import Fastify, { type FastifyReply, type FastifyRequest } from 'fastify';
import { randomBytes } from 'node:crypto';
import { readFileSync, unlinkSync, writeFileSync } from 'node:fs';
import { basename } from 'node:path';
import {
  MAX_PHOTO_BYTES,
  MAX_PHOTOS_PER_USER,
  MAX_RECIPE_BYTES,
  SESSION_COOKIE,
  SESSION_MAX_AGE_S,
  DUMMY_HASH,
  countPhotos,
  createPhoto,
  createRecipe,
  createSession,
  createUser,
  deleteAllPhotos,
  deletePhoto,
  deleteRecipe,
  deleteSession,
  findUserByEmail,
  listPhotos,
  listPhotosWithOwner,
  listRecipes,
  photoFile,
  photoPath,
  sessionUser,
  updateRecipe,
  verifyPassword,
  type Recipe,
  type User,
} from './db';

const PORT = Number(process.env.PORT || 3000);
const HOST = '0.0.0.0';

const EMAIL_RE = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
const MAX_EMAIL = 254;
const MIN_PASSWORD = 8;
const MAX_PASSWORD = 200;
const MAX_NAME = 120;

// Comma-separated allowlist from the environment. An allowlist over a role
// column keeps the privilege out of the database entirely: no migration, and
// no endpoint that could ever elevate someone.
const ADMIN_EMAILS = new Set(
  (process.env.ADMIN_EMAILS ?? '')
    .split(',')
    .map((s) => s.trim().toLowerCase())
    .filter(Boolean),
);
const isAdmin = (user: User) => ADMIN_EMAILS.has(user.email.toLowerCase());

const app = Fastify({
  logger: true,
  bodyLimit: 1024 * 1024,
  // The API is only reachable through nginx, so the forwarded headers are the
  // only source of truth for the original scheme (see the Secure cookie flag).
  trustProxy: true,
});

// Bodyless DELETE/logout requests still often carry Content-Type: application/json.
app.addContentTypeParser('application/json', { parseAs: 'string' }, (_req, body, done) => {
  const raw = (body as string).trim();
  if (raw === '') return done(null, undefined);
  try {
    done(null, JSON.parse(raw));
  } catch {
    done(Object.assign(new Error('invalid JSON body'), { statusCode: 400 }));
  }
});

// Photo uploads are the raw image bytes, not multipart: one file per request
// needs no boundary parsing, so no dependency and no parser attack surface.
app.addContentTypeParser(['image/jpeg', 'image/png', 'image/webp'], { parseAs: 'buffer' }, (_req, body, done) => {
  done(null, body);
});

// ---- rate limiting --------------------------------------------------------
// Fixed window keyed on what the caller is trying to abuse — an email, or a
// user id — rather than an address: the API sits behind two proxies, so a
// request's source address is not something it can honestly trust, but the
// account being attacked cannot be rotated by the attacker.
// ponytail: in-memory, one container. Swap for @fastify/rate-limit + Redis if
// the API is ever scaled beyond that.
function limiter(max: number, windowMs: number) {
  const hits = new Map<string, { n: number; until: number }>();
  return (key: string): boolean => {
    const t = Date.now();
    if (hits.size > 5000) for (const [k, v] of hits) if (v.until <= t) hits.delete(k);
    const row = hits.get(key);
    if (!row || row.until <= t) {
      hits.set(key, { n: 1, until: t + windowMs });
      return true;
    }
    row.n += 1;
    return row.n <= max;
  };
}
const allowLogin = limiter(20, 15 * 60_000);
const allowSignup = limiter(5, 60 * 60_000);
const allowUpload = limiter(60, 60 * 60_000);
const tooMany = (reply: FastifyReply) =>
  reply.header('retry-after', '900').status(429).send({ error: 'too_many_requests' });

