import type { MaybePromise } from '../../asyncs/MaybePromise';
import { createFetchWith, type FetchLike } from '../../fetch';
import { getGlobalThis } from '../../web/getGlobalThis';

export function createFetchWithProxyByUndici({
	proxy,
	token: _token,
	fetch,
	undici,
}: {
	proxy?: string;
	token?: string;
	fetch?: FetchLike;
	undici?: MaybePromise<{ fetch: any; ProxyAgent: any }>;
} = {}): FetchLike {
	if (!proxy) {
		return fetch || globalThis.fetch;
	}

	if ((getGlobalThis() as any).Bun) {
		return createFetchWith({
			fetch,
			onRequest: ({ url, req, next }) => {
				return next(url, {
					...req,
					// https://github.com/oven-sh/bun/issues/1829
					proxy,
				} as RequestInit);
			},
		});
	}

	let agent: any;
	// https://github.com/nodejs/undici/blob/main/docs/best-practices/proxy.md
	return async (...args) => {
		const init = (args[1] ||= {}) as RequestInit & { duplex?: string; dispatcher?: any };
		{
			const body = init.body;
			if (typeof body === 'object' && body && (body instanceof ReadableStream || Symbol.asyncIterator in body)) {
				// request.duplex must be set if request.body is ReadableStream or Async Iterables
				init.duplex ||= 'half';
			}
		}
		if (!agent) {
			let uri = proxy;
			let token = _token;
			{
				let u: URL | undefined;
				try {
					u = new URL(proxy);
				} catch (_e) {}
				if (!token && u && (u.username || u.password)) {
					token = `Basic ${btoa(`${u.username || ''}:${u.password}`)}`;
					u.username = '';
					u.password = '';
					uri = u.toString();
				}
			}
			// if in next use 'next/dist/compiled/undici'
			undici ||= import('undici');
			const mod = await undici;
			const ProxyAgent = mod.ProxyAgent as new (_: any) => any;
			fetch ||= mod.fetch as FetchLike;
			// https://github.com/nodejs/undici/blob/main/docs/api/ProxyAgent.md
			agent = new ProxyAgent({ uri, token });
			// https://github.com/nodejs/node/issues/43187#issuecomment-1134634174
			// (global as any)[Symbol.for('undici.globalDispatcher.1')] = agent;
			// fixme should unwrap error https://github.com/nodejs/undici/issues/1248
		}
		init.dispatcher = agent;
		return (await fetch?.(...args))!;
	};
}