import type { TrackingManager } from '../tracking.svelte.ts';
import type {
	EventParamsByName,
	StandardEventName,
	CommonParams,
	CustomParams,
	AdvancedMatching,
	InitOptions
} from '../types/fbq.js';
import { loadMetaPixel } from '../util/meta-pixel-loader.ts';
import { resolveGetter, type MaybeGetter } from '../util/getter.ts';
import log from 'loglevel';
import { dev } from '$app/environment';
import { CAPIClient } from '../capi/client.ts';
import {
	ActionSource,
	CAPIEvent,
	type CAPIEventOptions,
	type CAPIStandardParams
} from '../capi/event.ts';

const pixelParamsToCustomData = (params: CommonParams & CustomParams): CAPIStandardParams => {
	const customData: CAPIStandardParams = {};
	if (params.value) customData.value = params.value;
	if (params.currency) customData.currency = params.currency;
	if (params.content_name) customData.content_name = params.content_name;
	if (params.content_category) customData.content_category = params.content_category;
	if (params.content_ids) customData.content_ids = params.content_ids;
	if (params.contents) {
		const acc: CAPIStandardParams['contents'] = [];
		customData.contents = params.contents.reduce((acc, content) => {
			acc.push({
				id: content.id.toString(),
				quantity: content.quantity
			});
			return acc;
		}, acc);
	}
	if (params.num_items) customData.num_items = params.num_items;
	if (params.search_string) customData.search_string = params.search_string;
	if (params.predicted_ltv) customData.predicted_ltv = params.predicted_ltv;
	return customData;
};

/**
 * Options for configuring a PixelControl instance.
 */
export type PixelControlOptions = {
	/**
	 * if provided, events fired will always have this code attached
	 * to prevent them from polluting real analytics data.
	 */
	testEventCode?: string;
	/**
	 * if provided, all events fired will be passed to the server endpoint
	 * at this URL to be sent via the Conversion API. Any events sent
	 * without a event ID will be assigned a random one.
	 */
	conversionHref?: string;
	/** Advanced matching data */
	advancedMatching?: AdvancedMatching;
	/** Initialization options */
	initOptions?: InitOptions;
};

/**
 * Manages multiple Meta Pixel instances and provides methods to
 * interact with them, including consent management and event tracking.
 */
export class PixelControl {
	private _pixelID: string;
	private _testEventCode?: string = undefined;
	private _trackingManager: MaybeGetter<TrackingManager | undefined>;
	private _conversionClient?: CAPIClient = undefined;

	private static _baseLoaded: boolean = false;
	private static _registeredPixels: Record<string, PixelControl> = {};

	/** Indicates whether the Meta Pixel base script has been loaded. */
	static get baseLoaded(): boolean {
		return this._baseLoaded;
	}

	/**
	 * Ensures that the Meta Pixel base has been loaded before
	 * allowing further operations.
	 * @throws Error if the Meta Pixel API is not loaded.
	 */
	static loadGuard(): void {
		if (!this._baseLoaded || !window.fbq) {
			throw new Error('Meta Pixel API has not been loaded. Call PixelControl.load() first.');
		}
	}

	private constructor(
		trackingManager: MaybeGetter<TrackingManager | undefined>,
		pixelID: string,
		options?: PixelControlOptions
	) {
		this._trackingManager = trackingManager;
		this._pixelID = pixelID;
		this._testEventCode = options?.testEventCode;

		const resolvedTrackingManager = resolveGetter(trackingManager);
		if (options?.conversionHref && resolvedTrackingManager) {
			this._conversionClient = new CAPIClient(options.conversionHref, resolvedTrackingManager);
		} else if (options?.conversionHref) {
			log.warn(
				`${this.logPrefix} CAPI Client ${options.conversionHref} available but not initialized, TrackingManager is required for user consent.`
			);
		}
	}

	/** Loads the Meta Pixel base script. */
	static load() {
		if (this._baseLoaded && !!window.fbq) return;
		loadMetaPixel(); // Load the Meta Pixel script
		this._baseLoaded = true;
		log.debug('[PixelControl] Meta Pixel base script loaded.', this._baseLoaded);
	}

	/** Tells the Meta pixel that the user has given consent for tracking. */
	static grantConsent() {
		this.loadGuard();
		window.fbq?.('consent', 'grant');
		log.debug('[PixelControl] Pixel consent granted.');
	}

	/** Tells the Meta pixel that the user has revoked consent for tracking. */
	static revokeConsent() {
		this.loadGuard();
		window.fbq?.('consent', 'revoke');
		log.debug('[PixelControl] Pixel consent revoked.');
	}

	/**
	 * Registers a PixelControl instance for the given Meta Pixel ID. If
	 * the base Meta Pixel script has not been loaded yet, it will be
	 * loaded automatically. Optionally sets a test event code for the Pixel.
	 * Should only be called once for each Pixel ID, use PixelControl.get()
	 * to retrieve existing instances.
	 * @param trackingManager Tracking manager to handle user consent for tracking
	 * @param pixelID Meta Pixel ID
	 * @param options Optional settings
	 * @returns PixelControl instance
	 */
	static initialize(
		trackingManager: MaybeGetter<TrackingManager | undefined>,
		pixelID: string,
		options?: PixelControlOptions
	): PixelControl {
		// Load the base script if not already loaded
		PixelControl.load();

		// Check for existing PixelControl instance
		if (this._registeredPixels[pixelID]) {
			log.warn(
				`${this._registeredPixels[pixelID].logPrefix} Instance already exists. Returning existing instance.`
			);
			return this._registeredPixels[pixelID];
		}

		// Create and register the PixelControl instance
		const pixel = new PixelControl(trackingManager, pixelID, options);
		this._registeredPixels[pixelID] = pixel;

