const mongoose = require('mongoose');

const answerSchema = new mongoose.Schema({
  questionId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Question',
    required: true
  },
  selectedAnswers: {
    type: [String],
    default: []
  }
}, { _id: false });

const submissionSchema = new mongoose.Schema({
  studentId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'User',
    required: true
  },
  quizId: {
    type: mongoose.Schema.Types.ObjectId,
    ref: 'Quiz',
    required: true
  },
  answers: [answerSchema],
  score: {
    type: Number,
    default: 0
  },
  totalMarks: {
    type: Number,
    default: 0
  },
  percentage: {
    type: Number,
    default: 0
  },
  timeTaken: {
    type: Number, // in seconds
    default: 0
  },
  submittedAt: {
    type: Date,
    default: Date.now
  }
}, {
  timestamps: true
});

// Prevent duplicate submissions
submissionSchema.index({ studentId: 1, quizId: 1 }, { unique: true });

module.exports = mongoose.model('Submission', submissionSchema);
