/**
 * @file Folds the Changes panel's flat list of changed files into a folder
 * tree, JetBrains' commit-view shape: folders first, then files, each sorted
 * by name, and a chain of folders that hold nothing but one sub-folder drawn
 * as ONE row (`src/lib`), so a deep path does not cost a row per level.
 * @author Nguyễn Ngọc Trí Vĩ <vinnt@smartgift.vn>
 */

export interface ChangeTreeDir<T> {
  /** The row's label — one segment, or several joined by `/` when compacted. */
  name: string;
  /** The folder's repo-relative path ("" for the root). */
  path: string;
  dirs: ChangeTreeDir<T>[];
  files: { name: string; file: T }[];
  /** Every file anywhere below. */
  count: number;
}

export function changeTree<T extends { path: string }>(rows: T[]): ChangeTreeDir<T> {
  const root: ChangeTreeDir<T> = { name: "", path: "", dirs: [], files: [], count: 0 };
  for (const file of rows) {
    const parts = file.path.split("/");
    let dir = root;
    dir.count++;
    for (const seg of parts.slice(0, -1)) {
      const path = dir.path ? `${dir.path}/${seg}` : seg;
      let next = dir.dirs.find((d) => d.path === path);
      if (!next) dir.dirs.push((next = { name: seg, path, dirs: [], files: [], count: 0 }));
      next.count++;
      dir = next;
    }
    dir.files.push({ name: parts[parts.length - 1] ?? file.path, file });
  }
  const finish = (d: ChangeTreeDir<T>): ChangeTreeDir<T> => {
    // Never the root: its children are the group's top level.
    let only: ChangeTreeDir<T> | undefined;
    while (d.path && d.files.length === 0 && d.dirs.length === 1 && (only = d.dirs[0])) {
      d = { ...only, name: `${d.name}/${only.name}` };
    }
    d.dirs = d.dirs.map(finish).sort((a, b) => a.name.localeCompare(b.name));
    d.files.sort((a, b) => a.name.localeCompare(b.name));
    return d;
  };
  return finish(root);
}

/** Every file under a folder, for its stage/unstage-all button. */
export function treeFiles<T>(d: ChangeTreeDir<T>): T[] {
  return [...d.files.map((f) => f.file), ...d.dirs.flatMap(treeFiles)];
}