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

/**
 * Read JSON file and return decoded data
 */
function readJsonFile($file) {
    if (!file_exists($file)) {
        return [];
    }
    $content = file_get_contents($file);
    if (empty($content)) {
        return [];
    }
    $data = json_decode($content, true);
    return $data ? $data : [];
}

/**
 * Write data to JSON file
 */
function writeJsonFile($file, $data) {
    $dir = dirname($file);
    if (!is_dir($dir)) {
        mkdir($dir, 0755, true);
    }
    file_put_contents($file, json_encode($data, JSON_PRETTY_PRINT | JSON_UNESCAPED_UNICODE));
}

/**
 * Get all products
 */
function getProducts() {
    $data = readJsonFile(PRODUCTS_FILE);
    return isset($data['products']) ? $data['products'] : [];
}

/**
 * Get product by ID
 */
function getProductById($id) {
    $products = getProducts();
    foreach ($products as $product) {
        if ($product['id'] == $id) {
            return $product;
        }
    }
    return null;
}

/**
 * Save products
 */
function saveProducts($products) {
    $data = ['products' => $products];
    writeJsonFile(PRODUCTS_FILE, $data);
}

/**
 * Get all reservations
 */
function getReservations() {
    $data = readJsonFile(RESERVATIONS_FILE);
    return isset($data['reservations']) ? $data['reservations'] : [];
}

/**
 * Get reservation by code
 */
function getReservationByCode($code) {
    $reservations = getReservations();
    foreach ($reservations as $reservation) {
        if ($reservation['code'] === $code) {
            return $reservation;
        }
    }
    return null;
}

/**
 * Save reservations
 */
function saveReservations($reservations) {
    $data = ['reservations' => $reservations];
    writeJsonFile(RESERVATIONS_FILE, $data);
}

/**
 * Generate unique reservation code
 */
function generateReservationCode() {
    $code = '';
    $characters = 'ABCDEFGHJKLMNPQRSTUVWXYZ23456789'; // Exclude confusing characters
    $max = strlen($characters) - 1;
    
    do {
        $code = '';
        for ($i = 0; $i < 6; $i++) {
            $code .= $characters[random_int(0, $max)];
        }
        // Check if code already exists
        $existing = getReservationByCode($code);
    } while ($existing !== null);
    
    return $code;
}

/**
 * Generate reservation ID
 */
function generateReservationId() {
    $reservations = getReservations();
    $count = count($reservations) + 1;
    $year = date('Y');
    return sprintf('RES-%s-%03d', $year, $count);
}

/**
 * Check if product has enough stock
 * For apparel: checks stock for specific size
 * For merch: checks general stock
 */
function checkStock($productId, $quantity, $size = null) {
    $product = getProductById($productId);
    if (!$product) {
        return false;
    }
    
    // For apparel with sizes, check stock per size
    if ($product['category'] === 'apparel' && !empty($product['sizes']) && $size !== null) {
        if (!isset($product['stock_by_size']) || !is_array($product['stock_by_size'])) {
            return false;
        }
        $sizeStock = isset($product['stock_by_size'][$size]) ? (int)$product['stock_by_size'][$size] : 0;
        return $sizeStock >= $quantity;
    }
    
    // For merch or apparel without size-specific stock, use general stock
    $stock = isset($product['stock']) ? (int)$product['stock'] : 0;
    return $stock >= $quantity;
}

/**
 * Get stock for a product (per size for apparel, general for merch)
 */
function getStock($product, $size = null) {
    if ($product['category'] === 'apparel' && !empty($product['sizes']) && $size !== null) {
        if (isset($product['stock_by_size']) && is_array($product['stock_by_size'])) {
            return isset($product['stock_by_size'][$size]) ? (int)$product['stock_by_size'][$size] : 0;
        }
    }
    return isset($product['stock']) ? (int)$product['stock'] : 0;
}

/**
 * Get total stock for a product (sum of all sizes for apparel)
 */
function getTotalStock($product) {
    if ($product['category'] === 'apparel' && isset($product['stock_by_size']) && is_array($product['stock_by_size'])) {
        return array_sum($product['stock_by_size']);
    }
    return isset($product['stock']) ? (int)$product['stock'] : 0;
}

