const database = require('./database');

class Product {
  constructor(data = {}) {
    this.id = data.id || null;
    this.name = data.name || '';
    this.description = data.description || '';
    this.category = data.category || '';
    this.quantity = data.quantity || 0;
    this.unit = data.unit || '';
    this.barcode = data.barcode || null;
    this.qr_code = data.qr_code || null;
    this.location = data.location || '';
    this.min_stock_level = data.min_stock_level || 0;
    this.created_at = data.created_at || null;
    this.updated_at = data.updated_at || null;
  }

  /**
   * Validate product data
   * @returns {Object} validation result with isValid boolean and errors array
   */
  validate() {
    const errors = [];

    // Required field validation
    if (!this.name || this.name.trim().length === 0) {
      errors.push('Product name is required');
    }

    if (this.name && this.name.length > 255) {
      errors.push('Product name must be less than 255 characters');
    }

    // Quantity validation
    if (typeof this.quantity !== 'number' || this.quantity < 0) {
      errors.push('Quantity must be a non-negative number');
    }

    // Min stock level validation
    if (typeof this.min_stock_level !== 'number' || this.min_stock_level < 0) {
      errors.push('Minimum stock level must be a non-negative number');
    }

    // Barcode validation (if provided)
    if (this.barcode && (typeof this.barcode !== 'string' || this.barcode.trim().length === 0)) {
      errors.push('Barcode must be a non-empty string if provided');
    }

    // Category validation
    if (this.category && this.category.length > 100) {
      errors.push('Category must be less than 100 characters');
    }

    // Unit validation
    if (this.unit && this.unit.length > 20) {
      errors.push('Unit must be less than 20 characters');
    }

    return {
      isValid: errors.length === 0,
      errors: errors
    };
  }

  /**
   * Save product to database
   * @returns {Promise<Product>} saved product instance
   */
  async save() {
    const validation = this.validate();
    if (!validation.isValid) {
      throw new Error(`Validation failed: ${validation.errors.join(', ')}`);
    }

    const db = database.getDatabase();
    
    try {
      if (this.id) {
        // Update existing product
        const stmt = db.prepare(`
          UPDATE items 
          SET name = ?, description = ?, category = ?, quantity = ?, 
              unit = ?, barcode = ?, qr_code = ?, location = ?, 
              min_stock_level = ?, updated_at = CURRENT_TIMESTAMP
          WHERE id = ?
        `);
        
        stmt.run(
          this.name, this.description, this.category, this.quantity,
          this.unit, this.barcode, this.qr_code, this.location,
          this.min_stock_level, this.id
        );
      } else {
        // Insert new product
        const stmt = db.prepare(`
          INSERT INTO items (name, description, category, quantity, unit, barcode, qr_code, location, min_stock_level)
          VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)
        `);
        
        const result = stmt.run(
          this.name, this.description, this.category, this.quantity,
          this.unit, this.barcode, this.qr_code, this.location,
          this.min_stock_level
        );
        
        this.id = result.lastInsertRowid;
      }
      
      return this;
    } catch (error) {
      if (error.code === 'SQLITE_CONSTRAINT_UNIQUE') {
        throw new Error('A product with this barcode already exists');
      }
      throw error;
    }
  }

  /**
   * Find product by ID
   * @param {number} id - Product ID
   * @returns {Promise<Product|null>} Product instance or null if not found
   */
  static async findById(id) {
    const db = database.getDatabase();
    const stmt = db.prepare('SELECT * FROM items WHERE id = ?');
    const row = stmt.get(id);
    
    return row ? new Product(row) : null;
  }

  /**
   * Find product by barcode
   * @param {string} barcode - Product barcode
   * @returns {Promise<Product|null>} Product instance or null if not found
   */
  static async findByBarcode(barcode) {
    const db = database.getDatabase();
    const stmt = db.prepare('SELECT * FROM items WHERE barcode = ?');
    const row = stmt.get(barcode);
    
    return row ? new Product(row) : null;
  }

  /**
   * Get all products with optional filtering
   * @param {Object} filters - Optional filters
   * @returns {Promise<Product[]>} Array of Product instances
   */
  static async findAll(filters = {}) {
    const db = database.getDatabase();
    let query = 'SELECT * FROM items';
    const params = [];
    const conditions = [];

    if (filters.category) {
      conditions.push('category = ?');
      params.push(filters.category);
    }

    if (filters.name) {
      conditions.push('name LIKE ?');
      params.push(`%${filters.name}%`);
    }

    if (conditions.length > 0) {
      query += ' WHERE ' + conditions.join(' AND ');
    }

    query += ' ORDER BY name';

    const stmt = db.prepare(query);
    const rows = stmt.all(...params);
    
    return rows.map(row => new Product(row));
  }

  /**
   * Delete product by ID
   * @param {number} id - Product ID
   * @returns {Promise<boolean>} true if deleted, false if not found
   */
  static async deleteById(id) {
    const db = database.getDatabase();
    const stmt = db.prepare('DELETE FROM items WHERE id = ?');
    const result = stmt.run(id);
    
    return result.changes > 0;
  }

  /**
   * Convert product to plain object
   * @returns {Object} Plain object representation
   */
  toJSON() {
    return {
      id: this.id,
      name: this.name,
      description: this.description,
      category: this.category,
      quantity: this.quantity,
      unit: this.unit,
      barcode: this.barcode,
      qr_code: this.qr_code,
      location: this.location,
      min_stock_level: this.min_stock_level,
      created_at: this.created_at,
      updated_at: this.updated_at
    };
  }
  /**
   * Get all unique categories
   * @returns {Promise<Array>} Array of unique category names
   */
  static async getCategories() {
    const db = database.getDatabase();
    
    try {
      const stmt = db.prepare(`
        SELECT DISTINCT category 
        FROM products 
        WHERE category IS NOT NULL AND category != '' 
        ORDER BY category
      `);
      
      const rows = stmt.all();
      return rows.map(row => row.category);
    } catch (error) {
      console.error('Error getting categories:', error);
      throw error;
    }
  }
}

module.exports = Product;