<?php
require_once __DIR__ . '/../config.php';
require_once __DIR__ . '/../includes/functions.php';

// Check admin login
if (!isset($_SESSION['admin_logged_in']) || !$_SESSION['admin_logged_in']) {
    header('Location: login.php');
    exit;
}

$pageTitle = 'Produkte verwalten';
$message = '';
$messageType = '';
$categories = getCategories();

function handleImageUpload($fileInputName = 'image_file') {
    if (!isset($_FILES[$fileInputName]) || $_FILES[$fileInputName]['error'] === UPLOAD_ERR_NO_FILE) {
        return ['success' => true, 'filename' => null];
    }

    $file = $_FILES[$fileInputName];
    if ($file['error'] !== UPLOAD_ERR_OK) {
        return ['success' => false, 'message' => 'Upload fehlgeschlagen. Bitte erneut versuchen.'];
    }

    $allowedExtensions = ['jpg', 'jpeg', 'png', 'webp', 'gif'];
    $originalName = basename($file['name']);
    $extension = strtolower(pathinfo($originalName, PATHINFO_EXTENSION));
    if (!in_array($extension, $allowedExtensions, true)) {
        return ['success' => false, 'message' => 'Ungültiger Dateityp. Erlaubt: JPG, PNG, WEBP, GIF.'];
    }

    $finfo = new finfo(FILEINFO_MIME_TYPE);
    $mimeType = $finfo->file($file['tmp_name']);
    $allowedMimes = ['image/jpeg', 'image/png', 'image/webp', 'image/gif'];
    if (!in_array($mimeType, $allowedMimes, true)) {
        return ['success' => false, 'message' => 'Die hochgeladene Datei ist kein gültiges Bild.'];
    }

    $imagesDir = __DIR__ . '/../assets/images';
    if (!is_dir($imagesDir)) {
        mkdir($imagesDir, 0755, true);
    }

    $safeBaseName = preg_replace('/[^a-zA-Z0-9_-]/', '-', pathinfo($originalName, PATHINFO_FILENAME));
    $safeBaseName = trim((string) $safeBaseName, '-');
    if ($safeBaseName === '') {
        $safeBaseName = 'bild';
    }

    $targetFilename = $safeBaseName . '.' . $extension;
    $targetPath = $imagesDir . '/' . $targetFilename;
    $counter = 1;
    while (file_exists($targetPath)) {
        $targetFilename = $safeBaseName . '-' . $counter . '.' . $extension;
        $targetPath = $imagesDir . '/' . $targetFilename;
        $counter++;
    }

    if (!move_uploaded_file($file['tmp_name'], $targetPath)) {
        return ['success' => false, 'message' => 'Bild konnte nicht gespeichert werden.'];
    }

    return ['success' => true, 'filename' => $targetFilename];
}

function isValidProductCategoryInput($categoryId) {
    return getCategoryById($categoryId) !== null;
}

function getSubmittedProductCategoryIds($submittedValues) {
    $selectedCategoryIds = normalizeProductCategoryIds($submittedValues['categories'] ?? []);
    $validCategoryIds = [];

    foreach ($selectedCategoryIds as $categoryId) {
        if (isValidProductCategoryInput($categoryId)) {
            $validCategoryIds[] = $categoryId;
        }
    }

    return $validCategoryIds;
}

function buildProductSizeStock($sizesInput, $submittedValues = [], $existingValues = []) {
    $sizes = getProductSizes(['sizes' => (string) $sizesInput]);
    $stockBySize = [];

    foreach ($sizes as $size) {
        $stockKey = 'stock_' . str_replace([' ', ','], '_', $size);
        if (isset($submittedValues[$stockKey])) {
            $stockBySize[$size] = max(0, (int) $submittedValues[$stockKey]);
        } elseif (isset($existingValues[$size])) {
            $stockBySize[$size] = max(0, (int) $existingValues[$size]);
        } else {
            $stockBySize[$size] = 0;
        }
    }

    return [
        'sizes' => implode(',', $sizes),
        'stock_by_size' => $stockBySize
    ];
}

// Handle product operations
if ($_SERVER['REQUEST_METHOD'] === 'POST') {
    $products = getProducts();

    if (empty($categories)) {
        $message = 'Es ist keine Kategorie vorhanden. Bitte zuerst Kategorien anlegen.';
        $messageType = 'error';
    } elseif (isset($_POST['add_product'])) {
        $uploadResult = handleImageUpload();
        if (!$uploadResult['success']) {
            $message = $uploadResult['message'];
            $messageType = 'error';
        } else {
            $categoryIds = getSubmittedProductCategoryIds($_POST);
            $sizeData = buildProductSizeStock($_POST['sizes'] ?? '', $_POST);

            if (empty($categoryIds)) {
                $message = 'Bitte wählen Sie mindestens eine gültige Kategorie aus.';
                $messageType = 'error';
            } elseif ($sizeData['sizes'] === '') {
                $message = 'Bitte geben Sie mindestens eine Größe ein.';
                $messageType = 'error';
            } else {
                $newId = 1;
                if (!empty($products)) {
                    $ids = array_column($products, 'id');
                    $newId = max($ids) + 1;
                }

