/*
 * SPDX-FileCopyrightText: syuilo and misskey-project
 * SPDX-License-Identifier: AGPL-3.0-only
 */

// NIRAX --- A lightweight router

import { Component, onMounted, shallowRef, ShallowRef } from 'vue';
import { EventEmitter } from 'eventemitter3';

function safeURIDecode(str: string): string {
	try {
		return decodeURIComponent(str);
	} catch {
		return str;
	}
}

interface RouteDefBase {
	path: string;
	query?: Record<string, string>;
	loginRequired?: boolean;
	name?: string;
	hash?: string;
	globalCacheKey?: string;
	children?: RouteDef[];
}

interface RouteDefWithComponent extends RouteDefBase {
	component: Component,
}

interface RouteDefWithRedirect extends RouteDefBase {
	redirect: string | ((props: Map<string, string | boolean>) => string);
}

export type RouteDef = RouteDefWithComponent | RouteDefWithRedirect;

export type RouterFlag = 'forcePage';

type ParsedPath = (string | {
	name: string;
	startsWith?: string;
	wildcard?: boolean;
	optional?: boolean;
})[];

export type RouterEvent = {
	change: (ctx: {
		beforePath: string;
		path: string;
		resolved: Resolved;
		key: string;
	}) => void;
	replace: (ctx: {
		path: string;
		key: string;
	}) => void;
	push: (ctx: {
		beforePath: string;
		path: string;
		route: RouteDef | null;
		props: Map<string, string> | null;
		key: string;
	}) => void;
	same: () => void;
}

export type Resolved = {
	route: RouteDef;
	props: Map<string, string | boolean>;
	child?: Resolved;
	redirected?: boolean;

	/** @internal */
	_parsedRoute: {
		fullPath: string;
		queryString: string | null;
		hash: string | null;
	};
};

function parsePath(path: string): ParsedPath {
	const res = [] as ParsedPath;

	path = path.substring(1);

	for (const part of path.split('/')) {
		if (part.includes(':')) {
			const prefix = part.substring(0, part.indexOf(':'));
			const placeholder = part.substring(part.indexOf(':') + 1);
			const wildcard = placeholder.includes('(*)');
			const optional = placeholder.endsWith('?');
			res.push({
				name: placeholder.replace('(*)', '').replace('?', ''),
				startsWith: prefix !== '' ? prefix : undefined,
				wildcard,
				optional,
			});
		} else if (part.length !== 0) {
			res.push(part);
		}
	}

	return res;
}

export interface IRouter extends EventEmitter<RouterEvent> {
	current: Resolved;
	currentRef: ShallowRef<Resolved>;
	currentRoute: ShallowRef<RouteDef>;
	navHook: ((path: string, flag?: RouterFlag) => boolean) | null;

	/**
	 * ルートの初期化（eventListenerの定義後に必ず呼び出すこと）
	 */
	init(): void;

	resolve(path: string): Resolved | null;

	getCurrentPath(): string;

	getCurrentKey(): string;

	push(path: string, flag?: RouterFlag): void;

	replace(path: string, key?: string | null): void;

	/** @see EventEmitter */
	eventNames(): Array<EventEmitter.EventNames<RouterEvent>>;

	/** @see EventEmitter */
	listeners<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T
	): Array<EventEmitter.EventListener<RouterEvent, T>>;

	/** @see EventEmitter */
	listenerCount(
		event: EventEmitter.EventNames<RouterEvent>
	): number;

	/** @see EventEmitter */
	emit<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		...args: EventEmitter.EventArgs<RouterEvent, T>
	): boolean;

	/** @see EventEmitter */
	on<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		fn: EventEmitter.EventListener<RouterEvent, T>,
		context?: any
	): this;

	/** @see EventEmitter */
	addListener<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		fn: EventEmitter.EventListener<RouterEvent, T>,
		context?: any
	): this;

	/** @see EventEmitter */
	once<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		fn: EventEmitter.EventListener<RouterEvent, T>,
		context?: any
	): this;

	/** @see EventEmitter */
	removeListener<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		fn?: EventEmitter.EventListener<RouterEvent, T>,
		context?: any,
		once?: boolean | undefined
	): this;

