// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
// SPDX-License-Identifier: Apache-2.0

import { ConsoleLogger } from '@aws-amplify/core';
import { isBrowser } from '@aws-amplify/core/internals/utils';

import {
	PageViewTrackingOptions,
	TrackerEventRecorder,
	TrackerInterface,
} from '../types/trackers';

const logger = new ConsoleLogger('PageViewTracker');

const DEFAULT_EVENT_NAME = 'pageView';
const DEFAULT_APP_TYPE = 'singlePage';
const DEFAULT_URL_PROVIDER = () => {
	return window.location.origin + window.location.pathname;
};
const PREV_URL_STORAGE_KEY = 'aws-amplify-analytics-prevUrl';

export class PageViewTracker implements TrackerInterface {
	private trackerActive: boolean;
	private options: PageViewTrackingOptions;
	private eventRecorder: TrackerEventRecorder;

	// SPA tracking helpers
	private spaTrackingActive: boolean;
	private pushStateProxy?: any;
	private replaceStateProxy?: any;
	private originalPushState: any;
	private originalReplaceState: any;

	constructor(
		eventRecorder: TrackerEventRecorder,
		options?: PageViewTrackingOptions,
	) {
		this.options = {};
		this.trackerActive = true;
		this.eventRecorder = eventRecorder;
		this.spaTrackingActive = false;
		this.handleLocationChange = this.handleLocationChange.bind(this);

		this.configure(eventRecorder, options);
	}

	public configure(
		eventRecorder: TrackerEventRecorder,
		options?: PageViewTrackingOptions,
	) {
		this.eventRecorder = eventRecorder;

		// Clean up any existing listeners
		this.cleanup();

		// Apply defaults
		this.options = {
			appType: options?.appType ?? DEFAULT_APP_TYPE,
			attributes: options?.attributes ?? undefined,
			eventName: this.options?.eventName ?? DEFAULT_EVENT_NAME,
			urlProvider: this.options?.urlProvider ?? DEFAULT_URL_PROVIDER,
		};

		// Configure SPA or MPA page view tracking
		if (isBrowser()) {
			if (this.options.appType === 'singlePage') {
				this.setupSPATracking();
			} else {
				this.setupMPATracking();
			}

			this.trackerActive = true;
		}
	}

	public cleanup() {
		// No-op if document listener is not active
		if (!this.trackerActive) {
			return;
		}

		// Clean up SPA page view listeners
		if (this.spaTrackingActive) {
			window.history.pushState = this.originalPushState;
			window.history.replaceState = this.originalReplaceState;
			this.pushStateProxy?.revoke();
			this.replaceStateProxy?.revoke();
			window.removeEventListener('popstate', this.handleLocationChange);

			this.spaTrackingActive = false;
		}
	}

	private setupSPATracking() {
		if (!this.spaTrackingActive) {
			// Configure proxies on History APIs
			this.pushStateProxy = Proxy.revocable(window.history.pushState, {
				apply: (target, thisArg, args) => {
					target.apply(thisArg, args as any);
					this.handleLocationChange();
				},
			});
			this.replaceStateProxy = Proxy.revocable(window.history.replaceState, {
				apply: (target, thisArg, args) => {
					target.apply(thisArg, args as any);
					this.handleLocationChange();
				},
			});

			this.originalPushState = window.history.pushState;
			this.originalReplaceState = window.history.replaceState;
			window.history.pushState = this.pushStateProxy.proxy;
			window.history.replaceState = this.replaceStateProxy.proxy;
			window.addEventListener('popstate', this.handleLocationChange);
			sessionStorage.removeItem(PREV_URL_STORAGE_KEY);

			this.spaTrackingActive = true;
		}
	}

	private setupMPATracking() {
		this.handleLocationChange();
	}

	private handleLocationChange() {
		const currentUrl = this.options.urlProvider!();
		const eventName = this.options.eventName || DEFAULT_EVENT_NAME;

		if (this.urlHasChanged()) {
			sessionStorage.setItem(PREV_URL_STORAGE_KEY, currentUrl);

			// Assemble attribute list
			const attributes = Object.assign(
				{
					url: currentUrl,
				},
				this.options.attributes,
			);

			logger.debug('Recording automatically tracked page view event', {
				eventName,
				attributes,
			});

			this.eventRecorder(eventName, attributes);
		}
	}

	private urlHasChanged() {
		const prevUrl = sessionStorage.getItem(PREV_URL_STORAGE_KEY);
		const currUrl = this.options.urlProvider!();

		return currUrl !== prevUrl;
	}
}