grade_submission.php

<?php
session_start();
require_once 'db.php';

// Check if user is logged in and is a professor
if (!isset($_SESSION['user']) || $_SESSION['user']['role'] !== 'professor') {
    http_response_code(403);
    echo json_encode(['status' => 'error', 'message' => 'Unauthorized']);
    exit();
}

if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $submission_id = $_POST['submission_id'] ?? '';
    $grade = $_POST['grade'] ?? '';
    $feedback = $_POST['feedback'] ?? '';

    if (empty($submission_id) || empty($grade)) {
        echo json_encode(['status' => 'error', 'message' => 'Missing required fields']);
        exit();
    }

    // Validate grade
    $grade = intval($grade);
    if ($grade < 0 || $grade > 100) {
        echo json_encode(['status' => 'error', 'message' => 'Grade must be between 0 and 100']);
        exit();
    }

    // Update submission
    $stmt = $conn->prepare("UPDATE submissions SET grade = ?, status = 'graded' WHERE id = ?");
    $stmt->bind_param("ii", $grade, $submission_id);

    if ($stmt->execute()) {
        echo json_encode(['status' => 'success', 'message' => 'Grade submitted successfully']);
    } else {
        echo json_encode(['status' => 'error', 'message' => 'Failed to update grade']);
    }
} else {
    http_response_code(405);
    echo json_encode(['status' => 'error', 'message' => 'Method not allowed']);
}
?>