// ---- image sniffing -------------------------------------------------------
// The declared Content-Type is a claim; the first bytes are evidence. Both must
// agree, and only these three formats are accepted — SVG in particular is never
// accepted, because it is a script container that would run on our origin.
type ImageMime = 'image/jpeg' | 'image/png' | 'image/webp';
const PNG_MAGIC = Buffer.from([0x89, 0x50, 0x4e, 0x47, 0x0d, 0x0a, 0x1a, 0x0a]);

function sniffImage(buf: Buffer): ImageMime | null {
  if (buf.length >= 3 && buf[0] === 0xff && buf[1] === 0xd8 && buf[2] === 0xff) return 'image/jpeg';
  if (buf.length >= 8 && buf.subarray(0, 8).equals(PNG_MAGIC)) return 'image/png';
  if (buf.length >= 12 && buf.toString('ascii', 0, 4) === 'RIFF' && buf.toString('ascii', 8, 12) === 'WEBP')
    return 'image/webp';
  return null;
}
const EXT: Record<ImageMime, string> = { 'image/jpeg': 'jpg', 'image/png': 'png', 'image/webp': 'webp' };

// Single error shape for the whole API: { error: "..." }
app.setErrorHandler((err, req, reply) => {
  const e = err as { statusCode?: number; message?: string };
  const status = e.statusCode && e.statusCode >= 400 ? e.statusCode : 500;
  if (status >= 500) req.log.error(err);
  reply.status(status).send({ error: status >= 500 ? 'internal_error' : (e.message ?? 'error') });
});
app.setNotFoundHandler((_req, reply) => reply.status(404).send({ error: 'not_found' }));

// ---- cookie helpers (hand-rolled: only one cookie, no plugin needed) ----
function cookieOf(req: FastifyRequest, name: string): string | undefined {
  const raw = req.headers.cookie;
  if (!raw) return undefined;
  for (const part of raw.split(';')) {
    const eq = part.indexOf('=');
    if (eq === -1) continue;
    if (part.slice(0, eq).trim() === name) return part.slice(eq + 1).trim();
  }
  return undefined;
}

function setSession(req: FastifyRequest, reply: FastifyReply, token: string): void {
  // Secure only where the visitor actually arrived over TLS: nginx forwards the
  // original scheme, so the cookie is hardened in production without breaking
  // local http access to the same build.
  const secure = req.protocol === 'https' ? '; Secure' : '';
  reply.header(
    'set-cookie',
    `${SESSION_COOKIE}=${token}; Path=/; HttpOnly; SameSite=Lax; Max-Age=${SESSION_MAX_AGE_S}${secure}`,
  );
}

function clearSession(reply: FastifyReply): void {
  reply.header('set-cookie', `${SESSION_COOKIE}=; Path=/; HttpOnly; SameSite=Lax; Max-Age=0`);
}

// ---- validation at the trust boundary ----
type Json = Record<string, unknown>;

function bodyOf(req: FastifyRequest): Json | undefined {
  const b = req.body as unknown;
  return b !== null && typeof b === 'object' && !Array.isArray(b) ? (b as Json) : undefined;
}

function credentials(b: Json): { email: string; password: string } | string {
  const email = typeof b.email === 'string' ? b.email.trim().toLowerCase() : '';
  const password = typeof b.password === 'string' ? b.password : '';
  if (!email || email.length > MAX_EMAIL || !EMAIL_RE.test(email)) return 'invalid email';
  if (password.length < MIN_PASSWORD || password.length > MAX_PASSWORD)
    return `password must be ${MIN_PASSWORD}-${MAX_PASSWORD} characters`;
  return { email, password };
}

function recipePayload(b: Json): { name: string; recipe: Json } | string {
  const name = typeof b.name === 'string' ? b.name.trim() : '';
  const recipe = b.recipe;
  if (!name || name.length > MAX_NAME) return `name must be 1-${MAX_NAME} characters`;
  if (recipe === null || typeof recipe !== 'object' || Array.isArray(recipe)) return 'recipe must be an object';
  if (Buffer.byteLength(JSON.stringify(recipe)) > MAX_RECIPE_BYTES) return 'recipe too large';
  return { name, recipe: recipe as Json };
}

function auth(req: FastifyRequest): User | undefined {
  const token = cookieOf(req, SESSION_COOKIE);
  return token ? sessionUser(token) : undefined;
}

