import {
	getControllerOptions,
	getControllerPrefix,
} from "../decorators/Controller.ts";
import { getRoot, resolveViewRoot } from "../decorators/Root.ts";
import { getParamMetadata, type ParamMetadata } from "../decorators/Params.ts";
import { getRoutes, type RouteOptions } from "../decorators/Route.ts";
import { getViews, type ViewMetadata } from "../decorators/View.ts";
import type {
	Headers,
	HttpMethod,
	HttpResponse,
	StatusCode,
} from "../contracts/typegen/http/index.ts";
import type { RenderedView } from "../contracts/typegen/http/response.ts";
import type { RequestContext } from "../contracts/typegen/http/request.ts";
import { serveStaticFile } from "./http.ts";
import { existsSync } from "node:fs";
import { isAbsolute, resolve } from "node:path";
import type { ViewPath, ViewPropsOf } from "../contracts/typegen/views.ts";
import { RoutePipeline } from "./pipeline.ts";
import { getAuth } from "../decorators/Auth.ts";

/** Template rendered by a controller, the props are checked by the typegen. */
export interface ViewDescriptor<P extends string = string> {
	/** Template path, relative to the views directory or absolute. */
	template: P;
	/** Props handed to the template. */
	props?: P extends ViewPath ? ViewPropsOf<P> : Record<string, unknown>;
	/** Status code of the response. */
	status?: StatusCode;
	/** Headers of the response. */
	headers?: Headers;
}

export interface RouterOptions {
	/** Renders a view descriptor; injected by the application. */
	renderView?: (
		descriptor: ViewDescriptor,
		context: RequestContext,
	) => Promise<string | RenderedView> | string | RenderedView;
	pipeline?: RoutePipeline;
}

export interface RouteDefinition {
	method: HttpMethod;
	/** Full path, controller prefix included. */
	path: string;
	controller: object;
	methodName: string;
	options: RouteOptions;
	/** Template rendered by the route, declared with `@View()`. */
	view?: ResolvedView;
	/** Invokes the controller method with the resolved arguments. */
	invoke: (context: RequestContext) => Promise<unknown>;
}

export type RouteMatch =
	| { kind: "match"; route: RouteDefinition; params: Record<string, string> }
	| { kind: "method-not-allowed"; allowed: HttpMethod[] }
	| { kind: "not-found" };

/** Joins a controller prefix and a route path into a canonical path. */
export function joinPath(prefix: string, path: string): string {
	const raw = `${prefix}/${path}`.replace(/\/{2,}/g, "/");
	const trimmed = raw.replace(/\/+$/, "");
	return trimmed.length === 0 ? "/" : trimmed;
}

/** Splits a path into its segments. */
export function pathSegments(path: string): string[] {
	return path.split("/").filter((segment) => segment.length > 0);
}

/**
 * Matches the segments of a route against the segments of a request path.
 */
export function matchSegments(
	routeSegments: string[],
	requestSegments: string[],
): Record<string, string> | null {
	const params: Record<string, string> = {};

	for (let index = 0; index < routeSegments.length; index++) {
		const segment = routeSegments[index] as string;
		const actual = requestSegments[index];

		if (segment === "*") {
			params["*"] = requestSegments.slice(index).join("/");
			return params;
		}

		if (segment.startsWith(":")) {
			const optional = segment.endsWith("?");
			const name = segment.slice(1, optional ? -1 : undefined);
			if (actual === undefined) {
				if (optional) continue;
				return null;
			}
			params[name] = actual;
			continue;
		}

		if (actual === undefined || segment !== actual) return null;
	}

	if (requestSegments.length > routeSegments.length) return null;
	return params;
}

export interface RawRoute {
	method: string;
	path: string;
	handler: (
		request: Request,
		context: RequestContext,
	) => Promise<Response> | Response;
}

export interface StaticRoot {
	/** Prefix of the controller the files are served below. */
	prefix: string;
	/** Absolute path of the directory. */
	path: string;
}

