<?php
session_start();

if (!isset($_SESSION['user_id'])) {
    http_response_code(401);
    exit();
}

require_once 'db_connection.php';

header('Content-Type: application/json');

if (!isset($_GET['category_id'])) {
    echo json_encode(['error' => 'Category ID is required']);
    exit();
}

$categoryId = intval($_GET['category_id']);

try {
    $stmt = $conn->prepare("SELECT id, name FROM expense_heads WHERE category_id = ? ORDER BY name");
    $stmt->bind_param("i", $categoryId);
    $stmt->execute();
    $result = $stmt->get_result();
    $heads = $result->fetch_all(MYSQLI_ASSOC);
    $stmt->close();
    
    echo json_encode($heads);
} catch (Exception $e) {
    echo json_encode(['error' => 'Database error']);
    error_log("Get expense heads error: " . $e->getMessage());
}

$conn->close();
?>