import { readFileSync } from "node:fs";
import { dirname, join } from "node:path";

import {
  OMP_HARNESS_PACKAGE,
  OMP_NATIVES_PACKAGE,
  packageNodeModulesRoot,
} from "./host.ts";

export interface HarnessAttestation {
  path: string;
  version: string;
  nativePath: string;
}

/** Resolve the installed peer from this package's directory, never Bun's ambient cache. */
export function resolveHarnessEntry(moduleDir: string = import.meta.dir): string {
  return Bun.resolveSync(OMP_HARNESS_PACKAGE, moduleDir);
}

/** The installed peer version belonging to a resolved harness entry. */
export function harnessVersion(entry: string): string | undefined {
  const root = packageNodeModulesRoot(entry);
  if (root === undefined) return undefined;
  try {
    const parsed: unknown = JSON.parse(
      readFileSync(join(root, OMP_HARNESS_PACKAGE, "package.json"), "utf8"),
    );
    if (parsed === null || typeof parsed !== "object") return undefined;
    const version = Reflect.get(parsed, "version");
    return typeof version === "string" && version !== "" ? version : undefined;
  } catch {
    return undefined;
  }
}

/**
 * Exercise the worker's real import contract: explicitly anchored peer and
 * native-addon resolution, with the caller responsible for passing
 * `--no-install` so neither import can fall through to Bun's package cache.
 */
export async function probeHarness(moduleDir: string = import.meta.dir): Promise<HarnessAttestation> {
  const path = resolveHarnessEntry(moduleDir);
  await import(path);
  const version = harnessVersion(path);
  if (version === undefined) throw new Error(`cannot read the harness version for ${path}`);
  const nativePath = Bun.resolveSync(OMP_NATIVES_PACKAGE, dirname(path));
  await import(nativePath);
  return { path, version, nativePath };
}

if (import.meta.main) {
  try {
    process.stdout.write(`${JSON.stringify(await probeHarness())}\n`);
  } catch (cause) {
    process.stderr.write(`${cause instanceof Error ? cause.stack ?? cause.message : String(cause)}\n`);
    process.exitCode = 1;
  }
}