/** A view of a controller, resolved against the view folder. */
export interface ResolvedView {
	/** Absolute path of the template. */
	path: string;
	/** Route of the template, derived from its path. */
	route: string;
	/** Name of the method the view belongs to. */
	propertyKey: string;
	method: HttpMethod;
	status?: StatusCode;
	name?: string;
	description?: string;
	params?: Record<string, string>;
}

/**
 * Resolves the template of a view.
 */
export function resolveView(
	view: ViewMetadata,
	viewRoot: string,
): ResolvedView {
	const absolute = isAbsolute(view.path)
		? view.path
		: resolve(viewRoot, view.path);
	const path = existsSync(absolute)
		? absolute
		: existsSync(`${absolute}.spug`)
			? `${absolute}.spug`
			: absolute;

	let relative = path.startsWith(`${viewRoot}/`)
		? path.slice(viewRoot.length + 1)
		: (path.split("/").pop() ?? path);
	relative = relative.replace(/\.[^./]+$/, "");

	const segments = relative.split("/").filter((segment) => segment.length > 0);
	if (segments.length > 0 && segments[segments.length - 1] === "index") {
		segments.pop();
	}

	return {
		path,
		route: segments.length === 0 ? "/" : `/${segments.join("/")}`,
		propertyKey: view.propertyKey,
		method: view.method,
		status: view.status,
		name: view.name,
		description: view.description,
		params: view.params,
	};
}

export class Router {
	private readonly routes: RouteDefinition[] = [];
	private readonly rawRoutes: RawRoute[] = [];
	private readonly staticRoots: StaticRoot[] = [];

	constructor(private readonly options: RouterOptions = {}) {}

	/**
	 * Adds a route that is not bound to a controller.
	 */
	raw(method: string, path: string, handler: RawRoute["handler"]): void {
		this.rawRoutes.push({ method: method.toUpperCase(), path, handler });
	}

	/** Registers every route declared on a controller instance. */
	register(controllerType: object, instance: unknown): void {
		const prefix = getControllerPrefix(controllerType);
		const routes = getRoutes(controllerType);
		const views = getViews(controllerType);
		const viewRoot = resolveViewRoot(
			controllerType,
			getControllerOptions(controllerType).dir ?? process.cwd(),
		);

		const root = getRoot(controllerType);
		if (root) {
			this.staticRoots.push({ prefix, path: root.path });
		}

		for (const route of routes) {
			const view = views.find(
				(entry) => entry.propertyKey === route.propertyKey,
			);
			this.routes.push({
				method: route.method,
				path: joinPath(prefix, route.path),
				controller: controllerType,
				methodName: route.propertyKey,
				options: route.options,
				view: view ? resolveView(view, viewRoot) : undefined,
				invoke: (context) =>
					this.invokeHandler(
						instance,
						route.propertyKey,
						getParamMetadata(controllerType, route.propertyKey),
						context,
					),
			});
		}

		for (const view of views) {
			if (routes.some((route) => route.propertyKey === view.propertyKey)) {
				continue;
			}
			const resolved = resolveView(view, viewRoot);
			this.routes.push({
				method: view.method,
				path: joinPath(prefix, resolved.route ?? "/"),
				controller: controllerType,
				methodName: view.propertyKey,
				options: {},
				view: resolved,
				invoke: (context) =>
					this.invokeHandler(
						instance,
						view.propertyKey,
						getParamMetadata(controllerType, view.propertyKey),
						context,
					),
			});
		}
	}

	/** Every registered route definition. */
	list(): RouteDefinition[] {
		return [...this.routes];
	}

	/** Every route that is not bound to a controller. */
	listRaw(): RawRoute[] {
		return [...this.rawRoutes];
	}

