import { sql } from '@vercel/postgres';
import { getUserFromRequest } from '../../../lib/permission-middleware';

export default async function handler(req, res) {
  // Set CORS headers
  res.setHeader('Access-Control-Allow-Origin', '*');
  res.setHeader('Access-Control-Allow-Methods', 'GET, PUT, OPTIONS');
  res.setHeader('Access-Control-Allow-Headers', 'Content-Type, Authorization');

  // Handle preflight requests
  if (req.method === 'OPTIONS') {
    res.status(200).end();
    return;
  }

  try {
    // Get authenticated user
    const user = await getUserFromRequest(req);
    if (!user) {
      return res.status(401).json({ error: 'Authentication required' });
    }

    if (req.method === 'GET') {
      // Get user and settings
      const result = await sql`
        SELECT 
          id, email, role, first_name, last_name, username,
          collection_visibility, preferred_currency, cards_per_page, 
          default_view, notifications_email, notifications_marketing, 
          two_factor_enabled, theme, language,
          created_at, updated_at
        FROM users 
        WHERE id = ${user.userId}
      `;

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

      const userData = result.rows[0];
      
      // Structure response
      const response = {
        user: {
          id: userData.id,
          email: userData.email,
          role: userData.role,
          first_name: userData.first_name,
          last_name: userData.last_name,
          username: userData.username
        },
        settings: {
          // Account Settings
          collection_visibility: userData.collection_visibility || 'private',
          preferred_currency: userData.preferred_currency || 'USD',
          cards_per_page: userData.cards_per_page || 50,
          default_view: userData.default_view || 'grid',
          
          // Security Settings
          two_factor_enabled: userData.two_factor_enabled || false,
          
          // Notification Settings
          notifications_email: userData.notifications_email !== false, // Default to true
          notifications_marketing: userData.notifications_marketing || false,
          
          // Display Settings
          theme: userData.theme || 'system',
          language: userData.language || 'en'
        }
      };

      res.status(200).json(response);

    } else if (req.method === 'PUT') {
      // Update user settings
      const {
        collection_visibility,
        preferred_currency,
        cards_per_page,
        default_view,
        two_factor_enabled,
        notifications_email,
        notifications_marketing,
        theme,
        language
      } = req.body;

      // Validate enum values
      const validVisibility = ['private', 'public', 'unlisted'];
      const validCurrency = ['USD', 'EUR', 'GBP', 'CAD', 'JPY'];
      const validCardsPerPage = [25, 50, 100];
      const validView = ['grid', 'list'];
      const validTheme = ['light', 'dark', 'system'];
      const validLanguage = ['en', 'es', 'fr', 'de', 'ja'];

      // Validate inputs
      if (collection_visibility && !validVisibility.includes(collection_visibility)) {
        return res.status(400).json({ error: 'Invalid collection visibility' });
      }
      if (preferred_currency && !validCurrency.includes(preferred_currency)) {
        return res.status(400).json({ error: 'Invalid preferred currency' });
      }
      if (cards_per_page && !validCardsPerPage.includes(cards_per_page)) {
        return res.status(400).json({ error: 'Invalid cards per page value' });
      }
      if (default_view && !validView.includes(default_view)) {
        return res.status(400).json({ error: 'Invalid default view' });
      }
      if (theme && !validTheme.includes(theme)) {
        return res.status(400).json({ error: 'Invalid theme' });
      }
      if (language && !validLanguage.includes(language)) {
        return res.status(400).json({ error: 'Invalid language' });
      }

      // Build update query dynamically
      const updateFields = [];
      const updateValues = [];
      let paramIndex = 1;

      if (collection_visibility !== undefined) {
        updateFields.push(`collection_visibility = $${paramIndex}`);
        updateValues.push(collection_visibility);
        paramIndex++;
      }
      if (preferred_currency !== undefined) {
        updateFields.push(`preferred_currency = $${paramIndex}`);
        updateValues.push(preferred_currency);
        paramIndex++;
      }
      if (cards_per_page !== undefined) {
        updateFields.push(`cards_per_page = $${paramIndex}`);
        updateValues.push(cards_per_page);
        paramIndex++;
      }
      if (default_view !== undefined) {
        updateFields.push(`default_view = $${paramIndex}`);
        updateValues.push(default_view);
        paramIndex++;
      }
      if (two_factor_enabled !== undefined) {
        updateFields.push(`two_factor_enabled = $${paramIndex}`);
        updateValues.push(two_factor_enabled);
        paramIndex++;
      }
      if (notifications_email !== undefined) {
        updateFields.push(`notifications_email = $${paramIndex}`);
        updateValues.push(notifications_email);
        paramIndex++;
      }
      if (notifications_marketing !== undefined) {
        updateFields.push(`notifications_marketing = $${paramIndex}`);
        updateValues.push(notifications_marketing);
        paramIndex++;
      }
      if (theme !== undefined) {
        updateFields.push(`theme = $${paramIndex}`);
        updateValues.push(theme);
        paramIndex++;
      }
      if (language !== undefined) {
        updateFields.push(`language = $${paramIndex}`);
        updateValues.push(language);
        paramIndex++;
      }

      if (updateFields.length === 0) {
        return res.status(400).json({ error: 'No settings to update' });
      }

      // Add updated_at and user_id
      updateFields.push('updated_at = CURRENT_TIMESTAMP');
      updateValues.push(user.userId);

      // Execute update
      const updateQuery = `
        UPDATE users 
        SET ${updateFields.join(', ')}
        WHERE id = $${paramIndex}
        RETURNING 
          id, email, role, first_name, last_name, username,
          collection_visibility, preferred_currency, cards_per_page, 
          default_view, notifications_email, notifications_marketing, 
          two_factor_enabled, theme, language,
          created_at, updated_at
      `;

      const result = await sql.query(updateQuery, updateValues);

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

      const userData = result.rows[0];
      
      // Structure response
      const response = {
        user: {
          id: userData.id,
          email: userData.email,
          role: userData.role,
          first_name: userData.first_name,
          last_name: userData.last_name,
          username: userData.username
        },
        settings: {
          collection_visibility: userData.collection_visibility,
          preferred_currency: userData.preferred_currency,
          cards_per_page: userData.cards_per_page,
          default_view: userData.default_view,
          two_factor_enabled: userData.two_factor_enabled,
          notifications_email: userData.notifications_email,
          notifications_marketing: userData.notifications_marketing,
          theme: userData.theme,
          language: userData.language
        }
      };

      res.status(200).json(response);

    } else {
      res.status(405).json({ error: 'Method not allowed' });
    }

  } catch (error) {
    console.error('Settings API error:', error);
    res.status(500).json({ error: 'Internal server error' });
  }
}