import { error } from '@sveltejs/kit';

export const MAX_JSON_BODY_BYTES = 64 * 1024;

export function jsonOk(data: unknown, status = 200): Response {
	return new Response(JSON.stringify(data), {
		status,
		headers: { 'content-type': 'application/json' }
	});
}

export function jsonError(
	status: number,
	message: string,
	headers?: Record<string, string>
): Response {
	return new Response(JSON.stringify({ message }), {
		status,
		headers: { 'content-type': 'application/json', ...headers }
	});
}

/** Read and parse a JSON request body with a size cap. Throws 413 for
 * oversized bodies and 400 for invalid JSON / wrong content type. */
export async function readJsonBody(request: Request): Promise<unknown> {
	const contentType = request.headers.get('content-type') ?? '';
	if (!contentType.includes('application/json')) {
		throw error(400, 'content-type must be application/json');
	}

	const contentLength = Number(request.headers.get('content-length') ?? 0);
	if (contentLength > MAX_JSON_BODY_BYTES) {
		throw error(413, 'request body too large');
	}

	const raw = await request.text();
	if (raw.length === 0) {
		throw error(400, 'request body is required');
	}
	if (raw.length > MAX_JSON_BODY_BYTES) {
		throw error(413, 'request body too large');
	}

	try {
		return JSON.parse(raw);
	} catch {
		throw error(400, 'invalid JSON body');
	}
}

/** Build a 429 response with Retry-After set in seconds. */
export function rateLimited(retryAfterMs: number): Response {
	const retryAfterSeconds = Math.max(1, Math.ceil(retryAfterMs / 1000));
	return jsonError(429, 'rate limit exceeded', { 'retry-after': String(retryAfterSeconds) });
}

export function clientIp(request: Request): string {
	const fwd = request.headers.get('x-forwarded-for');
	if (fwd) {
		const first = fwd.split(',')[0]?.trim();
		if (first) return first;
	}
	return request.headers.get('x-real-ip') ?? 'unknown';
}