/**
 * DedupMerge page — Main deduplication & merge UI.
 * Search for duplicate contacts, review pairs, merge with field-level control.
 */

import React, { useState, useCallback } from 'react';
import { useTranslation } from 'react-i18next';
import { Search, CopyCheck, Loader2, AlertCircle } from 'lucide-react';
import { Button } from '@/components/ui/Button';
import { Input } from '@/components/ui/Input';
import { EmptyState } from '@/components/ui/EmptyState';
import { DuplicatePairCard } from '@/components/dedup/DuplicatePairCard';
import { MergeDialog } from '@/components/dedup/MergeDialog';
import { MergeHistory } from '@/components/dedup/MergeHistory';
import { useFindDuplicates, type DuplicatePair } from '@/api/dedup';

export function DedupMergePage() {
  const { t } = useTranslation();

  const [threshold, setThreshold] = useState(0.7);
  const [limit, setLimit] = useState(50);
  const [hasSearched, setHasSearched] = useState(false);
  const [mergePair, setMergePair] = useState<DuplicatePair | null>(null);
  const [mergeDialogOpen, setMergeDialogOpen] = useState(false);

  const findDuplicates = useFindDuplicates();
  const duplicates = findDuplicates.data ?? [];

  const handleSearch = useCallback(() => {
    setHasSearched(true);
    findDuplicates.mutate({ threshold, limit });
  }, [findDuplicates, threshold, limit]);

  const handleMergeClick = useCallback((pair: DuplicatePair) => {
    setMergePair(pair);
    setMergeDialogOpen(true);
  }, []);

  const handleMergeDialogClose = useCallback(() => {
    setMergeDialogOpen(false);
    setMergePair(null);
  }, []);

  const handleLimitChange = useCallback(
    (e: React.ChangeEvent<HTMLInputElement>) => {
      const val = parseInt(e.target.value, 10);
      if (isNaN(val) || val < 1) {
        setLimit(1);
      } else if (val > 500) {
        setLimit(500);
      } else {
        setLimit(val);
      }
    },
    [],
  );

  return (
    <div className="flex h-full flex-col overflow-y-auto">
      <div className="mx-auto w-full max-w-5xl space-y-6 p-6">
        {/* Header section */}
        <div className="rounded-lg border border-secondary-200 bg-white shadow-sm">
          <div className="border-b border-secondary-200 px-6 py-4">
            <h1 className="text-xl font-bold text-secondary-900">
              {t('dedup.title', 'Duplikate & Zusammenführen')}
            </h1>
            <p className="mt-1 text-sm text-secondary-500">
              {t(
                'dedup.description',
                'Suchen Sie nach dubletten Kontakten und führen Sie diese zusammen.',
              )}
            </p>
          </div>

          <div className="space-y-5 px-6 py-5">
            {/* Threshold slider */}
            <div>
              <div className="mb-2 flex items-center justify-between">
                <label htmlFor="threshold-slider" className="text-sm font-medium text-secondary-700">
                  {t('dedup.threshold', 'Ähnlichkeitsschwelle')}
                </label>
                <span className="text-sm font-semibold text-primary-700">
                  {Math.round(threshold * 100)}%
                </span>
              </div>
              <input
                id="threshold-slider"
                type="range"
                min={0.5}
                max={1.0}
                step={0.05}
                value={threshold}
                onChange={(e) => setThreshold(parseFloat(e.target.value))}
                className="w-full h-2 rounded-lg appearance-none cursor-pointer bg-secondary-200 accent-primary-600"
              />
              <div className="mt-1 flex justify-between text-xs text-secondary-400">
                <span>50%</span>
                <span>100%</span>
              </div>
            </div>

