const { Pool } = require('pg');
const jwt = require('jsonwebtoken');

const pool = new Pool({
  connectionString: process.env.DATABASE_URL,
  ssl: process.env.NODE_ENV === 'production' ? { rejectUnauthorized: false } : false,
});

// Verify JWT token and extract user info
function verifyAuth(req) {
  const authHeader = req.headers.authorization;
  if (!authHeader || !authHeader.startsWith('Bearer ')) {
    throw new Error('No authorization token provided');
  }

  const token = authHeader.substring(7);
  const jwtSecret = process.env.JWT_SECRET || 'fallback-secret-change-in-production';
  
  try {
    const decoded = jwt.verify(token, jwtSecret);
    return decoded;
  } catch (error) {
    throw new Error('Invalid or expired token');
  }
}

export default async function handler(req, res) {
  const client = await pool.connect();
  
  try {
    const user = verifyAuth(req);

    // Ensure ocr_settings column exists (auto-migration)
    try {
      await client.query(`
        ALTER TABLE user_preferences 
        ADD COLUMN IF NOT EXISTS ocr_settings JSONB DEFAULT '{
          "preferred_service": "openai",
          "openai_api_key": "",
          "ollama_url": "http://localhost:11434",
          "auto_add_to_collection": false,
          "confidence_threshold": 80
        }'::jsonb;
      `);
    } catch (error) {
      // Column might already exist, ignore error
      console.log('OCR settings column may already exist:', error.message);
    }

    if (req.method === 'GET') {
      // Get user preferences
      const result = await client.query(`
        SELECT 
          default_view,
          items_per_page,
          enable_animations,
          enable_ocr,
          theme,
          privacy_settings,
          ocr_settings,
          created_at,
          updated_at
        FROM user_preferences 
        WHERE user_id = $1
      `, [user.userId]);

      if (result.rows.length === 0) {
        // Create default preferences if none exist
        const defaultPrefs = {
          default_view: 'card',
          items_per_page: 20,
          enable_animations: true,
          enable_ocr: true,
          theme: 'light',
          privacy_settings: { collections_public: false, decks_public: false },
          ocr_settings: {
            preferred_service: 'openai',
            openai_api_key: '',
            ollama_url: 'http://localhost:11434',
            auto_add_to_collection: false,
            confidence_threshold: 80
          }
        };

        await client.query(`
          INSERT INTO user_preferences (
            user_id, default_view, items_per_page, enable_animations, 
            enable_ocr, theme, privacy_settings, ocr_settings
          ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8)
        `, [
          user.userId,
          defaultPrefs.default_view,
          defaultPrefs.items_per_page,
          defaultPrefs.enable_animations,
          defaultPrefs.enable_ocr,
          defaultPrefs.theme,
          JSON.stringify(defaultPrefs.privacy_settings),
          JSON.stringify(defaultPrefs.ocr_settings)
        ]);

        return res.status(200).json({
          success: true,
          preferences: defaultPrefs
        });
      }

      const preferences = result.rows[0];
      res.status(200).json({
        success: true,
        preferences: {
          defaultView: preferences.default_view,
          itemsPerPage: preferences.items_per_page,
          enableAnimations: preferences.enable_animations,
          enableOcr: preferences.enable_ocr,
          theme: preferences.theme,
          privacySettings: preferences.privacy_settings,
          ocrSettings: preferences.ocr_settings || {
            preferred_service: 'openai',
            openai_api_key: '',
            ollama_url: 'http://localhost:11434',
            auto_add_to_collection: false,
            confidence_threshold: 80
          },
          createdAt: preferences.created_at,
          updatedAt: preferences.updated_at
        }
      });

    } else if (req.method === 'PUT') {
      // Update user preferences
      const {
        defaultView,
        itemsPerPage,
        enableAnimations,
        enableOcr,
        theme,
        privacySettings,
        ocrSettings
      } = req.body;

      // Validate OCR settings if provided
      if (ocrSettings) {
        const allowedServices = ['openai', 'ollama'];
        if (ocrSettings.preferred_service && !allowedServices.includes(ocrSettings.preferred_service)) {
          return res.status(400).json({
            error: 'Invalid OCR service. Must be "openai" or "ollama"'
          });
        }

        if (ocrSettings.confidence_threshold && (ocrSettings.confidence_threshold < 0 || ocrSettings.confidence_threshold > 100)) {
          return res.status(400).json({
            error: 'Confidence threshold must be between 0 and 100'
          });
        }
      }

      // Update preferences (upsert)
      const result = await client.query(`
        INSERT INTO user_preferences (
          user_id, default_view, items_per_page, enable_animations, 
          enable_ocr, theme, privacy_settings, ocr_settings, updated_at
        ) VALUES ($1, $2, $3, $4, $5, $6, $7, $8, CURRENT_TIMESTAMP)
        ON CONFLICT (user_id) 
        DO UPDATE SET
          default_view = COALESCE($2, user_preferences.default_view),
          items_per_page = COALESCE($3, user_preferences.items_per_page),
          enable_animations = COALESCE($4, user_preferences.enable_animations),
          enable_ocr = COALESCE($5, user_preferences.enable_ocr),
          theme = COALESCE($6, user_preferences.theme),
          privacy_settings = COALESCE($7, user_preferences.privacy_settings),
          ocr_settings = COALESCE($8, user_preferences.ocr_settings),
          updated_at = CURRENT_TIMESTAMP
        RETURNING *
      `, [
        user.userId,
        defaultView,
        itemsPerPage,
        enableAnimations,
        enableOcr,
        theme,
        privacySettings ? JSON.stringify(privacySettings) : null,
        ocrSettings ? JSON.stringify(ocrSettings) : null
      ]);

      const preferences = result.rows[0];
      res.status(200).json({
        success: true,
        message: 'Preferences updated successfully',
        preferences: {
          defaultView: preferences.default_view,
          itemsPerPage: preferences.items_per_page,
          enableAnimations: preferences.enable_animations,
          enableOcr: preferences.enable_ocr,
          theme: preferences.theme,
          privacySettings: preferences.privacy_settings,
          ocrSettings: preferences.ocr_settings,
          updatedAt: preferences.updated_at
        }
      });

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

  } catch (error) {
    console.error('User preferences error:', error);
    
    if (error.message.includes('authorization') || error.message.includes('token')) {
      res.status(401).json({ error: 'Unauthorized' });
    } else {
      res.status(500).json({ 
        error: 'Failed to manage preferences',
        details: process.env.NODE_ENV === 'development' ? error.message : undefined
      });
    }
  } finally {
    client.release();
  }
}