                $products[] = [
                    'id' => $newId,
                    'name' => sanitize($_POST['name']),
                    'description' => sanitize($_POST['description']),
                    'price' => (float) ($_POST['price'] ?? 0),
                    'categories' => $categoryIds,
                    'image' => $uploadResult['filename'] !== null ? $uploadResult['filename'] : sanitize($_POST['image']),
                    'sizes' => $sizeData['sizes'],
                    'stock_by_size' => $sizeData['stock_by_size']
                ];

                saveProducts($products);
                $message = 'Produkt erfolgreich hinzugefügt.';
                $messageType = 'success';
            }
        }
    }

    if (isset($_POST['update_product'])) {
        $uploadResult = handleImageUpload();
        if (!$uploadResult['success']) {
            $message = $uploadResult['message'];
            $messageType = 'error';
        } else {
            $productId = (int) ($_POST['product_id'] ?? 0);
            $categoryIds = getSubmittedProductCategoryIds($_POST);

            $existingProduct = null;
            foreach ($products as $product) {
                if ($product['id'] === $productId) {
                    $existingProduct = $product;
                    break;
                }
            }

            $existingStockBySize = isset($existingProduct['stock_by_size']) && is_array($existingProduct['stock_by_size'])
                ? $existingProduct['stock_by_size']
                : [];
            $sizeData = buildProductSizeStock($_POST['sizes'] ?? '', $_POST, $existingStockBySize);

            if (empty($categoryIds)) {
                $message = 'Bitte wählen Sie mindestens eine gültige Kategorie aus.';
                $messageType = 'error';
            } elseif ($existingProduct === null) {
                $message = 'Produkt nicht gefunden.';
                $messageType = 'error';
            } elseif ($sizeData['sizes'] === '') {
                $message = 'Bitte geben Sie mindestens eine Größe ein.';
                $messageType = 'error';
            } else {
                foreach ($products as &$product) {
                    if ($product['id'] === $productId) {
                        $product['name'] = sanitize($_POST['name']);
                        $product['description'] = sanitize($_POST['description']);
                        $product['price'] = (float) ($_POST['price'] ?? 0);
                        $product['categories'] = $categoryIds;
                        $product['image'] = $uploadResult['filename'] !== null ? $uploadResult['filename'] : sanitize($_POST['image']);
                        $product['sizes'] = $sizeData['sizes'];
                        $product['stock_by_size'] = $sizeData['stock_by_size'];
                        unset($product['stock']);
                        break;
                    }
                }
                unset($product);

                saveProducts($products);
                $message = 'Produkt erfolgreich aktualisiert.';
                $messageType = 'success';
            }
        }
    }

    if (isset($_POST['delete_product'])) {
        $productId = (int) ($_POST['product_id'] ?? 0);
        $products = array_filter($products, function ($product) use ($productId) {
            return $product['id'] !== $productId;
        });
        $products = array_values($products);
        saveProducts($products);
        $message = 'Produkt erfolgreich gelöscht.';
        $messageType = 'success';
    }
}

$products = getProducts();
$editingProduct = null;

if (isset($_GET['edit'])) {
    $editingProduct = getProductById((int) $_GET['edit']);
}

$bodyClass = 'admin-page';
include __DIR__ . '/../includes/header.php';
?>

<div class="admin-header">
    <h2>Produkte verwalten</h2>
    <div>
        <a href="index.php" class="btn btn-secondary">Zurück zum Dashboard</a>
    </div>
</div>

<?php if ($message !== ''): ?>
    <div class="alert alert-<?php echo $messageType; ?>">
        <?php echo htmlspecialchars($message); ?>
    </div>
<?php endif; ?>

