import { describe, it, expect, beforeEach, vi } from 'vitest'
import { renderHook, act } from '@testing-library/react'
import { createElement, StrictMode, type ReactNode } from 'react'
import { usePlannedDays } from './usePlannedDays'
import * as api from '@/services/api'
import { useWorkspace } from '@/context'
import { makePlannedLeaveDay, makeWorkspaceContextValue } from '../../tests/fixtures'

vi.mock('@/services/api')
vi.mock('@/context')

describe('usePlannedDays', () => {
  let bumpPlanVersion: ReturnType<typeof vi.fn>

  beforeEach(() => {
    vi.clearAllMocks()
    bumpPlanVersion = vi.fn()
    vi.mocked(useWorkspace).mockReturnValue(
      makeWorkspaceContextValue({ planVersion: 0, bumpPlanVersion }),
    )
  })

  it('initializes with null data', () => {
    const { result } = renderHook(() => usePlannedDays())
    expect(result.current.data).toBeNull()
    expect(result.current.isLoading).toBe(false)
  })

  it('fetches planned days when childId provided', async () => {
    const mockData = [
      makePlannedLeaveDay({
        id: '1',
        workspaceId: 'ws1',
        childId: 'child1',
        parentPersonalDataUuid: 'parent1',
        date: '2026-06-15',
        dayType: 'vacation',
        isDubbeldag: false,
      }),
    ]

    vi.mocked(api.getPlannedDays).mockResolvedValue(mockData)

    renderHook(() => usePlannedDays('child1'))

    await act(async () => {
      await new Promise((resolve) => setTimeout(resolve, 0))
    })

    expect(api.getPlannedDays).toHaveBeenCalledWith('child1')
  })

  it('does not fetch without childId', () => {
    vi.mocked(api.getPlannedDays).mockResolvedValue([])

    renderHook(() => usePlannedDays())

    expect(api.getPlannedDays).not.toHaveBeenCalled()
  })

  it('handles fetch error and sets error state', async () => {
    const errorMessage = 'Network error'
    vi.mocked(api.getPlannedDays).mockRejectedValue(new Error(errorMessage))

    const { result } = renderHook(() => usePlannedDays('child1'))

    await act(async () => {
      await new Promise(resolve => setTimeout(resolve, 0))
    })

    expect(result.current.error).toBe(errorMessage)
    expect(result.current.data).toBeNull()
    expect(result.current.isLoading).toBe(false)
  })

  it('handles fetch error with non-Error object', async () => {
    vi.mocked(api.getPlannedDays).mockRejectedValue('Unknown error')

    const { result } = renderHook(() => usePlannedDays('child1'))

    await act(async () => {
      await new Promise(resolve => setTimeout(resolve, 0))
    })

    expect(result.current.error).toBe('Failed to fetch planned days')
    expect(result.current.data).toBeNull()
  })

  it('refreshes data explicitly', async () => {
    const mockData = [
      makePlannedLeaveDay({
        id: '1',
        workspaceId: 'ws1',
        childId: 'child1',
        parentPersonalDataUuid: 'parent1',
        date: '2026-06-15',
        dayType: 'vacation',
        isDubbeldag: false,
      }),
    ]

    vi.mocked(api.getPlannedDays).mockResolvedValue(mockData)

    const { result } = renderHook(() => usePlannedDays('child1'))

    await act(async () => {
      await new Promise(resolve => setTimeout(resolve, 0))
    })

    expect(api.getPlannedDays).toHaveBeenCalledWith('child1')
    const callCount = vi.mocked(api.getPlannedDays).mock.calls.length

    await act(async () => {
      await result.current.refresh()
    })

    expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBeGreaterThan(callCount)
  })

