import { access } from "node:fs/promises";
import { constants } from "node:fs";
import { dirname, join, resolve } from "node:path";
import { fileURLToPath } from "node:url";

export interface RuntimeResolverOptions {
  env?: NodeJS.ProcessEnv;
  homeDir?: string;
  skillDir?: string;
}

export interface WebAutomationRuntime {
  scriptsDir: string;
  checkInstall: {
    cwd: string;
    command: string;
    args: string[];
  };
}

async function assertFile(path: string, label: string): Promise<void> {
  try {
    await access(path, constants.F_OK);
  } catch {
    throw new Error(`web-automation runtime is missing ${label}: ${path}`);
  }
}

async function assertExecutableOrFile(path: string, label: string): Promise<void> {
  try {
    await access(path, constants.X_OK);
  } catch {
    await assertFile(path, label);
  }
}

function defaultSkillDir(): string {
  return resolve(dirname(fileURLToPath(import.meta.url)), "..");
}

export async function resolveWebAutomationRuntime(options: RuntimeResolverOptions = {}): Promise<WebAutomationRuntime> {
  const env = options.env ?? process.env;
  const homeDir = options.homeDir ?? process.env.HOME ?? "";
  const skillDir = options.skillDir ?? defaultSkillDir();
  const candidates = [
    env.AMAZON_SHOPPING_WEB_AUTOMATION_DIR,
    homeDir ? join(homeDir, ".openclaw", "workspace", "skills", "web-automation", "scripts") : undefined,
    resolve(skillDir, "..", "web-automation", "scripts")
  ].filter((candidate): candidate is string => Boolean(candidate));

  const errors: string[] = [];
  for (const scriptsDir of candidates) {
    try {
      await assertFile(join(scriptsDir, "check-install.js"), "check-install.js");
      await assertFile(join(scriptsDir, "package.json"), "package.json");
      await assertExecutableOrFile(join(scriptsDir, "node_modules", ".bin", "tsx"), "node_modules/.bin/tsx");
      return {
        scriptsDir,
        checkInstall: {
          cwd: scriptsDir,
          command: "node",
          args: ["check-install.js"]
        }
      };
    } catch (error: unknown) {
      errors.push(error instanceof Error ? error.message : String(error));
    }
  }

  throw new Error(`Unable to locate usable web-automation runtime.\n${errors.join("\n")}`);
}