<?php
/**
 * Bài 07: Phân trang (Pagination - 5 sinh viên/trang) kết hợp Tìm kiếm & Thêm/Sửa/Xóa với Bootstrap 5
 */
require_once __DIR__ . '/../../db_config.php';
require_once __DIR__ . '/../lab04_helper.php';

$connectionError = null;
$msg = '';
$err = '';
$perPage = 5;
$currentPage = max(1, (int)($_GET['page'] ?? 1));
$keyword = trim((string)($_GET['q'] ?? ''));

$students = [];
$totalRecords = 0;
$totalPages = 1;
$editStudent = null;

try {
    $pdo = getPdoConnection(true);
    ensureLab04StudentsTable($pdo, false);

    // Xử lý Thêm / Sửa / Xóa ngay trên trang Bài 07
    if ($_SERVER['REQUEST_METHOD'] === 'POST') {
        $action = (string)($_POST['action'] ?? '');

        if ($action === 'save') {
            $id       = (int)($_POST['id'] ?? 0);
            $name     = trim((string)($_POST['name'] ?? ''));
            $email    = trim((string)($_POST['email'] ?? ''));
            $phone    = trim((string)($_POST['phone'] ?? ''));
            $birthday = trim((string)($_POST['birthday'] ?? ''));

            if ($name === '' || !filter_var($email, FILTER_VALIDATE_EMAIL)) {
                $err = 'Vui lòng nhập đầy đủ Họ tên và Email hợp lệ.';
            } elseif ($id > 0) {
                $stmt = $pdo->prepare("UPDATE students SET name = :name, email = :email, phone = :phone, birthday = :birthday WHERE id = :id");
                $stmt->execute([
                    ':name'     => $name,
                    ':email'    => $email,
                    ':phone'    => $phone !== '' ? $phone : null,
                    ':birthday' => $birthday !== '' ? $birthday : null,
                    ':id'       => $id,
                ]);
                $msg = "Đã cập nhật sinh viên #{$id} ({$name}) thành công!";
            } else {
                $stmt = $pdo->prepare("INSERT INTO students (name, email, phone, birthday) VALUES (:name, :email, :phone, :birthday)");
                $stmt->execute([
                    ':name'     => $name,
                    ':email'    => $email,
                    ':phone'    => $phone !== '' ? $phone : null,
                    ':birthday' => $birthday !== '' ? $birthday : null,
                ]);
                $msg = "Đã thêm sinh viên mới \"{$name}\" thành công!";
            }
        } elseif ($action === 'delete') {
            $delId = (int)($_POST['id'] ?? 0);
            if ($delId > 0) {
                $stmt = $pdo->prepare("DELETE FROM students WHERE id = :id");
                $stmt->execute([':id' => $delId]);
                $msg = "Đã xóa sinh viên #{$delId} thành công!";
            }
        }
    }

    // Nếu người dùng bấm nút Sửa
    if (isset($_GET['edit_id'])) {
        $editStmt = $pdo->prepare("SELECT * FROM students WHERE id = :id");
        $editStmt->execute([':id' => (int)$_GET['edit_id']]);
        $editStudent = $editStmt->fetch() ?: null;
    }

    // 1. Đếm tổng số bản ghi khớp từ khóa tìm kiếm
    $whereSql = '';
    $params = [];
    if ($keyword !== '') {
        $whereSql = 'WHERE name LIKE :kw';
        $params[':kw'] = '%' . $keyword . '%';
    }

    $countStmt = $pdo->prepare("SELECT COUNT(*) FROM students {$whereSql}");
    $countStmt->execute($params);
    $totalRecords = (int)$countStmt->fetchColumn();

    $totalPages = max(1, (int)ceil($totalRecords / $perPage));
    if ($currentPage > $totalPages) {
        $currentPage = $totalPages;
    }
    $offset = ($currentPage - 1) * $perPage;

    // 2. Lấy dữ liệu phân trang bằng LIMIT & OFFSET
    $listSql = "SELECT id, name, email, phone, birthday, created_at
                FROM students
                {$whereSql}
                ORDER BY id ASC
                LIMIT :limit OFFSET :offset";
    $listStmt = $pdo->prepare($listSql);
    if ($keyword !== '') {
        $listStmt->bindValue(':kw', '%' . $keyword . '%', PDO::PARAM_STR);
    }
    $listStmt->bindValue(':limit', $perPage, PDO::PARAM_INT);
    $listStmt->bindValue(':offset', $offset, PDO::PARAM_INT);
    $listStmt->execute();
    $students = $listStmt->fetchAll();
} catch (Throwable $e) {
    $connectionError = $e;
}

function buildBai07PageUrl(int $page, string $keyword): string {
    $query = ['page' => $page];
    if ($keyword !== '') {
        $query['q'] = $keyword;
    }
    return 'index.php?' . http_build_query($query);
}
?>
<!DOCTYPE html>
<html lang="vi">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Bài 07 - Phân trang &amp; Tìm kiếm Sinh viên (Bootstrap 5 + PDO)</title>
    <link href="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/css/bootstrap.min.css" rel="stylesheet">
</head>
<body class="bg-light">
    <?php renderLab04Navbar('Bai07'); ?>

