'use client'

import { useMemo, useState } from 'react'
import { cn } from '@/lib/utils'
import { useLanguage } from '@/lib/i18n'

interface HeatmapDay {
  date: string
  count: number
}

interface RevisionHeatmapProps {
  data: HeatmapDay[]
  className?: string
  /** Révisions de flashcards, ou notes modifiées sur le tableau de bord. */
  kind?: 'reviews' | 'edits'
}

function intensityClass(count: number, max: number): string {
  if (count <= 0) return 'bg-black/[0.06] dark:bg-white/[0.08]'
  const ratio = count / Math.max(max, 1)
  if (ratio >= 0.75) return 'bg-brand-accent'
  if (ratio >= 0.5) return 'bg-brand-accent/70'
  if (ratio >= 0.25) return 'bg-brand-accent/40'
  return 'bg-brand-accent/20'
}

function resolveDateLocale(langCode: string): string {
  if (langCode === 'fa') return 'fa-IR-u-ca-persian-nu-arabext'
  return langCode
}

export function RevisionHeatmap({ data, className, kind = 'reviews' }: RevisionHeatmapProps) {
  const { t, language } = useLanguage()
  const [hovered, setHovered] = useState<{ label: string; count: number; date: string } | null>(null)
  const [selected, setSelected] = useState<{ label: string; count: number; date: string } | null>(null)

  const dateLocale = resolveDateLocale(language ?? 'en')
  const prefix = kind === 'edits' ? 'homeDashboard.activityHeatmap' : 'flashcards.heatmap'

  const dayLabel = (count: number) => {
    if (count <= 0) return t(`${prefix}DayNone`)
    if (count === 1) return t(`${prefix}DayOne`)
    return t(`${prefix}Day`, { count })
  }

  const { cells, maxCount, totalReviews, monthLabels } = useMemo(() => {
    const map = new Map(data.map((d) => [d.date, d.count]))
    const now = new Date()
    const todayUTC = new Date(Date.UTC(now.getUTCFullYear(), now.getUTCMonth(), now.getUTCDate()))

    const cells: { date: string; count: number; label: string }[] = []
    const monthLabels: { index: number; label: string }[] = []
    let lastMonth = -1

    for (let i = 89; i >= 0; i--) {
      const d = new Date(todayUTC)
      d.setUTCDate(d.getUTCDate() - i)
      const key = d.toISOString().slice(0, 10)
      const count = map.get(key) || 0
      const month = d.getUTCMonth()

      if (month !== lastMonth) {
        monthLabels.push({
          index: 89 - i,
          label: d.toLocaleDateString(dateLocale, { month: 'short', timeZone: 'UTC' }),
        })
        lastMonth = month
      }

      cells.push({
        date: key,
        count,
        label: d.toLocaleDateString(dateLocale, { weekday: 'long', day: 'numeric', month: 'long', timeZone: 'UTC' }),
      })
    }

    const maxCount = Math.max(1, ...cells.map((c) => c.count))
    const totalReviews = cells.reduce((s, c) => s + c.count, 0)
    return { cells, maxCount, totalReviews, monthLabels }
  }, [data, dateLocale])

  const pct = (index: number) => `${(index / 90) * 100}%`

  const activeInfo = hovered || selected

  return (
    <div className={cn('space-y-2', className)}>
      <div className="flex items-center justify-between">
        <p className="text-[13px] font-semibold uppercase tracking-wider text-concrete">
          {t(`${prefix}Title`)}
        </p>
        <span className="text-[13px] text-concrete/70">
          {totalReviews > 0
            ? t(`${prefix}Total`, { count: totalReviews })
            : t(kind === 'edits' ? 'homeDashboard.activityHeatmapLast90' : 'flashcards.heatmapLast90')}
        </span>
      </div>

      <div className="relative h-6">
        {monthLabels.map((m) => (
          <span
            key={m.label + m.index}
            className="absolute text-[13px] text-concrete/70 font-medium leading-tight"
            style={{ left: pct(m.index) }}
          >
            {m.label}
          </span>
        ))}
      </div>

      <div className="grid grid-cols-[repeat(15,minmax(0,1fr))] gap-1 sm:grid-cols-[repeat(18,minmax(0,1fr))]">
        {cells.map((cell) => {
          const isHovered = hovered?.date === cell.date
          const isSelected = selected?.date === cell.date
          const reviewText = dayLabel(cell.count)

          return (
            <button
              key={cell.date}
              type="button"
              title={`${reviewText} - ${cell.label}`}
              className={cn(
                'aspect-square rounded-[3px] transition-all cursor-pointer focus:outline-none focus:ring-2 focus:ring-brand-accent focus:ring-offset-1 focus:ring-offset-background',
                intensityClass(cell.count, maxCount),
                (isHovered || isSelected) && 'ring-2 ring-brand-accent ring-offset-1 ring-offset-background scale-105 z-10',
              )}
              onMouseEnter={() => setHovered({ label: cell.label, count: cell.count, date: cell.date })}
              onMouseLeave={() => setHovered(null)}
              onClick={() => {
                if (selected?.date === cell.date) {
                  setSelected(null)
                } else {
                  setSelected({ label: cell.label, count: cell.count, date: cell.date })
                }
              }}
            />
          )
        })}
      </div>

      <div className="min-h-7 flex items-center text-[13px] border-b border-border/20 pb-1">
        {activeInfo ? (
          <p className="flex items-center gap-1.5 animate-fadeIn">
            <span className="font-semibold text-foreground">
              {dayLabel(activeInfo.count)}
            </span>
            <span className="text-concrete">· {activeInfo.label}</span>
          </p>
        ) : (
          <p className="text-[13px] text-concrete/50 italic">
            {t(`${prefix}Hint`)}
          </p>
        )}
      </div>

      <div className="flex items-center gap-2 pt-0.5">
        <span className="text-[13px] text-concrete/60">{t('flashcards.heatmapLess')}</span>
        <div className="flex gap-0.5">
          {['bg-black/[0.06] dark:bg-white/[0.08]', 'bg-brand-accent/20', 'bg-brand-accent/40', 'bg-brand-accent/70', 'bg-brand-accent'].map((cls, i) => (
            <div key={i} className={cn('w-3 h-3 rounded-[3px]', cls)} />
          ))}
        </div>
        <span className="text-[13px] text-concrete/60">{t('flashcards.heatmapMore')}</span>
      </div>
    </div>
  )
}