import { useCallback, useEffect, useState } from 'react'
import * as api from '@/services/api'
import { useLatestRequest } from './useLatestRequest'
import { useWorkspace } from '@/context'
import type { DayOverride, DayOverrideCreateRequest } from '@/types'

interface UseDayOverridesResult {
  data: DayOverride[]
  /** True only while the initial (or workspace-switch) load is in flight —
   * safe to gate a full-page blocking spinner on. */
  isLoading: boolean
  /** True while a post-mutation background refresh is in flight. Never true
   * at the same time as `isLoading` — see `useLeaveWishes.ts`'s doc comment
   * for why a mutation's refetch must not flip the initial-load flag. */
  isRefreshing: boolean
  error: string | null
  upsert: (req: DayOverrideCreateRequest) => Promise<void>
  remove: (id: string) => Promise<void>
}

export function useDayOverrides(workspaceId: string): UseDayOverridesResult {
  const [data, setData] = useState<DayOverride[]>([])
  const [isLoading, setIsLoading] = useState(false)
  const [isRefreshing, setIsRefreshing] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const { start, isCurrent } = useLatestRequest()
  const { bumpPlanVersion } = useWorkspace()

  const fetch = useCallback(
    async (options?: { background?: boolean }) => {
      const requestId = start()
      if (!workspaceId) return
      const background = options?.background ?? false
      const setBusy = background ? setIsRefreshing : setIsLoading
      setBusy(true)
      setError(null)
      try {
        const result = await api.listDayOverridesByWorkspace(workspaceId)
        if (!isCurrent(requestId)) return
        setData(result)
      } catch (err: unknown) {
        if (!isCurrent(requestId)) return
        setError(err instanceof Error ? err.message : 'Failed to load day overrides')
      } finally {
        // Unguarded: `isCurrent` decides which response's DATA wins, not
        // whether a superseded call's own busy flag gets cleared — a stale
        // call must still release the flag IT raised, or it can strand
        // that flag true forever (see usePlannedDays.ts for the hang this
        // exact guard caused there).
        setBusy(false)
      }
    },
    [workspaceId, start, isCurrent],
  )

  useEffect(() => {
    void fetch()
  }, [fetch])

  const upsert = useCallback(
    async (req: DayOverrideCreateRequest) => {
      await api.upsertDayOverride(req)
      await fetch({ background: true })
      // An override changes which days count as free/working, which feeds
      // the at-risk-days analytics — bump the shared invalidation counter
      // so other hook instances (e.g. useAnalytics) refetch. See
      // `WorkspaceContext.planVersion`.
      bumpPlanVersion()
    },
    [fetch, bumpPlanVersion],
  )

  const remove = useCallback(
    async (id: string) => {
      await api.deleteDayOverride(id)
      await fetch({ background: true })
      bumpPlanVersion()
    },
    [fetch, bumpPlanVersion],
  )

  return { data, isLoading, isRefreshing, error, upsert, remove }
}