<?php if ($editingProduct): ?>
    <div class="panel" style="padding: 2rem;">
        <h3>Produkt bearbeiten</h3>
        <form method="POST" enctype="multipart/form-data">
            <input type="hidden" name="product_id" value="<?php echo $editingProduct['id']; ?>">
            <div class="form-group">
                <label for="name">Name *</label>
                <input type="text" id="name" name="name" required value="<?php echo htmlspecialchars($editingProduct['name']); ?>">
            </div>
            <div class="form-group">
                <label for="description">Beschreibung</label>
                <textarea id="description" name="description" rows="4"><?php echo htmlspecialchars($editingProduct['description']); ?></textarea>
            </div>
            <div class="form-group">
                <label for="price">Preis (€) *</label>
                <input type="number" id="price" name="price" step="0.01" min="0" required value="<?php echo $editingProduct['price']; ?>">
            </div>
            <div class="form-group">
                <label for="categories">Kategorien *</label>
                <select id="categories" name="categories[]" multiple size="<?php echo max(3, min(8, count($categories))); ?>" required>
                    <?php foreach ($categories as $category): ?>
                        <option value="<?php echo htmlspecialchars($category['id']); ?>" <?php echo in_array($category['id'], getProductCategoryIds($editingProduct), true) ? 'selected' : ''; ?>>
                            <?php echo htmlspecialchars($category['label']); ?>
                        </option>
                    <?php endforeach; ?>
                </select>
                <small>Mehrfachauswahl mit Strg/Cmd oder Umschalt. Auf Touch-Geräten können mehrere Einträge nacheinander markiert werden.</small>
            </div>
            <div class="form-group">
                <label for="sizes">Größen (kommagetrennt, z.B. Standard oder S,M,L,XL) *</label>
                <input type="text" id="sizes" name="sizes" required value="<?php echo htmlspecialchars($editingProduct['sizes'] ?? ''); ?>" placeholder="Standard" oninput="updateSizeStockFields()">
                <small>Alle Produkte nutzen größenbasierten Bestand. Für Artikel ohne Varianten z.B. <code>Standard</code> oder <code>Einheitsgröße</code> verwenden.</small>
            </div>
            <div id="size-stock-group">
                <?php
                $sizes = getProductSizes($editingProduct);
                $stockBySize = isset($editingProduct['stock_by_size']) && is_array($editingProduct['stock_by_size']) ? $editingProduct['stock_by_size'] : [];
                foreach ($sizes as $size):
                ?>
                    <div class="form-group">
                        <label>Lagerbestand für Größe "<?php echo htmlspecialchars($size); ?>" *</label>
                        <input type="number" name="stock_<?php echo htmlspecialchars(str_replace([' ', ','], '_', $size)); ?>" min="0" value="<?php echo isset($stockBySize[$size]) ? (int) $stockBySize[$size] : 0; ?>" required>
                    </div>
                <?php endforeach; ?>
            </div>
            <div class="form-group">
                <label for="image">Bilddateiname (z.B. tshirt.jpg)</label>
                <input type="text" id="image" name="image" value="<?php echo htmlspecialchars($editingProduct['image']); ?>">
            </div>
            <div class="form-group">
                <label for="image_file">Oder neues Bild hochladen</label>
                <input type="file" id="image_file" name="image_file" accept=".jpg,.jpeg,.png,.webp,.gif,image/*">
                <small>Upload nach <code>assets/images</code>; ersetzt den Dateinamen oben automatisch.</small>
            </div>
            <script>
                function updateSizeStockFields() {
                    const sizesInput = document.getElementById('sizes');
                    const sizeStockGroup = document.getElementById('size-stock-group');
                    const currentValues = {};

                    sizeStockGroup.querySelectorAll('input[type="number"]').forEach((input) => {
                        currentValues[input.name] = input.value;
                    });

                    const sizes = sizesInput.value.split(',').map((size) => size.trim()).filter((size, index, all) => size && all.indexOf(size) === index);
                    let html = '';

                    sizes.forEach((size) => {
                        const safeName = size.replace(/[ ,]/g, '_');
                        const fieldName = 'stock_' + safeName;
                        const currentValue = Object.prototype.hasOwnProperty.call(currentValues, fieldName) ? currentValues[fieldName] : '0';
                        html += '<div class="form-group">';
                        html += '<label>Lagerbestand für Größe "' + size.replace(/"/g, '&quot;') + '" *</label>';
                        html += '<input type="number" name="' + fieldName + '" min="0" value="' + currentValue + '" required>';
                        html += '</div>';
                    });

