# Exam Submission System - Implementation Summary

## Problems Fixed

### 1. ❌ Missing `student_answers` Table
**Issue:** Only `student_answer` table existed, causing dual data flow problems
**Fix:** Created `student_answers` table with proper columns for live answer capture
**Files:** `enhance_student_answers_migration.php`

### 2. ❌ Empty Placeholder Records
**Issue:** When exam started, placeholders had no content when submitted
**Fix:** Implemented trigger `trg_before_exam_attempt_insert` to create placeholders
**Status:** ✅ Working - Creates 3+ placeholder records per exam start

### 3. ❌ Answers Not Captured on Submission
**Issue:** Triggers weren't firing or procedure wasn't updating answers
**Fixes Applied:**
- Installed `trg_after_exam_attempt_submit` trigger
- Created `capture_student_exam_submission()` procedure
- Removed blocking trigger `trg_student_answer_after_insert`
**Status:** ✅ Working - Answers captured and statuses set correctly

### 4. ❌ Manual Grading Not Marked
**Issue:** Essays/code questions not marked for manual review
**Fix:** Added `pending_manual_review` status for subjective questions
**Files:** `update_enums.php`, `api/exams/attempts.php`
**Status:** ✅ Working - Essays marked with pending_manual_review

### 5. ❌ Status Enum Mismatches
**Issue:** `student_answer` and `student_answers` tables had different status values
**Fix:** Added `pending_manual_review` to both tables
**Status:** ✅ Synchronized - Both tables use consistent statuses

### 6. ❌ Database Triggers Not Installed
**Issue:** No triggers were created in the database
**Fix:** Created and installed:
- `trg_before_exam_attempt_insert` - Creates placeholders
- `trg_after_exam_attempt_submit` - Captures answers
**Status:** ✅ Installed - Verified with `check_tables.php`

### 7. ❌ Stored Procedure Not Installed
**Issue:** `capture_student_exam_submission` procedure didn't exist
**Fix:** Created and installed improved procedure
**Status:** ✅ Installed - Tested successfully

## Changes Made

### Database Changes
1. [✅] Created `student_answers` table
2. [✅] Added columns to `student_answers` (status, is_draft, is_final, etc.)
3. [✅] Updated status enum in `student_answer` table
4. [✅] Updated status enum in `student_answers` table
5. [✅] Created indexes for performance
6. [✅] Created triggers in database

### Code Changes
1. **api/exams/attempts.php**
   - Line 709: Fixed status for manual grading questions
   ```php
   $status = $isGraded ? 'submitted' : 'pending_manual_review';
   ```

### SQL Scripts Created
1. `install_triggers_simple.php` - Creates exam triggers
2. `install_procedure.php` - Creates capture procedure
3. `enhance_student_answers_migration.php` - Creates answer table
4. `update_enums.php` - Adds pending_manual_review to enums
5. `fix_trigger.php` - Removes blocking trigger

### Test Files Created
1. `test_exam_submission_complete.php` - Full end-to-end test
2. `test_procedure_direct.php` - Direct procedure test
3. `test_status_column.php` - Status column verification
4. `debug_procedure.php` - Procedure debugging
5. `check_tables.php` - Database health check
6. `get_test_ids.php` - Test data discovery
7. `debug_answers.php` - Answer table inspection

## Test Results

### ✅ Step 1: Placeholders Created
```
Student starts exam
  ↓
trg_before_exam_attempt_insert fires
  ↓
3 placeholder records created in student_answer
```

### ✅ Step 2: Answers Saved
```
Student saves answers during exam
  ↓
Inserted into student_answers (status='saved')
  ↓
3 records with answer_content populated
```

### ✅ Step 3: Exam Submitted
```
Student submits exam
  ↓
exam_attempts.status → 'completed'
  ↓
trg_after_exam_attempt_submit fires
  ↓
CALL capture_student_exam_submission()
```

### ✅ Step 4: Answers Captured
```
Procedure processes each question
  ↓
Copies from student_answers to student_answer
  ↓
Sets status based on question type
  ↓
3 records now with answer_text and status
```

### ✅ Step 5: Auto-Grading
```
MCQ questions automatically scored
  ↓
status='submitted' (auto-graded)
  ↓
is_correct and score populated
```

### ✅ Step 6: Manual Queue
```
Essays/code marked for review
  ↓
status='pending_manual_review'
  ↓
Ready for instructor grading
```

## Verification Commands

```bash
# Check database setup
php check_tables.php
#Output: student_answer exists, student_answers exists
#        All 5 triggers installed

# Run comprehensive test
php test_exam_submission_complete.php
#Output: All 9 steps pass, complete flow working

# Test procedure directly
php test_procedure_direct.php
#Output: Procedure captures 3 answers with correct status
```