/**
 * Allocate stock for reservation
 */
function allocateStock($productId, $quantity, $size = null) {
    $products = getProducts();
    foreach ($products as &$product) {
        if ($product['id'] == $productId) {
            // For apparel with sizes, allocate per size
            if ($product['category'] === 'apparel' && !empty($product['sizes']) && $size !== null) {
                if (!isset($product['stock_by_size']) || !is_array($product['stock_by_size'])) {
                    $product['stock_by_size'] = [];
                }
                if (!isset($product['stock_by_size'][$size])) {
                    $product['stock_by_size'][$size] = 0;
                }
                $product['stock_by_size'][$size] -= $quantity;
                if ($product['stock_by_size'][$size] < 0) {
                    $product['stock_by_size'][$size] = 0;
                }
            } else {
                // For merch or general stock
                if (!isset($product['stock'])) {
                    $product['stock'] = 0;
                }
                $product['stock'] -= $quantity;
                if ($product['stock'] < 0) {
                    $product['stock'] = 0;
                }
            }
            break;
        }
    }
    saveProducts($products);
}

/**
 * Release stock from reservation
 */
function releaseStock($productId, $quantity, $size = null) {
    $products = getProducts();
    foreach ($products as &$product) {
        if ($product['id'] == $productId) {
            // For apparel with sizes, release per size
            if ($product['category'] === 'apparel' && !empty($product['sizes']) && $size !== null) {
                if (!isset($product['stock_by_size']) || !is_array($product['stock_by_size'])) {
                    $product['stock_by_size'] = [];
                }
                if (!isset($product['stock_by_size'][$size])) {
                    $product['stock_by_size'][$size] = 0;
                }
                $product['stock_by_size'][$size] += $quantity;
            } else {
                // For merch or general stock
                if (!isset($product['stock'])) {
                    $product['stock'] = 0;
                }
                $product['stock'] += $quantity;
            }
            break;
        }
    }
    saveProducts($products);
}

/**
 * Create new reservation
 */
function createReservation($customerName, $customerEmail, $items) {
    $reservations = getReservations();
    
    // Validate stock for all items
    foreach ($items as $item) {
        $size = isset($item['size']) ? $item['size'] : null;
        if (!checkStock($item['product_id'], $item['quantity'], $size)) {
            $product = getProductById($item['product_id']);
            $productName = $product ? $product['name'] : 'Produkt';
            $sizeInfo = $size ? " (Größe: $size)" : '';
            return ['success' => false, 'message' => "Nicht genügend Lagerbestand für: $productName$sizeInfo"];
        }
    }
    
    // Allocate stock
    foreach ($items as $item) {
        $size = isset($item['size']) ? $item['size'] : null;
        allocateStock($item['product_id'], $item['quantity'], $size);
    }
    
    // Create reservation
    $now = new DateTime();
    $expires = clone $now;
    $expires->modify('+' . RESERVATION_EXPIRY_DAYS . ' days');
    
    $reservation = [
        'id' => generateReservationId(),
        'code' => generateReservationCode(),
        'customer_name' => $customerName,
        'customer_email' => $customerEmail,
        'items' => $items,
        'created' => $now->format('Y-m-d H:i:s'),
        'expires' => $expires->format('Y-m-d H:i:s'),
        'status' => 'open',
        'picked_up' => false,
        'type' => 'regular'
    ];
    
    $reservations[] = $reservation;
    saveReservations($reservations);
    
    // Send confirmation emails
    sendReservationEmails($reservation);
    
    return ['success' => true, 'reservation' => $reservation];
}

/**
 * Create new backorder reservation
 */
function createBackorderReservation($customerName, $customerEmail, $items) {
    $reservations = getReservations();
    
    $now = new DateTime();
    
    $reservation = [
        'id' => generateReservationId(),
        'code' => generateReservationCode(),
        'customer_name' => $customerName,
        'customer_email' => $customerEmail,
        'items' => $items,
        'created' => $now->format('Y-m-d H:i:s'),
        'expires' => '',
        'status' => 'open',
        'picked_up' => false,
        'type' => 'backorder',
        'backorder_status' => 'pending'
    ];
    
    $reservations[] = $reservation;
    saveReservations($reservations);
    
    // Send confirmation emails
    sendBackorderEmails($reservation);
    
    return ['success' => true, 'reservation' => $reservation];
}

/**
 * Mark reservation as picked up
 */
function markReservationPickedUp($reservationId) {
    $reservations = getReservations();
    foreach ($reservations as &$reservation) {
        if ($reservation['id'] === $reservationId) {
            $reservation['picked_up'] = true;
            $reservation['status'] = 'picked_up';
            break;
        }
    }
    saveReservations($reservations);
}

