import path from 'node:path';

export function isInsideDirectory(filePath: string, directory: string): boolean {
  const resolvedFile = path.resolve(filePath);
  const resolvedDirectory = path.resolve(directory);
  const relative = path.relative(resolvedDirectory, resolvedFile);
  return relative === '' || (!relative.startsWith('..') && !path.isAbsolute(relative));
}

export function findPageFromChangedFile(
  changedFile: string | undefined,
  pagesRoot: string,
): string | null {
  if (!changedFile) {
    return null;
  }

  const resolvedChanged = path.resolve(changedFile);
  const resolvedPagesRoot = path.resolve(pagesRoot);
  if (!isInsideDirectory(resolvedChanged, resolvedPagesRoot)) {
    return null;
  }

  const relative = path.relative(resolvedPagesRoot, resolvedChanged);
  const segments = relative.split(path.sep);
  return segments.length > 0 && segments[0] ? segments[0] : null;
}

export function relativePathWithin(filePath: string | undefined, directory: string): string | null {
  if (!filePath) {
    return null;
  }

  if (!isInsideDirectory(filePath, directory)) {
    return null;
  }

  return path.relative(path.resolve(directory), path.resolve(filePath));
}