    <div class="container pb-5">
        <?php if ($msg !== ''): ?>
            <div class="alert alert-success alert-dismissible fade show shadow-sm">
                ✅ <?= htmlspecialchars($msg) ?>
                <button type="button" class="btn-close" data-bs-dismiss="alert"></button>
            </div>
        <?php endif; ?>
        <?php if ($err !== ''): ?>
            <div class="alert alert-danger alert-dismissible fade show shadow-sm">
                ⚠️ <?= htmlspecialchars($err) ?>
                <button type="button" class="btn-close" data-bs-dismiss="alert"></button>
            </div>
        <?php endif; ?>

        <?php if ($connectionError): ?>
            <?php renderLab04DbError($connectionError); ?>
        <?php else: ?>
            <div class="row g-4">
                <!-- Cột trái: Form Thêm / Sửa nhanh -->
                <div class="col-lg-4">
                    <div class="card border-0 shadow-sm">
                        <div class="card-header <?= $editStudent ? 'bg-warning-subtle' : 'bg-primary text-white' ?> py-3">
                            <h5 class="mb-0 fw-bold">
                                <?= $editStudent ? '✏️ Sửa sinh viên #' . (int)$editStudent['id'] : '➕ Thêm sinh viên mới' ?>
                            </h5>
                        </div>
                        <div class="card-body">
                            <form method="post" action="<?= htmlspecialchars(buildBai07PageUrl($currentPage, $keyword)) ?>">
                                <input type="hidden" name="action" value="save">
                                <input type="hidden" name="id" value="<?= (int)($editStudent['id'] ?? 0) ?>">

                                <div class="mb-3">
                                    <label class="form-label fw-semibold">Họ và tên <span class="text-danger">*</span></label>
                                    <input type="text" name="name" class="form-control" required
                                           value="<?= htmlspecialchars((string)($editStudent['name'] ?? '')) ?>"
                                           placeholder="Nhập họ và tên">
                                </div>
                                <div class="mb-3">
                                    <label class="form-label fw-semibold">Email <span class="text-danger">*</span></label>
                                    <input type="email" name="email" class="form-control" required
                                           value="<?= htmlspecialchars((string)($editStudent['email'] ?? '')) ?>"
                                           placeholder="sinhvien@student.edu.vn">
                                </div>
                                <div class="mb-3">
                                    <label class="form-label fw-semibold">Số điện thoại</label>
                                    <input type="text" name="phone" class="form-control"
                                           value="<?= htmlspecialchars((string)($editStudent['phone'] ?? '')) ?>"
                                           placeholder="0901234567">
                                </div>
                                <div class="mb-3">
                                    <label class="form-label fw-semibold">Ngày sinh</label>
                                    <input type="date" name="birthday" class="form-control"
                                           value="<?= htmlspecialchars((string)($editStudent['birthday'] ?? '')) ?>">
                                </div>

                                <div class="d-flex gap-2">
                                    <button type="submit" class="btn <?= $editStudent ? 'btn-warning' : 'btn-primary' ?> flex-grow-1 fw-semibold">
                                        <?= $editStudent ? '💾 Cập nhật' : '💾 Thêm mới' ?>
                                    </button>
                                    <?php if ($editStudent): ?>
                                        <a href="<?= htmlspecialchars(buildBai07PageUrl($currentPage, $keyword)) ?>" class="btn btn-outline-secondary">Hủy</a>
                                    <?php endif; ?>
                                </div>
                            </form>
                        </div>
                    </div>
                </div>

                <!-- Cột phải: Tìm kiếm + Bảng phân trang -->
                <div class="col-lg-8">
                    <div class="card border-0 shadow-sm">
                        <div class="card-header bg-white py-3">
                            <div class="d-flex flex-wrap justify-content-between align-items-center gap-2">
                                <div>
                                    <h4 class="mb-0 fw-bold text-primary">Bài 07: Phân trang (<?= $perPage ?> SV/trang) &amp; Tìm kiếm</h4>
                                    <small class="text-muted">
                                        Hiển thị trang <strong><?= $currentPage ?>/<?= $totalPages ?></strong>
                                        (Tổng cộng <strong><?= $totalRecords ?></strong> sinh viên)
                                    </small>
                                </div>
                                <form method="get" action="index.php" class="d-flex gap-2">
                                    <input type="text" name="q" class="form-control form-control-sm"
                                           placeholder="Tìm theo tên sinh viên..."
                                           value="<?= htmlspecialchars($keyword) ?>">
                                    <button type="submit" class="btn btn-sm btn-primary">🔍 Tìm</button>
                                    <?php if ($keyword !== ''): ?>
                                        <a href="index.php" class="btn btn-sm btn-outline-secondary">Xóa lọc</a>
                                    <?php endif; ?>
                                </form>
                            </div>
                        </div>

