import { execSync } from "node:child_process";
import { existsSync, mkdirSync, readFileSync, writeFileSync } from "node:fs";
import { homedir, hostname, platform } from "node:os";
import { join } from "node:path";

const SCRIBE_DIR = join(homedir(), ".scribe");
const DEVICE_ID_FILE = join(SCRIBE_DIR, "device-id");

/**
 * Get the system's hardware machine ID
 * - macOS: IOPlatformUUID from ioreg
 * - Linux: /etc/machine-id
 * - Windows: MachineGuid from registry
 * - Fallback: hostname-based hash
 */
function getSystemMachineId(): string | null {
  try {
    const os = platform();

    if (os === "darwin") {
      // macOS: Get IOPlatformUUID
      const output = execSync(
        "ioreg -rd1 -c IOPlatformExpertDevice | grep IOPlatformUUID",
        { encoding: "utf-8" },
      );
      const match = output.match(/"IOPlatformUUID"\s*=\s*"([^"]+)"/);
      if (match) return match[1];
    } else if (os === "linux") {
      // Linux: Read /etc/machine-id
      if (existsSync("/etc/machine-id")) {
        return readFileSync("/etc/machine-id", "utf-8").trim();
      }
      // Fallback to dbus machine-id
      if (existsSync("/var/lib/dbus/machine-id")) {
        return readFileSync("/var/lib/dbus/machine-id", "utf-8").trim();
      }
    } else if (os === "win32") {
      // Windows: Get MachineGuid from registry
      const output = execSync(
        'reg query "HKEY_LOCAL_MACHINE\\SOFTWARE\\Microsoft\\Cryptography" /v MachineGuid',
        { encoding: "utf-8" },
      );
      const match = output.match(/MachineGuid\s+REG_SZ\s+([^\s]+)/);
      if (match) return match[1];
    }
  } catch {
    // Fall through to null
  }
  return null;
}

/**
 * Get a persistent device ID for this machine.
 * Checks ~/.scribe/device-id first, then system machine ID, then generates one.
 */
export function getMachineId(): string {
  // Check for cached ID first
  if (existsSync(DEVICE_ID_FILE)) {
    try {
      const cached = readFileSync(DEVICE_ID_FILE, "utf-8").trim();
      if (cached) return cached;
    } catch {
      // Fall through
    }
  }

  // Try to get system machine ID
  let machineId = getSystemMachineId();

  // Fallback to hostname-based ID
  if (!machineId) {
    const host = hostname() || "unknown";
    let hash = 0;
    for (let i = 0; i < host.length; i++) {
      const char = host.charCodeAt(i);
      hash = (hash << 5) - hash + char;
      hash = hash & hash;
    }
    machineId = `fallback_${Math.abs(hash).toString(36)}_${host.replace(/[^a-zA-Z0-9]/g, "")}`;
  }

  // Cache the ID for future use
  try {
    if (!existsSync(SCRIBE_DIR)) {
      mkdirSync(SCRIBE_DIR, { recursive: true });
    }
    writeFileSync(DEVICE_ID_FILE, machineId, "utf-8");
  } catch {
    // Caching failed, but we still have the ID
  }

  return machineId;
}

/**
 * Get a friendly device name (hostname)
 */
export function getDeviceName(): string {
  return hostname() || "Unknown Device";
}