	/** Public route metadata for client navigation and route-aware components. */
	clientRoutes(): {
		name: string;
		description?: string;
		path: string;
		method: HttpMethod;
		params: Record<string, string>;
	}[] {
		return this.routes.map((route) => {
			const view = route.view;
			const params = Object.fromEntries(
				pathSegments(route.path)
					.filter((part) => part.startsWith(":"))
					.map((part) => {
						const key = part.slice(1).replace(/[?*]$/, "");
						return [
							key,
							route.options.params?.[key] ?? view?.params?.[key] ?? "",
						];
					}),
			);
			return {
				name: route.options.name ?? view?.name ?? route.methodName,
				description: route.options.description ?? view?.description,
				path: route.path,
				method: route.method,
				params,
			};
		});
	}

	/** Finds the route matching a method and path. */
	match(method: string, path: string): RouteMatch {
		const segments = pathSegments(path);
		const allowed = new Set<HttpMethod>();
		for (const route of this.routes) {
			const params = matchSegments(pathSegments(route.path), segments);
			if (!params) continue;
			if (route.method === method) {
				return { kind: "match", route, params };
			}
			allowed.add(route.method);
		}
		if (allowed.size > 0) {
			return { kind: "method-not-allowed", allowed: [...allowed] };
		}
		return { kind: "not-found" };
	}

	/** Executes a request and normalises the handler result into a response. */
	async handle(context: RequestContext): Promise<HttpResponse> {
		for (const route of this.rawRoutes) {
			if (route.method !== context.method) continue;
			if (
				route.path.endsWith("*")
					? !context.path.startsWith(route.path.slice(0, -1))
					: route.path !== context.path
			)
				continue;
			const response = await route.handler(context.raw as Request, context);
			return {
				status: response.status as StatusCode,
				headers: Object.fromEntries(response.headers.entries()),
				body: new Uint8Array(await response.arrayBuffer()),
			};
		}

		const match = this.match(context.method, context.path);
		if (match.kind === "not-found") {
			const asset = await this.serveStatic(context.path);
			if (asset) return asset;
			return {
				status: 404,
				headers: { "content-type": "text/plain; charset=utf-8" },
				body: "Not Found",
			};
		}
		if (match.kind === "method-not-allowed") {
			return {
				status: 405,
				headers: {
					"content-type": "text/plain; charset=utf-8",
					allow: match.allowed.join(", "),
				},
				body: "Method Not Allowed",
			};
		}

		context.params = match.params;
		context.locals.routes = this.clientRoutes();
		const blocked = await this.options.pipeline?.run(context, match.route);
		if (blocked) return blocked;
		const auth = getAuth(match.route.controller, match.route.methodName);
		if (auth) {
			const identity = context.locals.auth as { roles?: string[] } | undefined;
			if (
				!identity ||
				(auth.roles?.some((role) => !identity.roles?.includes(role)) ?? false)
			) {
				return {
					status: auth.redirect ? 302 : identity ? 403 : 401,
					headers: auth.redirect
						? { location: auth.redirect }
						: { "content-type": "text/plain; charset=utf-8" },
					body: auth.redirect ? undefined : "Unauthorized",
				};
			}
		}
		const result = await match.route.invoke(context);
		return this.toResponse(result, context, match.route);
	}

	/**
	 * Serves a file of the static root of a controller.
	 */
	private async serveStatic(path: string): Promise<HttpResponse | undefined> {
		const candidates = this.staticRoots
			.filter((root) => path.startsWith(root.prefix))
			.sort((left, right) => right.prefix.length - left.prefix.length);

		for (const candidate of candidates) {
			const relative = path.slice(candidate.prefix.length) || "/";
			const file = await serveStaticFile(candidate.path, relative);
			if (file) return file;
		}
		return undefined;
	}

	private async invokeHandler(
		instance: unknown,
		methodName: string,
		paramMetadata: Map<number, ParamMetadata>,
		context: RequestContext,
	): Promise<unknown> {
		const handler = (instance as Record<string, unknown>)[methodName];
		if (typeof handler !== "function") {
			throw new Error(`Controller method ${methodName} is not callable`);
		}

