// lib/shopify-storefront.ts
const SHOP = process.env.SHOPIFY_STORE_DOMAIN!;         // yourstore.myshopify.com
const TOKEN = process.env.SHOPIFY_STOREFRONT_TOKEN!;    // public access token

interface StorefrontResponse<T> {
  data: T;
  errors?: Array<{ message: string }>;
}

// Shopify GraphQL Storefront API typed fetch wrapper
export async function storefrontQuery<T>(
  query: string,
  variables?: Record<string, unknown>,
  options?: RequestInit
): Promise<T> {
  const res = await fetch(`https://${SHOP}/api/2025-01/graphql.json`, {
    method: 'POST',
    headers: {
      'Content-Type': 'application/json',
      'X-Shopify-Storefront-Access-Token': TOKEN,
    },
    body: JSON.stringify({ query, variables }),
    ...options,
  });

  const json: StorefrontResponse<T> = await res.json();

  if (json.errors?.length) {
    throw new Error(json.errors[0].message);
  }

  return json.data;
}

// Get product catalogue from Shopify GraphQL Storefront API
export async function getProducts(first = 20, after?: string) {
  const data = await storefrontQuery<{
    products: {
      edges: Array<{
        cursor: string;
        node: { id: string; title: string; handle: string; priceRange: { minVariantPrice: { amount: string; currencyCode: string } }; featuredImage: { url: string; altText: string } | null };
      }>;
      pageInfo: { hasNextPage: boolean; endCursor: string };
    };
  }>(`
    query GetProducts($first: Int!, $after: String) {
      products(first: $first, after: $after, sortKey: BEST_SELLING) {
        pageInfo { hasNextPage endCursor }
        edges {
          cursor
          node {
            id
            title
            handle
            featuredImage { url altText }
            priceRange {
              minVariantPrice { amount currencyCode }
            }
          }
        }
      }
    }
  `, { first, after });

  return data.products;
}

// Get single product by handle from Shopify GraphQL Storefront API
export async function getProductByHandle(handle: string) {
  const data = await storefrontQuery<{
    productByHandle: {
      id: string; title: string; description: string;
      variants: { edges: Array<{ node: { id: string; title: string; price: { amount: string } } }> };
    } | null;
  }>(`
    query GetProduct($handle: String!) {
      productByHandle(handle: $handle) {
        id title description
        variants(first: 10) {
          edges { node { id title price { amount } } }
        }
      }
    }
  `, { handle });

  return data.productByHandle;
}

// Create a new cart via Shopify GraphQL Storefront API
export async function createCart() {
  const data = await storefrontQuery<{
    cartCreate: { cart: { id: string; checkoutUrl: string } }
  }>(`
    mutation CreateCart {
      cartCreate {
        cart { id checkoutUrl }
      }
    }
  `);
  return data.cartCreate.cart;
}

// Add line items to cart via Shopify GraphQL Storefront API
export async function addToCart(cartId: string, variantId: string, quantity: number) {
  const data = await storefrontQuery<{
    cartLinesAdd: {
      cart: {
        id: string;
        totalQuantity: number;
        lines: { edges: Array<{ node: { id: string; quantity: number; merchandise: { title: string } } }> };
        cost: { totalAmount: { amount: string; currencyCode: string } };
      };
    };
  }>(`
    mutation AddToCart($cartId: ID!, $lines: [CartLineInput!]!) {
      cartLinesAdd(cartId: $cartId, lines: $lines) {
        cart {
          id totalQuantity
          lines(first: 20) {
            edges { node { id quantity merchandise { ... on ProductVariant { title } } } }
          }
          cost { totalAmount { amount currencyCode } }
        }
      }
    }
  `, {
    cartId,
    lines: [{ merchandiseId: variantId, quantity }],
  });
  return data.cartLinesAdd.cart;
}