import { serve } from "bun";
import { join, normalize, sep } from "node:path";
import { ensureIcons, ICONS_DIR } from "../scripts/generate-icons.ts";
import { injectPrecacheManifest } from "./pwa/precache.ts";
import { auth } from "./server/auth.ts";
import { AUTH_ENABLED } from "./server/flags.ts";
import { transcribe } from "./server/transcribe.ts";

const ROOT = join(import.meta.dir, "..");
const IS_PRODUCTION = process.env.NODE_ENV === "production";

// ---------------------------------------------------------------------------
// Shared static helpers
// ---------------------------------------------------------------------------

const NOT_FOUND = () => new Response("Not Found", { status: 404 });

// onnxruntime-web fetches its .wasm binaries at runtime — from the jsdelivr
// CDN by default, which would break offline. The worker points
// `env.backends.onnx.wasm.wasmPaths` at /ort/ instead (see
// src/worker/inference.worker.ts), we serve the files from node_modules
// here (production: copied into dist/ort by scripts/build.ts), and the
// service worker runtime-caches them cache-first.
const ORT_DIST = join(ROOT, "node_modules/onnxruntime-web/dist");
export const ORT_FILE_RE = /^ort-wasm-simd-threaded(\.jsep|\.jspi|\.asyncify)?\.(wasm|mjs)$/;

const CONTENT_TYPES: Record<string, string> = {
  ".wasm": "application/wasm",
  ".mjs": "text/javascript; charset=utf-8",
  ".webmanifest": "application/manifest+json",
};

function contentTypeFor(path: string): string | undefined {
  const dot = path.lastIndexOf(".");
  return dot === -1 ? undefined : CONTENT_TYPES[path.slice(dot)];
}

async function serveFile(path: string, cacheControl?: string): Promise<Response> {
  const file = Bun.file(path);
  if (!(await file.exists())) return NOT_FOUND();
  const headers = new Headers();
  const type = contentTypeFor(path);
  if (type) headers.set("Content-Type", type);
  if (cacheControl) headers.set("Cache-Control", cacheControl);
  return new Response(file, { headers });
}

async function serveOrtFile(dir: string, name: string): Promise<Response> {
  if (!ORT_FILE_RE.test(name)) return NOT_FOUND();
  return serveFile(join(dir, name));
}

// ---------------------------------------------------------------------------
// API dispatcher — shared by development and production so /api/* behaves
// identically in both serve modes (the SW treats it as network-only, D-007).
// Auth endpoints are M4 (src/server/auth.ts); /api/transcribe joins in M5.
// ---------------------------------------------------------------------------

async function handleApiRequest(request: Request): Promise<Response> {
  const { pathname } = new URL(request.url);
  const apiIndex = pathname.indexOf("/api/");
  const apiPath = apiIndex !== -1 ? pathname.slice(apiIndex) : pathname;

  // Runtime feature flag (D-015): with auth disabled, the endpoints don't
  // exist — the client's /me probe reads the 404 as "feature off". The
  // server engine (M5) is session-gated, so it disappears along with auth.
  if (
    !AUTH_ENABLED &&
    (apiPath.startsWith("/api/auth/") || apiPath.startsWith("/api/transcribe"))
  ) {
    return NOT_FOUND();
  }
  switch (`${request.method} ${apiPath}`) {
    case "POST /api/auth/register":
      return auth.register(request);
    case "POST /api/auth/login":
      return auth.login(request);
    case "POST /api/auth/logout":
      return auth.logout(request);
    case "GET /api/auth/me":
      return auth.me(request);
    // Server engine (M5, D-011/D-013): availability probe + streamed run.
    case "GET /api/transcribe/status":
      return transcribe.status(request);
    case "POST /api/transcribe":
      return transcribe.post(request);
    default:
      return NOT_FOUND();
  }
}

// ---------------------------------------------------------------------------
// Production: serve the prebuilt dist/ directory (created by `bun run build`)
// so the URLs match the hashed asset paths precached by dist/sw.js (D-007).
// ---------------------------------------------------------------------------

type ServeOptions = Parameters<typeof serve>[0];

async function productionServeOptions(): Promise<ServeOptions> {
  const dist = join(ROOT, "dist");
  if (!(await Bun.file(join(dist, "sw.js")).exists())) {
    throw new Error("dist/ is missing or incomplete — run `bun run build` first.");
  }
  return {
    development: false,
    async fetch(request) {
      const url = new URL(request.url);
      // API routes are dynamic (M4/M5) and network-only in the SW (D-007).
      if (url.pathname.includes("/api/")) return handleApiRequest(request);

      let relative = url.pathname === "/" ? "index.html" : decodeURIComponent(url.pathname.slice(1));
      if (relative.endsWith("/")) relative += "index.html";
      
      let path = normalize(join(dist, relative));
      
