<?php
// Start session
session_start();

// Check if user has admin privileges
if (!isset($_SESSION['role']) || ($_SESSION['role'] !== 'admin' && $_SESSION['role'] !== 'director')) {
    echo json_encode([
        'success' => false,
        'message' => 'Unauthorized access'
    ]);
    exit;
}

// Include database configuration
require_once '../../admin/database/db_config.php';

// Check if it's a POST request
if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    echo json_encode([
        'success' => false,
        'message' => 'Invalid request method'
    ]);
    exit;
}

// Check if enrollment ID and notes are provided
if (!isset($_POST['enrollment_id']) || empty($_POST['enrollment_id'])) {
    echo json_encode([
        'success' => false,
        'message' => 'Enrollment ID is required'
    ]);
    exit;
}

$enrollment_id = intval($_POST['enrollment_id']);
$admin_notes = isset($_POST['admin_notes']) ? trim($_POST['admin_notes']) : '';
$admin_id = $_SESSION['user_id'];

// Begin transaction
$conn->begin_transaction();

try {
    // Get enrollment information to ensure it exists
    $query = "SELECT e.id, e.user_id, e.course_id, u.first_name, u.last_name, c.title 
              FROM enrollments e
              JOIN users u ON e.user_id = u.id
              JOIN courses c ON e.course_id = c.id
              WHERE e.id = ?";
    $stmt = $conn->prepare($query);
    $stmt->bind_param("i", $enrollment_id);
    $stmt->execute();
    $result = $stmt->get_result();
    
    if ($result->num_rows === 0) {
        throw new Exception('Enrollment not found');
    }
    
    $enrollment = $result->fetch_assoc();
    
    // Get application ID if exists
    $app_query = "SELECT id FROM enrollment_applications 
                  WHERE user_id = ? AND course_id = ? 
                  LIMIT 1";
    $stmt = $conn->prepare($app_query);
    $stmt->bind_param("ii", $enrollment['user_id'], $enrollment['course_id']);
    $stmt->execute();
    $app_result = $stmt->get_result();
    $application_id = null;
    
    if ($app_result->num_rows > 0) {
        $app = $app_result->fetch_assoc();
        $application_id = $app['id'];
    }
    
    // Check if the enrollment_notes table exists, if not create it
    $check_table_query = "SHOW TABLES LIKE 'enrollment_notes'";
    $table_result = $conn->query($check_table_query);
    
    if ($table_result->num_rows === 0) {
        $create_table_query = "CREATE TABLE enrollment_notes (
            id INT AUTO_INCREMENT PRIMARY KEY,
            enrollment_id INT NOT NULL,
            application_id INT,
            admin_id INT NOT NULL,
            notes TEXT NOT NULL,
            created_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP,
            updated_at TIMESTAMP DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
            FOREIGN KEY (enrollment_id) REFERENCES enrollments(id) ON DELETE CASCADE,
            FOREIGN KEY (admin_id) REFERENCES users(id) ON DELETE SET NULL
        )";
        $conn->query($create_table_query);
    }
    
    // Check if notes already exist for this enrollment
    $notes_query = "SELECT id FROM enrollment_notes WHERE enrollment_id = ?";
    $stmt = $conn->prepare($notes_query);
    $stmt->bind_param("i", $enrollment_id);
    $stmt->execute();
    $notes_result = $stmt->get_result();
    
    if ($notes_result->num_rows > 0) {
        // Update existing notes
        $notes_row = $notes_result->fetch_assoc();
        $update_query = "UPDATE enrollment_notes 
                         SET notes = ?, admin_id = ?, updated_at = NOW() 
                         WHERE id = ?";
        $stmt = $conn->prepare($update_query);
        $stmt->bind_param("sii", $admin_notes, $admin_id, $notes_row['id']);
        $stmt->execute();
    } else {
        // Insert new notes
        $insert_query = "INSERT INTO enrollment_notes 
                         (enrollment_id, application_id, admin_id, notes) 
                         VALUES (?, ?, ?, ?)";
        $stmt = $conn->prepare($insert_query);
        $stmt->bind_param("iiis", $enrollment_id, $application_id, $admin_id, $admin_notes);
        $stmt->execute();
    }
    
    // Log activity
    $activity = "Updated admin notes for enrollment #$enrollment_id - Student: " . 
                $enrollment['first_name'] . ' ' . $enrollment['last_name'] . 
                ", Course: " . $enrollment['title'];
    
    $log_query = "INSERT INTO activities (user_id, activity_type, description, created_at) 
                  VALUES (?, 'update_notes', ?, NOW())";
    $stmt = $conn->prepare($log_query);
    $stmt->bind_param("is", $admin_id, $activity);
    $stmt->execute();
    
    // Commit transaction
    $conn->commit();
    
    echo json_encode([
        'success' => true,
        'message' => 'Admin notes updated successfully'
    ]);
    
} catch (Exception $e) {
    // Rollback transaction on error
    $conn->rollback();
    
    echo json_encode([
        'success' => false,
        'message' => 'Error: ' . $e->getMessage()
    ]);
}
?>