import {
  generateRegistrationOptions,
  verifyRegistrationResponse,
  generateAuthenticationOptions,
  verifyAuthenticationResponse,
} from "@simplewebauthn/server";
import { isoBase64URL } from "@simplewebauthn/server/helpers";
import type {
  RegistrationResponseJSON,
  AuthenticationResponseJSON,
} from "@simplewebauthn/server";
import {
  createUser,
  getUserByUsername,
  getUserById,
  storeCredential,
  getCredentialById,
  updateCredentialCounter,
  createSession,
  getSession,
  deleteSession,
} from "./db";

const RP_NAME = "shukudai";

// Temporary challenge store (in-memory, keyed by random ID → challenge + metadata)
const challenges = new Map<
  string,
  { challenge: string; userId?: number; expires: number }
>();

// Cleanup expired challenges periodically
setInterval(() => {
  const now = Date.now();
  for (const [key, val] of challenges) {
    if (val.expires < now) challenges.delete(key);
  }
}, 60_000);

function getRpId(req: Request): string {
  const url = new URL(req.url);
  return url.hostname;
}

function getOrigin(req: Request): string {
  const url = new URL(req.url);
  return url.origin;
}

function getCookie(req: Request, name: string): string | undefined {
  const cookies = req.headers.get("cookie");
  if (!cookies) return undefined;
  const match = cookies.split(";").find((c) => c.trim().startsWith(`${name}=`));
  return match?.split("=").slice(1).join("=").trim();
}

function sessionCookie(token: string, maxAge = 7 * 24 * 60 * 60): string {
  return `session=${token}; HttpOnly; SameSite=Strict; Path=/; Max-Age=${maxAge}`;
}

function challengeCookie(key: string): string {
  return `challenge_key=${key}; HttpOnly; SameSite=Strict; Path=/; Max-Age=120`;
}

function clearChallengeCookie(): string {
  return `challenge_key=; HttpOnly; SameSite=Strict; Path=/; Max-Age=0`;
}

// ---- Route handlers ----

export async function registerOptions(req: Request): Promise<Response> {
  const { username } = (await req.json()) as { username: string };
  if (!username || username.length < 1 || username.length > 32) {
    return Response.json(
      { error: "Username must be 1-32 characters" },
      { status: 400 },
    );
  }

  // Check if username already taken
  const existing = await getUserByUsername(username);
  if (existing) {
    return Response.json({ error: "Username already taken" }, { status: 409 });
  }

  // Create user
  const user = await createUser(username);

  const rpID = getRpId(req);
  const options = await generateRegistrationOptions({
    rpName: RP_NAME,
    rpID,
    userName: username,
    userID: isoBase64URL.toBuffer(
      isoBase64URL.fromUTF8String(user.id.toString()),
    ),
    attestationType: "none",
    authenticatorSelection: {
      residentKey: "required",
      userVerification: "preferred",
    },
  });

  // Store challenge
  const challengeKey = crypto.randomUUID();
  challenges.set(challengeKey, {
    challenge: options.challenge,
    userId: user.id,
    expires: Date.now() + 120_000,
  });

  return new Response(JSON.stringify(options), {
    headers: {
      "Content-Type": "application/json",
      "Set-Cookie": challengeCookie(challengeKey),
    },
  });
}

export async function registerVerify(req: Request): Promise<Response> {
  const body = (await req.json()) as RegistrationResponseJSON;
  const challengeKey = getCookie(req, "challenge_key");
  if (!challengeKey) {
    return Response.json({ error: "No challenge found" }, { status: 400 });
  }

  const stored = challenges.get(challengeKey);
  if (!stored || stored.expires < Date.now()) {
    challenges.delete(challengeKey!);
    return Response.json({ error: "Challenge expired" }, { status: 400 });
  }
  challenges.delete(challengeKey);

  const rpID = getRpId(req);
  const origin = getOrigin(req);

  let verification;
  try {
    verification = await verifyRegistrationResponse({
      response: body,
      expectedChallenge: stored.challenge,
      expectedOrigin: origin,
      expectedRPID: rpID,
    });
  } catch (err) {
    return Response.json(
      { error: `Verification failed: ${err}` },
      { status: 400 },
    );
  }

  if (!verification.verified || !verification.registrationInfo) {
    return Response.json({ error: "Verification failed" }, { status: 400 });
  }

  const { credential } = verification.registrationInfo;
  await storeCredential(
    credential.id,
    stored.userId!,
    isoBase64URL.fromBuffer(credential.publicKey),
    credential.counter,
    credential.transports,
  );

