const express = require('express');
const router = express.Router();

// Get all import sessions for a user (named + unnamed)
router.get('/', async (req, res) => {
  try {
    const { user_id } = req.query;

    if (!user_id) {
      return res.status(400).json({ error: 'user_id query parameter is required' });
    }

    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    const result = await pool.query(`
      SELECT
        id,
        user_id,
        name,
        current_step,
        jsonb_array_length(data) as row_count,
        global_selections,
        created_at,
        updated_at
      FROM import_sessions
      WHERE user_id = $1
      ORDER BY
        CASE WHEN name IS NULL THEN 0 ELSE 1 END,
        updated_at DESC
    `, [user_id]);

    res.json(result.rows);
  } catch (error) {
    console.error('Error fetching import sessions:', error);
    res.status(500).json({
      error: 'Failed to fetch import sessions',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Get session by ID
router.get('/:id', async (req, res) => {
  try {
    const { id } = req.params;
    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    const result = await pool.query(`
      SELECT * FROM import_sessions
      WHERE id = $1
    `, [id]);

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

    res.json(result.rows[0]);
  } catch (error) {
    console.error('Error fetching import session:', error);
    res.status(500).json({
      error: 'Failed to fetch import session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Autosave - upsert unnamed session for user
// IMPORTANT: This must be defined before /:id routes to avoid Express matching "autosave" as an :id
router.put('/autosave', async (req, res) => {
  try {
    const {
      user_id,
      current_step,
      data,
      product_images,
      global_selections,
      validation_state
    } = req.body;

    // Validate required fields
    if (!user_id) {
      return res.status(400).json({ error: 'user_id is required' });
    }
    if (!current_step) {
      return res.status(400).json({ error: 'current_step is required' });
    }
    if (!data || !Array.isArray(data)) {
      return res.status(400).json({ error: 'data must be an array' });
    }

    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    // Upsert: insert or update the unnamed session for this user
    const result = await pool.query(`
      INSERT INTO import_sessions (
        user_id,
        name,
        current_step,
        data,
        product_images,
        global_selections,
        validation_state
      ) VALUES ($1, NULL, $2, $3, $4, $5, $6)
      ON CONFLICT (user_id) WHERE name IS NULL
      DO UPDATE SET
        current_step = EXCLUDED.current_step,
        data = EXCLUDED.data,
        product_images = EXCLUDED.product_images,
        global_selections = EXCLUDED.global_selections,
        validation_state = EXCLUDED.validation_state,
        updated_at = CURRENT_TIMESTAMP
      RETURNING id, user_id, name, current_step, created_at, updated_at
    `, [
      user_id,
      current_step,
      JSON.stringify(data),
      product_images ? JSON.stringify(product_images) : null,
      global_selections ? JSON.stringify(global_selections) : null,
      validation_state ? JSON.stringify(validation_state) : null
    ]);

    res.json(result.rows[0]);
  } catch (error) {
    console.error('Error autosaving import session:', error);
    res.status(500).json({
      error: 'Failed to autosave import session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Delete unnamed session for user (clear autosave)
// IMPORTANT: This must be defined before /:id routes
router.delete('/autosave/:user_id', async (req, res) => {
  try {
    const { user_id } = req.params;
    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    const result = await pool.query(
      'DELETE FROM import_sessions WHERE user_id = $1 AND name IS NULL RETURNING id, user_id, name, current_step, created_at, updated_at',
      [user_id]
    );

    if (result.rows.length === 0) {
      return res.status(404).json({ error: 'No autosave session found for user' });
    }

    res.json({ message: 'Autosave session deleted successfully' });
  } catch (error) {
    console.error('Error deleting autosave session:', error);
    res.status(500).json({
      error: 'Failed to delete autosave session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Create new named session
router.post('/', async (req, res) => {
  try {
    const {
      user_id,
      name,
      current_step,
      data,
      product_images,
      global_selections,
      validation_state
    } = req.body;