// ---- routes ----
app.get('/api/health', async () => ({ ok: true }));

app.post('/api/auth/signup', async (req, reply) => {
  const b = bodyOf(req);
  if (!b) return reply.status(400).send({ error: 'invalid body' });
  const creds = credentials(b);
  if (typeof creds === 'string') return reply.status(400).send({ error: creds });
  if (!allowSignup(creds.email)) return tooMany(reply);
  if (findUserByEmail(creds.email)) return reply.status(409).send({ error: 'email already registered' });
  const user = createUser(creds.email, creds.password);
  if (!user) return reply.status(409).send({ error: 'email already registered' });
  setSession(req, reply, createSession(user.id));
  return reply.status(201).send({ user });
});

app.post('/api/auth/login', async (req, reply) => {
  const b = bodyOf(req);
  if (!b || typeof b.email !== 'string' || typeof b.password !== 'string')
    return reply.status(400).send({ error: 'invalid body' });
  const email = b.email.trim().toLowerCase();
  if (!allowLogin(email)) return tooMany(reply);
  const row = findUserByEmail(email);
  const ok = verifyPassword(b.password, row?.password_hash ?? DUMMY_HASH);
  if (!row || !ok) return reply.status(401).send({ error: 'invalid credentials' });
  setSession(req, reply, createSession(row.id));
  return reply.status(200).send({ user: { id: row.id, email: row.email } });
});

app.post('/api/auth/logout', async (req, reply) => {
  const token = cookieOf(req, SESSION_COOKIE);
  if (token) deleteSession(token);
  clearSession(reply);
  return reply.status(204).send();
});

app.get('/api/auth/me', async (req, reply) => {
  // Signed out is an answer, not an error: "who am I?" with no session is
  // nobody. A 401 here would put a console error on every anonymous visit to
  // the landing page, which asks the same question to decide what to offer.
  const user = auth(req);
  return reply.status(200).send({ user: user ?? null });
});

app.get('/api/recipes', async (req, reply) => {
  const user = auth(req);
  if (!user) return reply.status(401).send({ error: 'unauthorized' });
  return reply.status(200).send({ recipes: listRecipes(user.id) });
});

app.post('/api/recipes', async (req, reply) => {
  const user = auth(req);
  if (!user) return reply.status(401).send({ error: 'unauthorized' });
  const b = bodyOf(req);
  const payload = b && recipePayload(b);
  if (typeof payload === 'string' || !payload)
    return reply.status(payload === 'recipe too large' ? 413 : 400).send({ error: payload ?? 'invalid body' });
  const recipe: Recipe = createRecipe(user.id, payload.name, payload.recipe);
  return reply.status(201).send({ recipe });
});

app.put<{ Params: { id: string } }>('/api/recipes/:id', async (req, reply) => {
  const user = auth(req);
  if (!user) return reply.status(401).send({ error: 'unauthorized' });
  const id = Number(req.params.id);
  if (!Number.isInteger(id) || id <= 0) return reply.status(404).send({ error: 'recipe not found' });
  const b = bodyOf(req);
  const payload = b && recipePayload(b);
  if (typeof payload === 'string' || !payload)
    return reply.status(payload === 'recipe too large' ? 413 : 400).send({ error: payload ?? 'invalid body' });
  const recipe = updateRecipe(user.id, id, payload.name, payload.recipe);
  if (!recipe) return reply.status(404).send({ error: 'recipe not found' });
  return reply.status(200).send({ recipe });
});

app.delete<{ Params: { id: string } }>('/api/recipes/:id', async (req, reply) => {
  const user = auth(req);
  if (!user) return reply.status(401).send({ error: 'unauthorized' });
  const id = Number(req.params.id);
  if (!Number.isInteger(id) || id <= 0) return reply.status(404).send({ error: 'recipe not found' });
  if (!deleteRecipe(user.id, id)) return reply.status(404).send({ error: 'recipe not found' });
  return reply.status(204).send();
});

