const prisma = require('../config/db');
const { safeErrorMessage } = require('../utils/errorUtils');
const { track, funnelFor } = require('../utils/analytics');

// @desc    Record a funnel step (event page view, registration started)
// @route   POST /api/analytics/track   { sessionId, eventId, stage: 'view'|'start', source? }
// @access  Public — only sent by browsers whose visitor accepted cookies
const trackStage = async (req, res) => {
  try {
    const { sessionId, eventId, stage, source } = req.body || {};
    await track({ sessionId, eventId, stage, source, userAgent: req.headers['user-agent'] });
  } catch (e) {
    console.warn('[analytics] track failed:', e?.message || e);
  }
  // Always a quiet 204 — tracking must never get in a visitor's way.
  res.status(204).end();
};

// @desc    Registration funnel for one or more events
// @route   GET /api/analytics/funnel?eventIds=a,b&from=YYYY-MM-DD&to=YYYY-MM-DD
// @access  Private/Supervisor
const getFunnel = async (req, res) => {
  try {
    const eventIds = String(req.query.eventIds || '').split(',').map(s => s.trim()).filter(Boolean).slice(0, 50);
    if (eventIds.length === 0) { res.status(400); throw new Error('Choose at least one event'); }
    const events = await prisma.event.findMany({ where: { id: { in: eventIds } }, select: { id: true, title: true } });
    const total = await funnelFor(eventIds, { from: req.query.from, to: req.query.to });
    // Per event too, so events can be compared.
    const perEvent = [];
    if (events.length > 1) {
      for (const ev of events) {
        const f = await funnelFor([ev.id], { from: req.query.from, to: req.query.to });
        perEvent.push({ eventId: ev.id, title: ev.title, totals: f.totals, conversion: f.conversion });
      }
    } else if (events[0]) {
      perEvent.push({ eventId: events[0].id, title: events[0].title, totals: total.totals, conversion: total.conversion });
    }
    res.json({ ...total, perEvent });
  } catch (error) {
    res.status(res.statusCode === 200 ? 400 : res.statusCode).json({ message: safeErrorMessage(error) });
  }
};

module.exports = { trackStage, getFunnel };