import { useState } from 'react'
import { zodResolver } from '@hookform/resolvers/zod'
import { useForm, useWatch } from 'react-hook-form'
import { toast } from 'sonner'
import { FormError, FormField } from '@/components/form-field'
import { Button } from '@/components/ui/button'
import { Input } from '@/components/ui/input'
import { ApiError } from '@/lib/api'
import { PageError, PageLoading } from '@/components/page'
import { formatDate } from '@/lib/format'
import { daysInclusive, isIsoDate, lastToEnd, suggestRanges } from '@/lib/period-dates'
import { useCreatePeriod, usePeriods, useUpdatePeriod } from '@/lib/periods'
import { t } from '@/lib/strings'
import type { Period } from '@/types/Period'
import { datesSchema, type DatesForm } from './schemas'
import { StepActions, StepIntro } from './wizard-ui'

const s = t.wizard.dates

const monthName = new Intl.DateTimeFormat('tr-TR', { month: 'long', year: 'numeric' })

/** Hızlı seçim etiketi: takvim ayıysa "Aralık 2026", değilse "15.11.2026 – 14.12.2026" */
function rangeLabel(r: { start: string; last: string }) {
  const [y, m, d] = r.start.split('-').map(Number)
  const monthEnd = new Date(Date.UTC(y, m, 0)).toISOString().slice(0, 10)
  return d === 1 && r.last === monthEnd
    ? monthName.format(new Date(y, m - 1, 1))
    : `${formatDate(r.start)} – ${formatDate(r.last)}`
}

/**
 * 1. adım: dönem yoksa açar, varsa (geri gelindiyse) günceller.
 * Öneriler son dönemin bitişinden başlar (erken kapatılan ay tekrar önerilmez).
 */
export function StepDates({ period, onDone }: { period: Period | null; onDone: () => void }) {
  const periods = usePeriods()
  if (periods.isPending) return <PageLoading />
  if (periods.isError)
    return <PageError message={periods.error.message} onRetry={periods.refetch} />
  // Liste en yeni başta; sihirbazda açık dönem varsa (geri gelindi) o hariç tutulur
  const previous = periods.data.find((p) => p.id !== period?.id)
  return <DatesStepForm period={period} prevEnd={previous?.end_date} onDone={onDone} />
}

function DatesStepForm({
  period,
  prevEnd,
  onDone,
}: {
  period: Period | null
  prevEnd?: string
  onDone: () => void
}) {
  const create = useCreatePeriod()
  const update = useUpdatePeriod()

  const [today] = useState(() => new Date()) // render başına değil, bir kez
  const presets = suggestRanges(today, prevEnd).map((range) => ({
    label: rangeLabel(range),
    range,
  }))

  const {
    register,
    control,
    handleSubmit,
    setValue,
    setError,
    formState: { errors, isSubmitting },
  } = useForm<DatesForm>({
    resolver: zodResolver(datesSchema),
    mode: 'onTouched',
    defaultValues: period
      ? { start: period.start_date, last: period.last_date, name: period.name }
      : { ...presets[0].range, name: '' },
  })

  const [start, last] = useWatch({ control, name: ['start', 'last'] })
  const days =
    isIsoDate(start) && isIsoDate(last) && last >= start ? daysInclusive(start, last) : null

  const onSubmit = handleSubmit(async (v) => {
    const end = lastToEnd(v.last)
    try {
      if (!period) {
        await create.mutateAsync({ start_date: v.start, end_date: end, name: v.name || undefined })
        toast.success(s.created)
      } else if (
        v.start !== period.start_date ||
        end !== period.end_date ||
        v.name !== period.name
      ) {
        await update.mutateAsync({
          id: period.id,
          version: period.version,
          start_date: v.start,
          end_date: end,
          name: v.name, // boş → backend tarihlere göre otomatik ad verir
        })
      }
      onDone()
    } catch (e) {
      setError('root', { message: e instanceof ApiError ? e.message : String(e) })
    }
  })

  return (
    <form onSubmit={onSubmit} noValidate>
      <StepIntro title={s.title} hint={s.hint} />

      <div className="space-y-5">
        <div role="group" aria-label={s.presetsLabel} className="flex flex-wrap gap-2">
          {presets.map((p) => {
            const selected = start === p.range.start && last === p.range.last
            return (
              <Button
                key={p.label}
                type="button"
                variant={selected ? 'default' : 'outline'}
                aria-pressed={selected}
                onClick={() => {
                  setValue('start', p.range.start, { shouldValidate: true })
                  setValue('last', p.range.last, { shouldValidate: true })
                }}
              >
                {p.label}
              </Button>
            )
          })}
        </div>

        <div className="grid gap-4 sm:grid-cols-2">
          <FormField label={s.start} error={errors.start}>
            {(f) => <Input {...f} type="date" {...register('start')} />}
          </FormField>
          <FormField label={s.last} error={errors.last}>
            {(f) => <Input {...f} type="date" min={start || undefined} {...register('last')} />}
          </FormField>
        </div>
        {days !== null && (
          <p className="text-sm text-muted-foreground" aria-live="polite">
            {s.days(days)}
          </p>
        )}

        <FormField label={s.name} error={errors.name} hint={s.nameHint}>
          {(f) => <Input {...f} maxLength={60} {...register('name')} />}
        </FormField>

        <FormError message={errors.root?.message} />
      </div>

      <StepActions pending={isSubmitting} />
    </form>
  )
}