const express = require('express');
const db = require('../db');
const { broadcast } = require('../lib/broadcast');
const PDFDocument = require('pdfkit');
const router = express.Router();

// GET /api/progress — all topics with pct calculation
router.get('/', (req, res) => {
  try {
    const rows = db.prepare('SELECT * FROM progress ORDER BY topic').all();
    const result = rows.map(r => {
      const pct = r.exercises_done > 0 ? Math.round((r.exercises_correct / r.exercises_done) * 100) : 0;
      return {
        topic: r.topic,
        exercises_done: r.exercises_done,
        exercises_correct: r.exercises_correct,
        percentage: pct,
        last_session: r.last_session,
        notes: r.notes,
      };
    });
    res.json(result);
  } catch (err) {
    console.error('[progress] list error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

// PUT /api/progress/:topic — update exercises (body: { correct: bool })
router.put('/:topic', (req, res) => {
  const topic = req.params.topic;
  const { correct } = req.body;

  if (correct === undefined) {
    return res.status(400).json({ error: 'correct is required' });
  }

  try {
    const existing = db.prepare('SELECT * FROM progress WHERE topic = ?').get(topic);
    if (existing) {
      db.prepare(`
        UPDATE progress SET
          exercises_done = exercises_done + 1,
          exercises_correct = exercises_correct + ?,
          last_session = datetime('now')
        WHERE topic = ?
      `).run(correct === true ? 1 : 0, topic);
    } else {
      db.prepare(`
        INSERT INTO progress (topic, exercises_done, exercises_correct, last_session, notes)
        VALUES (?, 1, ?, datetime('now'), '[]')
      `).run(topic, correct === true ? 1 : 0);
    }

    const row = db.prepare('SELECT * FROM progress WHERE topic = ?').get(topic);
    const pct = row.exercises_done > 0 ? Math.round((row.exercises_correct / row.exercises_done) * 100) : 0;
    const result = { ...row, percentage: pct };
    broadcast({ type: 'progress_update', data: result });
    res.json(result);
  } catch (err) {
    console.error('[progress] update error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

// DELETE /api/progress/:topic — reset
router.delete('/:topic', (req, res) => {
  const topic = req.params.topic;

  try {
    const info = db.prepare('DELETE FROM progress WHERE topic = ?').run(topic);
    if (info.changes === 0) {
      return res.status(404).json({ error: 'Topic not found' });
    }
    res.json({ deleted: true });
  } catch (err) {
    console.error('[progress] delete error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

// POST /api/progress/sessions — UPSERT daily minutes
router.post('/sessions', (req, res) => {
  const { date, minutes, topic } = req.body;
  if (!date || minutes === undefined) {
    return res.status(400).json({ error: 'date and minutes are required' });
  }
  try {
    // NULL != NULL in SQLite UNIQUE constraint — explicit NULL handling keeps things working
    const existing = db.prepare('SELECT * FROM study_sessions WHERE session_date = ? AND (topic = ? OR (topic IS NULL AND ? IS NULL))').get(date, topic || null, topic || null);
    if (existing) {
      db.prepare('UPDATE study_sessions SET minutes = minutes + ? WHERE id = ?').run(minutes, existing.id);
    } else {
      db.prepare('INSERT INTO study_sessions (session_date, minutes, topic) VALUES (?, ?, ?)').run(date, minutes, topic || null);
    }
    const row = db.prepare('SELECT * FROM study_sessions WHERE session_date = ? AND (topic = ? OR (topic IS NULL AND ? IS NULL))').get(date, topic || null, topic || null);
    res.json(row);
  } catch (err) {
    console.error('[progress] session error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

// GET /api/progress/heatmap — aggregated study minutes per day
router.get('/heatmap', (req, res) => {
  try {
    const days = parseInt(req.query.days, 10) || 365;
    const since = new Date();
    since.setDate(since.getDate() - days);
    const sinceStr = since.toISOString().split('T')[0];
    const rows = db.prepare(
      'SELECT session_date as date, SUM(minutes) as minutes FROM study_sessions WHERE session_date >= ? GROUP BY session_date ORDER BY session_date'
    ).all(sinceStr);
    res.json(rows);
  } catch (err) {
    console.error('[progress] heatmap error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

// GET /api/progress/exam/pdf — generate simulated exam PDF
router.get('/exam/pdf', (req, res) => {
  try {
    const rows = db.prepare(
      'SELECT * FROM progress ORDER BY last_session DESC LIMIT 20'
    ).all();

    if (!rows.length) {
      return res.status(404).json({ error: 'No progress data' });
    }

    const doc = new PDFDocument({ margin: 50 });
    const filename = `examen-simulado-${new Date().toISOString().slice(0, 10)}.pdf`;
    res.setHeader('Content-Type', 'application/pdf');
    res.setHeader('Content-Disposition', `attachment; filename="${filename}"`);
    doc.pipe(res);
    res.on('error', () => { try { doc.end(); } catch {} });

    // Header
    doc.fontSize(22).text('Examen Simulado', 50, 50);
    doc.fontSize(12).text(`Generado: ${new Date().toLocaleDateString('es-ES')}`, 50, 80);
    doc.moveDown(2);

    // Topics table
    doc.fontSize(14).text('Temas evaluados', 50, doc.y);
    doc.moveDown(0.5);
    doc.fontSize(10);
    rows.forEach((row, idx) => {
      const pct = row.exercises_done > 0 ? Math.round((row.exercises_correct / row.exercises_done) * 100) : 0;
      doc.text(`${idx + 1}. ${row.topic} — ${pct}% (${row.exercises_correct}/${row.exercises_done})`, 60, doc.y);
    });

    if (rows.length === 20) {
      doc.moveDown(1);
      doc.fontSize(9).fillColor('gray').text('Nota: se muestran los 20 temas más recientes.', 50, doc.y);
      doc.fillColor('black');
    }

    doc.moveDown(2);
    doc.fontSize(14).text('Ejercicios de muestra', 50, doc.y);
    doc.moveDown(0.5);
    doc.fontSize(11);
    rows.slice(0, 10).forEach((row, idx) => {
      doc.text(`${idx + 1}. Describe el tema "${row.topic}" con sus puntos clave.`, 60, doc.y);
      doc.moveDown(0.3);
      doc.text('   Respuesta: _______________________________________________', 60, doc.y);
      doc.moveDown(1);
    });

    doc.end();
  } catch (err) {
    console.error('[progress] exam/pdf error:', err.message);
    res.status(500).json({ error: err.message });
  }
});

module.exports = router;