const SUPABASE_URL = process.env.SUPABASE_URL || process.env.VITE_SUPABASE_URL || 'https://hwithddwaapyhnfwcesj.supabase.co';
const SUPABASE_SERVICE_KEY = process.env.SUPABASE_SERVICE_KEY || process.env.SUPABASE_SERVICE_ROLE_KEY || 'sb_publishable_fGXkh0bSrAOqSk2jWKAzSg_NJD9YPCv';

const DROPBOX_APP_KEY = process.env.DROPBOX_APP_KEY;
const DROPBOX_APP_SECRET = process.env.DROPBOX_APP_SECRET;
const DROPBOX_REFRESH_TOKEN = process.env.DROPBOX_REFRESH_TOKEN;
const BACKUP_SECRET = process.env.BACKUP_SECRET;
const BACKUP_CRON_ENABLED = process.env.BACKUP_CRON_ENABLED === 'true';

const DROPBOX_BACKUP_FOLDER = '/CrazeBackups';
const MAX_BACKUP_AGE_DAYS = 7;

async function getDropboxToken() {
  const res = await fetch('https://api.dropboxapi.com/oauth2/token', {
    method: 'POST',
    headers: { 'Content-Type': 'application/x-www-form-urlencoded' },
    body: new URLSearchParams({
      grant_type: 'refresh_token',
      refresh_token: DROPBOX_REFRESH_TOKEN,
      client_id: DROPBOX_APP_KEY,
      client_secret: DROPBOX_APP_SECRET,
    }),
  });
  const data = await res.json();
  if (!data.access_token) throw new Error('Dropbox token failed: ' + JSON.stringify(data));
  return data.access_token;
}

async function fetchSupabaseTable(table) {
  const PAGE_SIZE = 1000;
  const rows = [];
  let offset = 0;
  for (let page = 0; page < 50; page++) {
    const res = await fetch(
      `${SUPABASE_URL}/rest/v1/${table}?select=*&limit=${PAGE_SIZE}&offset=${offset}`,
      { headers: { apikey: SUPABASE_SERVICE_KEY, Authorization: `Bearer ${SUPABASE_SERVICE_KEY}` } }
    );
    if (!res.ok) {
      const txt = await res.text();
      throw new Error(`Supabase ${table} fetch failed (${res.status}): ${txt}`);
    }
    const batch = await res.json();
    rows.push(...batch);
    if (batch.length < PAGE_SIZE) break;
    offset += PAGE_SIZE;
  }
  return rows;
}

async function uploadToDropbox(token, path, content) {
  const res = await fetch('https://content.dropboxapi.com/2/files/upload', {
    method: 'POST',
    headers: {
      Authorization: `Bearer ${token}`,
      'Content-Type': 'application/octet-stream',
      'Dropbox-API-Arg': JSON.stringify({ path, mode: 'overwrite', autorename: false }),
    },
    body: content,
  });
  if (!res.ok) {
    const txt = await res.text();
    throw new Error(`Dropbox upload failed (${res.status}): ${txt}`);
  }
  return res.json();
}

async function deleteOldBackups(token) {
  const listRes = await fetch('https://api.dropboxapi.com/2/files/list_folder', {
    method: 'POST',
    headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
    body: JSON.stringify({ path: DROPBOX_BACKUP_FOLDER, limit: 200 }),
  });
  if (!listRes.ok) return; // folder may not exist yet — skip
  const list = await listRes.json();
  const cutoff = Date.now() - MAX_BACKUP_AGE_DAYS * 24 * 60 * 60 * 1000;

  for (const entry of list.entries || []) {
    if (entry['.tag'] !== 'file') continue;
    const modified = new Date(entry.server_modified).getTime();
    if (modified < cutoff) {
      await fetch('https://api.dropboxapi.com/2/files/delete_v2', {
        method: 'POST',
        headers: { Authorization: `Bearer ${token}`, 'Content-Type': 'application/json' },
        body: JSON.stringify({ path: entry.path_lower }),
      });
    }
  }
}

export default async function handler(req, res) {
  // Backup cron disabled by default to prevent noisy scheduled failures.
  if (!BACKUP_CRON_ENABLED) {
    return res.status(200).json({
      success: true,
      skipped: true,
      reason: 'backup cron disabled',
    });
  }

  const authHeader = req.headers['authorization'];
  const isCron = !req.headers.origin;
  const hasSecret = BACKUP_SECRET && authHeader === `Bearer ${BACKUP_SECRET}`;

  if (!isCron && !hasSecret) {
    return res.status(403).json({ error: 'Forbidden' });
  }

  if (req.method !== 'GET' && req.method !== 'POST') {
    return res.status(405).json({ error: 'Method not allowed' });
  }

  try {
    const [syncedRows, history] = await Promise.all([
      fetchSupabaseTable('products'),
      fetchSupabaseTable('products_history'),
    ]);

    const now = new Date();
    const timestamp = now.toISOString().replace(/[:.]/g, '-').slice(0, 19);
    const filename = `backup_${timestamp}.json`;
    const path = `${DROPBOX_BACKUP_FOLDER}/${filename}`;

    const payload = JSON.stringify({
      created_at: now.toISOString(),
      synced_rows_count: syncedRows.length,
      history_count: history.length,
      synced_rows: syncedRows,
      history,
    });

    const token = await getDropboxToken();
    await Promise.all([
      uploadToDropbox(token, path, payload),
      deleteOldBackups(token),
    ]);

    console.log(`[backup] OK — ${filename} | rows: ${syncedRows.length} | history: ${history.length}`);
    return res.json({
      success: true,
      filename,
      synced_rows_count: syncedRows.length,
      history_count: history.length,
    });
  } catch (err) {
    console.error('[backup] error:', err.message);
    return res.status(500).json({ success: false, error: err.message });
  }
}