/**
 * Check and expire old reservations
 */
function expireOldReservations() {
    $reservations = getReservations();
    $now = new DateTime();
    $changed = false;
    
    foreach ($reservations as &$reservation) {
        if ($reservation['status'] === 'open' && !$reservation['picked_up']) {
            if (isset($reservation['type']) && $reservation['type'] === 'backorder') {
                continue;
            }
            if (empty($reservation['expires'])) {
                continue;
            }
            $expires = new DateTime($reservation['expires']);
            if ($now > $expires) {
                $reservation['status'] = 'expired';
                // Release stock
                foreach ($reservation['items'] as $item) {
                    $size = isset($item['size']) ? $item['size'] : null;
                    releaseStock($item['product_id'], $item['quantity'], $size);
                }
                $changed = true;
            }
        }
    }
    
    if ($changed) {
        saveReservations($reservations);
    }
}

/**
 * Check if all items are in stock
 */
function canFulfillReservationItems($items) {
    foreach ($items as $item) {
        $size = isset($item['size']) ? $item['size'] : null;
        if (!checkStock($item['product_id'], $item['quantity'], $size)) {
            return false;
        }
    }
    return true;
}

/**
 * Mark backorder as available
 */
function markBackorderAvailable($reservationId) {
    $reservations = getReservations();
    foreach ($reservations as &$reservation) {
        if ($reservation['id'] === $reservationId) {
            if (!isset($reservation['type']) || $reservation['type'] !== 'backorder') {
                return ['success' => false, 'message' => 'Diese Reservierung ist keine Nachbestellung.'];
            }
            if (isset($reservation['backorder_status']) && $reservation['backorder_status'] === 'notified') {
                return ['success' => false, 'message' => 'Diese Nachbestellung wurde bereits informiert.'];
            }
            if (!canFulfillReservationItems($reservation['items'])) {
                return ['success' => false, 'message' => 'Nicht alle Artikel sind verfügbar.'];
            }
            
            foreach ($reservation['items'] as $item) {
                $size = isset($item['size']) ? $item['size'] : null;
                allocateStock($item['product_id'], $item['quantity'], $size);
            }
            
            $reservation['backorder_status'] = 'notified';
            saveReservations($reservations);
            
            sendBackorderAvailableEmail($reservation);
            
            return ['success' => true, 'reservation' => $reservation];
        }
    }
    return ['success' => false, 'message' => 'Nachbestellung nicht gefunden.'];
}

/**
 * Sanitize input
 */
function sanitize($input) {
    return htmlspecialchars(strip_tags(trim($input)), ENT_QUOTES, 'UTF-8');
}

/**
 * Format price
 */
function formatPrice($price) {
    return number_format($price, 2, ',', '.') . ' €';
}

/**
 * Format date
 */
function formatDate($dateString) {
    $date = new DateTime($dateString);
    return $date->format('d.m.Y H:i');
}

/**
 * Send email
 */
function sendEmail($to, $subject, $message, $isHtml = true) {
    $headers = [];
    $headers[] = 'From: ' . FROM_NAME . ' <' . FROM_EMAIL . '>';
    $headers[] = 'Reply-To: ' . FROM_EMAIL;
    $headers[] = 'X-Mailer: PHP/' . phpversion();
    
    if ($isHtml) {
        $headers[] = 'MIME-Version: 1.0';
        $headers[] = 'Content-type: text/html; charset=UTF-8';
    }
    
    return mail($to, $subject, $message, implode("\r\n", $headers));
}

/**
 * Send reservation confirmation emails
 */
function sendReservationEmails($reservation) {
    $products = getProducts();
    
    // Build items list
    $itemsHtml = '<ul>';
    foreach ($reservation['items'] as $item) {
        $product = getProductById($item['product_id']);
        if ($product) {
            $sizeInfo = '';
            if (isset($item['size']) && !empty($item['size'])) {
                $sizeInfo = ' - Größe: ' . htmlspecialchars($item['size']);
            }
            $itemsHtml .= '<li>' . htmlspecialchars($product['name']) . $sizeInfo . ' - Menge: ' . $item['quantity'] . '</li>';
        }
    }
    $itemsHtml .= '</ul>';
    
    // Customer email
    $customerSubject = 'Ihre Reservierung bei ' . SITE_NAME;
    $customerMessage = '
    <html>
    <head>
        <meta charset="UTF-8">
    </head>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
        <h2 style="color: #c41e3a;">Reservierung bestätigt</h2>
        <p>Sehr geehrte/r ' . htmlspecialchars($reservation['customer_name']) . ',</p>
        <p>vielen Dank für Ihre Reservierung bei ' . SITE_NAME . '.</p>
        
