import * as fs from "fs";
import * as path from "path";

interface LockData {
  pid: number;
  started: string;
}

function isProcessRunning(pid: number): boolean {
  try {
    process.kill(pid, 0);
    return true;
  } catch {
    return false;
  }
}

export async function acquireLock(lockPath: string): Promise<() => void> {
  if (fs.existsSync(lockPath)) {
    const raw = fs.readFileSync(lockPath, "utf-8");
    let data: LockData;
    try {
      data = JSON.parse(raw) as LockData;
    } catch {
      // Corrupted lock file — treat as stale, overwrite
      data = { pid: 0, started: "" };
    }

    if (data.pid && isProcessRunning(data.pid)) {
      throw new Error(
        `DisClaw bereits aktiv (PID ${data.pid}). Lockfile: ${lockPath}`
      );
    }
    // Stale lock — fall through and overwrite
  }

  // Ensure parent directory exists
  const dir = path.dirname(lockPath);
  if (!fs.existsSync(dir)) {
    fs.mkdirSync(dir, { recursive: true });
  }

  const lockData: LockData = {
    pid: process.pid,
    started: new Date().toISOString(),
  };

  fs.writeFileSync(lockPath, JSON.stringify(lockData), "utf-8");

  const release = (): void => {
    if (fs.existsSync(lockPath)) {
      fs.unlinkSync(lockPath);
    }
  };

  return release;
}