import path from "pathe";
import { exists } from "./exists.ts";
import { findWorkspaceRoot } from "./find-workspace-root.ts";

export type PackageManager = "bun" | "pnpm" | "yarn" | "npm" | "deno";

export async function detectPackageManager(
  root: string = process.cwd(),
): Promise<PackageManager> {
  root = await findWorkspaceRoot(root);

  if (await exists(path.resolve(root, "deno.lock"))) return "deno";
  if (
    (await exists(path.resolve(root, "deno.json"))) ||
    (await exists(path.resolve(root, "deno.jsonc")))
  )
    return "deno";
  if (await exists(path.resolve(root, "bun.lockb"))) return "bun";
  if (await exists(path.resolve(root, "bun.lock"))) return "bun";
  if (await exists(path.resolve(root, "pnpm-lock.yaml"))) return "pnpm";
  if (await exists(path.resolve(root, "yarn.lock"))) return "yarn";

  if (process.env.npm_execpath?.includes("bun")) {
    return "bun";
  }

  if (process.env.DENO) {
    return "deno";
  }

  const userAgent = process.env.npm_config_user_agent;
  if (userAgent) {
    if (userAgent.startsWith("deno")) return "deno";
    if (userAgent.startsWith("bun")) return "bun";
    if (userAgent.startsWith("pnpm")) return "pnpm";
    if (userAgent.startsWith("yarn")) return "yarn";
    if (userAgent.startsWith("npm")) return "npm";
  }

  return "npm";
}

export async function getPackageManagerRunner(): Promise<string> {
  const packageManager = await detectPackageManager();
  return {
    bun: "bun run",
    pnpm: "pnpm",
    yarn: "yarn",
    npm: "npx",
    deno: "deno run",
  }[packageManager];
}