const { get, run } = require('./postgres');

const TIKTOK_ACCOUNT_KEY = 'greenlens';
const LEGACY_TIKTOK_ACCOUNT_KEY = 'hermes-agent';
let refreshInFlight = null;

const saveTiktokTokens = async (db, tokens) => {
  const now = Date.now();
  const accessExpiresAt = new Date(now + Number(tokens.expires_in || 0) * 1000);
  const refreshExpiresAt = tokens.refresh_expires_in !== undefined && tokens.refresh_expires_in !== null
    ? new Date(now + Number(tokens.refresh_expires_in) * 1000)
    : null;

  await run(
    db,
    `INSERT INTO tiktok_tokens (account_key, open_id, access_token, refresh_token, scope, access_token_expires_at, refresh_token_expires_at, updated_at)
     VALUES (?, ?, ?, ?, ?, ?, ?, CURRENT_TIMESTAMP)
     ON CONFLICT (account_key) DO UPDATE SET
       open_id = EXCLUDED.open_id,
       access_token = EXCLUDED.access_token,
       refresh_token = EXCLUDED.refresh_token,
       scope = EXCLUDED.scope,
       access_token_expires_at = EXCLUDED.access_token_expires_at,
       refresh_token_expires_at = COALESCE(EXCLUDED.refresh_token_expires_at, tiktok_tokens.refresh_token_expires_at),
       updated_at = CURRENT_TIMESTAMP`,
    [
      TIKTOK_ACCOUNT_KEY,
      tokens.open_id,
      tokens.access_token,
      tokens.refresh_token,
      tokens.scope || null,
      accessExpiresAt,
      refreshExpiresAt,
    ],
  );
};

const getTiktokTokens = async (db) => {
  const current = await get(db, `SELECT * FROM tiktok_tokens WHERE account_key = ?`, [TIKTOK_ACCOUNT_KEY]);
  if (current) return current;

  // Preserve an existing production connection when upgrading from the old,
  // generic key. Future writes use the brand-specific key.
  const legacy = await get(db, `SELECT * FROM tiktok_tokens WHERE account_key = ?`, [LEGACY_TIKTOK_ACCOUNT_KEY]);
  if (!legacy) return null;
  await saveTiktokTokens(db, {
    ...legacy,
    expires_in: Math.max(0, Math.floor((new Date(legacy.access_token_expires_at).getTime() - Date.now()) / 1000)),
    refresh_expires_in: legacy.refresh_token_expires_at
      ? Math.max(0, Math.floor((new Date(legacy.refresh_token_expires_at).getTime() - Date.now()) / 1000))
      : undefined,
  });
  return get(db, `SELECT * FROM tiktok_tokens WHERE account_key = ?`, [TIKTOK_ACCOUNT_KEY]);
};

const exchangeCodeForTokens = async ({ code, clientKey, clientSecret, redirectUri }) => {
  const response = await fetch('https://open.tiktokapis.com/v2/oauth/token/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: new URLSearchParams({
      client_key: clientKey,
      client_secret: clientSecret,
      code,
      grant_type: 'authorization_code',
      redirect_uri: redirectUri,
    }),
  });

  const data = await response.json();
  if (!response.ok || data.error) {
    const message = data.error_description || data.error || 'TikTok token exchange failed.';
    const error = new Error(message);
    error.status = 502;
    throw error;
  }
  return data;
};

const performTiktokRefresh = async (db, { clientKey, clientSecret }) => {
  const existing = await getTiktokTokens(db);
  if (!existing) {
    const error = new Error('No TikTok account connected.');
    error.status = 404;
    throw error;
  }

  const refreshExpiresAt = existing.refresh_token_expires_at
    ? new Date(existing.refresh_token_expires_at).getTime()
    : null;
  if (refreshExpiresAt !== null && (!Number.isFinite(refreshExpiresAt) || refreshExpiresAt <= Date.now())) {
    const error = new Error('TikTok authorization has expired. Reconnect the GreenLens TikTok account.');
    error.status = 401;
    error.code = 'TIKTOK_RECONNECT_REQUIRED';
    throw error;
  }

  const response = await fetch('https://open.tiktokapis.com/v2/oauth/token/', {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: new URLSearchParams({
      client_key: clientKey,
      client_secret: clientSecret,
      grant_type: 'refresh_token',
      refresh_token: existing.refresh_token,
    }),
  });

  const data = await response.json();
  if (!response.ok || data.error) {
    const providerCode = typeof data.error === 'string' ? data.error : data.error?.code;
    const message = data.error_description || data.error?.message || providerCode || 'TikTok token refresh failed.';
    const error = new Error(message);
    error.status = providerCode === 'invalid_grant' ? 401 : 502;
    error.code = providerCode === 'invalid_grant' ? 'TIKTOK_RECONNECT_REQUIRED' : 'TIKTOK_REFRESH_FAILED';
    throw error;
  }

  await saveTiktokTokens(db, data);
  return getTiktokTokens(db);
};

const refreshTiktokTokens = async (db, credentials) => {
  if (!refreshInFlight) {
    refreshInFlight = performTiktokRefresh(db, credentials).finally(() => {
      refreshInFlight = null;
    });
  }
  return refreshInFlight;
};

const assertExpectedTiktokAccount = (openId, expectedOpenId) => {
  const expected = String(expectedOpenId || '').trim();
  if (!expected) {
    const error = new Error('TIKTOK_EXPECTED_OPEN_ID is not configured for GreenLens.');
    error.status = 500;
    error.code = 'TIKTOK_ACCOUNT_NOT_CONFIGURED';
    throw error;
  }
  if (String(openId || '').trim() !== expected) {
    const error = new Error('Connected TikTok account does not match the configured GreenLens account.');
    error.status = 409;
    error.code = 'TIKTOK_ACCOUNT_MISMATCH';
    throw error;
  }
};

module.exports = {
  exchangeCodeForTokens,
  assertExpectedTiktokAccount,
  getTiktokTokens,
  refreshTiktokTokens,
  saveTiktokTokens,
};