tolaria/src/extensions/zoomCursorFix.behavior.test.ts

import { afterEach, beforeEach, describe, expect, it, vi } from 'vitest'

const { defineMock } = vi.hoisted(() => ({
  defineMock: vi.fn((factory: (view: unknown) => unknown) => factory),
}))

vi.mock('@codemirror/view', () => ({
  EditorView: class EditorView {},
  ViewPlugin: {
    define: defineMock,
  },
}))

import { getDocumentZoom, zoomCursorFix } from './zoomCursorFix'

function mockComputedZoom(value: string) {
  const real = window.getComputedStyle.bind(window)
  return vi.spyOn(window, 'getComputedStyle').mockImplementation((elt, pseudo) => {
    const style = real(elt, pseudo)
    if (elt === document.documentElement) {
      return new Proxy(style, {
        get(target, prop) {
          if (prop === 'zoom') return value
          const next = Reflect.get(target, prop)
          return typeof next === 'function' ? next.bind(target) : next
        },
      })
    }
    return style
  })
}

function mockInlineZoom(value: string) {
  return vi.spyOn(document.documentElement.style, 'getPropertyValue').mockImplementation((name: string) => {
    if (name === 'zoom') return value
    return ''
  })
}

function createView() {
  const contentDOM = document.createElement('div')
  const textNode = document.createTextNode('hello')
  contentDOM.appendChild(textNode)

  const origPosAtCoords = vi.fn(() => 11)
  const origPosAndSideAtCoords = vi.fn(() => ({ pos: 13, assoc: -1 as const }))
  const prototype = {
    posAtCoords: origPosAtCoords,
    posAndSideAtCoords: origPosAndSideAtCoords,
  }

  const view = Object.assign(Object.create(prototype), {
    contentDOM,
    posAtDOM: vi.fn(() => 17),
  })

  return {
    view,
    textNode,
    origPosAtCoords,
    origPosAndSideAtCoords,
  }
}

describe('zoomCursorFix behavior', () => {
  beforeEach(() => {
    document.documentElement.style.removeProperty('zoom')
    delete (document as Document & {
      caretRangeFromPoint?: (x: number, y: number) => Range | null
    }).caretRangeFromPoint
  })

  afterEach(() => {
    vi.restoreAllMocks()
  })

  it('reads inline percentage zoom values when computed zoom is normal', () => {
    const computedSpy = mockComputedZoom('normal')
    const inlineSpy = mockInlineZoom('125%')

    expect(getDocumentZoom()).toBe(1.25)

    inlineSpy.mockRestore()
    computedSpy.mockRestore()
  })

  it('falls back to 1 for invalid inline zoom values', () => {
    const computedSpy = mockComputedZoom('normal')
    const inlineSpy = mockInlineZoom('banana')

    expect(getDocumentZoom()).toBe(1)

    inlineSpy.mockRestore()
    computedSpy.mockRestore()
  })

  it('uses caretRangeFromPoint when CSS zoom is active and restores prototype methods on destroy', () => {
    const computedSpy = mockComputedZoom('normal')
    const inlineSpy = mockInlineZoom('150%')
    const { view, textNode } = createView()

    Object.defineProperty(document, 'caretRangeFromPoint', {
      configurable: true,
      value: vi.fn(() => ({ startContainer: textNode, startOffset: 2 })),
    })

    const pluginFactory = zoomCursorFix() as unknown as (view: typeof view) => { destroy: () => void }
    const plugin = pluginFactory(view)

    expect(view.posAtCoords({ x: 30, y: 40 }, true)).toBe(17)
    expect(view.posAndSideAtCoords({ x: 30, y: 40 }, false)).toEqual({ pos: 17, assoc: 1 })
    expect(view.posAtDOM).toHaveBeenCalledWith(textNode, 2)
    expect(Object.hasOwn(view, 'posAtCoords')).toBe(true)

    plugin.destroy()

    expect(Object.hasOwn(view, 'posAtCoords')).toBe(false)
    expect(view.posAtCoords({ x: 5, y: 6 }, false)).toBe(11)

    inlineSpy.mockRestore()
    computedSpy.mockRestore()
  })

  it('falls back to adjusted coordinates when the browser API is unavailable or returns an unusable range', () => {
    const computedSpy = mockComputedZoom('normal')
    const inlineSpy = mockInlineZoom('200%')

    const pluginFactory = zoomCursorFix() as unknown as (view: ReturnType<typeof createView>['view']) => { destroy: () => void }

    const first = createView()
    pluginFactory(first.view)
    expect(first.view.posAtCoords({ x: 40, y: 60 }, true)).toBe(11)
    expect(first.origPosAtCoords).toHaveBeenCalledWith({ x: 20, y: 30 }, true)
    expect(first.view.posAndSideAtCoords({ x: 40, y: 60 }, false)).toEqual({ pos: 13, assoc: -1 })
    expect(first.origPosAndSideAtCoords).toHaveBeenCalledWith({ x: 20, y: 30 }, false)

    const second = createView()
    Object.defineProperty(document, 'caretRangeFromPoint', {
      configurable: true,
      value: vi.fn(() => ({ startContainer: document.createTextNode('outside'), startOffset: 0 })),
    })
    pluginFactory(second.view)
    expect(second.view.posAtCoords({ x: 50, y: 70 }, false)).toBe(11)
    expect(second.origPosAtCoords).toHaveBeenCalledWith({ x: 25, y: 35 }, false)

    const third = createView()
    third.view.posAtDOM.mockImplementation(() => {
      throw new Error('boom')
    })
    Object.defineProperty(document, 'caretRangeFromPoint', {
      configurable: true,
      value: vi.fn(() => ({ startContainer: third.textNode, startOffset: 1 })),
    })
    pluginFactory(third.view)
    expect(third.view.posAtCoords({ x: 60, y: 80 }, false)).toBe(11)
    expect(third.origPosAtCoords).toHaveBeenCalledWith({ x: 30, y: 40 }, false)

    inlineSpy.mockRestore()
    computedSpy.mockRestore()
  })
})