                        <div class="card-body p-0">
                            <div class="table-responsive">
                                <table class="table table-hover table-bordered align-middle mb-0">
                                    <thead class="table-light">
                                        <tr>
                                            <th class="text-center" style="width:65px;">ID</th>
                                            <th>Họ và tên</th>
                                            <th>Email</th>
                                            <th>Điện thoại</th>
                                            <th>Ngày sinh</th>
                                            <th class="text-center" style="width:140px;">Thao tác</th>
                                        </tr>
                                    </thead>
                                    <tbody>
                                        <?php if (empty($students)): ?>
                                            <tr>
                                                <td colspan="6" class="text-center text-muted py-4">
                                                    Không tìm thấy sinh viên nào phù hợp.
                                                </td>
                                            </tr>
                                        <?php else: ?>
                                            <?php foreach ($students as $sv): ?>
                                                <tr>
                                                    <td class="text-center fw-bold">#<?= (int)$sv['id'] ?></td>
                                                    <td class="fw-semibold"><?= htmlspecialchars((string)$sv['name']) ?></td>
                                                    <td><?= htmlspecialchars((string)$sv['email']) ?></td>
                                                    <td><?= htmlspecialchars((string)($sv['phone'] ?? '—')) ?></td>
                                                    <td><?= !empty($sv['birthday']) ? date('d/m/Y', strtotime((string)$sv['birthday'])) : '—' ?></td>
                                                    <td class="text-center">
                                                        <a href="<?= htmlspecialchars(buildBai07PageUrl($currentPage, $keyword) . '&edit_id=' . (int)$sv['id']) ?>"
                                                           class="btn btn-sm btn-outline-warning">Sửa</a>
                                                        <form method="post" action="<?= htmlspecialchars(buildBai07PageUrl($currentPage, $keyword)) ?>"
                                                              class="d-inline"
                                                              onsubmit="return confirm('Bạn có chắc chắn muốn xóa sinh viên này?');">
                                                            <input type="hidden" name="action" value="delete">
                                                            <input type="hidden" name="id" value="<?= (int)$sv['id'] ?>">
                                                            <button type="submit" class="btn btn-sm btn-outline-danger">Xóa</button>
                                                        </form>
                                                    </td>
                                                </tr>
                                            <?php endforeach; ?>
                                        <?php endif; ?>
                                    </tbody>
                                </table>
                            </div>
                        </div>

                        <!-- Thanh phân trang Bootstrap 5 -->
                        <div class="card-footer bg-white d-flex flex-wrap justify-content-between align-items-center py-3">
                            <span class="small text-muted">
                                LIMIT <?= $perPage ?> OFFSET <?= ($currentPage - 1) * $perPage ?>
                            </span>
                            <nav aria-label="Pagination">
                                <ul class="pagination pagination-sm mb-0">
                                    <li class="page-item <?= $currentPage <= 1 ? 'disabled' : '' ?>">
                                        <a class="page-link" href="<?= htmlspecialchars(buildBai07PageUrl(max(1, $currentPage - 1), $keyword)) ?>">&laquo; Trước</a>
                                    </li>
                                    <?php for ($p = 1; $p <= $totalPages; $p++): ?>
                                        <li class="page-item <?= $p === $currentPage ? 'active' : '' ?>">
                                            <a class="page-link" href="<?= htmlspecialchars(buildBai07PageUrl($p, $keyword)) ?>"><?= $p ?></a>
                                        </li>
                                    <?php endfor; ?>
                                    <li class="page-item <?= $currentPage >= $totalPages ? 'disabled' : '' ?>">
                                        <a class="page-link" href="<?= htmlspecialchars(buildBai07PageUrl(min($totalPages, $currentPage + 1), $keyword)) ?>">Sau &raquo;</a>
                                    </li>
                                </ul>
                            </nav>
                        </div>
                    </div>
                </div>
            </div>
        <?php endif; ?>
    </div>
    <script src="https://cdn.jsdelivr.net/npm/bootstrap@5.3.3/dist/js/bootstrap.bundle.min.js"></script>
</body>
</html>