<?php
/**
 * API Endpoint: Get Last Payment Receipt Image
 * 
 * Returns the receipt image (PNG) of the last payment made by a student.
 * 
 * Method: GET
 * URL: /api/students/last_receipt?student_id=...
 * 
 * Response: PNG image (binary)
 * 
 * Error Response: JSON with error message
 */

require_once '../../db_config.php';
require_once '../../includes/ReceiptGenerator.php';
require_once '../../includes/ApiValidator.php';
require_once '../../config/api_config.php';

// Initialize validator
$validator = new ApiValidator($pdo, defined('API_KEYS') ? API_KEYS : []);

// 1. Validate Request
$validation = $validator->validateRequest(['GET']);
if (!$validation['valid']) {
    http_response_code($validation['http_code']);
    header('Content-Type: application/json');
    echo json_encode(['status' => 'error', 'message' => $validation['error']]);
    exit;
}

// 2. Validate Input Parameters
$studentId = trim($_GET['student_id'] ?? '');

if (empty($studentId)) {
    http_response_code(400);
    header('Content-Type: application/json');
    echo json_encode(['status' => 'error', 'message' => 'Student ID is required']);
    exit;
}

// 3. Validate Student Exists
$studentCheck = $validator->validateStudentExists($studentId);
if (!$studentCheck['valid']) {
    http_response_code($studentCheck['http_code']);
    header('Content-Type: application/json');
    echo json_encode(['status' => 'error', 'message' => $studentCheck['error']]);
    exit;
}

// Prevent output from messing up image headers
ob_start();
ini_set('display_errors', 0);
error_reporting(E_ALL & ~E_DEPRECATED & ~E_NOTICE);

try {
    // 4. Fetch Last Payment Receipt Number
    $sqlLastReceipt = "SELECT receipt_no, payment_date
                       FROM tb_account_payment_registers
                       WHERE student_id = :student_id
                       ORDER BY payment_date DESC, id DESC
                       LIMIT 1";

    $stmt = $pdo->prepare($sqlLastReceipt);
    $stmt->execute(['student_id' => $studentId]);
    $lastPayment = $stmt->fetch(PDO::FETCH_ASSOC);

    if (!$lastPayment) {
        http_response_code(404);
        header('Content-Type: application/json');
        echo json_encode([
            'status' => 'error',
            'message' => 'No payment records found for this student'
        ]);
        exit;
    }

    $receiptNo = $lastPayment['receipt_no'];
    $paymentDate = $lastPayment['payment_date'];

    // 5. Fetch Receipt Meta Info (Student, Date)
    $sqlInfo = "SELECT pr.student_id, pr.payment_date, 
                       sr.last_name, sr.first_name, sr.other_name, sr.student_code,
                       al.level_name
                FROM tb_account_payment_registers pr
                JOIN tb_student_registrations sr ON pr.student_id = sr.id
                LEFT JOIN tb_academic_levels al ON sr.level_id = al.id
                WHERE pr.receipt_no = :receipt_no
                LIMIT 1";

    $stmt = $pdo->prepare($sqlInfo);
    $stmt->execute(['receipt_no' => $receiptNo]);
    $receiptInfo = $stmt->fetch(PDO::FETCH_ASSOC);

    if (!$receiptInfo) {
        http_response_code(500);
        header('Content-Type: application/json');
        echo json_encode([
            'status' => 'error',
            'message' => 'Receipt information not found'
        ]);
        exit;
    }

    $studentId = $receiptInfo['student_id'];

    // 6. Fetch All Fees for Student (from receivables)
    $sqlFees = "SELECT ar.fee_id, ar.actual_value as amount_billed,
                       ar.academic_session, ar.term_of_session,
                       sf.description as fee_description
                FROM tb_account_receivables ar
                JOIN tb_account_school_fees sf ON ar.fee_id = sf.id
                WHERE ar.student_id = :sid
                ORDER BY ar.academic_session ASC, ar.term_of_session ASC";

