const express = require('express');
const { db, canAccessTrip } = require('../db/database');
const { authenticate } = require('../middleware/auth');
const { broadcast } = require('../websocket');

const router = express.Router({ mergeParams: true });

function verifyTripOwnership(tripId, userId) {
  return canAccessTrip(tripId, userId);
}

function getAssignmentWithPlace(assignmentId) {
  const a = db.prepare(`
    SELECT da.*, p.id as place_id, p.name as place_name, p.description as place_description,
      p.lat, p.lng, p.address, p.category_id, p.price, p.currency as place_currency,
      COALESCE(da.assignment_time, p.place_time) as place_time,
      COALESCE(da.assignment_end_time, p.end_time) as end_time,
      p.duration_minutes, p.notes as place_notes,
      p.image_url, p.transport_mode, p.google_place_id, p.website, p.phone,
      c.name as category_name, c.color as category_color, c.icon as category_icon
    FROM day_assignments da
    JOIN places p ON da.place_id = p.id
    LEFT JOIN categories c ON p.category_id = c.id
    WHERE da.id = ?
  `).get(assignmentId);

  if (!a) return null;

  const tags = db.prepare(`
    SELECT t.* FROM tags t
    JOIN place_tags pt ON t.id = pt.tag_id
    WHERE pt.place_id = ?
  `).all(a.place_id);

  const participants = db.prepare(`
    SELECT ap.user_id, u.username, u.avatar
    FROM assignment_participants ap
    JOIN users u ON ap.user_id = u.id
    WHERE ap.assignment_id = ?
  `).all(a.id);

  return {
    id: a.id,
    day_id: a.day_id,
    order_index: a.order_index,
    notes: a.notes,
    participants,
    created_at: a.created_at,
    place: {
      id: a.place_id,
      name: a.place_name,
      description: a.place_description,
      lat: a.lat,
      lng: a.lng,
      address: a.address,
      category_id: a.category_id,
      price: a.price,
      currency: a.place_currency,
      place_time: a.place_time,
      end_time: a.end_time,
      duration_minutes: a.duration_minutes,
      notes: a.place_notes,
      image_url: a.image_url,
      transport_mode: a.transport_mode,
      google_place_id: a.google_place_id,
      website: a.website,
      phone: a.phone,
      category: a.category_id ? {
        id: a.category_id,
        name: a.category_name,
        color: a.category_color,
        icon: a.category_icon,
      } : null,
      tags,
    }
  };
}

// GET /api/trips/:tripId/days/:dayId/assignments
router.get('/trips/:tripId/days/:dayId/assignments', authenticate, (req, res) => {
  const { tripId, dayId } = req.params;

  const trip = verifyTripOwnership(tripId, req.user.id);
  if (!trip) return res.status(404).json({ error: 'Trip not found' });

  const day = db.prepare('SELECT id FROM days WHERE id = ? AND trip_id = ?').get(dayId, tripId);
  if (!day) return res.status(404).json({ error: 'Day not found' });

  const assignments = db.prepare(`
    SELECT da.*, p.id as place_id, p.name as place_name, p.description as place_description,
      p.lat, p.lng, p.address, p.category_id, p.price, p.currency as place_currency,
      COALESCE(da.assignment_time, p.place_time) as place_time,
      COALESCE(da.assignment_end_time, p.end_time) as end_time,
      p.duration_minutes, p.notes as place_notes,
      p.image_url, p.transport_mode, p.google_place_id, p.website, p.phone,
      c.name as category_name, c.color as category_color, c.icon as category_icon
    FROM day_assignments da
    JOIN places p ON da.place_id = p.id
    LEFT JOIN categories c ON p.category_id = c.id
    WHERE da.day_id = ?
    ORDER BY da.order_index ASC, da.created_at ASC
  `).all(dayId);

  // Batch-load all tags for all places in one query to avoid N+1
  const placeIds = [...new Set(assignments.map(a => a.place_id))];
  const tagsByPlaceId = {};
  if (placeIds.length > 0) {
    const placeholders = placeIds.map(() => '?').join(',');
    const allTags = db.prepare(`
      SELECT t.*, pt.place_id FROM tags t
      JOIN place_tags pt ON t.id = pt.tag_id
      WHERE pt.place_id IN (${placeholders})
    `).all(...placeIds);
    for (const tag of allTags) {
      if (!tagsByPlaceId[tag.place_id]) tagsByPlaceId[tag.place_id] = [];
      tagsByPlaceId[tag.place_id].push({ id: tag.id, name: tag.name, color: tag.color, created_at: tag.created_at });
    }
  }