		// Fire initialization
		window.fbq('init', pixel._pixelID, options?.advancedMatching, options?.initOptions);
		log.debug(`${pixel.logPrefix} initialized.`);

		return pixel;
	}

	/**
	 * Returns an existing PixelControl instance for the given Meta Pixel ID.
	 * @param pixelID Meta Pixel ID
	 * @returns PixelControl instance
	 * @throws Error if no PixelControl instance is found for the given ID.
	 */
	static get(pixelID: string): PixelControl {
		const pixel = this._registeredPixels[pixelID];
		if (!pixel) {
			throw new Error(`No PixelControl instance found for Meta Pixel ID: ${pixelID}`);
		}
		return pixel;
	}

	/**
	 * Checks if the Meta Pixel has consent to track user data
	 * and if the Pixel has been loaded.
	 * @returns true if tracking is allowed, false otherwise.
	 * @throws Error if the Meta Pixel is not loaded.
	 */
	consentGuard(): boolean {
		PixelControl.loadGuard();
		const trackingManager = resolveGetter(this._trackingManager);
		return trackingManager?.haveUserConsent() ?? false;
	}

	/** Warns if we're in dev mode and no test code is set */
	private devModeWarn() {
		if (dev && !this._testEventCode) {
			log.warn(
				`${this.logPrefix} Sending events in dev mode without a test event code. ` +
					'Consider providing a test event code to avoid affecting real data.'
			);
		}
	}

	/** Returns the log prefix including the pixel ID */
	private get logPrefix(): string {
		return `[PixelControl] [${this._pixelID}]`;
	}

	/**
	 * Shorthand utility to send a PageView event
	 * @param disableCAPI If true, disables sending this event to the Conversion API
	 * @throws Error if the Meta Pixel is not initialized.
	 */
	pageView(disableCAPI: boolean = false) {
		this.track('PageView', undefined, undefined, disableCAPI);
	}

	/**
	 * Forwards an event to the Conversion API client if configured.
	 *
	 * @param event - The event name.
	 * @param params - The event parameters.
	 * @param eventID - Optional event ID for deduplication.
	 * @returns The event ID used, either provided or generated.
	 */
	private forwardToCAPI(
		event: StandardEventName | string,
		params?: CommonParams & CustomParams,
		eventID?: string
	): string | undefined {
		if (!this._conversionClient) return eventID;

		if (!eventID) {
			eventID = crypto.randomUUID();
		}

		const opts: CAPIEventOptions = {
			eventName: event,
			eventID: eventID,
			actionSource: ActionSource.Website,
			eventSourceURL: window.location.href,
			eventTime: new Date(),
			userData: {
				clientUserAgent: navigator.userAgent
			},
			customData: params ? pixelParamsToCustomData(params) : undefined
		};
		const ev = CAPIEvent.fromOpts(opts);

		log.debug(
			`${this.logPrefix} ${ev.readableName} forwarding to CAPI with body: ${JSON.stringify(ev.params, null, 2)}`
		);

		this._conversionClient
			.trackEvent(ev)
			.then((response) => {
				log.debug(
					`${this.logPrefix} ${ev.readableName} forwarded to CAPI, response: ${JSON.stringify(
						response,
						null,
						2
					)}`
				);
			})
			.catch((error) => {
				log.error(`${this.logPrefix} ${ev.readableName} failed to forward to CAPI. Error: `, error);
			});

		return eventID;
	}

	private getEventReadableName(
		event: StandardEventName | string,
		eventID?: string,
		testCode?: string
	): string {
		return (
			event + (eventID ? ` (${eventID})` : '') + (testCode ? ` [test_event_code: ${testCode}]` : '')
		);
	}

	/**
	 * Tracks a standard event for this pixel (uses `trackSingle` under the hood)
	 * @param event Standard event name
	 * @param params Event parameters
	 * @param eventID Optional event ID for deduplication with Conversion API
	 * @param disableCAPI If true, disables sending this event to the Conversion API
	 * @throws Error if the Meta Pixel is not initialized.
	 */
	track<K extends StandardEventName>(
		event: K,
		params?: EventParamsByName[K],
		eventID?: string,
		disableCAPI: boolean = false
	) {
		if (!this.consentGuard()) return;
		this.devModeWarn();

		// Optionally, send to conversion API endpoint
		if (!disableCAPI) {
			eventID = this.forwardToCAPI(event, params, eventID);
		}

		// Send the event to Meta via the pixel
		window.fbq('trackSingle', this._pixelID, event, params, {
			eventID,
			test_event_code: this._testEventCode
		});
		log.debug(
			`${this.logPrefix} ${this.getEventReadableName(event, eventID, this._testEventCode)} sent.`
		);
	}

	/**
	 * Tracks a custom event for this pixel (uses `trackSingleCustom` under the hood)
	 * @param event Custom event name
	 * @param params Event parameters
	 * @param eventID Optional event ID for deduplication with Conversion API
	 * @param disableCAPI If true, disables sending this event to the Conversion API
	 * @throws Error if the Meta Pixel is not initialized.
	 */
	trackCustom(
		event: string,
		params?: CommonParams & CustomParams,
		eventID?: string,
		disableCAPI: boolean = false
	) {
		if (!this.consentGuard()) return;
		this.devModeWarn();

		// Optionally, send to conversion API endpoint
		if (!disableCAPI) {
			eventID = this.forwardToCAPI(event, params, eventID);
		}

		// Send the event to Meta via the pixel
		window.fbq('trackSingleCustom', this._pixelID, event, params, {
			eventID,
			test_event_code: this._testEventCode
		});
		log.debug(
			`${this.logPrefix} ${this.getEventReadableName(event, eventID, this._testEventCode)} sent.`
		);
	}
}