<?php
declare(strict_types=1);

require_once __DIR__ . '/db/pos_bootstrap.php';

if (session_status() === PHP_SESSION_NONE) {
    session_start();
}

date_default_timezone_set('UTC');
pos_bootstrap();

function pos_project_name(): string
{
    $name = trim((string)($_SERVER['PROJECT_NAME'] ?? ''));
    return $name !== '' ? $name : 'Senior POS';
}

function pos_project_description(): string
{
    $description = trim((string)($_SERVER['PROJECT_DESCRIPTION'] ?? ''));
    return $description !== ''
        ? $description
        : 'Punto de venta accesible con categorías, canasta visible, recibos simples y alertas de stock bajo.';
}

function pos_project_image_url(): string
{
    return trim((string)($_SERVER['PROJECT_IMAGE_URL'] ?? ''));
}

function pos_demo_users(): array
{
    return [
        'ADMIN01' => [
            'pin' => '4321',
            'name' => 'María Ortega',
            'role' => 'admin',
            'role_label' => 'Administrador',
            'branch' => 'Sucursal Centro',
        ],
        'CAJA01' => [
            'pin' => '1234',
            'name' => 'Luis Rivera',
            'role' => 'cashier',
            'role_label' => 'Cajero',
            'branch' => 'Sucursal Centro',
        ],
        'CAJA02' => [
            'pin' => '2468',
            'name' => 'Ana Torres',
            'role' => 'cashier',
            'role_label' => 'Cajero',
            'branch' => 'Sucursal Norte',
        ],
    ];
}

function pos_category_meta(): array
{
    return [
        'Frutas' => [
            'icon' => 'bi-apple',
            'description' => 'Selecciona frutas frescas con un toque.',
        ],
        'Verduras' => [
            'icon' => 'bi-flower1',
            'description' => 'Verduras y hortalizas de salida rápida.',
        ],
        'Lácteos' => [
            'icon' => 'bi-cup-hot',
            'description' => 'Lácteos básicos para venta diaria.',
        ],
        'Despensa' => [
            'icon' => 'bi-basket2',
            'description' => 'Productos básicos y de reposición.',
        ],
    ];
}

function pos_current_user(): ?array
{
    return isset($_SESSION['pos_user']) && is_array($_SESSION['pos_user'])
        ? $_SESSION['pos_user']
        : null;
}

function pos_is_admin(): bool
{
    $user = pos_current_user();
    return $user !== null && (($user['role'] ?? '') === 'admin');
}

function pos_redirect(string $path): void
{
    header('Location: ' . $path);
    exit;
}

function pos_flash_add(string $type, string $message): void
{
    $_SESSION['pos_flashes'][] = [
        'type' => $type,
        'message' => $message,
    ];
}

function pos_pull_flashes(): array
{
    $flashes = isset($_SESSION['pos_flashes']) && is_array($_SESSION['pos_flashes'])
        ? $_SESSION['pos_flashes']
        : [];
    unset($_SESSION['pos_flashes']);
    return $flashes;
}

function pos_login_user(string $accessCode, string $pin): bool
{
    $users = pos_demo_users();
    $accessCode = strtoupper(trim($accessCode));
    $pin = preg_replace('/\D+/', '', $pin) ?? '';

    if (!isset($users[$accessCode])) {
        return false;
    }

    $candidate = $users[$accessCode];
    if (!hash_equals((string)$candidate['pin'], (string)$pin)) {
        return false;
    }

    session_regenerate_id(true);
    $_SESSION['pos_user'] = [
        'code' => $accessCode,
        'name' => (string)$candidate['name'],
        'role' => (string)$candidate['role'],
        'role_label' => (string)$candidate['role_label'],
        'branch' => (string)$candidate['branch'],
    ];

    return true;
}

function pos_logout_user(bool $clearCart = true): void
{
    unset($_SESSION['pos_user']);
    if ($clearCart) {
        unset($_SESSION['pos_cart']);
    }
    session_regenerate_id(true);
}

function pos_cart(): array
{
    return isset($_SESSION['pos_cart']) && is_array($_SESSION['pos_cart'])
        ? $_SESSION['pos_cart']
        : [];
}

function pos_save_cart(array $cart): void
{
    $normalized = [];
    foreach ($cart as $productId => $quantity) {
        $productId = (int)$productId;
        $quantity = (int)$quantity;
        if ($productId > 0 && $quantity > 0) {
            $normalized[$productId] = $quantity;
        }
    }
    ksort($normalized);
    $_SESSION['pos_cart'] = $normalized;
}

function pos_format_money(float $value): string
{
    return '$' . number_format($value, 2, '.', ',');
}

function pos_format_datetime(?string $value): string
{
    if (!$value) {
        return '—';
    }

