/**
 * TASK-0103 — the file picker's pure filter/sort logic (Requirements §4,
 * Tests: "picker filter/sort logic").
 *
 * Kept out of the component so it is unit-testable without a DOM: the picker
 * fetches a server-ordered page of files, then applies a client-side name
 * filter (spec: "search box (client filter by name)") and a sort, then maps
 * the result to the grid tiles.
 */
import type { FileListItem } from "./api";

export type PickerSort = "updated" | "name" | "size" | "date";

/**
 * Case-insensitive substring match on the file name. An empty / whitespace
 * query returns the input unchanged (so the grid shows everything).
 */
export function filterByName(files: FileListItem[], query: string): FileListItem[] {
  const q = query.trim().toLowerCase();
  if (!q) return files;
  return files.filter((f) => f.name.toLowerCase().includes(q));
}

/**
 * Sort a picker result. `name` is a locale-aware ascending compare; the rest
 * are descending (most-recent / largest first) — the natural "show me the
 * interesting ones" order for a picker. Returns a NEW array (the caller's
 * input is not mutated).
 */
export function sortPickerFiles(files: FileListItem[], sort: PickerSort): FileListItem[] {
  const arr = [...files];
  switch (sort) {
    case "name":
      arr.sort((a, b) => a.name.localeCompare(b.name));
      break;
    case "size":
      arr.sort((a, b) => b.size - a.size);
      break;
    case "date":
      arr.sort((a, b) => new Date(b.createdAt).getTime() - new Date(a.createdAt).getTime());
      break;
    case "updated":
    default:
      arr.sort((a, b) => new Date(b.updatedAt).getTime() - new Date(a.updatedAt).getTime());
  }
  return arr;
}