  // Load all participants for this day's assignments in one query
  const assignmentIds = assignments.map(a => a.id)
  const allParticipants = assignmentIds.length > 0
    ? db.prepare(`SELECT ap.assignment_id, ap.user_id, u.username, u.avatar FROM assignment_participants ap JOIN users u ON ap.user_id = u.id WHERE ap.assignment_id IN (${assignmentIds.map(() => '?').join(',')})`)
      .all(...assignmentIds)
    : []
  const participantsByAssignment = {}
  for (const p of allParticipants) {
    if (!participantsByAssignment[p.assignment_id]) participantsByAssignment[p.assignment_id] = []
    participantsByAssignment[p.assignment_id].push({ user_id: p.user_id, username: p.username, avatar: p.avatar })
  }

  const result = assignments.map(a => {
    return {
      id: a.id,
      day_id: a.day_id,
      order_index: a.order_index,
      notes: a.notes,
      participants: participantsByAssignment[a.id] || [],
      created_at: a.created_at,
      place: {
        id: a.place_id,
        name: a.place_name,
        description: a.place_description,
        lat: a.lat,
        lng: a.lng,
        address: a.address,
        category_id: a.category_id,
        price: a.price,
        currency: a.place_currency,
        place_time: a.place_time,
        duration_minutes: a.duration_minutes,
        notes: a.place_notes,
        image_url: a.image_url,
        transport_mode: a.transport_mode,
        google_place_id: a.google_place_id,
        website: a.website,
        phone: a.phone,
        category: a.category_id ? {
          id: a.category_id,
          name: a.category_name,
          color: a.category_color,
          icon: a.category_icon,
        } : null,
        tags: tagsByPlaceId[a.place_id] || [],
      }
    };
  });

  res.json({ assignments: result });
});

// POST /api/trips/:tripId/days/:dayId/assignments
router.post('/trips/:tripId/days/:dayId/assignments', authenticate, (req, res) => {
  const { tripId, dayId } = req.params;
  const { place_id, notes } = req.body;

  const trip = verifyTripOwnership(tripId, req.user.id);
  if (!trip) return res.status(404).json({ error: 'Trip not found' });

  const day = db.prepare('SELECT id FROM days WHERE id = ? AND trip_id = ?').get(dayId, tripId);
  if (!day) return res.status(404).json({ error: 'Day not found' });

  const place = db.prepare('SELECT id FROM places WHERE id = ? AND trip_id = ?').get(place_id, tripId);
  if (!place) return res.status(404).json({ error: 'Place not found' });

  const maxOrder = db.prepare('SELECT MAX(order_index) as max FROM day_assignments WHERE day_id = ?').get(dayId);
  const orderIndex = (maxOrder.max !== null ? maxOrder.max : -1) + 1;

  const result = db.prepare(
    'INSERT INTO day_assignments (day_id, place_id, order_index, notes) VALUES (?, ?, ?, ?)'
  ).run(dayId, place_id, orderIndex, notes || null);

  const assignment = getAssignmentWithPlace(result.lastInsertRowid);
  res.status(201).json({ assignment });
  broadcast(tripId, 'assignment:created', { assignment }, req.headers['x-socket-id']);
});

// DELETE /api/trips/:tripId/days/:dayId/assignments/:id
router.delete('/trips/:tripId/days/:dayId/assignments/:id', authenticate, (req, res) => {
  const { tripId, dayId, id } = req.params;

  const trip = verifyTripOwnership(tripId, req.user.id);
  if (!trip) return res.status(404).json({ error: 'Trip not found' });

  const assignment = db.prepare(
    'SELECT da.id FROM day_assignments da JOIN days d ON da.day_id = d.id WHERE da.id = ? AND da.day_id = ? AND d.trip_id = ?'
  ).get(id, dayId, tripId);

  if (!assignment) return res.status(404).json({ error: 'Assignment not found' });

  db.prepare('DELETE FROM day_assignments WHERE id = ?').run(id);
  res.json({ success: true });
  broadcast(tripId, 'assignment:deleted', { assignmentId: Number(id), dayId: Number(dayId) }, req.headers['x-socket-id']);
});

// PUT /api/trips/:tripId/days/:dayId/assignments/reorder
router.put('/trips/:tripId/days/:dayId/assignments/reorder', authenticate, (req, res) => {
  const { tripId, dayId } = req.params;
  const { orderedIds } = req.body;

  const trip = verifyTripOwnership(tripId, req.user.id);
  if (!trip) return res.status(404).json({ error: 'Trip not found' });

  const day = db.prepare('SELECT id FROM days WHERE id = ? AND trip_id = ?').get(dayId, tripId);
  if (!day) return res.status(404).json({ error: 'Day not found' });

  const update = db.prepare('UPDATE day_assignments SET order_index = ? WHERE id = ? AND day_id = ?');
  db.exec('BEGIN');
  try {
    orderedIds.forEach((id, index) => {
      update.run(index, id, dayId);
    });
    db.exec('COMMIT');
  } catch (e) {
    db.exec('ROLLBACK');
    throw e;
  }
  res.json({ success: true });
  broadcast(tripId, 'assignment:reordered', { dayId: Number(dayId), orderedIds }, req.headers['x-socket-id']);
});

