<?php
header('Content-Type: application/json');
require_once __DIR__ . '/../includes/uuid.php';
require_once __DIR__ . '/../db/config.php';

$db = db();

if ($_SERVER['REQUEST_METHOD'] !== 'POST') {
    http_response_code(405);
    echo json_encode(['error' => 'Method not allowed']);
    exit();
}

$data = json_decode(file_get_contents('php://input'), true);

// Basic validation
$required_fields = ['student_number', 'first_name', 'last_name', 'date_of_birth', 'gender', 'admission_date'];
foreach ($required_fields as $field) {
    if (empty($data[$field])) {
        http_response_code(400);
        echo json_encode(['error' => "Missing required field: {$field}"]);
        exit();
    }
}

$db->beginTransaction();

try {
    // 1. Create Subledger Entry
    $subledger_id = UUID::v4();
    $student_id = UUID::v4(); // Generate student ID in advance

    $stmt = $db->prepare(
        'INSERT INTO subledgers (id, subledger_type, reference_id) VALUES (?, ?, ?)'
    );
    $stmt->execute([$subledger_id, 'Student', $student_id]);

    // 2. Create Student Entry
    $stmt = $db->prepare(
        'INSERT INTO students (id, student_number, first_name, middle_name, last_name, date_of_birth, gender, admission_date, subledger_id) VALUES (?, ?, ?, ?, ?, ?, ?, ?, ?)'
    );
    $stmt->execute([
        $student_id,
        $data['student_number'],
        $data['first_name'],
        $data['middle_name'] ?? null,
        $data['last_name'],
        $data['date_of_birth'],
        $data['gender'],
        $data['admission_date'],
        $subledger_id
    ]);

    $db->commit();

    // Fetch the created student to return it
    $stmt = $db->prepare('SELECT * FROM students WHERE id = ?');
    $stmt->execute([$student_id]);
    $student = $stmt->fetch(PDO::FETCH_ASSOC);

    http_response_code(201);
    echo json_encode($student);

} catch (Exception $e) {
    $db->rollBack();
    http_response_code(500);
    // Check for unique constraint violation for student_number
    if ($e->errorInfo[1] == 1062) { // 1062 is the MySQL error code for duplicate entry
         echo json_encode(['error' => 'A student with this student number already exists.', 'details' => $e->getMessage()]);
    } else {
         echo json_encode(['error' => 'Database error occurred.', 'details' => $e->getMessage()]);
    }
}