const { DataTypes } = require("sequelize");
const sequelize = require("../../config/db.config");

const CoursePrerequisite = sequelize.define("CoursePrerequisite", {
  prereq_id:  { type: DataTypes.BIGINT, primaryKey: true, autoIncrement: true },
  course_id:  { type: DataTypes.BIGINT, allowNull: false },  // the course that HAS this prereq
  ref_type:   { type: DataTypes.ENUM("course", "unit", "lesson"), allowNull: false },
  ref_id:     { type: DataTypes.BIGINT, allowNull: false },   // FK to courses/units/lessons
  order_index:{ type: DataTypes.INTEGER, defaultValue: 0 },
}, {
  tableName: "course_prerequisites",
  timestamps: true,
});

module.exports = CoursePrerequisite