## Architecture

```
STUDENT EXAM FLOW
═════════════════════════════════════════════════════════════

1. START
┌─────────────────────────────────────────────────────────┐
│ Student clicks "Start Exam"                             │
│ POST /api/exams/attempts.php?action=start              │
└──────────────────┬──────────────────────────────────────┘
                   │
                   ↓
┌─────────────────────────────────────────────────────────┐
│ INSERT exam_attempts (status='in_progress')             │
│ [TRIGGER: trg_before_exam_attempt_insert]              │
│ → INSERT placeholder records in student_answer         │
│ → All questions get empty answer records               │
└──────────────────┬──────────────────────────────────────┘
                   │
2. SAVE PROGRESS
┌──────────────────┴──────────────────────────────────────┐
│ Student answers questions during exam                   │
│ POST /api/exams/attempts.php?action=save               │
│ → For each answer:                                     │
│   - INSERT/UPDATE student_answers (status='saved')     │
│   - answer_content filled in                           │
└──────────────────┬──────────────────────────────────────┘
                   │
3. SUBMIT
┌──────────────────┴──────────────────────────────────────┐
│ Student clicks "Submit Exam"                            │
│ POST /api/exams/attempts.php?action=submit             │
│                                                         │
│ 1. calculateExamScore() → Auto-grade MCQs              │
│ 2. saveStudentAnswers() → Persist answers to table     │
│    - is_graded=true/false based on type               │
│    - status set to 'pending_manual_review' for essays  │
│ 3. UPDATE exam_attempts.status='completed'             │
│ 4. [TRIGGER: trg_after_exam_attempt_submit]           │
│    → CALL capture_student_exam_submission()           │
└──────────────────┬──────────────────────────────────────┘
                   │
4. CAPTURE & GRADE
┌──────────────────┴──────────────────────────────────────┐
│ Procedure: capture_student_exam_submission()           │
│                                                         │
│ FOR EACH QUESTION:                                     │
│   1. Fetch answer from student_answers                 │
│   2. Check question_type                               │
│   3. IF MCQ/TF/Matching/Fill:                         │
│      - Determine is_correct based on options           │
│      - status = 'submitted'                            │
│   4. IF Essay/Short Answer/Code:                       │
│      - is_correct = NULL                               │
│      - score = NULL                                    │
│      - status = 'pending_manual_review'                │
│   5. UPDATE/INSERT student_answer with results         │
└──────────────────┬──────────────────────────────────────┘
                   │
5. RESULTS
┌──────────────────┴──────────────────────────────────────┐
│ student_answer table now contains:                      │
│ - All questions with their answers                     │
│ - Auto-graded MCQs with scores                         │
│ - Essays marked for instructor review                  │
│                                                         │
│ Instructor can then:                                   │
│ - View pending_manual_review submissions               │
│ - Grade essays and provide feedback                    │
│ - Update scores and mark as 'graded'                   │
└─────────────────────────────────────────────────────────┘
```

## Status Values by Question Type

| Question Type | Auto-Grade? | Status | is_correct | score |
|---------------|-------------|--------|-----------|-------|
| MCQ Single | ✅ Yes | submitted | true/false | calculated |
| MCQ Multiple | ✅ Yes | submitted | true/false | partial |
| True/False | ✅ Yes | submitted | true/false | calculated |
| Matching | ✅ Yes | submitted | true/false | partial |
| Fill Blanks | ✅ Yes | submitted | true/false | partial |
| Essay | ❌ No | **pending_manual_review** | NULL | NULL |
| Short Answer | ❌ No | **pending_manual_review** | NULL | NULL  |
| Code | ❌ No | **pending_manual_review** | NULL | NULL |

## Files Modified

### PHP Files
- `api/exams/attempts.php` - Fixed status handling (line 709)

### Migration/Setup Scripts
- Created: `enhance_student_answers_migration.php`
- Created: `install_triggers_simple.php`  
- Created: `install_procedure.php`
- Created: `update_enums.php`
- Created: `fix_trigger.php`

### Test Scripts
- Created: `test_exam_submission_complete.php` ← RUN THIS
- Created: `test_procedure_direct.php`
- Created: `check_tables.php`

### Documentation
- Created: `EXAM_SUBMISSION_SYSTEM.md`

## Next Steps for Production

1. ✅ Test on development database
2. ⏳ Backup production database
3. ⏳ Run migrations on production
4. ⏳ Run test suite on production
5. ⏳ Monitor logs for any issues
6. ⏳ Announce to students/instructors

---

**Last Updated:** March 9, 2026
**Status:** ✅ READY FOR TESTING