    $timestamp = strtotime($value);
    return $timestamp ? date('d/m/Y H:i', $timestamp) : '—';
}

function pos_cart_summary(): array
{
    $cart = pos_cart();
    $products = pos_products_by_ids(array_keys($cart));
    $items = [];
    $subtotal = 0.0;
    $itemCount = 0;

    foreach ($cart as $productId => $quantity) {
        $productId = (int)$productId;
        $quantity = (int)$quantity;
        if (!isset($products[$productId])) {
            continue;
        }

        $product = $products[$productId];
        $price = (float)$product['price'];
        $stock = (int)$product['stock'];
        $lineTotal = $price * $quantity;
        $subtotal += $lineTotal;
        $itemCount += $quantity;

        $items[] = [
            'id' => $productId,
            'name' => (string)$product['name'],
            'category' => (string)$product['category'],
            'price' => $price,
            'stock' => $stock,
            'unit_label' => (string)$product['unit_label'],
            'quantity' => $quantity,
            'line_total' => $lineTotal,
            'max_reached' => $quantity >= $stock,
            'low_stock' => $stock <= (int)$product['low_stock_threshold'],
        ];
    }

    return [
        'items' => $items,
        'subtotal' => $subtotal,
        'total' => $subtotal,
        'item_count' => $itemCount,
    ];
}

function pos_complete_sale(): ?int
{
    $user = pos_current_user();
    $cart = pos_cart();
    if ($user === null || $cart === []) {
        pos_flash_add('warning', 'La canasta está vacía. Agrega productos antes de registrar la venta.');
        return null;
    }

    $pdo = db();

    try {
        $pdo->beginTransaction();
        $lockStmt = $pdo->prepare(
            "SELECT id, name, category, price, stock, low_stock_threshold, unit_label
             FROM pos_products
             WHERE id = :id AND is_active = 1
             LIMIT 1 FOR UPDATE"
        );
        $updateStmt = $pdo->prepare(
            "UPDATE pos_products
             SET stock = :stock
             WHERE id = :id
             LIMIT 1"
        );
        $insertStmt = $pdo->prepare(
            "INSERT INTO pos_sales (
                receipt_number,
                cashier_code,
                cashier_name,
                cashier_role,
                item_count,
                subtotal,
                total,
                items_json
            ) VALUES (
                :receipt_number,
                :cashier_code,
                :cashier_name,
                :cashier_role,
                :item_count,
                :subtotal,
                :total,
                :items_json
            )"
        );

        $items = [];
        $subtotal = 0.0;
        $itemCount = 0;

        foreach ($cart as $productId => $quantity) {
            $productId = (int)$productId;
            $quantity = (int)$quantity;
            if ($quantity < 1) {
                continue;
            }

            $lockStmt->execute(['id' => $productId]);
            $product = $lockStmt->fetch();
            if (!$product) {
                throw new RuntimeException('Uno de los productos ya no está disponible.');
            }

            $stock = (int)$product['stock'];
            if ($stock < $quantity) {
                throw new RuntimeException('Stock insuficiente para ' . (string)$product['name'] . '.');
            }

            $newStock = $stock - $quantity;
            $updateStmt->execute([
                'stock' => $newStock,
                'id' => $productId,
            ]);

            $price = (float)$product['price'];
            $lineTotal = $price * $quantity;
            $subtotal += $lineTotal;
            $itemCount += $quantity;
            $items[] = [
                'product_id' => $productId,
                'name' => (string)$product['name'],
                'category' => (string)$product['category'],
                'unit_label' => (string)$product['unit_label'],
                'price' => $price,
                'quantity' => $quantity,
                'line_total' => round($lineTotal, 2),
            ];
        }

        if ($items === []) {
            throw new RuntimeException('La canasta está vacía.');
        }

        $receiptNumber = 'VT-' . gmdate('ymd-His') . '-' . strtoupper(bin2hex(random_bytes(2)));
        $encodedItems = json_encode($items, JSON_UNESCAPED_UNICODE);
        if ($encodedItems === false) {
            $encodedItems = '[]';
        }

        $insertStmt->execute([
            'receipt_number' => $receiptNumber,
            'cashier_code' => (string)$user['code'],
            'cashier_name' => (string)$user['name'],
            'cashier_role' => (string)$user['role_label'],
            'item_count' => $itemCount,
            'subtotal' => $subtotal,
            'total' => $subtotal,
            'items_json' => $encodedItems,
        ]);

        $saleId = (int)$pdo->lastInsertId();
        $pdo->commit();

        unset($_SESSION['pos_cart']);
        $_SESSION['pos_last_receipt_id'] = $saleId;
        pos_flash_add('success', 'Venta registrada correctamente. Se generó un recibo simple.');

        return $saleId;
    } catch (Throwable $exception) {
        if ($pdo->inTransaction()) {
            $pdo->rollBack();
        }
        error_log('POS checkout error: ' . $exception->getMessage());
        $message = $exception instanceof RuntimeException
            ? $exception->getMessage()
            : 'Intenta nuevamente en unos segundos.';
        pos_flash_add('danger', 'No se pudo registrar la venta. ' . $message);
        return null;
    }
}

function pos_require_login(): array
{
    $user = pos_current_user();
    if ($user === null) {
        pos_flash_add('warning', 'Inicia sesión para acceder al punto de venta.');
        pos_redirect('index.php');
    }

    return $user;
}

function pos_handle_post_request(): void
{
    if (($_SERVER['REQUEST_METHOD'] ?? 'GET') !== 'POST') {
        return;
    }