	/** @see EventEmitter */
	off<T extends EventEmitter.EventNames<RouterEvent>>(
		event: T,
		fn?: EventEmitter.EventListener<RouterEvent, T>,
		context?: any,
		once?: boolean | undefined
	): this;

	/** @see EventEmitter */
	removeAllListeners(
		event?: EventEmitter.EventNames<RouterEvent>
	): this;
}

export class Router extends EventEmitter<RouterEvent> implements IRouter {
	private routes: RouteDef[];
	public current: Resolved;
	public currentRef: ShallowRef<Resolved>;
	public currentRoute: ShallowRef<RouteDef>;
	private currentPath: string;
	private isLoggedIn: boolean;
	private notFoundPageComponent: Component;
	private currentKey = Date.now().toString();
	private redirectCount = 0;

	public navHook: ((path: string, flag?: RouterFlag) => boolean) | null = null;

	constructor(routes: Router['routes'], currentPath: Router['currentPath'], isLoggedIn: boolean, notFoundPageComponent: Component) {
		super();

		this.routes = routes;
		this.current = this.resolve(currentPath)!;
		this.currentRef = shallowRef(this.current);
		this.currentRoute = shallowRef(this.current.route);
		this.currentPath = currentPath;
		this.isLoggedIn = isLoggedIn;
		this.notFoundPageComponent = notFoundPageComponent;
	}

	public init() {
		const res = this.navigate(this.currentPath, null, false);
		this.emit('replace', {
			path: res._parsedRoute.fullPath,
			key: this.currentKey,
		});
	}

	public resolve(path: string): Resolved | null {
		const fullPath = path;
		let queryString: string | null = null;
		let hash: string | null = null;
		if (path[0] === '/') path = path.substring(1);
		if (path.includes('#')) {
			hash = path.substring(path.indexOf('#') + 1);
			path = path.substring(0, path.indexOf('#'));
		}
		if (path.includes('?')) {
			queryString = path.substring(path.indexOf('?') + 1);
			path = path.substring(0, path.indexOf('?'));
		}

		const _parsedRoute = {
			fullPath,
			queryString,
			hash,
		};

		if (_DEV_) console.log('Routing: ', path, queryString);

		function check(routes: RouteDef[], _parts: string[]): Resolved | null {
			forEachRouteLoop:
			for (const route of routes) {
				let parts = [..._parts];
				const props = new Map<string, string>();

				pathMatchLoop:
				for (const p of parsePath(route.path)) {
					if (typeof p === 'string') {
						if (p === parts[0]) {
							parts.shift();
						} else {
							continue forEachRouteLoop;
						}
					} else {
						if (parts[0] == null && !p.optional) {
							continue forEachRouteLoop;
						}
						if (p.wildcard) {
							if (parts.length !== 0) {
								props.set(p.name, safeURIDecode(parts.join('/')));
								parts = [];
							}
							break pathMatchLoop;
						} else {
							if (p.startsWith) {
								if (parts[0] == null || !parts[0].startsWith(p.startsWith)) continue forEachRouteLoop;

								props.set(p.name, safeURIDecode(parts[0].substring(p.startsWith.length)));
								parts.shift();
							} else {
								if (parts[0]) {
									props.set(p.name, safeURIDecode(parts[0]));
								}
								parts.shift();
							}
						}
					}
				}

				if (parts.length === 0) {
					if (route.children) {
						const child = check(route.children, []);
						if (child) {
							return {
								route,
								props,
								child,
								_parsedRoute,
							};
						} else {
							continue forEachRouteLoop;
						}
					}

					if (route.hash != null && hash != null) {
						props.set(route.hash, safeURIDecode(hash));
					}

					if (route.query != null && queryString != null) {
						const queryObject = [...new URLSearchParams(queryString).entries()]
							.reduce((obj, entry) => ({ ...obj, [entry[0]]: entry[1] }), {});

						for (const q in route.query) {
							const as = route.query[q];
							if (queryObject[q]) {
								props.set(as, safeURIDecode(queryObject[q]));
							}
						}
					}

