import { useCallback, useEffect, useState } from 'react'
import * as api from '@/services/api'
import { useLatestRequest } from './useLatestRequest'
import type { ParentBalanceInitial } from '@/components/modals/ParentBalanceForm'
import type { ParentalLeaveFetch } from '@/types'

interface UseLatestBalanceResult {
  initial: ParentBalanceInitial | undefined
  /** The full saved record — `source`/`fetchedAt`/`daysLeft`/`totalDays`
   * that `initial` (deliberately scoped to just `ParentBalanceForm`'s
   * prefill fields) doesn't carry. `null` while loading or when nothing has
   * been saved yet; consumers that show a status line (`BalanceFlow`'s
   * per-member row) read this instead of `initial`. */
  raw: ParentalLeaveFetch | null
  isLoading: boolean
  error: string | null
  /** Re-runs the fetch — used after an FK scrape completes so a row already
   * on screen picks up the newly persisted balance without a remount. */
  refresh: () => Promise<void>
}

/**
 * Loads a parent's latest saved parental-leave balance so `ParentBalanceForm`
 * can be reopened pre-filled with the real figures instead of always
 * falling back to its 195/45/60 preset. Shared by `Settings` ("Dagar kvar")
 * and `Dashboard` ("Ange manuellt") so a saved balance shows the same way
 * from either entry point.
 *
 * Imported directly from this file (not the `@/hooks` barrel) by both pages
 * so their tests can drive it through a mocked `api.getParentalLeave`
 * instead of mocking the hook itself, while the rest of `@/hooks` stays
 * blanket-mocked.
 *
 * `personalDataUuid`/`childId` are null when no balance form is open — the
 * hook then no-ops and reports no saved balance, rather than fetching.
 */
export function useLatestBalance(
  personalDataUuid: string | null,
  childId: string | null,
): UseLatestBalanceResult {
  const [initial, setInitial] = useState<ParentBalanceInitial | undefined>(undefined)
  const [raw, setRaw] = useState<ParentalLeaveFetch | null>(null)
  const [isLoading, setIsLoading] = useState(false)
  const [error, setError] = useState<string | null>(null)
  const { start, isCurrent } = useLatestRequest()

  const fetch = useCallback(async () => {
    const requestId = start()
    if (!personalDataUuid || !childId) {
      setInitial(undefined)
      setRaw(null)
      setError(null)
      return
    }
    setIsLoading(true)
    setError(null)
    try {
      const response = await api.getParentalLeave(personalDataUuid, childId)
      if (!isCurrent(requestId)) return
      // `null` means nothing has been saved for this parent/child yet (a
      // brand-new partner, or self before any fetch) — not an error, so the
      // form is left to fall back to its own preset.
      setInitial(
        response
          ? {
              sjukpenningLeft: response.tierData.sjukpenningLeft,
              lagstaNivaLeft: response.tierData.lagstaNivaLeft,
              dubbeldagarLeft: response.dubbeldagarLeft,
              reservedDaysLeft: response.reservedDaysLeft,
            }
          : undefined,
      )
      setRaw(response)
    } catch (err) {
      if (!isCurrent(requestId)) return
      setError(err instanceof Error ? err.message : 'Failed to load parental leave balance')
      setInitial(undefined)
      setRaw(null)
    } finally {
      if (isCurrent(requestId)) setIsLoading(false)
    }
  }, [personalDataUuid, childId, start, isCurrent])

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

  return { initial, raw, isLoading, error, refresh: fetch }
}