import type { RuneConfig } from "../types.ts";

export const DEFAULT_PREFIX = "bunx @lanyuanxiaoyao/rune";

export function inferFromEnvironment(
  execPath: string,
  userAgent: string | undefined,
): string | null {
  if (execPath.includes("bun")) return "bunx @lanyuanxiaoyao/rune";
  if (userAgent?.includes("pnpm")) return "pnpx @lanyuanxiaoyao/rune";
  if (userAgent?.includes("npm")) return "npx @lanyuanxiaoyao/rune";
  return null;
}

export async function checkCommandAvailable(command: string): Promise<boolean> {
  const which = process.platform === "win32" ? "where" : "which";
  try {
    const proc = Bun.spawn([which, command], {
      stdout: "ignore",
      stderr: "ignore",
    });
    const exitCode = await proc.exited;
    return exitCode === 0;
  } catch {
    return false;
  }
}

export async function detectCommandPrefix(): Promise<string | null> {
  if (await checkCommandAvailable("rune")) return "rune";

  const inferred = inferFromEnvironment(process.execPath, process.env.npm_config_user_agent);
  if (inferred) return inferred;

  for (const pm of ["bunx", "pnpx", "npx"]) {
    if (await checkCommandAvailable(pm)) return `${pm} @lanyuanxiaoyao/rune`;
  }

  return null;
}

export function getPmPrefix(config?: RuneConfig): string {
  return config?.metadata?.command ?? DEFAULT_PREFIX;
}

export function getFallbackNote(): string {
  return `如果没有安装 bun，可使用 \`pnpx @lanyuanxiaoyao/rune\` 或 \`npx @lanyuanxiaoyao/rune\` 替代`;
}

export function applyCommandPrefix(text: string, config?: RuneConfig): string {
  const prefix = getPmPrefix(config);
  const hasCommand = /\brune(?=\s)/.test(text);
  const result = text.replace(/\brune(?=\s)/g, prefix);
  if (!config?.metadata?.command && hasCommand) {
    return result + "\n\n" + getFallbackNote();
  }
  return result;
}