import { existsSync } from "node:fs";
import { spawn, type ChildProcess } from "node:child_process";
import { join, resolve } from "node:path";

export interface PreviewOptions {
  port?: number;
  hostname?: string;
  stdio?: "inherit" | "pipe";
  /** Enable the production artifact's reconnecting DOM-morph client. */
  developmentRuntime?: boolean;
}

export function productionEntry(appRoot: string): string {
  const entry = join(resolve(appRoot), "dist", "server.js");
  if (!existsSync(entry)) {
    throw new Error("WRN-PREVIEW-NO-BUILD: run `wrnexus build` before `wrnexus preview`.");
  }
  return entry;
}

export function runPreview(appRoot: string, options: PreviewOptions = {}): ChildProcess {
  const entry = productionEntry(appRoot);
  const port = options.port ?? 3000;
  const hostname = options.hostname ?? "::";
  console.log(
    `\n  ▶ WrNexus production preview — http://${hostname === "::" ? "localhost" : hostname}:${port}`,
  );
  return spawn(process.execPath, [entry], {
    cwd: resolve(appRoot),
    stdio: options.stdio ?? "inherit",
    env: {
      ...process.env,
      NODE_ENV: "production",
      WRNEXUS_PROFILE: process.env.WRNEXUS_PROFILE ?? "production",
      PORT: String(port),
      HOST: hostname,
      ...(options.developmentRuntime ? { WRNEXUS_PRODUCTION_DEV: "1" } : {}),
    },
  });
}