  it('M7 part 1 — a mutation results in exactly one background refetch, never isLoading (only isRefreshing flips)', async () => {
    // This is the exact regression a browser verification pass caught: an
    // earlier version had this hook's own mutators call `fetch({ background:
    // true })` themselves AND rely on their own resulting `planVersion` bump
    // to re-run this hook's effect a second time — and that second,
    // effect-triggered fetch used the *blocking* default, so a save still
    // blanked the page via a second GET. The writers (`useDayAssertions`,
    // `usePlanSync`) now only ever call `bumpPlanVersion()`; the effect
    // below is the ONLY place that fetches, so there is exactly one fetch,
    // and it decides for itself whether that's the (blocking) first load or
    // a (background) mutation refetch — see usePlannedDays.ts's doc comment.
    vi.mocked(api.getPlannedDays).mockResolvedValue([])
    // A bare `vi.fn()` `bumpPlanVersion` (this file's default) never causes
    // a re-render on its own — wire up a real counter so calling it (as a
    // writer hook would) and then `rerender()`ing genuinely reproduces what
    // the real `WorkspaceProvider`'s state update would do.
    let planVersion = 0
    const bump = () => {
      planVersion += 1
    }
    vi.mocked(useWorkspace).mockImplementation(() =>
      makeWorkspaceContextValue({ planVersion, bumpPlanVersion: bump }),
    )

    const { result, rerender } = renderHook(() => usePlannedDays('child1'))

    await act(async () => {
      await new Promise((resolve) => setTimeout(resolve, 0))
    })
    expect(result.current.isLoading).toBe(false)
    const callCountAfterMount = vi.mocked(api.getPlannedDays).mock.calls.length

    // The refetch that follows the mutation's bump should hang so the
    // in-flight state is observable before it resolves.
    let resolveRefetch: (value: ReturnType<typeof makePlannedLeaveDay>[]) => void = () => {}
    vi.mocked(api.getPlannedDays).mockReturnValueOnce(
      new Promise((resolve) => {
        resolveRefetch = resolve
      }),
    )

    await act(async () => {
      // Stands in for a writer hook's post-mutation `bumpPlanVersion()`.
      bump()
    })
    // The bump only takes effect on this instance's next render — nothing
    // has refetched yet.
    expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBe(callCountAfterMount)

    rerender()
    await act(async () => {
      await new Promise((resolve) => setTimeout(resolve, 0))
    })

    // Exactly one refetch so far, and it's non-blocking.
    expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBe(callCountAfterMount + 1)
    expect(result.current.isRefreshing).toBe(true)
    expect(result.current.isLoading).toBe(false)

    await act(async () => {
      resolveRefetch([])
    })
    expect(result.current.isRefreshing).toBe(false)
    expect(result.current.isLoading).toBe(false)
    // Settling further (no further bump) raises no additional GET.
    rerender()
    await act(async () => {
      await new Promise((resolve) => setTimeout(resolve, 0))
    })
    expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBe(callCountAfterMount + 1)
  })

  describe('M7 follow-up — the StrictMode double-mount hang', () => {
    const strictModeWrapper = ({ children }: { children: ReactNode }) =>
      createElement(StrictMode, null, children)

    it('reproduces the reported hang: navigating to a page that mounts with childId already known must not strand isLoading true', async () => {
      // React 18 StrictMode double-invokes a fresh mount's effect,
      // back-to-back, before either invocation's fetch has resolved. On a
      // real SPA navigation `childId` is already known at mount (unlike a
      // hard reload, where it's still `undefined` on the very first
      // render) — this is exactly what the bug report's "works on hard
      // reload, hangs on in-app navigation" symptom traced back to.
      vi.mocked(api.getPlannedDays).mockResolvedValue([])

      const { result } = renderHook(() => usePlannedDays('child1'), {
        wrapper: strictModeWrapper,
      })

      await act(async () => {
        await new Promise((resolve) => setTimeout(resolve, 0))
      })

      expect(result.current.isLoading).toBe(false)
      expect(result.current.isRefreshing).toBe(false)
      expect(result.current.data).toEqual([])
      // The dedup fix means the double-invoked mount effect still issues
      // exactly one real HTTP request, not two.
      expect(api.getPlannedDays).toHaveBeenCalledTimes(1)
    })

