/**
 * Path canonicalization and lossless re-serialization for cross-platform tool
 * input.
 *
 * @module pi-hashline-edit/pi
 */

import { homedir } from "node:os";
import { isAbsolute, join, relative, resolve, sep } from "node:path";
import { fileURLToPath, pathToFileURL } from "node:url";

const UNICODE_SPACES = /[\u00A0\u2000-\u200A\u202F\u205F\u3000]/g;
const WINDOWS_SHELL_DRIVE = /^\/(?:mnt\/|cygdrive\/)?([a-z])(?:\/(.*))?$/i;

/** Resolve model-supplied paths with the same input conventions as Pi's built-in file tools. */
export function canonicalPath(cwd: string, path: string): string {
  let normalized = path.replace(UNICODE_SPACES, " ");
  if (normalized.startsWith("@")) normalized = normalized.slice(1);
  if (
    process.platform === "win32" &&
    normalized.startsWith("/") &&
    !normalized.startsWith("//") &&
    !normalized.includes("\\")
  ) {
    const match = WINDOWS_SHELL_DRIVE.exec(normalized);
    if (match) normalized = `${match[1].toUpperCase()}:\\${match[2]?.replaceAll("/", "\\") ?? ""}`;
  }
  if (normalized === "~") normalized = homedir();
  else if (
    normalized.startsWith("~/") ||
    (process.platform === "win32" && normalized.startsWith("~\\"))
  ) {
    normalized = join(homedir(), normalized.slice(2));
  }
  if (normalized.startsWith("file://")) normalized = fileURLToPath(normalized);
  return isAbsolute(normalized) ? resolve(normalized) : resolve(cwd, normalized);
}

/** Return a readable path that resolves back to the same file through the tools' input syntax. */
export function serializePath(cwd: string, path: string): string {
  const absolute = resolve(cwd, path);
  const rel = relative(cwd, absolute);
  const local = rel && rel !== ".." && !rel.startsWith(`..${sep}`) && !isAbsolute(rel);
  // Windows accepts "/" too: one separator keeps paths alike inside and outside the cwd.
  const native = local ? rel : absolute;
  const candidate = sep === "\\" ? native.replaceAll(sep, "/") : native;
  // A file URL preserves names whose spaces are normalized on input, and keeps headers single-line.
  if (!/[\r\n]/.test(candidate)) {
    if (canonicalPath(cwd, candidate) === absolute) return candidate;
    if (local && canonicalPath(cwd, `./${candidate}`) === absolute) return `./${candidate}`;
  }
  return pathToFileURL(absolute).href;
}