            {/* Limit input + search button */}
            <div className="flex flex-col gap-4 sm:flex-row sm:items-end">
              <div className="w-full sm:w-40">
                <Input
                  type="number"
                  label={t('dedup.limit', 'Max. Ergebnisse')}
                  value={limit}
                  onChange={handleLimitChange}
                  min={1}
                  max={500}
                  helperText={t('dedup.limitHelper', '1–500')}
                />
              </div>
              <div className="flex-shrink-0">
                <Button
                  variant="primary"
                  size="md"
                  isLoading={findDuplicates.isPending}
                  icon={<Search className="h-4 w-4" />}
                  onClick={handleSearch}
                >
                  {t('dedup.search', 'Duplikate suchen')}
                </Button>
              </div>
            </div>
          </div>
        </div>

        {/* Results section */}
        <div className="space-y-4">
          {/* Loading state */}
          {findDuplicates.isPending && (
            <div className="flex flex-col items-center justify-center py-16 text-center">
              <Loader2 className="h-8 w-8 animate-spin text-primary-500" aria-hidden="true" />
              <p className="mt-3 text-sm text-secondary-500">
                {t('dedup.searching', 'Suche nach Duplikaten…')}
              </p>
            </div>
          )}

          {/* Error state */}
          {findDuplicates.isError && (
            <div className="flex flex-col items-center justify-center py-12 text-center">
              <AlertCircle className="h-8 w-8 text-danger-500" aria-hidden="true" />
              <p className="mt-3 text-sm font-medium text-danger-700">
                {t('dedup.searchError', 'Fehler bei der Duplikatssuche.')}
              </p>
              <p className="mt-1 text-xs text-secondary-400">
                {findDuplicates.error instanceof Error
                  ? findDuplicates.error.message
                  : t('common.unknownError', 'Unbekannter Fehler')}
              </p>
              <Button
                variant="secondary"
                size="sm"
                className="mt-4"
                onClick={handleSearch}
              >
                {t('common.retry', 'Erneut versuchen')}
              </Button>
            </div>
          )}

          {/* Empty state: no search yet */}
          {!findDuplicates.isPending && !findDuplicates.isError && !hasSearched && (
            <EmptyState
              icon={<CopyCheck className="h-12 w-12" />}
              title={t('dedup.emptyTitle', 'Keine Suche durchgeführt')}
              description={t(
                'dedup.emptyDescription',
                'Stellen Sie die Schwellwerte ein und klicken Sie auf „Duplikate suchen“, um mögliche Dubletten zu finden.',
              )}
            />
          )}

          {/* Empty results: search done, no duplicates found */}
          {!findDuplicates.isPending && !findDuplicates.isError && hasSearched && duplicates.length === 0 && (
            <EmptyState
              icon={<CopyCheck className="h-12 w-12" />}
              title={t('dedup.noDuplicates', 'Keine Duplikate gefunden')}
              description={t(
                'dedup.noDuplicatesDescription',
                'Mit den aktuellen Einstellungen wurden keine Duplikate gefunden. Versuchen Sie eine niedrigere Schwellwert.',
              )}
            />
          )}

          {/* Results list */}
          {!findDuplicates.isPending && !findDuplicates.isError && duplicates.length > 0 && (
            <>
              <div className="flex items-center justify-between">
                <h2 className="text-lg font-semibold text-secondary-900">
                  {t('dedup.results', 'Gefundene Duplikate')}
                </h2>
                <span className="rounded-full bg-secondary-100 px-3 py-0.5 text-sm font-medium text-secondary-600">
                  {duplicates.length}
                </span>
              </div>
              <div className="space-y-4">
                {duplicates.map((pair, idx) => (
                  <DuplicatePairCard
                    key={`${pair.source_contact.id}-${pair.target_contact.id}-${idx}`}
                    pair={pair}
                    onMerge={handleMergeClick}
                  />
                ))}
              </div>
            </>
          )}
        </div>

        {/* Merge History section */}
        <MergeHistory />
      </div>

      {/* Merge Dialog */}
      <MergeDialog
        open={mergeDialogOpen}
        pair={mergePair}
        onClose={handleMergeDialogClose}
      />
    </div>
  );
}