import { normalize } from "node:path";
import { type CommandRunner, runChecked } from "./process.js";

export interface GitWorktreeEntry {
  readonly path: string;
  readonly head: string | null;
  readonly branch: string | null;
}

function comparablePath(value: string): string {
  return normalize(value).replace(/\/+$/u, "");
}

/**
 * Reads the worktrees Git itself knows about. Herdr reports what it did; this is the
 * independent check that the repository really changed the same way.
 *
 * `-z` ends every record with a NUL, so a path that contains a newline cannot pretend to be
 * another record. It needs Git 2.36 or newer.
 */
export async function readGitWorktrees(
  runner: CommandRunner,
  cwd: string,
  signal: AbortSignal | undefined,
): Promise<readonly GitWorktreeEntry[]> {
  const result = await runChecked(
    runner,
    "git",
    ["worktree", "list", "--porcelain", "-z"],
    { cwd, signal },
    "Unable to list the Git worktrees",
  );

  const entries: GitWorktreeEntry[] = [];
  let path: string | undefined;
  let head: string | null = null;
  let branch: string | null = null;

  const flush = () => {
    if (path) {
      entries.push({ path: comparablePath(path), head, branch });
    }
    path = undefined;
    head = null;
    branch = null;
  };

  // An unrecognised record, such as `bare` or `locked`, is ignored rather than read as a path.
  for (const record of result.stdout.split("\0")) {
    if (record.startsWith("worktree ")) {
      flush();
      path = record.slice("worktree ".length);
    } else if (record.startsWith("HEAD ")) {
      head = record.slice("HEAD ".length);
    } else if (record.startsWith("branch refs/heads/")) {
      branch = record.slice("branch refs/heads/".length);
    }
  }
  flush();
  return entries;
}

export function findGitWorktree(
  entries: readonly GitWorktreeEntry[],
  path: string,
): GitWorktreeEntry | undefined {
  const wanted = comparablePath(path);
  return entries.find((entry) => entry.path === wanted);
}