const crypto = require('crypto');
const db = require('./db');

const TOKEN_TTL_DAYS = 30;

function parseJsonMaybe(value) {
  if (!value) {
    return null;
  }
  if (typeof value === 'object') {
    return value;
  }
  try {
    return JSON.parse(value);
  } catch (error) {
    return null;
  }
}

function sha256(value) {
  return crypto.createHash('sha256').update(String(value || '')).digest('hex');
}

function randomToken(size) {
  return crypto.randomBytes(size).toString('base64').replace(/\+/g, '-').replace(/\//g, '_').replace(/=+$/g, '');
}

function normalizeEmail(email) {
  return String(email || '').trim().toLowerCase();
}

function hashPassword(password) {
  return new Promise(function(resolve, reject) {
    var salt = crypto.randomBytes(16).toString('base64');
    crypto.scrypt(String(password), salt, 64, function(error, derivedKey) {
      if (error) {
        reject(error);
        return;
      }
      resolve('scrypt$' + salt + '$' + derivedKey.toString('base64'));
    });
  });
}

function verifyPassword(password, storedHash) {
  return new Promise(function(resolve, reject) {
    var parts = String(storedHash || '').split('$');
    if (parts.length !== 3 || parts[0] !== 'scrypt') {
      resolve(false);
      return;
    }
    var salt = parts[1];
    var expected = Buffer.from(parts[2], 'base64');
    crypto.scrypt(String(password), salt, expected.length, function(error, derivedKey) {
      if (error) {
        reject(error);
        return;
      }
      resolve(crypto.timingSafeEqual(expected, derivedKey));
    });
  });
}

async function createAuthToken(userId, deviceFingerprint) {
  var rawToken = randomToken(32);
  var expiresAt = new Date(Date.now() + TOKEN_TTL_DAYS * 24 * 60 * 60 * 1000);
  await db.execute(
    'INSERT INTO auth_tokens (user_id, token_hash, device_fingerprint, expires_at, last_seen_at) VALUES (?, ?, ?, ?, CURRENT_TIMESTAMP)',
    [userId, sha256(rawToken), deviceFingerprint || null, expiresAt]
  );
  return rawToken;
}

async function touchAuthToken(tokenHash) {
  await db.execute('UPDATE auth_tokens SET last_seen_at = CURRENT_TIMESTAMP WHERE token_hash = ?', [tokenHash]);
}

async function revokeAuthToken(tokenHash) {
  await db.execute('UPDATE auth_tokens SET revoked_at = CURRENT_TIMESTAMP WHERE token_hash = ? AND revoked_at IS NULL', [tokenHash]);
}

async function getAuthContextFromToken(rawToken) {
  if (!rawToken) {
    return null;
  }
  var tokenHash = sha256(rawToken);
  var rows = await db.query(
    'SELECT t.id AS token_id, t.user_id, t.token_hash, t.device_fingerprint, t.expires_at, t.revoked_at, u.email, u.status, k.wrapped_dek, k.kdf_salt, k.kdf_params, k.key_version FROM auth_tokens t INNER JOIN users u ON u.id = t.user_id LEFT JOIN user_keyrings k ON k.user_id = u.id WHERE t.token_hash = ? LIMIT 1',
    [tokenHash]
  );
  if (!rows.length) {
    return null;
  }
  var row = rows[0];
  if (row.revoked_at) {
    return null;
  }
  if (new Date(row.expires_at).getTime() <= Date.now()) {
    return null;
  }
  if (Number(row.status || 0) !== 1) {
    return null;
  }
  await touchAuthToken(tokenHash);
  return {
    tokenHash: tokenHash,
    tokenId: row.token_id,
    user: {
      id: row.user_id,
      email: row.email
    },
    keyring: row.wrapped_dek ? {
      wrappedDek: row.wrapped_dek,
      kdfSalt: row.kdf_salt,
      kdfParams: parseJsonMaybe(row.kdf_params),
      keyVersion: Number(row.key_version || 1)
    } : null
  };
}

async function requireAuth(request, reply) {
  var header = request.headers.authorization || '';
  var match = String(header).match(/^Bearer\s+(.+)$/i);
  if (!match) {
    reply.code(401);
    throw new Error('未登录');
  }
  var authContext = await getAuthContextFromToken(match[1]);
  if (!authContext) {
    reply.code(401);
    throw new Error('登录已失效');
  }
  request.authContext = authContext;
}

module.exports = {
  createAuthToken,
  getAuthContextFromToken,
  hashPassword,
  normalizeEmail,
  parseJsonMaybe,
  requireAuth,
  revokeAuthToken,
  sha256,
  verifyPassword
};