      // Auto-strip proxy subpaths for static assets
      while (relative.includes("/") && !(await Bun.file(path).exists())) {
        relative = relative.substring(relative.indexOf("/") + 1);
        path = normalize(join(dist, relative));
      }

      if (!path.startsWith(dist + sep) && path !== dist) return NOT_FOUND(); // traversal guard

      const response = await serveFile(
        path,
        // Hashed chunks are immutable; everything else must revalidate so the
        // SW update flow sees new versions.
        /(^|\/)(chunk|index)-[a-z0-9]+\./.test(relative)
          ? "public, max-age=31536000, immutable"
          : "no-cache",
      );
      if (response.status !== 404) return response;
      // SPA fallback: serve the app shell for unknown navigations.
      return serveFile(join(dist, "index.html"), "no-cache");
    },
  };
}

// ---------------------------------------------------------------------------
// Development: HTML imports + on-the-fly bundles
// ---------------------------------------------------------------------------

/**
 * Bun's bundler does not currently follow `new Worker(...)` graphs (verified
 * with Bun 1.3: both `bun build` and the dev server leave the call untouched),
 * so worker-like entrypoints are bundled at startup and served from stable
 * URLs. The UI spawns `new Worker("/inference.worker.js")`; the service
 * worker registers as "/sw.js".
 */
async function bundleEntrypoint(relativePath: string): Promise<string> {
  const build = await Bun.build({
    entrypoints: [join(import.meta.dir, relativePath)],
    target: "browser",
    format: "esm",
    // Never minify: sw.ts relies on its placeholder string literals surviving
    // bundling verbatim (src/pwa/precache.ts), and dev builds favor debuggability.
    minify: false,
  });
  const artifact = build.outputs[0];
  if (!artifact) throw new Error(`Failed to bundle src/${relativePath}`);
  return artifact.text();
}

async function developmentServeOptions(): Promise<ServeOptions> {
  // src/pwa/icons/*.png are generated, not checked in; index.html links them,
  // so they must exist before the HTML import bundles it.
  await ensureIcons();
  const { default: index } = await import("./index.html");

  const workerScript = await bundleEntrypoint("./worker/inference.worker.ts");
  // Dev SW: empty precache list — assets are unhashed here, so the shell is
  // runtime-cached network-first instead (see src/pwa/sw.ts).
  const swScript = injectPrecacheManifest(
    await bundleEntrypoint("./pwa/sw.ts"),
    [],
    "dev",
  );
  const scriptHeaders = { "Content-Type": "text/javascript; charset=utf-8" };

  return {
    routes: {
      // The HTML import is an HTMLBundle, which Bun only serves as a route
      // value — returning it from fetch() throws "Expected a Response object".
      "/": index,
    },

    // Fallback for everything the route table doesn't match, including
    // subpath-proxied requests (/proxy/api/..., /proxy/sw.js, ...).
    async fetch(request, server) {
      const url = new URL(request.url);
      const pathname = url.pathname;

      if (pathname.includes("/api/")) return handleApiRequest(request);

      if (pathname.endsWith("/inference.worker.js")) {
        return new Response(workerScript, { headers: scriptHeaders });
      }
      if (pathname.endsWith("/sw.js")) {
        return new Response(swScript, { headers: { ...scriptHeaders, "Cache-Control": "no-cache" } });
      }
      if (pathname.endsWith("/manifest.webmanifest")) {
        return serveFile(join(import.meta.dir, "pwa/manifest.webmanifest"));
      }

      const iconsMatch = pathname.match(/\/icons\/(icon-\d+\.png)$/);
      if (iconsMatch?.[1]) {
        return serveFile(join(ICONS_DIR, iconsMatch[1]));
      }

      const ortMatch = pathname.match(/\/ort\/(.*(?:wasm|mjs))$/);
      if (ortMatch?.[1]) {
        return serveOrtFile(ORT_DIST, ortMatch[1]);
      }

      // SPA fallback: unknown navigations (including subpath ones) get the
      // app shell. The HTMLBundle itself can only live in `routes`, so
      // re-enter the server at "/" to let it produce the dev-bundled HTML.
      return fetch(new URL("/", server.url));
    },

    development: {
      // Enable browser hot reloading in development
      hmr: true,

      // Echo console logs from the browser to the server
      console: true,
    },
  };
}

// ---------------------------------------------------------------------------

const options = IS_PRODUCTION ? await productionServeOptions() : await developmentServeOptions();
options.port = process.env.PORT || 3000;

const server = serve(options);

console.log(
  `Server running at ${server.url} (${IS_PRODUCTION ? "production, serving dist/" : "development"})`,
);