    $action = trim((string)($_POST['action'] ?? ''));
    if ($action === '') {
        return;
    }

    if ($action === 'login') {
        $accessCode = (string)($_POST['access_code'] ?? '');
        $pin = (string)($_POST['pin'] ?? '');
        if (pos_login_user($accessCode, $pin)) {
            pos_flash_add('success', 'Sesión iniciada correctamente.');
        } else {
            pos_flash_add('danger', 'Código o PIN incorrecto. Usa uno de los accesos de prueba visibles.');
        }
        pos_redirect('index.php');
    }

    if ($action === 'logout') {
        pos_logout_user();
        pos_flash_add('secondary', 'Sesión cerrada.');
        pos_redirect('index.php');
    }

    $user = pos_current_user();
    if ($user === null) {
        pos_flash_add('warning', 'Debes iniciar sesión para continuar.');
        pos_redirect('index.php');
    }

    if ($action === 'add_to_cart') {
        $productId = (int)($_POST['product_id'] ?? 0);
        $product = pos_product_by_id($productId);
        if (!$product) {
            pos_flash_add('danger', 'No encontramos ese producto.');
            pos_redirect('index.php#catalogo');
        }

        $cart = pos_cart();
        $currentQuantity = (int)($cart[$productId] ?? 0);
        $availableStock = (int)$product['stock'];
        if ($availableStock <= $currentQuantity) {
            pos_flash_add('warning', 'No hay más stock disponible para ' . (string)$product['name'] . '.');
            pos_redirect('index.php#catalogo');
        }

        $cart[$productId] = $currentQuantity + 1;
        pos_save_cart($cart);
        pos_flash_add('success', 'Producto agregado a la canasta.');
        pos_redirect('index.php#carrito');
    }

    if ($action === 'change_qty') {
        $productId = (int)($_POST['product_id'] ?? 0);
        $delta = (int)($_POST['delta'] ?? 0);
        $cart = pos_cart();
        $product = pos_product_by_id($productId);
        if (!$product || !isset($cart[$productId])) {
            pos_flash_add('warning', 'Ese producto ya no está en la canasta.');
            pos_redirect('index.php#carrito');
        }

        $currentQuantity = (int)$cart[$productId];
        $nextQuantity = $currentQuantity + $delta;
        if ($delta > 0 && $nextQuantity > (int)$product['stock']) {
            pos_flash_add('warning', 'Stock insuficiente para aumentar la cantidad.');
            pos_redirect('index.php#carrito');
        }

        if ($nextQuantity <= 0) {
            unset($cart[$productId]);
            pos_save_cart($cart);
            pos_flash_add('info', 'Producto quitado de la canasta.');
            pos_redirect('index.php#carrito');
        }

        $cart[$productId] = $nextQuantity;
        pos_save_cart($cart);
        pos_flash_add('success', 'Cantidad actualizada.');
        pos_redirect('index.php#carrito');
    }

    if ($action === 'remove_item') {
        $productId = (int)($_POST['product_id'] ?? 0);
        $cart = pos_cart();
        if (isset($cart[$productId])) {
            unset($cart[$productId]);
            pos_save_cart($cart);
            pos_flash_add('info', 'Producto quitado de la canasta.');
        }
        pos_redirect('index.php#carrito');
    }

    if ($action === 'cancel_cart') {
        unset($_SESSION['pos_cart']);
        pos_flash_add('warning', 'Venta anulada. La canasta quedó vacía.');
        pos_redirect('index.php#carrito');
    }

    if ($action === 'adjust_stock') {
        if (!pos_is_admin()) {
            pos_flash_add('danger', 'Solo el administrador puede ajustar stock.');
            pos_redirect('index.php#stock');
        }

        $productId = (int)($_POST['product_id'] ?? 0);
        $delta = (int)($_POST['delta'] ?? 0);
        $allowed = [-5, -1, 1, 5];
        if (!in_array($delta, $allowed, true)) {
            pos_flash_add('danger', 'Ajuste de stock inválido.');
            pos_redirect('index.php#stock');
        }

        $updated = pos_adjust_stock($productId, $delta);
        if ($updated === null) {
            pos_flash_add('danger', 'No se pudo actualizar el stock.');
            pos_redirect('index.php#stock');
        }

        $message = $delta > 0
            ? 'Stock aumentado correctamente.'
            : 'Stock reducido correctamente.';
        pos_flash_add('success', $message);
        pos_redirect('index.php#stock');
    }

    if ($action === 'checkout') {
        $saleId = pos_complete_sale();
        if ($saleId !== null) {
            pos_redirect('receipt.php?id=' . $saleId);
        }
        pos_redirect('index.php#carrito');
    }
}