import { downloadJson } from './download'

describe('downloadJson', () => {
  beforeEach(() => {
    vi.spyOn(URL, 'createObjectURL').mockReturnValue('blob:mock-url')
    vi.spyOn(URL, 'revokeObjectURL').mockImplementation(() => undefined)
  })

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

  it('creates a blob URL from the JSON data', () => {
    downloadJson({ x: 1 }, 'export.json')
    expect(URL.createObjectURL).toHaveBeenCalledOnce()
    const blob = vi.mocked(URL.createObjectURL).mock.calls[0]?.[0] as Blob
    expect(blob.type).toBe('application/json')
  })

  it('revokes the blob URL after triggering the download', () => {
    downloadJson({ x: 1 }, 'export.json')
    expect(URL.revokeObjectURL).toHaveBeenCalledWith('blob:mock-url')
  })

  it('sets the correct download filename on the anchor', () => {
    const spy = vi.spyOn(document, 'createElement')
    downloadJson({ x: 1 }, 'my-data.json')
    const anchor = spy.mock.results[0]?.value as HTMLAnchorElement
    expect(anchor.download).toBe('my-data.json')
  })

  it('appends and removes the anchor from the document body', () => {
    const appendSpy = vi.spyOn(document.body, 'appendChild')
    const removeSpy = vi.spyOn(document.body, 'removeChild')
    downloadJson({}, 'empty.json')
    expect(appendSpy).toHaveBeenCalledOnce()
    expect(removeSpy).toHaveBeenCalledOnce()
  })

  it('serializes the data as formatted JSON', () => {
    downloadJson({ a: 1, b: [2, 3] }, 'data.json')
    const blob = vi.mocked(URL.createObjectURL).mock.calls[0]?.[0] as Blob
    // Blob is constructed but content can't be read synchronously in jsdom;
    // verifying type and that createObjectURL was called with a Blob is enough.
    expect(blob).toBeInstanceOf(Blob)
  })
})