// ---- contributed strip photos -------------------------------------------
// Anyone may read the strip; only a signed-in account may add to it. The bytes
// are written under a server-generated name, so a caller's own filename never
// reaches the filesystem, and the row is the only place the real mime lives.
app.get('/api/photos', async () => ({ photos: listPhotos() }));

app.post('/api/photos', { bodyLimit: MAX_PHOTO_BYTES + 8192 }, async (req, reply) => {
  const user = auth(req);
  if (!user) return reply.status(401).send({ error: 'unauthorized' });
  if (!allowUpload(String(user.id))) return tooMany(reply);

  const body = req.body;
  if (!Buffer.isBuffer(body) || body.length === 0) return reply.status(400).send({ error: 'invalid body' });
  if (body.length > MAX_PHOTO_BYTES) return reply.status(413).send({ error: 'photo too large' });

  const declared = (req.headers['content-type'] ?? '').split(';')[0].trim().toLowerCase();
  const mime = sniffImage(body);
  if (!mime || mime !== declared) return reply.status(415).send({ error: 'unsupported image type' });

  if (countPhotos(user.id) >= MAX_PHOTOS_PER_USER)
    return reply.status(429).send({ error: 'photo quota reached' });

  const file = `${randomBytes(16).toString('hex')}.${EXT[mime]}`;
  writeFileSync(photoPath(file), body, { flag: 'wx' });
  const photo = createPhoto(user.id, file, mime, body.length);
  return reply.status(201).send({ photo });
});

app.get<{ Params: { id: string } }>('/api/photos/:id/file', async (req, reply) => {
  const id = Number(req.params.id);
  if (!Number.isInteger(id) || id <= 0) return reply.status(404).send({ error: 'not_found' });
  const row = photoFile(id);
  // The column is server-generated, but re-check it on the way out: a single
  // path segment is the only thing that can ever be opened.
  if (!row || basename(row.file) !== row.file) return reply.status(404).send({ error: 'not_found' });
  let data: Buffer;
  try {
    data = readFileSync(photoPath(row.file));
  } catch {
    return reply.status(404).send({ error: 'not_found' });
  }
  return reply
    .header('content-type', row.mime)
    .header('x-content-type-options', 'nosniff')
    // Belt and braces on top of the mime allowlist: even a hostile still cannot
    // act as a document on this origin.
    .header('content-security-policy', "default-src 'none'; sandbox")
    // Short, not immutable: an admin deleting a contribution has to be able to
    // take it off the web, and a cached copy would outlive the removal.
    .header('cache-control', 'public, max-age=60')
    .send(data);
});

// ---- admin ---------------------------------------------------------------
// Moderation only: the allowlist can list everything and clean up. There is
// deliberately no endpoint here that grants the privilege itself.
function admin(req: FastifyRequest): User | { status: number } {
  const user = auth(req);
  if (!user) return { status: 401 };
  if (!isAdmin(user)) return { status: 403 };
  return user;
}

function unlink(file: string): void {
  try {
    unlinkSync(photoPath(file));
  } catch {
    // Already gone; the row is what matters.
  }
}

app.get('/api/admin/photos', async (req, reply) => {
  const user = admin(req);
  if ('status' in user) return reply.status(user.status).send({ error: user.status === 401 ? 'unauthorized' : 'forbidden' });
  return reply.status(200).send({ photos: listPhotosWithOwner() });
});

app.delete<{ Params: { id: string } }>('/api/admin/photos/:id', async (req, reply) => {
  const user = admin(req);
  if ('status' in user) return reply.status(user.status).send({ error: user.status === 401 ? 'unauthorized' : 'forbidden' });
  const id = Number(req.params.id);
  if (!Number.isInteger(id) || id <= 0) return reply.status(404).send({ error: 'photo not found' });
  const file = deletePhoto(id);
  if (!file) return reply.status(404).send({ error: 'photo not found' });
  unlink(file);
  return reply.status(204).send();
});

app.delete('/api/admin/photos', async (req, reply) => {
  const user = admin(req);
  if ('status' in user) return reply.status(user.status).send({ error: user.status === 401 ? 'unauthorized' : 'forbidden' });
  const files = deleteAllPhotos();
  for (const file of files) unlink(file);
  return reply.status(200).send({ removed: files.length });
});

app
  .listen({ port: PORT, host: HOST })
  .catch((err) => {
    app.log.error(err);
    process.exit(1);
  });