const express = require('express');
const pool = require('../db/pool');
const router = express.Router();

// Validation helper
const validateExercise = (data) => {
  const errors = [];
  if (!data.name || typeof data.name !== 'string' || !data.name.trim()) {
    errors.push('name is required and must be non-empty');
  }
  if (data.difficulty && !['beginner', 'intermediate', 'advanced'].includes(data.difficulty)) {
    errors.push('difficulty must be beginner, intermediate, or advanced');
  }
  if (data.muscle_groups && !Array.isArray(data.muscle_groups)) {
    errors.push('muscle_groups must be an array');
  }
  if (data.equipment_needed && !Array.isArray(data.equipment_needed)) {
    errors.push('equipment_needed must be an array');
  }
  return errors;
};

// CREATE - Add new exercise
router.post('/', async (req, res) => {
  try {
    const { name, description, instructions, muscle_groups, difficulty, equipment_needed, video_url, created_by } = req.body;
    
    const errors = validateExercise({ name, difficulty, muscle_groups, equipment_needed });
    if (errors.length > 0) {
      return res.status(400).json({ error: 'Validation failed', details: errors });
    }

    const query = `
      INSERT INTO exercises (name, description, instructions, muscle_groups, difficulty, equipment_needed, video_url, created_by)
      VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
      RETURNING *
    `;
    
    const result = await pool.query(query, [
      name.trim(),
      description || null,
      instructions || null,
      muscle_groups || [],
      difficulty || 'intermediate',
      equipment_needed || [],
      video_url || null,
      created_by || 'system'
    ]);

    res.status(201).json(result.rows[0]);
  } catch (err) {
    if (err.code === '23505') {
      return res.status(409).json({ error: 'Exercise name already exists' });
    }
    console.error('Error creating exercise:', err);
    res.status(500).json({ error: 'Failed to create exercise' });
  }
});

// READ - Get all exercises with search/filter
router.get('/', async (req, res) => {
  try {
    const { search, difficulty, muscle_group, limit = 50, offset = 0 } = req.query;
    
    let query = 'SELECT * FROM exercises WHERE 1=1';
    const params = [];
    let paramCount = 1;

    if (search) {
      query += ` AND (name ILIKE $${paramCount} OR description ILIKE $${paramCount})`;
      params.push(`%${search}%`);
      paramCount++;
    }

    if (difficulty) {
      query += ` AND difficulty = $${paramCount}`;
      params.push(difficulty);
      paramCount++;
    }

    if (muscle_group) {
      query += ` AND $${paramCount} = ANY(muscle_groups)`;
      params.push(muscle_group);
      paramCount++;
    }

    query += ` ORDER BY name ASC LIMIT $${paramCount} OFFSET $${paramCount + 1}`;
    params.push(parseInt(limit), parseInt(offset));

    const result = await pool.query(query, params);
    res.json(result.rows);
  } catch (err) {
    console.error('Error fetching exercises:', err);
    res.status(500).json({ error: 'Failed to fetch exercises' });
  }
});

// READ - Get single exercise
router.get('/:id', async (req, res) => {
  try {
    const result = await pool.query('SELECT * FROM exercises WHERE id = $1', [req.params.id]);
    
    if (result.rows.length === 0) {
      return res.status(404).json({ error: 'Exercise not found' });
    }

    res.json(result.rows[0]);
  } catch (err) {
    console.error('Error fetching exercise:', err);
    res.status(500).json({ error: 'Failed to fetch exercise' });
  }
});

// UPDATE - Modify exercise
router.put('/:id', async (req, res) => {
  try {
    const { name, description, instructions, muscle_groups, difficulty, equipment_needed, video_url } = req.body;
    
    const errors = validateExercise({ name, difficulty, muscle_groups, equipment_needed });
    if (errors.length > 0) {
      return res.status(400).json({ error: 'Validation failed', details: errors });
    }

    const query = `
      UPDATE exercises 
      SET name = $1, description = $2, instructions = $3, muscle_groups = $4, 
          difficulty = $5, equipment_needed = $6, video_url = $7, updated_at = CURRENT_TIMESTAMP
      WHERE id = $8
      RETURNING *
    `;

    const result = await pool.query(query, [
      name.trim(),
      description || null,
      instructions || null,
      muscle_groups || [],
      difficulty || 'intermediate',
      equipment_needed || [],
      video_url || null,
      req.params.id
    ]);

    if (result.rows.length === 0) {
      return res.status(404).json({ error: 'Exercise not found' });
    }

    res.json(result.rows[0]);
  } catch (err) {
    if (err.code === '23505') {
      return res.status(409).json({ error: 'Exercise name already exists' });
    }
    console.error('Error updating exercise:', err);
    res.status(500).json({ error: 'Failed to update exercise' });
  }
});

// DELETE - Remove exercise
router.delete('/:id', async (req, res) => {
  try {
    const result = await pool.query('DELETE FROM exercises WHERE id = $1 RETURNING *', [req.params.id]);

    if (result.rows.length === 0) {
      return res.status(404).json({ error: 'Exercise not found' });
    }

    res.json({ message: 'Exercise deleted', id: req.params.id });
  } catch (err) {
    console.error('Error deleting exercise:', err);
    res.status(500).json({ error: 'Failed to delete exercise' });
  }
});

module.exports = router;