type StatusCode = number;
type HeaderRecord = Record<string, string | string[]>;
type Data = string | ArrayBuffer | ReadableStream;

class ResponseHelper {
	json(data: any, arg?: StatusCode | ResponseInit, headers?: HeaderRecord) {
		return new Response(JSON.stringify(data), {
			headers: {
				'Content-Type': 'application/json',
				...headers,
			},
		});
	}

	redirect(location: string, status: StatusCode = 302) {
		return this.of(null, {
			status,
			headers: {
				Location: location,
			},
		});
	}

	of(data: Data | null | Response, arg?: StatusCode | ResponseInit, headers?: HeaderRecord): Response {
		if (data instanceof Response) {
			return data;
		}
		let init: ResponseInit;
		if (typeof arg === 'number') {
			init = {
				status: arg,
			};
		} else {
			init = arg || {};
		}
		if (headers) {
			const hdr = Array.from(new Headers(init.headers).entries());
			for (const [k, v] of Object.entries(headers)) {
				if (Array.isArray(v)) {
					v.forEach((v) => hdr.push([k, v]));
				} else {
					hdr.push([k, v]);
				}
			}
			init.headers = hdr;
		}
		return new Response(data, init);
	}
}

function merge(a?: StatusCode | ResponseInit, b?: StatusCode | ResponseInit) {
	const ia = typeof a === 'number' ? { status: a } : a || {};
	const ib = typeof b === 'number' ? { status: b } : b || {};
	return {
		...ia,
		...ib,
		headers: {
			...ia.headers,
			...ib.headers,
		},
	};
}

export const Responses = new ResponseHelper();