import { useQuery } from '@tanstack/react-query';
import { useTranslation } from 'react-i18next';
import { getGatewayKeyUsage } from '../../api';

interface Props {
  keyId: string;
  onClose: () => void;
}

function fmtTokens(n: number): string {
  if (n >= 1_000_000) return `${(n / 1_000_000).toFixed(2)}M`;
  if (n >= 1_000) return `${(n / 1_000).toFixed(1)}K`;
  return n.toLocaleString();
}

/**
 * Per-key usage detail. Shows current-month stats (with a progress bar
 * vs budget) and a simple bar chart of the last 6-12 months of token
 * usage. No external chart library — pure CSS bars keep the UI bundle
 * lean.
 */
export function GatewayKeyUsagePanel({ keyId, onClose }: Props) {
  const { t } = useTranslation('settings');
  const { data, isLoading, error } = useQuery({
    queryKey: ['gateway-key-usage', keyId],
    queryFn: () => getGatewayKeyUsage(keyId),
    staleTime: 5_000,
  });

  const maxHistTokens = data
    ? Math.max(1, ...data.history.map(h => h.tokensIn + h.tokensOut))
    : 1;

  const pctUsed =
    data && data.tokensBudget !== null && data.tokensBudget > 0
      ? Math.min(100, (data.tokensTotal / data.tokensBudget) * 100)
      : null;

  return (
    <div className="fixed inset-0 z-50 flex items-center justify-center bg-black/40">
      <div className="bg-surface rounded-lg shadow-xl max-w-2xl w-full mx-4 p-6">
        <div className="flex justify-between items-start mb-4">
          <div>
            <h3 className="text-lg font-semibold text-slate-800">{t('gateway.usagePanel.title')}</h3>
            <p className="text-xs text-slate-500 font-mono">{keyId}</p>
          </div>
          <button
            type="button"
            onClick={onClose}
            className="text-slate-400 hover:text-slate-700 text-xl leading-none"
            aria-label="Close"
          >
            ×
          </button>
        </div>

        {isLoading && <div className="text-sm text-slate-500">Loading…</div>}
        {error && (
          <div className="text-sm text-red-600">{t('gateway.keys.fetchError', { msg: String((error as Error).message ?? error) })}</div>
        )}

        {data && (
          <>
            {/* Current period summary */}
            <div className="border border-hairline rounded p-3 mb-4">
              <div className="flex justify-between items-baseline mb-2">
                <span className="text-xs font-medium text-slate-600 uppercase tracking-wide">
                  {t('gateway.usagePanel.thisMonth', { period: data.currentPeriod })}
                </span>
                <span className="text-xs text-slate-500">
                  Requests: {data.requestsThisMonth.toLocaleString()}
                </span>
              </div>
              <div className="grid grid-cols-3 gap-3 text-sm">
                <div>
                  <div className="text-xs text-slate-500">Input tokens</div>
                  <div className="font-mono">{fmtTokens(data.tokensIn)}</div>
                </div>
                <div>
                  <div className="text-xs text-slate-500">Output tokens</div>
                  <div className="font-mono">{fmtTokens(data.tokensOut)}</div>
                </div>
                <div>
                  <div className="text-xs text-slate-500">Total / Budget</div>
                  <div className="font-mono">
                    {fmtTokens(data.tokensTotal)}{' '}
                    <span className="text-slate-400">
                      / {data.tokensBudget !== null ? fmtTokens(data.tokensBudget) : '∞'}
                    </span>
                  </div>
                </div>
              </div>
              {pctUsed !== null && (
                <div className="mt-3">
                  <div className="h-2 rounded bg-slate-100 overflow-hidden">
                    <div
                      className={`h-full ${pctUsed >= 100 ? 'bg-red-500' : pctUsed >= 80 ? 'bg-amber-500' : 'bg-accent'}`}
                      style={{ width: `${pctUsed}%` }}
                    />
                  </div>
                  <div className="text-xs text-slate-500 mt-1 text-right">
                    {pctUsed.toFixed(1)}% used
                    {data.remaining !== null && ` · ${fmtTokens(data.remaining)} remaining`}
                  </div>
                </div>
              )}
              {data.rateLimitRpm !== null && (
                <div className="text-xs text-slate-500 mt-2">
                  Rate limit: {data.rateLimitRpm} rpm
                </div>
              )}
            </div>

            {/* History bars */}
            <div className="border border-hairline rounded p-3">
              <div className="text-xs font-medium text-slate-600 uppercase tracking-wide mb-2">
                {t('gateway.usagePanel.past12')}
              </div>
              {data.history.length === 0 ? (
                <div className="text-sm text-slate-400 italic">{t('gateway.usagePanel.noHistory')}</div>
              ) : (
                <div className="space-y-1.5">
                  {data.history.map((h) => {
                    const total = h.tokensIn + h.tokensOut;
                    const widthPct = (total / maxHistTokens) * 100;
                    return (
                      <div key={h.period} className="flex items-center gap-2 text-xs">
                        <span className="font-mono w-16 text-slate-500">{h.period}</span>
                        <div className="flex-1 h-3 bg-slate-100 rounded overflow-hidden">
                          <div
                            className="h-full bg-accent/70"
                            style={{ width: `${Math.max(2, widthPct)}%` }}
                          />
                        </div>
                        <span className="font-mono w-20 text-right text-slate-600">
                          {fmtTokens(total)}
                        </span>
                        <span className="font-mono w-12 text-right text-slate-400">
                          {h.requests.toLocaleString()} rq
                        </span>
                      </div>
                    );
                  })}
                </div>
              )}
            </div>
          </>
        )}
      </div>
    </div>
  );
}