ame/src/common/fetch.ts

export function fetchCors(input: RequestInfo | URL, init?: RequestInit): Promise<Response> {
	return new Promise<Response>((resolve, reject) => {
		const fetchReq = new Request(input, init);

		GM.xmlHttpRequest({
			method: fetchReq.method as any,
			url: fetchReq.url,
			headers: Object.fromEntries(Array.from(fetchReq.headers)),
			responseType: 'blob',
			onload(res) {
				const headers = res.responseHeaders
					.split('\r\n')
					.slice(0, -1)
					.map(line => line.split(': '));

				const fetchRes = new Response(res.response, {
					headers: Object.fromEntries(headers),
					status: res.status,
					statusText: res.statusText
				});

				Object.defineProperty(fetchRes, 'url', { value: fetchReq.url });

				resolve(fetchRes);
			},
			onerror() {
				reject(new TypeError('Network request errored.'));
			},
			ontimeout() {
				reject(new TypeError('Network request timed out.'));
			}
		});
	});
}