/**
 * Single-user passkey auth + favorites.
 *
 * - どのパスキーでログインしても同じ「オーナー」としてログインする（ユーザーは1人）
 * - 未ログイン時のパスキー登録は、DATA_DIR/registration-token に書かれたトークンが必要
 *   - パスキーが1つも無ければ起動後の初回アクセス時に自動生成される
 *   - 全デバイスを失った場合は、このファイルを手で作れば再登録できる
 * - ログイン済みなら追加のパスキー（別デバイス）をトークン無しで登録できる
 */
import crypto from "crypto";
import fs from "fs";
import path from "path";
import {
  generateAuthenticationOptions,
  generateRegistrationOptions,
  verifyAuthenticationResponse,
  verifyRegistrationResponse,
  type AuthenticationResponseJSON,
  type RegistrationResponseJSON,
} from "@simplewebauthn/server";
import { DATA_DIR, getDb, normalizeTerm } from "./db.server";

const SESSION_COOKIE = "sid";
const CHALLENGE_COOKIE = "wa_chal";
const SESSION_DAYS = 90;
const CHALLENGE_MINUTES = 5;
const RP_NAME = "ライブに行くしかない";
const TOKEN_PATH = path.join(DATA_DIR, "registration-token");

// ---------- Request helpers ----------

/** Origin/RP ID as seen by the browser. Behind Caddy, the app itself receives plain http. */
function relyingParty(request: Request): { origin: string; rpID: string } {
  const url = new URL(request.url);
  const host = request.headers.get("x-forwarded-host") ?? request.headers.get("host") ?? url.host;
  const proto = request.headers.get("x-forwarded-proto") ?? url.protocol.replace(/:$/, "");
  return { origin: `${proto}://${host}`, rpID: host.replace(/:\d+$/, "") };
}

function readCookie(request: Request, name: string): string | null {
  const header = request.headers.get("cookie");
  if (!header) return null;
  for (const part of header.split(";")) {
    const [k, ...v] = part.trim().split("=");
    if (k === name) return decodeURIComponent(v.join("="));
  }
  return null;
}

function cookie(request: Request, name: string, value: string, maxAgeSec: number): string {
  const secure = relyingParty(request).origin.startsWith("https:") ? "; Secure" : "";
  return `${name}=${encodeURIComponent(value)}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${maxAgeSec}${secure}`;
}

function sqlTimeIn(seconds: number): string {
  return new Date(Date.now() + seconds * 1000).toISOString().replace("T", " ").slice(0, 19);
}

// ---------- Sessions ----------

export function isLoggedIn(request: Request): boolean {
  const sid = readCookie(request, SESSION_COOKIE);
  if (!sid) return false;
  const row = getDb()
    .prepare("SELECT 1 FROM sessions WHERE id = ? AND expires_at > datetime('now')")
    .get(sid);
  return !!row;
}

export function requireLogin(request: Request): void {
  if (!isLoggedIn(request)) {
    const url = new URL(request.url);
    throw new Response(null, {
      status: 302,
      headers: { Location: `/login?next=${encodeURIComponent(url.pathname + url.search)}` },
    });
  }
}

function createSession(request: Request): string {
  const db = getDb();
  db.prepare("DELETE FROM sessions WHERE expires_at <= datetime('now')").run();
  const sid = crypto.randomBytes(32).toString("base64url");
  const maxAge = SESSION_DAYS * 86400;
  db.prepare("INSERT INTO sessions (id, expires_at) VALUES (?, ?)").run(sid, sqlTimeIn(maxAge));
  return cookie(request, SESSION_COOKIE, sid, maxAge);
}

export function logout(request: Request): string {
  const sid = readCookie(request, SESSION_COOKIE);
  if (sid) getDb().prepare("DELETE FROM sessions WHERE id = ?").run(sid);
  return cookie(request, SESSION_COOKIE, "", 0);
}

// ---------- Challenges (one-time, short-lived) ----------

function storeChallenge(request: Request, challenge: string): string {
  const db = getDb();
  db.prepare("DELETE FROM auth_challenges WHERE expires_at <= datetime('now')").run();
  const id = crypto.randomBytes(16).toString("base64url");
  const maxAge = CHALLENGE_MINUTES * 60;
  db.prepare("INSERT INTO auth_challenges (id, challenge, expires_at) VALUES (?, ?, ?)").run(
    id, challenge, sqlTimeIn(maxAge)
  );
  return cookie(request, CHALLENGE_COOKIE, id, maxAge);
}

function consumeChallenge(request: Request): string | null {
  const id = readCookie(request, CHALLENGE_COOKIE);
  if (!id) return null;
  const db = getDb();
  const row = db
    .prepare("SELECT challenge FROM auth_challenges WHERE id = ? AND expires_at > datetime('now')")
    .get(id) as { challenge: string } | undefined;
  db.prepare("DELETE FROM auth_challenges WHERE id = ?").run(id);
  return row?.challenge ?? null;
}

// ---------- Registration token ----------

function passkeyCount(): number {
  return (getDb().prepare("SELECT COUNT(*) AS n FROM passkeys").get() as { n: number }).n;
}

/** Ensure a registration token exists while no passkey is registered (first-time setup). */
export function ensureSetupToken(): void {
  if (passkeyCount() > 0 || fs.existsSync(TOKEN_PATH)) return;
  fs.writeFileSync(TOKEN_PATH, crypto.randomBytes(24).toString("base64url") + "\n", { mode: 0o600 });
  console.log(`[auth] No passkey registered. Registration token written to ${TOKEN_PATH}`);
}

function checkToken(token: string | null): boolean {
  if (!token || !fs.existsSync(TOKEN_PATH)) return false;
  const expected = Buffer.from(fs.readFileSync(TOKEN_PATH, "utf8").trim());
  const given = Buffer.from(token.trim());
  return expected.length === given.length && crypto.timingSafeEqual(expected, given);
}

export function canRegister(request: Request, token: string | null): boolean {
  return isLoggedIn(request) || checkToken(token);
}