                    sizeStockGroup.innerHTML = html;
                }
            </script>
            <button type="submit" name="update_product" class="btn">Produkt aktualisieren</button>
            <a href="products.php" class="btn btn-secondary">Abbrechen</a>
        </form>
    </div>
<?php else: ?>
    <div class="panel" style="padding: 2rem;">
        <h3>Neues Produkt hinzufügen</h3>
        <form method="POST" enctype="multipart/form-data">
            <div class="form-group">
                <label for="name">Name *</label>
                <input type="text" id="name" name="name" required>
            </div>
            <div class="form-group">
                <label for="description">Beschreibung</label>
                <textarea id="description" name="description" rows="4"></textarea>
            </div>
            <div class="form-group">
                <label for="price">Preis (€) *</label>
                <input type="number" id="price" name="price" step="0.01" min="0" required>
            </div>
            <div class="form-group">
                <label for="categories">Kategorien *</label>
                <select id="categories" name="categories[]" multiple size="<?php echo max(3, min(8, count($categories))); ?>" required>
                    <?php foreach ($categories as $category): ?>
                        <option value="<?php echo htmlspecialchars($category['id']); ?>">
                            <?php echo htmlspecialchars($category['label']); ?>
                        </option>
                    <?php endforeach; ?>
                </select>
                <small>Mehrfachauswahl mit Strg/Cmd oder Umschalt. Auf Touch-Geräten können mehrere Einträge nacheinander markiert werden.</small>
            </div>
            <div class="form-group">
                <label for="sizes">Größen (kommagetrennt, z.B. Standard oder S,M,L,XL) *</label>
                <input type="text" id="sizes" name="sizes" required placeholder="Standard" oninput="updateSizeStockFields()">
                <small>Alle Produkte nutzen größenbasierten Bestand. Für Artikel ohne Varianten z.B. <code>Standard</code> oder <code>Einheitsgröße</code> verwenden.</small>
            </div>
            <div id="size-stock-group"></div>
            <div class="form-group">
                <label for="image">Bilddateiname (z.B. tshirt.jpg)</label>
                <input type="text" id="image" name="image">
            </div>
            <div class="form-group">
                <label for="image_file">Oder Bild hochladen</label>
                <input type="file" id="image_file" name="image_file" accept=".jpg,.jpeg,.png,.webp,.gif,image/*">
                <small>Upload nach <code>assets/images</code>; Dateiname wird automatisch übernommen.</small>
            </div>
            <script>
                function updateSizeStockFields() {
                    const sizesInput = document.getElementById('sizes');
                    const sizeStockGroup = document.getElementById('size-stock-group');
                    const currentValues = {};

                    sizeStockGroup.querySelectorAll('input[type="number"]').forEach((input) => {
                        currentValues[input.name] = input.value;
                    });

                    const sizes = sizesInput.value.split(',').map((size) => size.trim()).filter((size, index, all) => size && all.indexOf(size) === index);
                    let html = '';

                    sizes.forEach((size) => {
                        const safeName = size.replace(/[ ,]/g, '_');
                        const fieldName = 'stock_' + safeName;
                        const currentValue = Object.prototype.hasOwnProperty.call(currentValues, fieldName) ? currentValues[fieldName] : '0';
                        html += '<div class="form-group">';
                        html += '<label>Lagerbestand für Größe "' + size.replace(/"/g, '&quot;') + '" *</label>';
                        html += '<input type="number" name="' + fieldName + '" min="0" value="' + currentValue + '" required>';
                        html += '</div>';
                    });

                    sizeStockGroup.innerHTML = html;
                }
            </script>
            <button type="submit" name="add_product" class="btn">Produkt hinzufügen</button>
        </form>
    </div>
<?php endif; ?>

<h3>Alle Produkte</h3>
<?php if (empty($products)): ?>
    <p>Keine Produkte vorhanden.</p>
<?php else: ?>
    <div class="table-responsive">
        <table class="responsive-table">
            <thead>
                <tr>
                    <th>ID</th>
                    <th>Name</th>
                    <th>Kategorien</th>
                    <th>Preis</th>
                    <th>Lagerbestand</th>
                    <th>Aktionen</th>
                </tr>
            </thead>
            <tbody>
                <?php foreach ($products as $product): ?>
                    <tr>
                        <td data-label="ID"><?php echo $product['id']; ?></td>
                        <td data-label="Name"><?php echo htmlspecialchars($product['name']); ?></td>
                        <td data-label="Kategorien"><?php echo htmlspecialchars(implode(', ', getCategoryLabels(getProductCategoryIds($product)))); ?></td>
                        <td data-label="Preis"><?php echo formatPrice($product['price']); ?></td>
                        <td data-label="Lagerbestand">
                            <?php
                            $stockInfo = [];
                            foreach (($product['stock_by_size'] ?? []) as $size => $stock) {
                                $stockInfo[] = $size . ': ' . (int) $stock;
                            }
                            echo !empty($stockInfo) ? htmlspecialchars(implode(', ', $stockInfo)) : '0';
                            ?>
                        </td>
                        <td data-label="Aktionen">
                            <a href="?edit=<?php echo $product['id']; ?>" class="btn btn-small">Bearbeiten</a>
                            <form method="POST" style="display: inline;" onsubmit="return confirm('Möchten Sie dieses Produkt wirklich löschen?');">
                                <input type="hidden" name="product_id" value="<?php echo $product['id']; ?>">
                                <button type="submit" name="delete_product" class="btn btn-secondary btn-small">Löschen</button>
                            </form>
                        </td>
                    </tr>
                <?php endforeach; ?>
            </tbody>
        </table>
    </div>
<?php endif; ?>

<?php include __DIR__ . '/../includes/footer.php'; ?>