import cookieSession from "cookie-session";
import express, { type NextFunction, type Request, type Response } from "express";

import { loadConfig } from "./config.ts";
import { beginAuth, completeAuth, isAuthorised } from "./oidc.ts";
import { deniedPage, pairingPage, qrPayload } from "./pages.ts";
import { TokenStore } from "./tokens.ts";
import { UploadDir, isValidObjectName } from "./upload.ts";

const config = loadConfig();
const tokens = new TokenStore(config.stateDir, config.pairingCodeTtlSeconds * 1000);
const uploads = new UploadDir(config.downloadsDir, config.maxUploadBytes);

const app = express();
app.disable("x-powered-by");
// TLS terminates at the Cilium ingress; without this `secure` cookies die.
app.set("trust proxy", 1);

app.use(
  cookieSession({
    name: "puploader",
    secret: config.cookieSecret,
    httpOnly: true,
    sameSite: "lax",
    secure: true,
    maxAge: 8 * 60 * 60 * 1000,
  }),
);

app.get("/healthz", (_req, res) => {
  res.type("text/plain").send("ok");
});

/** Browser SSO gate: redirects to authentik when there is no session. */
function requireBrowserSso(req: Request, res: Response, next: NextFunction): void {
  const session = req.session as CookieSessionInterfaces.CookieSessionObject;
  if (typeof session.username === "string") {
    next();
    return;
  }
  beginAuth(config)
    .then((auth) => {
      session.oidcState = auth.state;
      session.oidcVerifier = auth.codeVerifier;
      session.returnTo = req.path;
      res.redirect(auth.url);
    })
    .catch(next);
}

app.get("/oidc/callback", (req, res, next) => {
  const session = req.session as CookieSessionInterfaces.CookieSessionObject;
  const state = session.oidcState;
  const codeVerifier = session.oidcVerifier;
  if (typeof state !== "string" || typeof codeVerifier !== "string") {
    res.status(400).type("text/plain").send("no login in progress");
    return;
  }
  completeAuth(config, req, { state, codeVerifier })
    .then((identity) => {
      delete session.oidcState;
      delete session.oidcVerifier;
      if (!isAuthorised(config, identity)) {
        res.status(403).type("html").send(deniedPage(identity.username, config.oidc.requiredGroup));
        return;
      }
      session.username = identity.username;
      const returnTo = typeof session.returnTo === "string" ? session.returnTo : "/";
      delete session.returnTo;
      res.redirect(returnTo);
    })
    .catch(next);
});

app.get("/", requireBrowserSso, (req, res, next) => {
  const session = req.session as CookieSessionInterfaces.CookieSessionObject;
  const username = session.username as string;
  const pairing = tokens.issuePairingCode(username);
  pairingPage(username, qrPayload(config.publicOrigin, pairing.code), config.pairingCodeTtlSeconds)
    .then((html) => res.type("html").send(html))
    .catch(next);
});

/**
 * App-initiated SSO: the app opens this in a Custom Tab; after the same
 * browser login the pairing code goes back through the deep link. The app
 * never sees OIDC — the phone's browser does, exactly like the QR path.
 */
app.get("/pair/app", requireBrowserSso, (req, res) => {
  const session = req.session as CookieSessionInterfaces.CookieSessionObject;
  const pairing = tokens.issuePairingCode(session.username as string);
  res.redirect(`${config.appScheme}://pair?c=${pairing.code}`);
});

app.post("/api/pair", express.json({ limit: "4kb" }), (req, res) => {
  const code = (req.body as { code?: unknown })?.code;
  if (typeof code !== "string" || !/^[0-9a-f]{64}$/.test(code)) {
    res.status(400).json({ error: "malformed pairing code" });
    return;
  }
  const redeemed = tokens.redeemPairingCode(code);
  if (!redeemed) {
    res.status(410).json({ error: "pairing code expired or already used" });
    return;
  }
  console.log(`paired device #${tokens.deviceCount} for ${redeemed.username}`);
  res.json({ token: redeemed.token, name: redeemed.username });
});

/** Bearer gate for the upload API. */
function requireDeviceToken(req: Request, res: Response, next: NextFunction): void {
  const header = req.headers.authorization ?? "";
  const token = header.startsWith("Bearer ") ? header.slice(7) : undefined;
  const username = token ? tokens.authenticate(token) : undefined;
  if (!username) {
    res.status(401).json({ error: "invalid device token" });
    return;
  }
  res.locals.username = username;
  next();
}

app.head("/api/object/:name", requireDeviceToken, (req, res) => {
  const name = req.params.name;
  if (typeof name !== "string" || !isValidObjectName(name)) {
    res.status(400).end();
    return;
  }
  uploads
    .exists(name)
    .then((exists) => res.status(exists ? 204 : 404).end())
    .catch(() => res.status(500).end());
});

app.put("/api/upload", requireDeviceToken, (req, res, next) => {
  const name = req.query.name;
  if (typeof name !== "string" || !isValidObjectName(name)) {
    res.status(400).json({ error: "name must be <sha256 hex>.<extension>" });
    return;
  }
  uploads
    .receive(name, req)
    .then((outcome) => {
      switch (outcome.status) {
        case "created":
          console.log(`stored ${name} for ${res.locals.username}`);
          res.status(201).json({ stored: name });
          return;
        case "exists":
          res.status(200).json({ stored: name, existed: true });
          return;
        case "hash-mismatch":
          res.status(409).json({ error: "content hash mismatch", actual: outcome.actual });
          return;
        case "too-large":
          res.status(413).json({ error: "upload exceeds the configured maximum" });
          return;
      }
    })
    .catch(next);
});

// Uniform error surface; the details go to the log, not the client.
app.use((error: unknown, _req: Request, res: Response, _next: NextFunction) => {
  console.error(error);
  if (!res.headersSent) {
    res.status(500).json({ error: "internal error" });
  }
});

async function main(): Promise<void> {
  await uploads.init();
  app.listen(config.port, () => {
    console.log(`internaluploader-server listening on :${config.port}`);
  });
}

void main();