    $stmtFees = $pdo->prepare($sqlFees);
    $stmtFees->execute(['sid' => $studentId]);
    $allFees = $stmtFees->fetchAll(PDO::FETCH_ASSOC);

    $allocations = [];
    $receiptTotalPaid = 0;

    foreach ($allFees as $fee) {
        // Calculate Paid To Date (up to this receipt's date)
        $sqlPaid = "SELECT SUM(amount_paid) as total_paid
                    FROM tb_account_payment_registers
                    WHERE student_id = :sid
                      AND fee_id = :fid
                      AND academic_session = :as
                      AND term_of_session = :ts
                      AND payment_date <= :pd";

        $stmtPaid = $pdo->prepare($sqlPaid);
        $stmtPaid->execute([
            'sid' => $studentId,
            'fid' => $fee['fee_id'],
            'as' => $fee['academic_session'],
            'ts' => $fee['term_of_session'],
            'pd' => $paymentDate
        ]);
        $paidResult = $stmtPaid->fetch(PDO::FETCH_ASSOC);
        $paidToDate = floatval($paidResult['total_paid'] ?? 0);

        // Calculate Amount paid IN THIS RECEIPT (for total calculation)
        $sqlReceiptPay = "SELECT SUM(amount_paid) as receipt_paid
                          FROM tb_account_payment_registers
                          WHERE receipt_no = :rno
                            AND fee_id = :fid
                            AND academic_session = :as
                            AND term_of_session = :ts";
        $stmtReceiptPay = $pdo->prepare($sqlReceiptPay);
        $stmtReceiptPay->execute([
            'rno' => $receiptNo,
            'fid' => $fee['fee_id'],
            'as' => $fee['academic_session'],
            'ts' => $fee['term_of_session']
        ]);
        $receiptPayResult = $stmtReceiptPay->fetch(PDO::FETCH_ASSOC);
        $paidInReceipt = floatval($receiptPayResult['receipt_paid'] ?? 0);

        $receiptTotalPaid += $paidInReceipt;
        $balance = floatval($fee['amount_billed']) - $paidToDate;

        // Condition: Show if (Balance > 0) OR (PaidInReceipt > 0)
        // Helps filter out old fully paid fees, but keeps current payments even if they zeroed the balance
        if ($balance > 0.001 || $paidInReceipt > 0.001) {
            $allocations[] = [
                'description' => $fee['fee_description'],
                'academic_session' => $fee['academic_session'],
                'term_of_session' => $fee['term_of_session'],
                'amount_billed' => floatval($fee['amount_billed']),
                'amount' => $paidInReceipt,
                'total_paid_to_date' => $paidToDate,
                'balance' => $balance
            ];
        }
    }

    // 7. Prepare data structure for generator
    $data = [
        'receipt_no' => $receiptNo,
        'student_name' => trim($receiptInfo['last_name'] . ' ' . $receiptInfo['first_name'] . ' ' . ($receiptInfo['other_name'] ?? '')),
        'student_code' => $receiptInfo['student_code'],
        'level_name' => $receiptInfo['level_name'] ?? '',
        'payment_date' => $paymentDate,
        'total_paid' => $receiptTotalPaid,
        'allocations' => $allocations
    ];

    // 8. Generate Image
    $generator = new ReceiptGenerator();
    $imageData = $generator->generate($data);

    // 9. Output Image
    ob_end_clean(); // Discard any warnings/output buffered so far
    header('Content-Type: image/png');
    header('Content-Disposition: inline; filename="receipt_' . $receiptNo . '.png"');
    header('Content-Length: ' . strlen($imageData));
    echo $imageData;

} catch (Exception $e) {
    ob_end_clean();
    http_response_code(500);
    header('Content-Type: application/json');
    echo json_encode([
        'status' => 'error',
        'message' => 'Error generating receipt: ' . $e->getMessage()
    ]);
}