					return {
						route,
						props,
						_parsedRoute,
					};
				} else {
					if (route.children) {
						const child = check(route.children, parts);
						if (child) {
							return {
								route,
								props,
								child,
								_parsedRoute,
							};
						} else {
							continue forEachRouteLoop;
						}
					} else {
						continue forEachRouteLoop;
					}
				}
			}

			return null;
		}

		const _parts = path.split('/').filter(part => part.length !== 0);

		return check(this.routes, _parts);
	}

	private navigate(path: string, key: string | null | undefined, emitChange = true, _redirected = false): Resolved {
		const beforePath = this.currentPath;
		this.currentPath = path;

		const res = this.resolve(this.currentPath);

		if (res == null) {
			throw new Error('no route found for: ' + path);
		}

		if ('redirect' in res.route) {
			let redirectPath: string;
			if (typeof res.route.redirect === 'function') {
				redirectPath = res.route.redirect(res.props);
			} else {
				redirectPath = res.route.redirect + (res._parsedRoute.queryString ? '?' + res._parsedRoute.queryString : '') + (res._parsedRoute.hash ? '#' + res._parsedRoute.hash : '');
			}
			if (_DEV_) console.log('Redirecting to: ', redirectPath);
			if (_redirected && this.redirectCount++ > 10) {
				throw new Error('redirect loop detected');
			}
			return this.navigate(redirectPath, null, emitChange, true);
		}

		if (res.route.loginRequired && !this.isLoggedIn) {
			res.route.component = this.notFoundPageComponent;
			res.props.set('showLoginPopup', true);
		}

		const isSamePath = beforePath === path;
		if (isSamePath && key == null) key = this.currentKey;
		this.current = res;
		this.currentRef.value = res;
		this.currentRoute.value = res.route;
		this.currentKey = res.route.globalCacheKey ?? key ?? path;

		if (emitChange && res.route.path !== '/:(*)') {
			this.emit('change', {
				beforePath,
				path,
				resolved: res,
				key: this.currentKey,
			});
		}

		this.redirectCount = 0;
		return {
			...res,
			redirected: _redirected,
		};
	}

	public getCurrentPath() {
		return this.currentPath;
	}

	public getCurrentKey() {
		return this.currentKey;
	}

	public push(path: string, flag?: RouterFlag) {
		const beforePath = this.currentPath;
		if (path === beforePath) {
			this.emit('same');
			return;
		}
		if (this.navHook) {
			const cancel = this.navHook(path, flag);
			if (cancel) return;
		}
		const res = this.navigate(path, null);
		if (res.route.path === '/:(*)') {
			location.href = path;
		} else {
			this.emit('push', {
				beforePath,
				path: res._parsedRoute.fullPath,
				route: res.route,
				props: res.props,
				key: this.currentKey,
			});
		}
	}

	public replace(path: string, key?: string | null) {
		const res = this.navigate(path, key);
		this.emit('replace', {
			path: res._parsedRoute.fullPath,
			key: this.currentKey,
		});
	}
}

export function useScrollPositionManager(getScrollContainer: () => HTMLElement | null, router: IRouter) {
	const scrollPosStore = new Map<string, number>();

	onMounted(() => {
		const scrollContainer = getScrollContainer();
		if (scrollContainer == null) return;

		scrollContainer.addEventListener('scroll', () => {
			scrollPosStore.set(router.getCurrentKey(), scrollContainer.scrollTop);
		}, { passive: true });

		router.addListener('change', ctx => {
			const scrollPos = scrollPosStore.get(ctx.key) ?? 0;
			scrollContainer.scroll({ top: scrollPos, behavior: 'instant' });
			if (scrollPos !== 0) {
				window.setTimeout(() => { // 遷移直後はタイミングによってはコンポーネントが復元し切ってない可能性も考えられるため少し時間を空けて再度スクロール
					scrollContainer.scroll({ top: scrollPos, behavior: 'instant' });
				}, 100);
			}
		});

		router.addListener('same', () => {
			scrollContainer.scroll({ top: 0, behavior: 'smooth' });
		});
	});
}