import { describe, expect, test } from "bun:test";
import { createInitialAppState } from "@editor/initial-state";
import type { AppState } from "@editor/state";
import { createAppStateSelectorSnapshot, shallowEqual } from "./useAppState";

describe("app state selector snapshot", () => {
  test("reuses selected snapshots when equality reports no relevant changes", () => {
    const state = createInitialAppState("Test");
    const snapshot = createAppStateSelectorSnapshot(selectShellLikeState, shallowEqual);
    const selected = snapshot.getSnapshot(state);
    const previewOnlyUpdate: AppState = {
      ...state,
      editor: {
        ...state.editor,
        brushStrokePreview: { layerId: "layer", assetId: "asset", source: "preview" },
      },
    };

    expect(snapshot.updateSnapshot(previewOnlyUpdate)).toBe(false);
    expect(snapshot.getSnapshot(previewOnlyUpdate)).toBe(selected);
  });

  test("can collapse brush preview updates to presence instead of position", () => {
    const state = createInitialAppState("Test");
    const snapshot = createAppStateSelectorSnapshot((next: AppState) => ({ hasBrushPreview: Boolean(next.editor.brushPreview) }), shallowEqual);
    const withoutPreview = snapshot.getSnapshot(state);
    const withPreview: AppState = {
      ...state,
      editor: {
        ...state.editor,
        brushPreview: { position: { x: 10, y: 20 } },
      },
    };

    expect(snapshot.updateSnapshot(withPreview)).toBe(true);
    const previewPresent = snapshot.getSnapshot(withPreview);
    expect(previewPresent).not.toBe(withoutPreview);
    expect(previewPresent.hasBrushPreview).toBe(true);

    const movedPreview: AppState = {
      ...withPreview,
      editor: {
        ...withPreview.editor,
        brushPreview: { position: { x: 30, y: 40 } },
      },
    };

    expect(snapshot.updateSnapshot(movedPreview)).toBe(false);
    expect(snapshot.getSnapshot(movedPreview)).toBe(previewPresent);
  });

  test("shallow equality uses object keys and Object.is value checks", () => {
    expect(shallowEqual({ id: "a", value: Number.NaN }, { id: "a", value: Number.NaN })).toBe(true);
    expect(shallowEqual({ id: "a", value: 0 }, { id: "a", value: -0 })).toBe(false);
    expect(shallowEqual({ id: "a" }, { id: "a", extra: true })).toBe(false);
  });
});

function selectShellLikeState(state: AppState) {
  return {
    document: state.document,
    selection: state.editor.selection,
    viewport: state.editor.viewport,
    tools: state.editor.tools,
    transformSession: state.editor.transformSession,
    maskEdit: state.editor.maskEdit,
  };
}