packages/ui/src/preview/path.ts

// Adapted from ZCode path.ts (Apache-2.0), commit 872ad960.
// See licenses/third-party-notices.txt and docs/internals/previews.md.
const WINDOWS_ABSOLUTE_PATH_RE = /^[a-zA-Z]:[\\/]/;
const UNC_PATH_RE = /^\\\\/;
const URI_ESCAPE_RE = /%[0-9A-Fa-f]{2}/;

export function getPathLeaf(path: string): string {
  const normalizedPath = path.replace(/\\/g, "/").replace(/\/+$/, "");
  const segments = normalizedPath.split("/").filter(Boolean);
  return segments[segments.length - 1] ?? path;
}

export function isAbsoluteFilePath(path: string): boolean {
  return path.startsWith("/") || WINDOWS_ABSOLUTE_PATH_RE.test(path) || UNC_PATH_RE.test(path);
}

export function decodeFilePathUriEscapes(path: string): string {
  if (!URI_ESCAPE_RE.test(path)) {
    return path;
  }

  try {
    return decodeURIComponent(path);
  } catch {
    return path;
  }
}

export function parseFileUrlPath(value: string): string | null {
  try {
    const url = new URL(value);
    if (url.protocol !== "file:") return null;
    const pathname = decodeFilePathUriEscapes(url.pathname);
    if (/^\/[a-zA-Z]:\//.test(pathname)) return pathname.slice(1);
    if (url.hostname && url.hostname !== "localhost") return `//${url.hostname}${pathname}`;
    return pathname;
  } catch {
    return null;
  }
}

export function normalizeWorkspaceRelativeFilePath(relativePath: string): string | null {
  const segments: string[] = [];
  for (const segment of relativePath.replace(/\\/g, "/").split("/")) {
    if (!segment || segment === ".") continue;
    if (segment === "..") {
      if (segments.length === 0) return null;
      segments.pop();
      continue;
    }
    segments.push(segment);
  }
  return segments.join("/");
}

export function joinFilePath(basePath: string, childPath: string): string {
  if (!childPath) {
    return basePath;
  }

  if (isAbsoluteFilePath(childPath)) {
    return childPath;
  }

  const separator = basePath.includes("\\") && !basePath.includes("/") ? "\\" : "/";
  const normalizedBasePath = basePath.replace(/[\\/]+$/, "");
  const normalizedChildPath = childPath.replace(/^[\\/]+/, "");
  return `${normalizedBasePath}${separator}${normalizedChildPath}`;
}
function encodeUriPathForFileUrl(value: string): string {
  return encodeURI(value).replace(/#/g, "%23").replace(/\?/g, "%3F");
}

export function toFileUrl(path: string): string {
  const normalizedPath = path.replace(/\\/g, "/");

  if (WINDOWS_ABSOLUTE_PATH_RE.test(path)) {
    return `file:///${encodeUriPathForFileUrl(normalizedPath)}`;
  }

  if (normalizedPath.startsWith("/")) {
    return `file://${encodeUriPathForFileUrl(normalizedPath)}`;
  }

  if (UNC_PATH_RE.test(path)) {
    return `file:${encodeUriPathForFileUrl(normalizedPath)}`;
  }

  return encodeUriPathForFileUrl(normalizedPath);
}