import express from 'express';
import cors from 'cors';
import { readFileSync, writeFileSync, existsSync } from 'fs';
import { join, dirname } from 'path';
import { fileURLToPath } from 'url';

const __dirname = dirname(fileURLToPath(import.meta.url));
const DATA_FILE = join(__dirname, 'data', 'popularity.json');
const DOWNLOADS_LOG = join(__dirname, 'data', 'downloads.json');

const app = express();
app.use(cors());
app.use(express.json());

// Ensure data dir exists
import { mkdirSync } from 'fs';
mkdirSync(join(__dirname, 'data'), { recursive: true });

// Load or init popularity data
function loadPopularity() {
  if (existsSync(DATA_FILE)) {
    return JSON.parse(readFileSync(DATA_FILE, 'utf8'));
  }
  return {};
}

function savePopularity(data) {
  writeFileSync(DATA_FILE, JSON.stringify(data, null, 2));
}

function loadDownloads() {
  if (existsSync(DOWNLOADS_LOG)) {
    return JSON.parse(readFileSync(DOWNLOADS_LOG, 'utf8'));
  }
  return { total: 0, history: [] };
}

function saveDownloads(data) {
  writeFileSync(DOWNLOADS_LOG, JSON.stringify(data, null, 2));
}

// POST /api/analytics/download — record a bundle download
app.post('/api/analytics/download', (req, res) => {
  const { apps, timestamp } = req.body;
  if (!apps || !Array.isArray(apps)) {
    return res.status(400).json({ error: 'apps array required' });
  }

  // Update popularity counts
  const popularity = loadPopularity();
  for (const appId of apps) {
    popularity[appId] = (popularity[appId] || 0) + 1;
  }
  savePopularity(popularity);

  // Log the download
  const downloads = loadDownloads();
  downloads.total += 1;
  downloads.history.push({
    timestamp: timestamp || new Date().toISOString(),
    apps,
    count: apps.length,
  });
  // Keep last 10,000 entries to avoid unbounded growth
  if (downloads.history.length > 10000) {
    downloads.history = downloads.history.slice(-10000);
  }
  saveDownloads(downloads);

  res.json({ ok: true, total_downloads: downloads.total });
});

// GET /api/analytics/popularity — get app download counts
app.get('/api/analytics/popularity', (req, res) => {
  const popularity = loadPopularity();
  res.json(popularity);
});

// GET /api/analytics/stats — overview stats
app.get('/api/analytics/stats', (req, res) => {
  const popularity = loadPopularity();
  const downloads = loadDownloads();

  // Top apps
  const sorted = Object.entries(popularity)
    .sort((a, b) => b[1] - a[1]);

  res.json({
    total_downloads: downloads.total,
    unique_apps_selected: sorted.length,
    top_20: sorted.slice(0, 20).map(([id, count]) => ({ id, count })),
    recent: downloads.history.slice(-10).reverse(),
  });
});

// GET /api/analytics/app/:id — stats for a specific app
app.get('/api/analytics/app/:id', (req, res) => {
  const popularity = loadPopularity();
  const count = popularity[req.params.id] || 0;
  const downloads = loadDownloads();
  const total = downloads.total || 1;
  const percentage = ((count / total) * 100).toFixed(1);

  res.json({
    id: req.params.id,
    download_count: count,
    percentage: `${percentage}%`,
    total_bundles: total,
  });
});

const PORT = process.env.PORT || 3052;
app.listen(PORT, () => {
  console.log(`StackPilot Analytics API running on port ${PORT}`);
});