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

function deferred<T>() {
  let resolve!: (value: T) => void
  const promise = new Promise<T>((done) => {
    resolve = done
  })
  return { promise, resolve }
}

let store: typeof import('../../src/stores/settingsStore').useSettingsStore
beforeEach(async () => {
  vi.resetModules()
  vi.mocked(window.opsxApi.settingsGet).mockReset().mockResolvedValue({ success: true })
  vi.mocked(window.opsxApi.settingsSet).mockReset().mockResolvedValue({ success: true })
  store = (await import('../../src/stores/settingsStore')).useSettingsStore
})

describe('settings persistence', () => {
  it('serializes writes while keeping later edits visible', async () => {
    const first = deferred<{ success: boolean }>()
    vi.mocked(window.opsxApi.settingsSet).mockImplementationOnce(() => first.promise)
    const saveTheme = store.getState().setSetting('theme', 'light')
    const saveFont = store.getState().setSetting('fontSize', 20)
    expect(store.getState().settings).toMatchObject({ theme: 'light', fontSize: 20 })
    await Promise.resolve()
    expect(window.opsxApi.settingsSet).toHaveBeenCalledTimes(1)
    first.resolve({ success: true })
    await Promise.all([saveTheme, saveFont])
    expect(window.opsxApi.settingsSet).toHaveBeenLastCalledWith(
      'app-settings',
      expect.objectContaining({ theme: 'light', fontSize: 20 })
    )
  })

  it('rolls back a rejected envelope without persisting the failed patch in the next write', async () => {
    vi.mocked(window.opsxApi.settingsSet).mockResolvedValueOnce({ success: false, error: 'disk full' })
    await Promise.all([store.getState().setSetting('theme', 'light'), store.getState().setSetting('fontSize', 20)])
    expect(store.getState().settings).toMatchObject({ theme: 'dark', fontSize: 20 })
    expect(window.opsxApi.settingsSet).toHaveBeenLastCalledWith(
      'app-settings',
      expect.objectContaining({ theme: 'dark', fontSize: 20 })
    )
    const { useToastStore } = await import('../../src/stores/toastStore')
    expect(useToastStore.getState().toasts.at(-1)).toMatchObject({
      type: 'error',
      message: expect.stringContaining('disk full'),
    })
  })

  it('continues saving after a thrown IPC failure, including edits to the same field', async () => {
    vi.mocked(window.opsxApi.settingsSet).mockRejectedValueOnce(new Error('IPC unavailable'))
    await Promise.all([store.getState().setSetting('fontSize', 18), store.getState().setSetting('fontSize', 22)])
    expect(store.getState().settings.fontSize).toBe(22)
    expect(window.opsxApi.settingsSet).toHaveBeenCalledTimes(2)
  })

  it('merges edits made while initial settings are loading into the persisted snapshot', async () => {
    const read = deferred<{ success: boolean; value: unknown }>()
    vi.mocked(window.opsxApi.settingsGet).mockReturnValueOnce(read.promise)
    const load = store.getState().loadSettings()
    const save = store.getState().setSetting('fontSize', 22)
    read.resolve({ success: true, value: { theme: 'light', agentSafetyMode: 'relaxed' } })
    await Promise.all([load, save])
    expect(store.getState().settings).toMatchObject({ theme: 'light', fontSize: 22 })
    expect(window.opsxApi.settingsSet).toHaveBeenLastCalledWith(
      'app-settings',
      expect.objectContaining({ theme: 'light', fontSize: 22 })
    )
  })
})