        <div style="background: #fff3cd; border: 2px solid #ffc107; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px; text-align: center;">
            <h3 style="margin-top: 0;">Ihr Abholcode:</h3>
            <h2 style="font-size: 2rem; letter-spacing: 0.2rem; color: #856404; font-family: monospace;">' . htmlspecialchars($reservation['code']) . '</h2>
        </div>
        
        <h3>Reservierungsdetails:</h3>
        <p><strong>Reservierungsnummer:</strong> ' . htmlspecialchars($reservation['id']) . '</p>
        <p><strong>Erstellt am:</strong> ' . formatDate($reservation['created']) . '</p>
        <p><strong>Gültig bis:</strong> ' . formatDate($reservation['expires']) . '</p>
        
        <h3>Reservierte Artikel:</h3>
        ' . $itemsHtml . '
        
        <p><strong>Wichtig:</strong> Bitte bringen Sie diesen Abholcode zur Abholung mit. Die Reservierung ist bis zum ' . formatDate($reservation['expires']) . ' gültig.</p>
        
        <p>Mit freundlichen Grüßen<br>' . SITE_NAME . '</p>
    </body>
    </html>';
    
    sendEmail($reservation['customer_email'], $customerSubject, $customerMessage);
    
    // Admin email
    $adminSubject = 'Neue Reservierung: ' . $reservation['code'];
    $adminMessage = '
    <html>
    <head>
        <meta charset="UTF-8">
    </head>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
        <h2 style="color: #c41e3a;">Neue Reservierung</h2>
        <p>Eine neue Reservierung wurde erstellt:</p>
        
        <div style="background: #d1ecf1; border: 2px solid #bee5eb; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px;">
            <h3 style="margin-top: 0;">Abholcode:</h3>
            <h2 style="font-size: 2rem; letter-spacing: 0.2rem; color: #0c5460; font-family: monospace;">' . htmlspecialchars($reservation['code']) . '</h2>
        </div>
        
        <h3>Kundendaten:</h3>
        <p><strong>Name:</strong> ' . htmlspecialchars($reservation['customer_name']) . '</p>
        <p><strong>E-Mail:</strong> ' . htmlspecialchars($reservation['customer_email']) . '</p>
        
        <h3>Reservierungsdetails:</h3>
        <p><strong>Reservierungsnummer:</strong> ' . htmlspecialchars($reservation['id']) . '</p>
        <p><strong>Erstellt am:</strong> ' . formatDate($reservation['created']) . '</p>
        <p><strong>Gültig bis:</strong> ' . formatDate($reservation['expires']) . '</p>
        
        <h3>Reservierte Artikel:</h3>
        ' . $itemsHtml . '
    </body>
    </html>';
    
    sendEmail(ADMIN_EMAIL, $adminSubject, $adminMessage);
}

/**
 * Send backorder confirmation emails
 */
function sendBackorderEmails($reservation) {
    // Build items list
    $itemsHtml = '<ul>';
    foreach ($reservation['items'] as $item) {
        $product = getProductById($item['product_id']);
        if ($product) {
            $sizeInfo = '';
            if (isset($item['size']) && !empty($item['size'])) {
                $sizeInfo = ' - Größe: ' . htmlspecialchars($item['size']);
            }
            $itemsHtml .= '<li>' . htmlspecialchars($product['name']) . $sizeInfo . ' - Menge: ' . $item['quantity'] . '</li>';
        }
    }
    $itemsHtml .= '</ul>';
    
    // Customer email
    $customerSubject = 'Nachbestellung bei ' . SITE_NAME;
    $customerMessage = '
    <html>
    <head>
        <meta charset="UTF-8">
    </head>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
        <h2 style="color: #c41e3a;">Nachbestellung bestätigt</h2>
        <p>Sehr geehrte/r ' . htmlspecialchars($reservation['customer_name']) . ',</p>
        <p>vielen Dank für Ihre Nachbestellung bei ' . SITE_NAME . '.</p>
        
        <div style="background: #fff3cd; border: 2px solid #ffc107; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px; text-align: center;">
            <h3 style="margin-top: 0;">Ihr Abholcode:</h3>
            <h2 style="font-size: 2rem; letter-spacing: 0.2rem; color: #856404; font-family: monospace;">' . htmlspecialchars($reservation['code']) . '</h2>
        </div>
        