  // Create session
  const token = await createSession(stored.userId!);
  const user = await getUserById(stored.userId!);

  return new Response(
    JSON.stringify({ verified: true, username: user?.username }),
    {
      headers: {
        "Content-Type": "application/json",
        "Set-Cookie": [sessionCookie(token), clearChallengeCookie()].join(", "),
      },
    },
  );
}

export async function loginOptions(req: Request): Promise<Response> {
  const rpID = getRpId(req);

  const options = await generateAuthenticationOptions({
    rpID,
    userVerification: "preferred",
    // Empty allowCredentials = discoverable credentials (passkey prompt)
  });

  const challengeKey = crypto.randomUUID();
  challenges.set(challengeKey, {
    challenge: options.challenge,
    expires: Date.now() + 120_000,
  });

  return new Response(JSON.stringify(options), {
    headers: {
      "Content-Type": "application/json",
      "Set-Cookie": challengeCookie(challengeKey),
    },
  });
}

export async function loginVerify(req: Request): Promise<Response> {
  const body = (await req.json()) as AuthenticationResponseJSON;
  const challengeKey = getCookie(req, "challenge_key");
  if (!challengeKey) {
    return Response.json({ error: "No challenge found" }, { status: 400 });
  }

  const stored = challenges.get(challengeKey);
  if (!stored || stored.expires < Date.now()) {
    challenges.delete(challengeKey!);
    return Response.json({ error: "Challenge expired" }, { status: 400 });
  }
  challenges.delete(challengeKey);

  // Look up credential
  const credentialId = body.id;
  const credential = await getCredentialById(credentialId);
  if (!credential) {
    return Response.json({ error: "Unknown credential" }, { status: 400 });
  }

  const rpID = getRpId(req);
  const origin = getOrigin(req);

  let verification;
  try {
    verification = await verifyAuthenticationResponse({
      response: body,
      expectedChallenge: stored.challenge,
      expectedOrigin: origin,
      expectedRPID: rpID,
      credential: {
        id: credential.id,
        publicKey: isoBase64URL.toBuffer(credential.public_key),
        counter: credential.counter,
        transports: credential.transports
          ? JSON.parse(credential.transports)
          : undefined,
      },
    });
  } catch (err) {
    return Response.json(
      { error: `Verification failed: ${err}` },
      { status: 400 },
    );
  }

  if (!verification.verified) {
    return Response.json({ error: "Verification failed" }, { status: 400 });
  }

  // Update counter
  await updateCredentialCounter(
    credentialId,
    verification.authenticationInfo.newCounter,
  );

  // Create session
  const token = await createSession(credential.user_id);
  const user = await getUserById(credential.user_id);

  return new Response(
    JSON.stringify({ verified: true, username: user?.username }),
    {
      headers: {
        "Content-Type": "application/json",
        "Set-Cookie": [sessionCookie(token), clearChallengeCookie()].join(", "),
      },
    },
  );
}

export async function me(req: Request): Promise<Response> {
  const token = getCookie(req, "session");
  if (!token) {
    return Response.json({ user: null });
  }

  const session = await getSession(token);
  if (!session) {
    return new Response(JSON.stringify({ user: null }), {
      headers: {
        "Content-Type": "application/json",
        "Set-Cookie": sessionCookie("", 0), // clear expired cookie
      },
    });
  }

  return Response.json({
    user: { id: session.user_id, username: session.username },
  });
}

export async function logout(req: Request): Promise<Response> {
  const token = getCookie(req, "session");
  if (token) {
    await deleteSession(token);
  }
  return new Response(JSON.stringify({ ok: true }), {
    headers: {
      "Content-Type": "application/json",
      "Set-Cookie": sessionCookie("", 0),
    },
  });
}