import { mkdir, rename, rm, writeFile } from "node:fs/promises";
import { dirname, join, resolve } from "node:path";
import type { App } from "../core/app.ts";
import { getRenderAhead } from "../decorators/RenderAhead.ts";
import { getRenderRoutes, type RenderRouteSource } from "../decorators/RenderRoute.ts";
import { ContentRegistry } from "../core/content.ts";
import { predictLayout, type LayoutPredictionOptions } from "./prediction.ts";

export interface PrerenderOptions {
	/** Routes that are rendered at build time. */
	routes?: string[];
	/** Directory the html files are written to. */
	outDir: string;
	/** Hostname used while rendering, defaults to `localhost`. */
	hostname?: string;
	/** Protocol used while rendering. */
	protocol?: string;
	/** Adds discovered dynamic routes before rendering. */
	discover?: (pattern: string) => Promise<string[]> | string[];
	progress?: (event: { current: number; total: number; route: string }) => void;
	predict?: LayoutPredictionOptions;
}

export interface PrerenderResult {
	/** Rendered route. */
	route: string;
	/** File the html was written to. */
	file: string;
	/** Status code of the response. */
	status: number;
}

/** Renders the routes of the application into static html files. */
export async function prerender(
	app: App,
	options: PrerenderOptions,
): Promise<PrerenderResult[]> {
	const outDir = resolve(options.outDir);
	const stageDir = `${outDir}.staging`;
	await rm(stageDir, { recursive: true, force: true });
	await mkdir(stageDir, { recursive: true });
	const origin = `${options.protocol ?? "http"}://${options.hostname ?? "localhost"}`;
	const results: PrerenderResult[] = [];

	const routes = new Set(options.routes ?? []);
	const content = app.resolvedConfig ? new ContentRegistry(app.resolvedConfig) : undefined;
	if (content) await content.load();
	for (const route of app.router.list()) {
		if (route.method !== "GET") continue;
		if (!route.path.includes(":")) routes.add(route.path);
		else {
			for (const source of getRenderRoutes(route.controller, route.methodName)) {
				for (const path of resolveRenderRoute(source, content)) routes.add(path);
			}
			const ahead = getRenderAhead(route.controller, route.methodName);
			const values = ahead ? (typeof ahead === "function" ? await ahead() : ahead) : await options.discover?.(route.path);
			for (const value of values ?? []) routes.add(value.startsWith("/") ? value : route.path.replace(/:[^/]+\??/, value));
		}
	}
	const orderedRoutes = [...routes].sort();
	for (const [index, route] of orderedRoutes.entries()) {
		if (app.router.match("GET", route).kind === "not-found") {
			throw new Error(`Cannot prerender unknown route "${route}"`);
		}
		options.progress?.({ current: index + 1, total: orderedRoutes.length, route });
		const request = new Request(new URL(route, origin).toString());
		const response = await app.fetch(request);
		const contentType = response.headers.get("content-type") ?? "";

		if (response.status >= 300 && response.status < 400) {
			const location = response.headers.get("location");
			if (location) {
				console.log(`muddle: ${route} redirects to ${location}, skipped`);
			}
			continue;
		}

		if (!contentType.includes("text/html")) {
			continue;
		}

		let html = await response.text();
		// Relation anchors and STCSS prediction markers are static inputs to the
		// layout pass. Run Playwright automatically so consumers never need to
		// ship a geometry bridge merely because a page uses `$refer`.
		const hasRelations = /data-muddle-anchor|muddle-predict\s*:|--muddle-relate-/.test(html);
		if (options.predict || hasRelations) {
			const assetHtml = await inlinePredictionStyles(app, html, origin);
			html = (await predictLayout(assetHtml, options.predict ?? {})).html;
		}
		const file = fileFor(stageDir, route);
		await mkdir(dirname(file), { recursive: true });
		const asset = await app.transformAsset({ path: file, contentType, content: html });
		const reports = await app.analyzePage({ route, html: await inlinePredictionStyles(app, html, origin) });
		if (Object.keys(reports).length) await writeFile(`${file}.analysis.json`, JSON.stringify(reports, null, 2));
		await writeFile(file, asset.content);
		results.push({ route, file, status: response.status });
	}

	for (const route of app.router.listRaw()) {
		if (route.method !== "GET") continue;
		if (route.path.includes("*")) continue;
		const request = new Request(new URL(route.path, origin).toString());
		const response = await app.fetch(request);
		const file = join(stageDir, route.path.replace(/^\//, ""));
		await mkdir(dirname(file), { recursive: true });
		const contentType = response.headers.get("content-type") ?? "application/octet-stream";
		const asset = await app.transformAsset({ path: file, contentType, content: new Uint8Array(await response.arrayBuffer()) });
		await writeFile(file, asset.content);
		results.push({ route: route.path, file, status: response.status });
	}

	const backup = `${outDir}.previous`;
	await rm(backup, { recursive: true, force: true });
	try {
		await rename(outDir, backup);
	} catch (error) {
		if ((error as NodeJS.ErrnoException).code !== "ENOENT") throw error;
	}
	await rename(stageDir, outDir);
	return results;
}

/** Inlines same-origin styles so Playwright can measure a complete document. */
export async function inlinePredictionStyles(app: App, html: string, origin: string): Promise<string> {
	for (const match of [...html.matchAll(/<link\b[^>]*href="([^"]+)"[^>]*>/g)]) {
		const url = new URL(match[1]!, origin);
		if (url.origin !== origin || !match[0].includes('rel="stylesheet"')) continue;
		const response = await app.fetch(new Request(url.href));
		if (response.ok) html = html.replace(match[0], `<style>${await response.text()}</style>`);
	}
	return html;
}

function resolveRenderRoute(source: RenderRouteSource, content?: ContentRegistry): string[] {
	if (typeof source === "string") return [source];
	if (Array.isArray(source)) return source;
	return (content?.entries(source.collection) ?? []).map((entry) => source.path.replace(/:id\??/g, encodeURIComponent(entry.id)));
}

/** Path of the html file of a route. */
export function fileFor(outDir: string, route: string): string {
	const clean = route.split("?")[0] ?? "/";
	if (clean === "/" || clean === "") return join(outDir, "index.html");
	const segments = clean.split("/").filter((segment) => segment.length > 0);
	const last = segments.pop();
	if (segments.length === 0) {
		return join(outDir, `${last as string}.html`);
	}
	return join(outDir, ...segments, last as string, "index.html");
}