export default class Api {

	constructor({server, processPage, timezone, csrfToken, errorCode, lang}) {
		this.server = server;
		this.processPage = processPage;
		this.timezone = timezone;
		this.csrfToken = csrfToken;
		this.errorCode = errorCode;
		this.lang = lang;
	}

	async get(sAction, asParams = {}) {
		const oResponse = await this.request(sAction, asParams, 'GET');
		return oResponse.data;
	}

	async post(sAction, asParams = {}) {
		const oResponse = await this.request(sAction, asParams, 'POST');
		return oResponse.data;
	}

	/**
	 * Fire-and-forget POST that survives the page going away. Used for the
	 * close-the-entry call on unload, where a fetch would simply be cancelled.
	 * sendBeacon cannot set headers, so the CSRF token rides in the body -
	 * which the controller accepts as a fallback for exactly this case.
	 */
	beacon(sAction, asParams = {}) {
		if(!navigator.sendBeacon) return false;

		const oBody = new URLSearchParams({
			...asParams,
			a: sAction,
			t: this.timezone,
			csrf_token: this.csrfToken
		});

		return navigator.sendBeacon(
			new URL(this.processPage, this.server),
			new Blob([oBody.toString()], {type: 'application/x-www-form-urlencoded;charset=UTF-8'})
		);
	}

	async request(sAction, asParams = {}, sMethod = 'GET') {
		const oUrl = new URL(this.processPage, this.server);

		const sUrlParams = new URLSearchParams({
			...asParams,
			a: sAction,
			t: this.timezone
		}).toString();

		const asOptions = {
			method: sMethod,
			headers: {'Accept': 'application/json'}
		};

		if(sMethod === 'GET') {
			oUrl.search = sUrlParams;
		}
		else {
			asOptions.headers['Content-Type'] = 'application/x-www-form-urlencoded;charset=UTF-8';
			asOptions.headers['X-CSRF-Token'] = this.csrfToken;
			asOptions.body = sUrlParams;
		}

		const oRequest = await fetch(oUrl, asOptions);

		if(!oRequest.ok) {
			throw new Error('Error HTTP ' + oRequest.status + ': ' + oRequest.statusText);
		}

		const oResponse = await oRequest.json();
		oResponse.desc_lang_text = this.lang.get(oResponse.desc_lang_id, oResponse.desc_lang_params);

		if(oResponse.result == this.errorCode) {
			const oError = new Error(oResponse.desc_lang_text || oResponse.desc_lang_id);
			oError.desc_lang_id = oResponse.desc_lang_id;
			oError.desc_lang_params = oResponse.desc_lang_params;
			oError.desc_lang_text = oResponse.desc_lang_text;
			throw oError;
		}

		return oResponse;
	}
}