import type { Tree } from '@nrwl/devkit';
import { joinPathFragments, readJson } from '@nrwl/devkit';
import { dirname } from 'path';

export function locateLibraryEntryPointFromDirectory(
  tree: Tree,
  directory: string,
  projectRoot: string,
  projectSourceRoot: string
): string | null {
  const ngPackageJsonPath = joinPathFragments(directory, 'ng-package.json');
  let entryPointFile = tree.exists(ngPackageJsonPath)
    ? readJson(tree, ngPackageJsonPath).lib?.entryFile ?? 'src/public_api.ts'
    : null;

  if (entryPointFile) {
    return joinPathFragments(directory, entryPointFile);
  }

  if (directory === projectRoot) {
    const indexFile = joinPathFragments(projectSourceRoot, 'index.ts');

    return tree.exists(indexFile) ? indexFile : null;
  }

  return locateLibraryEntryPointFromDirectory(
    tree,
    dirname(directory),
    projectRoot,
    projectSourceRoot
  );
}