import { dev } from '$app/environment';
import log from 'loglevel';
import type { CAPIEvent } from './event.ts';
import * as v from 'valibot';
import { capiResponseBodySchema, type CAPIResponseBody } from './handle.ts';

const GRAPH_VERSION = 'v24.0';

/**
 * Connector class for Meta Conversion API (CAPI). Abstraction over direct HTTP
 * requests to Meta's CAPI endpoint.
 *
 * See https://developers.facebook.com/docs/marketing-api/conversions-api/get-started
 * for more information.
 */
export class CAPIConnector {
	private _accessToken: string;
	private _pixelID: string;
	private _testEventCode?: string;

	/**
	 * Creates a new MCAPIControl instance.
	 *
	 * @param accessToken - Your Meta Pixel Conversion API access token.
	 * @param pixelID - Your Meta Pixel ID.
	 * @param testEventCode - Optional test event code used for all events if provided.
	 */
	constructor(accessToken: string, pixelID: string, testEventCode?: string) {
		this._accessToken = accessToken;
		this._pixelID = pixelID;
		this._testEventCode = testEventCode;
	}

	/**
	 * Sends conversion events to the Meta Conversion API.
	 *
	 * @param events - Array of CAPIEvent instances to send.
	 * @returns The response from the Meta CAPI.
	 * @throws Will throw an error if the request fails or the API returns an error.
	 */
	async sendEvents(events: CAPIEvent[]): Promise<CAPIResponseBody> {
		if (dev && !this._testEventCode) {
			log.warn(
				`[CAPIConnector] Sending ${events.length} event(s) in dev mode without a test event code. ` +
					'Consider providing a test event code to avoid affecting real data.'
			);
		}

		const url = `https://graph.facebook.com/${GRAPH_VERSION}/${this._pixelID}/events`;

		const body = {
			data: events.map((e) => e.toObject()),
			test_event_code: this._testEventCode
		};
		log.debug(
			`[CAPIConnector] [${this._pixelID}] Sending ${events.length} event(s) to Meta CAPI at ${url} with body: ${JSON.stringify(body, null, 2)}`
		);

		const resp = await fetch(`${url}?access_token=${this._accessToken}`, {
			method: 'POST',
			headers: {
				'Content-Type': 'application/json'
			},
			body: JSON.stringify(body)
		});
		const json = await resp.json();

		if (!resp.ok) {
			throw new Error(`Meta CAPI error ${resp.status}: ${JSON.stringify(json, null, 2)}`);
		}

		try {
			const parsed = v.parse(capiResponseBodySchema, json);
			log.info(
				`[CAPIConnector] [${this._pixelID}] Successfully sent ${events.length} event(s) to Meta CAPI.`
			);
			return parsed as CAPIResponseBody;
		} catch (err) {
			throw new Error(`[CAPIConnector] Invalid response shape: ${(err as Error).message}`);
		}
	}

	/**
	 * Shorthand for sending a single event to the Meta Conversion API.
	 *
	 * @param event - The CAPIEvent instance to send.
	 * @returns The response from the Meta CAPI.
	 * @throws Will throw an error if the request fails or the API returns an error.
	 */
	async trackEvent(event: CAPIEvent): Promise<CAPIResponseBody> {
		return this.sendEvents([event]);
	}
}