worker = new Worker("worker.js"); // We could pass { type: "module" } as the 2nd argument here to allow Rollup code splitting to function as normal, but it's not supported by browsers yet
	}
	
	/**
	 * Sets up the Web Worker that does the TensorFlow prediction.
	 * Using a web worker avoids hanging the main thread.
	 * @return	{Promise}	A Promise that resolves when setup is complete.
	 */
	setup(map_bounds, index) {
		// Arrow functions inherit the parent scope, including the "this" 
		// special variable.
		return new Promise((resolve, reject) => {
			// Attach the listener first
			this.worker.addEventListener("message", (event) => {
				if(event.data.event !== "setup-complete") {
					reject(`Error: AIWorker responded with event ${event.data.event}, but 'setup-complete' was expected.`, event.data);
					return;
				}
				
				resolve();
			}, { once: true });
			
			// Ask the web worker to set itself up
			this.worker.postMessage({
				event: "setup",
				setup_info: {
					bounds: map_bounds,
					index,
					Config
				}
			});
		})
	}
	
	/**
	 * Uses the Web Worker to predict a row of signal strength values.
	 * @param	{number}	latitude	The latitude for which predictions should be made.
	 * @return	{Promise<number[]>}		A Promise returning the array of predictions calculated by the web worker.
	 */
	predict_row(latitude) {
		return new Promise((resolve, reject) => {
			// Attach the event listener....
			this.worker.addEventListener("message", (event) => {
				if(event.data.event !== "result") {
					reject(`Error: AIWorker responded with event ${event.data.event}, but 'result' was expected.`, event.data);
					return;
				}
				
				resolve(event.data);
				
			}, { once: true });
			
			// ....and send the request
			this.worker.postMessage({
				event: "predict-row",
				latitude
			});
		});
	}
	
	end() {
		this.worker.postMessage({
			event: "end"
		})
	}
}

export default WorkerWrapper;