// PUT /api/trips/:tripId/assignments/:id/move
router.put('/trips/:tripId/assignments/:id/move', authenticate, (req, res) => {
  const { tripId, id } = req.params;
  const { new_day_id, order_index } = req.body;

  const trip = verifyTripOwnership(tripId, req.user.id);
  if (!trip) return res.status(404).json({ error: 'Trip not found' });

  const assignment = db.prepare(`
    SELECT da.* FROM day_assignments da
    JOIN days d ON da.day_id = d.id
    WHERE da.id = ? AND d.trip_id = ?
  `).get(id, tripId);

  if (!assignment) return res.status(404).json({ error: 'Assignment not found' });

  const newDay = db.prepare('SELECT id FROM days WHERE id = ? AND trip_id = ?').get(new_day_id, tripId);
  if (!newDay) return res.status(404).json({ error: 'Target day not found' });

  const oldDayId = assignment.day_id;
  db.prepare('UPDATE day_assignments SET day_id = ?, order_index = ? WHERE id = ?').run(new_day_id, order_index || 0, id);

  const updated = getAssignmentWithPlace(id);
  res.json({ assignment: updated });
  broadcast(tripId, 'assignment:moved', { assignment: updated, oldDayId: Number(oldDayId), newDayId: Number(new_day_id) }, req.headers['x-socket-id']);
});

// GET /api/trips/:tripId/assignments/:id/participants
router.get('/trips/:tripId/assignments/:id/participants', authenticate, (req, res) => {
  const { tripId, id } = req.params;
  if (!canAccessTrip(Number(tripId), req.user.id)) return res.status(404).json({ error: 'Trip not found' });

  const participants = db.prepare(`
    SELECT ap.user_id, u.username, u.avatar
    FROM assignment_participants ap
    JOIN users u ON ap.user_id = u.id
    WHERE ap.assignment_id = ?
  `).all(id);

  res.json({ participants });
});

// PUT /api/trips/:tripId/assignments/:id/time — update per-assignment time
router.put('/trips/:tripId/assignments/:id/time', authenticate, (req, res) => {
  const { tripId, id } = req.params;
  if (!canAccessTrip(Number(tripId), req.user.id)) return res.status(404).json({ error: 'Trip not found' });

  const assignment = db.prepare(`
    SELECT da.* FROM day_assignments da
    JOIN days d ON da.day_id = d.id
    WHERE da.id = ? AND d.trip_id = ?
  `).get(id, tripId);
  if (!assignment) return res.status(404).json({ error: 'Assignment not found' });

  const { place_time, end_time } = req.body;
  db.prepare('UPDATE day_assignments SET assignment_time = ?, assignment_end_time = ? WHERE id = ?')
    .run(place_time ?? null, end_time ?? null, id);

  const updated = getAssignmentWithPlace(id);
  res.json({ assignment: updated });
  broadcast(Number(tripId), 'assignment:updated', { assignment: updated }, req.headers['x-socket-id']);
});

// PUT /api/trips/:tripId/assignments/:id/participants — set participants (replace all)
router.put('/trips/:tripId/assignments/:id/participants', authenticate, (req, res) => {
  const { tripId, id } = req.params;
  if (!canAccessTrip(Number(tripId), req.user.id)) return res.status(404).json({ error: 'Trip not found' });

  const { user_ids } = req.body; // array of user IDs, empty array = everyone
  if (!Array.isArray(user_ids)) return res.status(400).json({ error: 'user_ids must be an array' });

  // Delete existing and insert new
  db.prepare('DELETE FROM assignment_participants WHERE assignment_id = ?').run(id);
  if (user_ids.length > 0) {
    const insert = db.prepare('INSERT OR IGNORE INTO assignment_participants (assignment_id, user_id) VALUES (?, ?)');
    for (const userId of user_ids) insert.run(id, userId);
  }

  const participants = db.prepare(`
    SELECT ap.user_id, u.username, u.avatar
    FROM assignment_participants ap
    JOIN users u ON ap.user_id = u.id
    WHERE ap.assignment_id = ?
  `).all(id);

  res.json({ participants });
  broadcast(Number(tripId), 'assignment:participants', { assignmentId: Number(id), participants }, req.headers['x-socket-id']);
});

module.exports = router;