const { DataTypes } = require('sequelize');
const { sequelize } = require('../config/database');

const GrammarMapping = sequelize.define('GrammarMapping', {
  id: {
    type: DataTypes.UUID,
    defaultValue: DataTypes.UUIDV4,
    primaryKey: true
  },
  grammar_id: {
    type: DataTypes.UUID,
    allowNull: false,
    references: {
      model: 'grammars',
      key: 'id'
    },
    onDelete: 'CASCADE',
    comment: 'Foreign key to grammars table'
  },
  book_id: {
    type: DataTypes.STRING(100),
    allowNull: false,
    comment: 'Book identifier (e.g., "global-success-2")'
  },
  grade: {
    type: DataTypes.INTEGER,
    allowNull: false,
    comment: 'Grade level'
  },
  unit: {
    type: DataTypes.INTEGER,
    allowNull: true,
    comment: 'Unit number in the book'
  },
  lesson: {
    type: DataTypes.INTEGER,
    allowNull: true,
    comment: 'Lesson number within the unit'
  },
  context_note: {
    type: DataTypes.TEXT,
    allowNull: true,
    comment: 'Additional context about where this grammar appears'
  }
}, {
  tableName: 'grammar_mappings',
  timestamps: true,
  indexes: [
    { fields: ['grammar_id'] },
    { fields: ['book_id'] },
    { fields: ['grade'] },
    { fields: ['book_id', 'grade', 'unit', 'lesson'] }
  ]
});

module.exports = GrammarMapping;