<?php
/**
 * API Endpoint: Fetch Student Outstanding Balance
 * 
 * Returns the total outstanding balance and a breakdown of fees
 * for all terms and sessions.
 * 
 * Method: GET
 * URL: /api/students/balance?student_id=...
 */

require_once '../../db_config.php';
require_once '../../includes/PaymentProcessor.php';
require_once '../../includes/ApiValidator.php';
require_once '../../config/api_config.php';

// Initialize core classes
$validator = new ApiValidator($pdo, defined('API_KEYS') ? API_KEYS : []);
$processor = new PaymentProcessor($pdo);

// 1. Validate Request (Method & Auth)
$validation = $validator->validateRequest(['GET']);
if (!$validation['valid']) {
    http_response_code($validation['http_code']);
    echo json_encode(['status' => 'error', 'message' => $validation['error']]);
    exit;
}

// 2. Validate Student ID
$studentId = trim($_GET['student_id'] ?? '');
if (empty($studentId)) {
    http_response_code(400);
    echo json_encode(['status' => 'error', 'message' => 'Student ID is required']);
    exit;
}

$studentCheck = $validator->validateStudentExists($studentId);
if (!$studentCheck['valid']) {
    http_response_code($studentCheck['http_code']);
    echo json_encode(['status' => 'error', 'message' => $studentCheck['error']]);
    exit;
}

try {
    // 3. Fetch Data
    $data = $processor->getTotalOutstandingBalance($studentId);

    // 4. Send Response
    echo json_encode([
        'status' => 'success',
        'data' => $data
    ]);

} catch (Exception $e) {
    // Log error (if logging enabled)
    if (function_exists('log_api_request')) {
        // log_api_request would be defined in api_config or similar, 
        // but for now we just handle the output.
    }

    http_response_code(500);
    echo json_encode(['status' => 'error', 'message' => 'Internal server error: ' . $e->getMessage()]);
}