'use client'

import { useQuery } from '@tanstack/react-query'
import { Loader2, BarChart2 } from 'lucide-react'
import { useLanguage } from '@/lib/i18n'
import { cn } from '@/lib/utils'

interface BalanceData {
  totalRemaining: number | null
  subscriptionRemaining: number | null
  purchasedRemaining: number
  subscriptionGranted: number | null
  spentThisPeriod: number
  unlimited: boolean
}

interface BreakdownRow {
  feature: string
  creditsUsed: number
  actionsCount: number
  percentOfSpent: number
}

/** Toutes les fonctions IA — même liste que le compteur sidebar. */
const FEATURE_LABEL_KEYS: Record<string, string> = {
  semantic_search: 'usageMeter.featureSearch',
  auto_tag: 'usageMeter.featureTags',
  auto_title: 'usageMeter.featureTitles',
  reformulate: 'usageMeter.featureReformulate',
  chat: 'usageMeter.featureChat',
  brainstorm_create: 'usageMeter.featureBrainstormSessions',
  brainstorm_expand: 'usageMeter.featureBrainstormExpand',
  brainstorm_enrich: 'usageMeter.featureBrainstormEnrich',
  suggest_charts: 'usageMeter.featureCharts',
  publish_enhance: 'usageMeter.featurePublishEnhance',
  ai_flashcard: 'usageMeter.featureFlashcards',
  voice_transcribe: 'usageMeter.featureVoice',
  slide_generate: 'usageMeter.featureSlides',
  excalidraw_generate: 'usageMeter.featureDiagrams',
}

function UsageBar({ percent }: { percent: number }) {
  return (
    <div className="h-1.5 w-full rounded-full bg-foreground/10 overflow-hidden">
      <div
        className={cn(
          'h-full rounded-full transition-all',
          percent >= 40 ? 'bg-primary' : 'bg-primary/60',
        )}
        style={{ width: `${Math.min(Math.max(percent, 0), 100)}%` }}
      />
    </div>
  )
}

export function UsageBreakdown() {
  const { t } = useLanguage()

  const { data, isLoading } = useQuery({
    queryKey: ['usage', 'current'],
    queryFn: async () => {
      const res = await fetch('/api/usage/current')
      if (!res.ok) throw new Error('Failed to fetch usage')
      return res.json() as Promise<{
        balance: BalanceData
        breakdown: BreakdownRow[]
        period: string
        tier: string
      }>
    },
  })

  const balance = data?.balance
  const byFeature = new Map((data?.breakdown ?? []).map((r) => [r.feature, r]))
  const spent = balance?.spentThisPeriod ?? 0

  const rows = Object.keys(FEATURE_LABEL_KEYS).map((key) => {
    const row = byFeature.get(key)
    return {
      feature: key,
      label: t(FEATURE_LABEL_KEYS[key]),
      creditsUsed: row?.creditsUsed ?? 0,
      actionsCount: row?.actionsCount ?? 0,
    }
  })

  return (
    <div className="rounded-xl border border-border/40 bg-paper p-6 space-y-4">
      <div className="flex items-center gap-2">
        <BarChart2 className="h-4 w-4 text-muted-foreground" />
        <h3 className="text-sm font-semibold text-foreground">
          {t('billing.usageThisPeriod')}
        </h3>
      </div>

      {isLoading ? (
        <div className="flex justify-center py-4">
          <Loader2 className="h-5 w-5 animate-spin text-muted-foreground" />
        </div>
      ) : !balance ? (
        <p className="text-xs text-muted-foreground py-2">{t('billing.noUsage')}</p>
      ) : (
        <>
          <div className="grid grid-cols-1 sm:grid-cols-3 gap-3">
            <div className="rounded-lg border border-border/40 p-3">
              <p className="text-[10px] uppercase tracking-wider text-muted-foreground font-bold">
                {t('billing.creditsRemaining')}
              </p>
              <p className="text-lg font-semibold tabular-nums mt-1">
                {balance.unlimited ? t('billing.unlimited') : balance.totalRemaining}
              </p>
            </div>
            <div className="rounded-lg border border-border/40 p-3">
              <p className="text-[10px] uppercase tracking-wider text-muted-foreground font-bold">
                {t('billing.creditsSpent')}
              </p>
              <p className="text-lg font-semibold tabular-nums mt-1">
                {balance.spentThisPeriod}
              </p>
            </div>
            <div className="rounded-lg border border-border/40 p-3">
              <p className="text-[10px] uppercase tracking-wider text-muted-foreground font-bold">
                {t('billing.creditsFromPacks')}
              </p>
              <p className="text-lg font-semibold tabular-nums mt-1">
                {balance.purchasedRemaining}
              </p>
            </div>
          </div>

          <p className="text-xs font-medium text-foreground pt-1">
            {t('billing.creditsWhereTitle')}
          </p>
          <p className="text-[11px] text-muted-foreground leading-relaxed">
            {t('billing.creditsUsageLegend')}
          </p>

          <div className="space-y-3">
            {rows.map((row) => {
              const barPct =
                spent > 0 && row.creditsUsed > 0
                  ? Math.min(100, (row.creditsUsed / spent) * 100)
                  : 0
              return (
                <div key={row.feature} className="space-y-1">
                  <div className="flex items-center justify-between gap-2">
                    <span className="text-xs text-muted-foreground">{row.label}</span>
                    <span
                      className={cn(
                        'text-xs font-medium tabular-nums shrink-0',
                        row.creditsUsed > 0 ? 'text-foreground' : 'text-muted-foreground/60',
                      )}
                    >
                      {row.creditsUsed > 0
                        ? `${row.creditsUsed} cr. · ${row.actionsCount}×`
                        : '0'}
                    </span>
                  </div>
                  <UsageBar percent={barPct} />
                </div>
              )
            })}
          </div>
        </>
      )}
    </div>
  )
}