TypeScript

Types below match the API Reference shapes - money/decimal fields are string, never number.

A small typed client

const BASE_URL = "https://dev-api.theprioryshop.co.uk";
const API_KEY = process.env.EPOS_API_KEY as string; // never hardcode this

interface EposErrorBody {
  error: { code: string; message: string; details: Record<string, unknown>; requestId: string };
}

class EposApiError extends Error {
  constructor(public code: string, public requestId: string, public status: number, message: string) {
    super(message);
  }
}

async function eposGet<T>(path: string): Promise<T> {
  const res = await fetch(`${BASE_URL}${path}`, {
    headers: { Authorization: `Bearer ${API_KEY}` }
  });
  if (!res.ok) {
    const body = (await res.json()) as EposErrorBody;
    throw new EposApiError(body.error.code, body.error.requestId, res.status, body.error.message);
  }
  return res.json() as Promise<T>;
}

interface CatalogProduct {
  id: string;
  storeId: string;
  categoryId: string | null;
  name: string;
  sku: string;
  barcode: string | null;
  sellingPriceGross: string; // decimal string, not a number
  sellingPriceNet: string;
  isActive: boolean;
  updatedAt: string; // ISO 8601
}

interface CatalogProductListResponse {
  rows: CatalogProduct[];
  page: number;
  pageSize: number;
  total: number;
  totalPages: number;
}

List products

const products = await eposGet<CatalogProductListResponse>("/v1/catalog/products?pageSize=20");

Handle an error

try {
  await eposGet<CatalogProduct>("/v1/catalog/products/does-not-exist");
} catch (err) {
  if (err instanceof EposApiError) {
    if (err.code === "not_found") {
      // ...
    } else if (err.code === "rate_limited") {
      // back off and retry - see Rate Limits
    } else {
      console.error(`EPOS API error ${err.code} (request ${err.requestId})`);
    }
  } else {
    throw err;
  }
}

Paginate through every product

async function* allProducts(): AsyncGenerator<CatalogProduct> {
  let page = 1;
  while (true) {
    const { rows, totalPages } = await eposGet<CatalogProductListResponse>(
      `/v1/catalog/products?pageSize=100&page=${page}`
    );
    yield* rows;
    if (page >= totalPages) break;
    page += 1;
  }
}

The full field list for every response type is generated straight from the OpenAPI document - see the API Reference rather than re-declaring every interface here by hand.