    it('two overlapping calls for the same childId — one foreground, one background, started before either resolves — both end up cleared: isLoading false, isRefreshing false, exactly one request', async () => {
      // The same hazard, exercised directly (per the coordinator's
      // alternative to a StrictMode wrapper): two calls for the identical
      // childId, racing, with DIFFERENT background flags — the exact shape
      // that stranded `isLoading` before this fix (the stale call raised
      // one flag, the current call raised the other, and only the current
      // call's own — guarded — clear ever ran).
      let resolveFetch: (value: ReturnType<typeof makePlannedLeaveDay>[]) => void = () => {}
      vi.mocked(api.getPlannedDays).mockReturnValue(
        new Promise((resolve) => {
          resolveFetch = resolve
        }),
      )

      const { result } = renderHook(() => usePlannedDays('child1'))
      // The mount effect already started one (foreground) call — fire a
      // second, differently-classified call for the SAME childId before it
      // resolves.
      let secondCall: Promise<unknown> = Promise.resolve()
      act(() => {
        secondCall = result.current.refresh({ background: true })
      })

      expect(result.current.isLoading).toBe(true)

      await act(async () => {
        resolveFetch([])
        await secondCall
      })

      expect(result.current.isLoading).toBe(false)
      expect(result.current.isRefreshing).toBe(false)
      // Deduped into a single request.
      expect(api.getPlannedDays).toHaveBeenCalledTimes(1)
    })
  })

  describe('M7 part 2 — one trailing bump for a whole batch of writes', () => {
    // The per-write `skipRefresh` option itself lives on the writer hook
    // now (`useDayAssertions.assertDay` — see its tests); this covers the
    // reader's side of that contract.
    it('a batch of skipRefresh writes followed by one bumpPlanVersion() call (Calendar.tsx\'s multi-day save pattern) produces exactly one trailing background GET', async () => {
      vi.mocked(api.getPlannedDays).mockResolvedValue([])
      // A real counter (not this file's default inert `vi.fn()`) so calling
      // `bump()` — standing in for `Calendar.tsx handleSavePinnedDay`'s
      // trailing `bumpPlanVersion()` — then `rerender()`ing genuinely
      // reproduces the real `WorkspaceProvider` state update that follows.
      let planVersion = 0
      const bump = () => {
        planVersion += 1
      }
      vi.mocked(useWorkspace).mockImplementation(() =>
        makeWorkspaceContextValue({ planVersion, bumpPlanVersion: bump }),
      )

      const { result, rerender } = renderHook(() => usePlannedDays('child1'))
      await act(async () => {
        await new Promise((resolve) => setTimeout(resolve, 0))
      })
      const callCountAfterMount = vi.mocked(api.getPlannedDays).mock.calls.length

      await act(async () => {
        // Simulates Calendar.tsx's multi-day save loop: N writes through
        // `useDayAssertions.assertDay(..., { skipRefresh: true })`, none of
        // which touch this hook, then exactly ONE trailing bump for the
        // whole batch (mirrors `handleSavePinnedDay`'s `finally`).
        bump()
      })

      // The bump only takes effect on this instance's next render — nothing
      // has refetched yet.
      expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBe(callCountAfterMount)

      rerender()
      await act(async () => {
        await new Promise((resolve) => setTimeout(resolve, 0))
      })

      // Exactly one trailing GET for the whole batch, and it never blocked.
      expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBe(callCountAfterMount + 1)
      expect(result.current.isLoading).toBe(false)
      expect(result.current.isRefreshing).toBe(false)
    })
  })

  it('sets loading state during fetch (M7 part 1 — the initial mount load DOES block, unlike a post-mutation refetch)', async () => {
    let resolveGetPlannedDays: (value: Awaited<ReturnType<typeof api.getPlannedDays>>) => void
    const getPlannedDaysPromise: ReturnType<typeof api.getPlannedDays> = new Promise(resolve => {
      resolveGetPlannedDays = resolve
    })

    vi.mocked(api.getPlannedDays).mockReturnValue(getPlannedDaysPromise)

    const { result } = renderHook(() => usePlannedDays('child1'))

