DndGamePlayer/app/main/sceneView/sceneViewStore.test.ts

import assert from 'node:assert/strict';
import { describe, it } from 'node:test';

import {
  DEFAULT_SCENE_VIEW_CAMERA,
  sceneViewPanBy,
  sceneViewZoomAt,
} from '../../shared/types/sceneView';

import { SceneViewStore } from './sceneViewStore';

describe('SceneViewStore', () => {
  it('resets to default camera', () => {
    const store = new SceneViewStore();
    store.dispatch({ kind: 'set', camera: { scale: 2, ox: 0.2, oy: 0.8 } });
    const next = store.dispatch({ kind: 'reset' });
    assert.equal(next.scale, 1);
    assert.equal(next.ox, 0.5);
    assert.equal(next.oy, 0.5);
  });

  it('clamps scale and origin', () => {
    const store = new SceneViewStore();
    const next = store.dispatch({ kind: 'set', camera: { scale: 99, ox: -1, oy: 2 } });
    assert.equal(next.scale, 8);
    assert.equal(next.ox, 0);
    assert.equal(next.oy, 1);
  });
});

describe('sceneViewZoomAt / panBy', () => {
  it('zooms toward cursor and keeps that content point under cursor', () => {
    const hostW = 1000;
    const hostH = 500;
    const containW = 800;
    const containH = 400;
    const hostX = 700;
    const hostY = 250;
    const next = sceneViewZoomAt(DEFAULT_SCENE_VIEW_CAMERA, {
      hostW,
      hostH,
      containW,
      containH,
      hostX,
      hostY,
      factor: 2,
    });
    assert.ok(next.scale > 1.5);
    const displayW = containW * next.scale;
    const displayH = containH * next.scale;
    const left = hostW / 2 - next.ox * displayW;
    const top = hostH / 2 - next.oy * displayH;
    const ix = (hostX - left) / displayW;
    const iy = (hostY - top) / displayH;
    // At scale=1 contain is centered; cursor was at content x=(700-100)/800=0.75
    assert.ok(Math.abs(ix - 0.75) < 1e-6);
    assert.ok(Math.abs(iy - 0.5) < 1e-6);
  });

  it('pans in host pixels', () => {
    const cam = { scale: 2, ox: 0.5, oy: 0.5 };
    const next = sceneViewPanBy(cam, { containW: 400, containH: 200, dx: 80, dy: 0 });
    // displayW=800; dx=80 → ox decreases by 0.1
    assert.ok(Math.abs(next.ox - 0.4) < 1e-6);
    assert.equal(next.oy, 0.5);
  });
});