const handleRequest = async (request) => {
	try {
		const url = new URL(request.url);
		let query;
		let dropHeaders = false;

		if (url.search.includes('&dh')) {
			url.search = url.search.replace('&dh', '');
			dropHeaders = true;
		}

		if (url.search.includes('?q=')) {
			query = url.search.split('?q=')[1];
		} else if (url.search.includes('?d=')) {
			query = atob(url.search.split('?d=')[1]);
		} else if (url.search.includes('?d2=')) {
			const fullEncodedURL = url.search.split('?d2=')[1];
			const key = parseInt(fullEncodedURL.slice(-2));

			query = atob(fullEncodedURL.slice(0, -2))
				.split(':')
				.map((char) => String.fromCharCode(char - key))
				.join('');
		} else {
			return new Response(null, {
				status: 400,
				statusText: 'Bad Request',
			});
		}

		request = new Request(query, request);

		request.headers.set('Host', new URL(query).origin);
		request.headers.set('Referrer', new URL(query));
		request.headers.set('Origin', new URL(query));
		request.headers.set('Access-Control-Allow-Credentials', 'true');
		request.headers.delete('X-Content-Type-Options');

		let response = await fetch(request);

		response = new Response(response.body, response);

		if (dropHeaders) response.headers.forEach((_, key) => response.headers.delete(key));

		response.headers.set('Access-Control-Allow-Origin', 'https://due.moe');
		response.headers.append('Vary', 'Origin');
		response.headers.set('Cache-Control', 'max-age=300');

		return response;
	} catch {
		return new Response(null, {
			status: 400,
			statusText: 'Bad Request',
		});
	}
};

const handleOptions = async (request) => {
	if (
		request.headers.get('Origin') !== null &&
		request.headers.get('Access-Control-Request-Method') !== null &&
		request.headers.get('Access-Control-Request-Headers') !== null
	) {
		return new Response(null, {
			headers: {
				'Access-Control-Allow-Origin': '*',
				'Access-Control-Allow-Methods': 'GET, HEAD, POST, OPTIONS',
				'Access-Control-Allow-Headers': '*',
			},
		});
	} else {
		return new Response(null, {
			headers: {
				Allow: 'GET, HEAD, POST, OPTIONS',
			},
		});
	}
};

addEventListener('fetch', (event) => {
	const request = event.request;

	try {
		switch (request.method) {
			case 'OPTIONS':
				event.respondWith(handleOptions(request));

				break;

			case 'GET':
			case 'HEAD':
			case 'POST':
				event.respondWith(handleRequest(request));

				break;

			default:
				event.respondWith(async () => {
					return new Response(null, {
						status: 405,
						statusText: 'Method Not Allowed',
					});
				});

				break;
		}
	} catch {
		return new Response(null, {
			status: 400,
			statusText: 'Bad Request',
		});
	}
});