import type { Gateway } from './context.ts';
import { handleGit } from './git.ts';
import { NSID as NPM_CLOSURE } from '@nibling/npm-gateway/protocol';
import { handleNpm } from './npm.ts';
import { handleXrpc } from './xrpc.ts';

export type { Gateway } from './context.ts';
export { memoryCache, type ResponseCache } from './cache.ts';

/** Request headers a cross-origin caller may send: XRPC reads, git's, and the cache bypass. */
const PREFLIGHT = {
  'access-control-allow-origin': '*',
  'access-control-allow-methods': 'GET, POST, OPTIONS',
  'access-control-allow-headers': 'content-type, git-protocol, x-nib-fresh',
  'access-control-max-age': '86400',
};

export function preflight(): Response {
  return new Response(null, { status: 204, headers: PREFLIGHT });
}

/**
 * The read gateway (D22): repo reads, identity, backlinks, git fetches, and npm closures, each answered from a
 * per-data-center cache or from upstream. Undefined when the path is not one of its routes.
 * `x-nib-fresh: 1` skips the cache read, so a writer sees their own write.
 */
export async function handleGateway(request: Request, g: Gateway): Promise<Response | undefined> {
  const url = new URL(request.url);
  const bypass = request.headers.get('x-nib-fresh') === '1';
  if (url.pathname.startsWith('/git/')) return handleGit(g, request, bypass);
  if (request.method !== 'GET') return undefined;
  // This worker's did:web names it as an npm gateway (D23), so a client build names it as any other.
  if (url.pathname === `/xrpc/${NPM_CLOSURE}` || url.pathname === '/.well-known/did.json') return handleNpm(g, request);
  if (!url.pathname.startsWith('/xrpc/')) return undefined;
  return handleXrpc(g, url.pathname.slice('/xrpc/'.length), url.searchParams, bypass);
}