    // Validate required fields
    if (!user_id) {
      return res.status(400).json({ error: 'user_id is required' });
    }
    if (!name || typeof name !== 'string' || name.trim().length === 0) {
      return res.status(400).json({ error: 'name is required for creating a named session' });
    }
    if (!current_step) {
      return res.status(400).json({ error: 'current_step is required' });
    }
    if (!data || !Array.isArray(data)) {
      return res.status(400).json({ error: 'data must be an array' });
    }

    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    const result = await pool.query(`
      INSERT INTO import_sessions (
        user_id,
        name,
        current_step,
        data,
        product_images,
        global_selections,
        validation_state
      ) VALUES ($1, $2, $3, $4, $5, $6, $7)
      RETURNING id, user_id, name, current_step, created_at, updated_at
    `, [
      user_id,
      name.trim(),
      current_step,
      JSON.stringify(data),
      product_images ? JSON.stringify(product_images) : null,
      global_selections ? JSON.stringify(global_selections) : null,
      validation_state ? JSON.stringify(validation_state) : null
    ]);

    res.status(201).json(result.rows[0]);
  } catch (error) {
    console.error('Error creating import session:', error);
    res.status(500).json({
      error: 'Failed to create import session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Update named session by ID
router.put('/:id', async (req, res) => {
  try {
    const { id } = req.params;
    const {
      name,
      current_step,
      data,
      product_images,
      global_selections,
      validation_state
    } = req.body;

    if (!current_step) {
      return res.status(400).json({ error: 'current_step is required' });
    }
    if (!data || !Array.isArray(data)) {
      return res.status(400).json({ error: 'data must be an array' });
    }

    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    // Build update query - optionally include name if provided
    const hasName = name !== undefined;
    const result = await pool.query(`
      UPDATE import_sessions
      SET
        ${hasName ? 'name = $1,' : ''}
        current_step = $${hasName ? 2 : 1},
        data = $${hasName ? 3 : 2},
        product_images = $${hasName ? 4 : 3},
        global_selections = $${hasName ? 5 : 4},
        validation_state = $${hasName ? 6 : 5},
        updated_at = CURRENT_TIMESTAMP
      WHERE id = $${hasName ? 7 : 6}
      RETURNING id, user_id, name, current_step, created_at, updated_at
    `, hasName ? [
      typeof name === 'string' ? name.trim() : name,
      current_step,
      JSON.stringify(data),
      product_images ? JSON.stringify(product_images) : null,
      global_selections ? JSON.stringify(global_selections) : null,
      validation_state ? JSON.stringify(validation_state) : null,
      id
    ] : [
      current_step,
      JSON.stringify(data),
      product_images ? JSON.stringify(product_images) : null,
      global_selections ? JSON.stringify(global_selections) : null,
      validation_state ? JSON.stringify(validation_state) : null,
      id
    ]);

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

    res.json(result.rows[0]);
  } catch (error) {
    console.error('Error updating import session:', error);
    res.status(500).json({
      error: 'Failed to update import session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Delete session by ID
router.delete('/:id', async (req, res) => {
  try {
    const { id } = req.params;
    const pool = req.app.locals.pool;
    if (!pool) {
      throw new Error('Database pool not initialized');
    }

    const result = await pool.query('DELETE FROM import_sessions WHERE id = $1 RETURNING id, user_id, name, current_step, created_at, updated_at', [id]);

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

    res.json({ message: 'Import session deleted successfully' });
  } catch (error) {
    console.error('Error deleting import session:', error);
    res.status(500).json({
      error: 'Failed to delete import session',
      details: error instanceof Error ? error.message : 'Unknown error'
    });
  }
});

// Error handling middleware
router.use((err, req, res, next) => {
  console.error('Import sessions route error:', err);
  res.status(500).json({
    error: 'Internal server error',
    details: err.message
  });
});

module.exports = router;