		if (paramMetadata.size === 0) {
			return (handler as (ctx: RequestContext) => unknown).call(
				instance,
				context,
			);
		}

		const args: unknown[] = [];
		for (const [index, meta] of paramMetadata) {
			args[index] = resolveParam(meta, context);
		}
		return (handler as (...args: unknown[]) => unknown).apply(instance, args);
	}

	private async toResponse(
		result: unknown,
		context: RequestContext,
		route: RouteDefinition,
	): Promise<HttpResponse> {
		const status = route.options.status ?? 200;

		if (route.view) {
			const descriptor: ViewDescriptor = isViewDescriptor(result)
				? result
				: {
						template: route.view.path,
						props: (result ?? {}) as Record<string, unknown>,
					};
			const rendered = await this.renderView(descriptor, context);
			return {
				status: descriptor.status ?? status,
				headers: {
					"content-type": "text/html; charset=utf-8",
					...(descriptor.headers ?? {}),
				},
				body: rendered,
			};
		}

		if (result === undefined || result === null) {
			return { status, headers: {}, body: result ?? undefined };
		}

		if (isHttpResponse(result)) {
			return {
				status: result.status,
				headers: result.headers ?? {},
				body: result.body,
			};
		}

		if (isViewDescriptor(result)) {
			const rendered = await this.renderView(result, context);
			return {
				status: result.status ?? status,
				headers: {
					"content-type": "text/html; charset=utf-8",
					...(result.headers ?? {}),
				},
				body: rendered,
			};
		}

		if (typeof result === "string") {
			return {
				status,
				headers: { "content-type": "text/html; charset=utf-8" },
				body: result,
			};
		}

		return {
			status,
			headers: { "content-type": "application/json; charset=utf-8" },
			body: result,
		};
	}

	private async renderView(
		descriptor: ViewDescriptor,
		context: RequestContext,
	): Promise<string | ReadableStream<Uint8Array>> {
		const renderer = this.options.renderView;
		if (!renderer) {
			throw new Error(
				`Template "${descriptor.template}" cannot be rendered: no view renderer configured`,
			);
		}
		const rendered = await renderer(descriptor, context);
		if (typeof rendered === "string") return rendered;
		if (rendered.deferred && rendered.deferred.length > 0) {
			return toStream(rendered);
		}
		return rendered.html;
	}
}

/** Builds a stream that sends the shell first and the deferred chunks after. */
export function toStream(rendered: RenderedView): ReadableStream<Uint8Array> {
	const encoder = new TextEncoder();
	return new ReadableStream<Uint8Array>({
		async start(controller) {
			controller.enqueue(encoder.encode(rendered.html));
			for (const chunk of rendered.deferred ?? []) {
				const content = await chunk.content;
				controller.enqueue(
					encoder.encode(
						`<div data-muddle-deferred="${chunk.id}">${content}</div>`,
					),
				);
			}
			controller.close();
		},
	});
}

function resolveParam(meta: ParamMetadata, context: RequestContext): unknown {
	switch (meta.kind) {
		case "param":
			return meta.name
				? (context.params as Record<string, string>)[meta.name]
				: context.params;
		case "body":
			return context.body;
		case "form":
			return context.form;
		case "query":
			return meta.name ? context.query[meta.name] : context.query;
		case "request":
			return context;
		case "response":
			return context.respond;
		case "locals":
			return context.locals;
	}
}

function isHttpResponse(value: unknown): value is HttpResponse {
	return (
		typeof value === "object" &&
		value !== null &&
		typeof (value as HttpResponse).status === "number" &&
		"headers" in value
	);
}

function isViewDescriptor(value: unknown): value is ViewDescriptor {
	return (
		typeof value === "object" &&
		value !== null &&
		typeof (value as ViewDescriptor).template === "string"
	);
}