    // The very first fetch for a childId has nothing to render yet — it
    // must block, unlike every subsequent mutation-triggered refetch.
    expect(result.current.isLoading).toBe(true)
    expect(result.current.isRefreshing).toBe(false)

    await act(async () => {
      resolveGetPlannedDays!([])
      await getPlannedDaysPromise
    })

    expect(result.current.isLoading).toBe(false)
  })

  it('clears error on successful fetch after error', async () => {
    vi.mocked(api.getPlannedDays).mockRejectedValueOnce(new Error('Network error'))
    vi.mocked(api.getPlannedDays).mockResolvedValueOnce([])

    const { result, rerender } = renderHook(({ childId }: { childId: string }) => usePlannedDays(childId), {
      initialProps: { childId: 'child1' },
    })

    await act(async () => {
      await new Promise(resolve => setTimeout(resolve, 0))
    })

    expect(result.current.error).toBe('Network error')

    rerender({ childId: 'child2' })

    await act(async () => {
      await new Promise(resolve => setTimeout(resolve, 0))
    })

    expect(result.current.error).toBeNull()
  })

  it('discards a stale response for a previous childId (P1 stale-response guard)', async () => {
    let resolveFirst: (value: ReturnType<typeof makePlannedLeaveDay>[]) => void = () => {}
    let resolveSecond: (value: ReturnType<typeof makePlannedLeaveDay>[]) => void = () => {}
    const firstPromise = new Promise<ReturnType<typeof makePlannedLeaveDay>[]>((resolve) => {
      resolveFirst = resolve
    })
    const secondPromise = new Promise<ReturnType<typeof makePlannedLeaveDay>[]>((resolve) => {
      resolveSecond = resolve
    })

    vi.mocked(api.getPlannedDays).mockReturnValueOnce(firstPromise).mockReturnValueOnce(secondPromise)

    const { result, rerender } = renderHook(
      ({ childId }: { childId: string }) => usePlannedDays(childId),
      { initialProps: { childId: 'child1' } },
    )

    // Switching childId while the first (slower) request is still in
    // flight fires a second request for the new child.
    rerender({ childId: 'child2' })

    const child1Data = [
      makePlannedLeaveDay({
        id: 'p1',
        workspaceId: 'ws1',
        childId: 'child1',
        parentPersonalDataUuid: 'parent1',
        date: '2026-06-01',
        dayType: 'vacation',
        isDubbeldag: false,
      }),
    ]
    const child2Data = [
      makePlannedLeaveDay({
        id: 'p2',
        workspaceId: 'ws1',
        childId: 'child2',
        parentPersonalDataUuid: 'parent1',
        date: '2026-07-01',
        dayType: 'vacation',
        isDubbeldag: false,
      }),
    ]

    // The newer (child2) request resolves first...
    await act(async () => {
      resolveSecond(child2Data)
      await secondPromise
    })
    expect(result.current.data).toEqual(child2Data)

    // ...then the stale child1 response arrives late and must not overwrite it.
    await act(async () => {
      resolveFirst(child1Data)
      await firstPromise
    })
    expect(result.current.data).toEqual(child2Data)
  })

  describe('plan-version invalidation', () => {
    it('refetches when planVersion changes, even without a local mutation (invalidation from another hook, e.g. useDayAssertions or usePlanSync)', async () => {
      vi.mocked(api.getPlannedDays).mockResolvedValue([])
      const { rerender } = renderHook(() => usePlannedDays('child1'))

      await act(async () => {
        await new Promise((resolve) => setTimeout(resolve, 0))
      })
      const callCountBefore = vi.mocked(api.getPlannedDays).mock.calls.length

      // Simulate another hook (e.g. useDayAssertions) bumping the shared counter.
      vi.mocked(useWorkspace).mockReturnValue(
        makeWorkspaceContextValue({ planVersion: 1, bumpPlanVersion }),
      )
      rerender()

      await act(async () => {
        await new Promise((resolve) => setTimeout(resolve, 0))
      })

      expect(vi.mocked(api.getPlannedDays).mock.calls.length).toBeGreaterThan(callCountBefore)
    })
  })
})