// ---------- WebAuthn ceremonies ----------

interface PasskeyRow {
  id: string;
  public_key: Buffer;
  counter: number;
  transports: string | null;
}

const OWNER_ID = new TextEncoder().encode("owner");

export async function registrationOptions(request: Request) {
  const { rpID } = relyingParty(request);
  const existing = getDb().prepare("SELECT id, transports FROM passkeys").all() as PasskeyRow[];
  const options = await generateRegistrationOptions({
    rpName: RP_NAME,
    rpID,
    userID: OWNER_ID,
    userName: "owner",
    userDisplayName: "オーナー",
    attestationType: "none",
    excludeCredentials: existing.map((p) => ({
      id: p.id,
      transports: p.transports ? JSON.parse(p.transports) : undefined,
    })),
    authenticatorSelection: { residentKey: "required", userVerification: "preferred" },
  });
  return { options, setCookie: storeChallenge(request, options.challenge) };
}

export async function verifyRegistration(
  request: Request,
  response: RegistrationResponseJSON,
  label: string | null,
  usedToken: boolean
): Promise<string> {
  const expectedChallenge = consumeChallenge(request);
  if (!expectedChallenge) throw new Error("challenge expired");
  const { origin, rpID } = relyingParty(request);
  const result = await verifyRegistrationResponse({
    response,
    expectedChallenge,
    expectedOrigin: origin,
    expectedRPID: rpID,
    requireUserVerification: false,
  });
  if (!result.verified) throw new Error("registration not verified");

  const { credential } = result.registrationInfo;
  getDb()
    .prepare("INSERT INTO passkeys (id, public_key, counter, transports, label) VALUES (?, ?, ?, ?, ?)")
    .run(
      credential.id,
      Buffer.from(credential.publicKey),
      credential.counter,
      credential.transports ? JSON.stringify(credential.transports) : null,
      label?.slice(0, 60) || null
    );

  // Token is single-use
  if (usedToken) fs.rmSync(TOKEN_PATH, { force: true });

  return createSession(request);
}

export async function authenticationOptions(request: Request) {
  const { rpID } = relyingParty(request);
  const options = await generateAuthenticationOptions({ rpID, userVerification: "preferred" });
  return { options, setCookie: storeChallenge(request, options.challenge) };
}

export async function verifyAuthentication(
  request: Request,
  response: AuthenticationResponseJSON
): Promise<string> {
  const expectedChallenge = consumeChallenge(request);
  if (!expectedChallenge) throw new Error("challenge expired");
  const db = getDb();
  const passkey = db.prepare("SELECT * FROM passkeys WHERE id = ?").get(response.id) as
    | PasskeyRow
    | undefined;
  if (!passkey) throw new Error("unknown passkey");

  const { origin, rpID } = relyingParty(request);
  const result = await verifyAuthenticationResponse({
    response,
    expectedChallenge,
    expectedOrigin: origin,
    expectedRPID: rpID,
    credential: {
      id: passkey.id,
      publicKey: new Uint8Array(passkey.public_key),
      counter: passkey.counter,
      transports: passkey.transports ? JSON.parse(passkey.transports) : undefined,
    },
    requireUserVerification: false,
  });
  if (!result.verified) throw new Error("authentication not verified");

  db.prepare("UPDATE passkeys SET counter = ?, last_used_at = datetime('now') WHERE id = ?").run(
    result.authenticationInfo.newCounter,
    passkey.id
  );
  return createSession(request);
}

// ---------- Passkey management ----------

export interface PasskeyInfo {
  id: string;
  label: string | null;
  created_at: string;
  last_used_at: string | null;
}

export function listPasskeys(): PasskeyInfo[] {
  return getDb()
    .prepare("SELECT id, label, created_at, last_used_at FROM passkeys ORDER BY created_at")
    .all() as PasskeyInfo[];
}

/** Refuses to delete the last passkey so the owner can't lock themselves out. */
export function deletePasskey(id: string): boolean {
  if (passkeyCount() <= 1) return false;
  return getDb().prepare("DELETE FROM passkeys WHERE id = ?").run(id).changes > 0;
}

// ---------- Favorites ----------

export interface Favorite {
  id: number;
  term: string;
  upcoming_count: number;
}

export function listFavorites(): Favorite[] {
  return getDb()
    .prepare(
      `SELECT f.id, f.term,
              (SELECT COUNT(*) FROM events e
               WHERE e.date >= date('now', 'localtime')
                 AND instr(nfkc_lower(e.title || ' ' || COALESCE(e.artist, '')), f.term_norm) > 0
              ) AS upcoming_count
       FROM favorites f ORDER BY f.term COLLATE NOCASE`
    )
    .all() as Favorite[];
}

export function addFavorite(term: string): boolean {
  const trimmed = term.trim().slice(0, 100);
  const norm = normalizeTerm(trimmed);
  if (!norm) return false;
  return (
    getDb()
      .prepare("INSERT OR IGNORE INTO favorites (term, term_norm) VALUES (?, ?)")
      .run(trimmed, norm).changes > 0
  );
}

export function deleteFavorite(id: number): void {
  getDb().prepare("DELETE FROM favorites WHERE id = ?").run(id);
}