/**
 * Favorites Manager pattern.
 */
import {
  Default,
  handler,
  NAME,
  pattern,
  UI,
  wish,
  Writable,
} from "commonfabric";

// This manager's PROJECTION of a stored favorite: only the fields it renders.
// Naming a field it does not read costs compatibility for nothing — the row is
// re-staged and validated against this type on every pattern swap, so a field
// declared here must hold for every vintage in durable storage. Discovery tags
// are the cautionary case: rows written before #4197 carry `tag` (singular),
// rows written after carry `tags` (plural), and this manager reads neither
// (`cf-tags` renders `item.userTags`). Declaring `tag: string` required made
// every post-#4197 row fail validation; requiring `tags` would fail every
// pre-#4197 row the same way. Omitting both is what accepts all of them.
type Favorite = {
  cell: Writable<{ [NAME]?: string }>;
  userTags: Writable<string[]>;
  spaceName?: string;
  // Stable key the favorite entity is addressed by (the piece's identity),
  // stored on the entry by home's addFavorite so the remove reaches it.
  id?: string;
};

const onRemoveFavorite = handler<
  Record<string, never>,
  {
    favorites: Writable<Array<Favorite> | Default<[]>>;
    id?: string;
    item?: Writable<unknown>;
  }
>((_, { favorites, id, item }) => {
  // A favorite added through the keyed path carries an id. Drop its membership
  // by that id — the same key home's addFavorite used, so both reach the same
  // entity — and clear the entity, since it outlives its link.
  if (id) {
    favorites.removeByValue(favorites.elementById(id));
    const entry: Writable<Favorite | undefined> = favorites.elementById(id);
    entry.set(undefined);
    return;
  }
  // A favorite added before keyed addressing has no id; remove it by matching
  // its piece cell.
  if (!item) return;
  favorites.set(favorites.get().filter((f) => !f.cell.equals(item)));
});

const onUpdateUserTags = handler<
  { detail: { tags: string[] } },
  { userTags: Writable<string[]> }
>(({ detail }, { userTags }) => {
  userTags.set(detail?.tags ?? []);
});

export default pattern<Record<string, never>>((_) => {
  // Use wish() to access favorites from home.tsx via defaultPattern
  const { result: favorites } = wish<Array<Favorite> | Default<[]>>({
    query: "#favorites",
  });

  return {
    [NAME]: "Favorites Manager",
    [UI]: (
      <cf-vstack gap="3">
        {favorites!.map((item) => (
          <cf-vstack gap="2">
            <cf-hstack gap="2" align="center">
              <cf-cell-link $cell={item.cell} spaceName={item.spaceName} />
              <cf-button
                variant="destructive"
                size="sm"
                onClick={onRemoveFavorite({
                  favorites: favorites!,
                  id: item.id,
                  item: item.cell,
                })}
              >
                Remove
              </cf-button>
            </cf-hstack>
            <cf-tags
              tags={item.userTags}
              oncf-change={onUpdateUserTags({ userTags: item.userTags })}
            />
          </cf-vstack>
        ))}
        {favorites!.length === 0 && <p>No favorites yet.</p>}
      </cf-vstack>
    ),
  };
});