import fs from "node:fs";
import os from "node:os";
import path from "node:path";
import { spawn, type ChildProcess } from "node:child_process";

let noReplyProcess: ChildProcess | null = null;

const LOCK_FILE = path.join(os.tmpdir(), "dirigent-sidecar.lock");

function readLock(): { pid: number } | null {
  try {
    const raw = fs.readFileSync(LOCK_FILE, "utf8").trim();
    return { pid: Number(raw) };
  } catch {
    return null;
  }
}

function writeLock(pid: number): void {
  try { fs.writeFileSync(LOCK_FILE, String(pid)); } catch { /* ignore */ }
}

function clearLock(): void {
  try { fs.unlinkSync(LOCK_FILE); } catch { /* ignore */ }
}

function isLockHeld(): boolean {
  const lock = readLock();
  if (!lock) return false;
  try {
    process.kill(lock.pid, 0);
    return true;
  } catch {
    return false;
  }
}

export function startSideCar(
  logger: { info: (m: string) => void; warn: (m: string) => void },
  pluginDir: string,
  port = 8787,
  moderatorToken?: string,
  pluginApiToken?: string,
  gatewayPort?: number,
  debugMode?: boolean,
): void {
  logger.info(`dirigent: startSideCar called, pluginDir=${pluginDir}`);

  if (noReplyProcess) {
    logger.info("dirigent: no-reply API already running (local ref), skipping");
    return;
  }

  if (isLockHeld()) {
    logger.info("dirigent: no-reply API already running (lock file), skipping");
    return;
  }

  // services/main.mjs lives alongside the plugin directory in the distribution
  const serverPath = path.resolve(pluginDir, "services", "main.mjs");
  logger.info(`dirigent: resolved serverPath=${serverPath}`);

  if (!fs.existsSync(serverPath)) {
    logger.warn(`dirigent: services/main.mjs not found at ${serverPath}, skipping`);
    return;
  }

  logger.info("dirigent: services/main.mjs found, spawning process...");

  // Build plugin API URL from gateway port, or use a default
  const pluginApiUrl = gatewayPort
    ? `http://127.0.0.1:${gatewayPort}`
    : "http://127.0.0.1:18789";

  const env: NodeJS.ProcessEnv = {
    ...process.env,
    SERVICES_PORT: String(port),
    PLUGIN_API_URL: pluginApiUrl,
  };

  if (moderatorToken) {
    env.MODERATOR_TOKEN = moderatorToken;
  }
  if (pluginApiToken) {
    env.PLUGIN_API_TOKEN = pluginApiToken;
  }
  if (debugMode !== undefined) {
    env.DEBUG_MODE = debugMode ? "true" : "false";
  }

  noReplyProcess = spawn(process.execPath, [serverPath], {
    env,
    stdio: ["ignore", "pipe", "pipe"],
    detached: false,
  });

  if (noReplyProcess.pid) {
    writeLock(noReplyProcess.pid);
  }

  noReplyProcess.stdout?.on("data", (d: Buffer) => logger.info(`dirigent: services: ${d.toString().trim()}`));
  noReplyProcess.stderr?.on("data", (d: Buffer) => logger.warn(`dirigent: services: ${d.toString().trim()}`));

  noReplyProcess.on("exit", (code, signal) => {
    logger.info(`dirigent: services exited (code=${code}, signal=${signal})`);
    clearLock();
    noReplyProcess = null;
  });

  logger.info(`dirigent: services started (pid=${noReplyProcess.pid}, port=${port})`);
}

export function stopSideCar(logger: { info: (m: string) => void }): void {
  if (!noReplyProcess) return;
  logger.info("dirigent: stopping sidecar");
  noReplyProcess.kill("SIGTERM");
  noReplyProcess = null;
  clearLock();
}