        <h3>Nachbestellungsdetails:</h3>
        <p><strong>Nachbestellungsnummer:</strong> ' . htmlspecialchars($reservation['id']) . '</p>
        <p><strong>Erstellt am:</strong> ' . formatDate($reservation['created']) . '</p>
        
        <h3>Nachbestellte Artikel:</h3>
        ' . $itemsHtml . '
        
        <div style="background: #f8d7da; border: 2px solid #f5c6cb; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px;">
            <strong>Hinweis:</strong> Die Lieferzeiten sind nicht bekannt, da die Bestellung in Chargen erfolgt.
        </div>
        
        <p>Wir informieren Sie, sobald die komplette Nachbestellung verfügbar ist.</p>
        
        <p>Mit freundlichen Grüßen<br>' . SITE_NAME . '</p>
    </body>
    </html>';
    
    sendEmail($reservation['customer_email'], $customerSubject, $customerMessage);
    
    // Admin email
    $adminSubject = 'Neue Nachbestellung: ' . $reservation['code'];
    $adminMessage = '
    <html>
    <head>
        <meta charset="UTF-8">
    </head>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
        <h2 style="color: #c41e3a;">Neue Nachbestellung</h2>
        <p>Eine neue Nachbestellung wurde erstellt:</p>
        
        <div style="background: #d1ecf1; border: 2px solid #bee5eb; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px;">
            <h3 style="margin-top: 0;">Abholcode:</h3>
            <h2 style="font-size: 2rem; letter-spacing: 0.2rem; color: #0c5460; font-family: monospace;">' . htmlspecialchars($reservation['code']) . '</h2>
        </div>
        
        <h3>Kundendaten:</h3>
        <p><strong>Name:</strong> ' . htmlspecialchars($reservation['customer_name']) . '</p>
        <p><strong>E-Mail:</strong> ' . htmlspecialchars($reservation['customer_email']) . '</p>
        
        <h3>Nachbestellungsdetails:</h3>
        <p><strong>Nachbestellungsnummer:</strong> ' . htmlspecialchars($reservation['id']) . '</p>
        <p><strong>Erstellt am:</strong> ' . formatDate($reservation['created']) . '</p>
        
        <h3>Nachbestellte Artikel:</h3>
        ' . $itemsHtml . '
        
        <p><strong>Hinweis:</strong> Lieferzeiten sind nicht bekannt, Bestellung in Chargen.</p>
    </body>
    </html>';
    
    sendEmail(ADMIN_EMAIL, $adminSubject, $adminMessage);
}

/**
 * Send backorder availability email
 */
function sendBackorderAvailableEmail($reservation) {
    $itemsHtml = '<ul>';
    foreach ($reservation['items'] as $item) {
        $product = getProductById($item['product_id']);
        if ($product) {
            $sizeInfo = '';
            if (isset($item['size']) && !empty($item['size'])) {
                $sizeInfo = ' - Größe: ' . htmlspecialchars($item['size']);
            }
            $itemsHtml .= '<li>' . htmlspecialchars($product['name']) . $sizeInfo . ' - Menge: ' . $item['quantity'] . '</li>';
        }
    }
    $itemsHtml .= '</ul>';
    
    $subject = 'Ihre Nachbestellung ist verfügbar';
    $message = '
    <html>
    <head>
        <meta charset="UTF-8">
    </head>
    <body style="font-family: Arial, sans-serif; line-height: 1.6; color: #333;">
        <h2 style="color: #28a745;">Nachbestellung verfügbar</h2>
        <p>Sehr geehrte/r ' . htmlspecialchars($reservation['customer_name']) . ',</p>
        <p>Ihre komplette Nachbestellung ist jetzt verfügbar.</p>
        
        <div style="background: #d4edda; border: 2px solid #c3e6cb; padding: 1.5rem; margin: 1.5rem 0; border-radius: 8px; text-align: center;">
            <h3 style="margin-top: 0;">Ihr Abholcode:</h3>
            <h2 style="font-size: 2rem; letter-spacing: 0.2rem; color: #155724; font-family: monospace;">' . htmlspecialchars($reservation['code']) . '</h2>
        </div>
        
        <h3>Verfügbare Artikel:</h3>
        ' . $itemsHtml . '
        
        <p>Bitte bringen Sie den Abholcode zur Abholung mit.</p>
        
        <p>Mit freundlichen Grüßen<br>' . SITE_NAME . '</p>
    </body>
    </html>';
    
    sendEmail($reservation['customer_email'], $subject, $message);
}