import { app } from "electron";
import fs from "node:fs";
import http, { type Server } from "node:http";
import path from "node:path";

let server: Server | null = null;
let currentUrl = "";

function fixtureRoot(): string {
  const candidates = [
    process.resourcesPath ? path.join(process.resourcesPath, "fixture") : "",
    path.join(app.getAppPath(), "resources", "fixture"),
    path.join(__dirname, "../../resources/fixture")
  ].filter(Boolean);
  const found = candidates.find((candidate) => fs.existsSync(path.join(candidate, "index.html")));
  if (!found) throw new Error(`fixture index.html not found; tried ${candidates.join(", ")}`);
  return found;
}

export async function startFixtureServer(preferredPort = 17863): Promise<string> {
  if (server && currentUrl) return currentUrl;
  const root = fixtureRoot();
  server = http.createServer((request, response) => {
    const url = new URL(request.url || "/", "http://127.0.0.1");
    if (url.pathname === "/download.csv") {
      response.writeHead(200, { "Content-Type": "text/csv; charset=utf-8", "Content-Disposition": "attachment; filename=orders.csv" });
      response.end("name,amount,status\r\nRPA,128,created\r\n");
      return;
    }
    if (url.pathname !== "/" && url.pathname !== "/index.html") {
      response.writeHead(404).end("Not found");
      return;
    }
    response.writeHead(200, { "Content-Type": "text/html; charset=utf-8", "Cache-Control": "no-store" });
    fs.createReadStream(path.join(root, "index.html")).pipe(response);
  });

  const attempts = preferredPort === 0 ? [0] : Array.from({ length: 10 }, (_, index) => preferredPort + index);
  for (const port of attempts) {
    try {
      await new Promise<void>((resolve, reject) => {
        const onError = (error: Error) => { server?.removeListener("listening", onListening); reject(error); };
        const onListening = () => { server?.removeListener("error", onError); resolve(); };
        server!.once("error", onError);
        server!.once("listening", onListening);
        server!.listen(port, "127.0.0.1");
      });
      const address = server.address();
      const activePort = typeof address === "object" && address ? address.port : port;
      currentUrl = `http://127.0.0.1:${activePort}/`;
      return currentUrl;
    } catch (error) {
      if ((error as NodeJS.ErrnoException).code !== "EADDRINUSE") throw error;
    }
  }
  throw new Error("无法启动本地演示站：17863-17872 端口均被占用");
}

export async function stopFixtureServer(): Promise<void> {
  const active = server;
  server = null;
  currentUrl = "";
  if (!active) return;
  await new Promise<void>((resolve) => active.close(() => resolve()));
}

export function fixtureUrl(): string {
  return currentUrl;
}