import React, { useCallback, useEffect, useState } from 'react';
import { Box, Text, useInput } from 'ink';
import type { ArticleDTO, SalesUnitDTO, Unit, PriceModel } from '@effigenix/api-client';
import { UNIT_LABELS, PRICE_MODEL_LABELS } from '@effigenix/api-client';
import { useNavigation } from '../../../state/navigation-context.js';
import { useArticles } from '../../../hooks/useArticles.js';
import { LoadingSpinner } from '../../shared/LoadingSpinner.js';
import { ErrorDisplay } from '../../shared/ErrorDisplay.js';
import { SuccessDisplay } from '../../shared/SuccessDisplay.js';
import { ConfirmDialog } from '../../shared/ConfirmDialog.js';
import { client } from '../../../utils/api-client.js';

type MenuAction = 'toggle-status' | 'add-sales-unit' | 'remove-sales-unit' | 'back';
type Mode = 'menu' | 'confirm-status' | 'select-sales-unit';

const MENU_ITEMS: { id: MenuAction; label: (a: ArticleDTO) => string }[] = [
  { id: 'toggle-status', label: (a) => a.status === 'ACTIVE' ? '[Deaktivieren]' : '[Aktivieren]' },
  { id: 'add-sales-unit', label: () => '[Verkaufseinheit hinzufügen]' },
  { id: 'remove-sales-unit', label: (a) => a.salesUnits.length > 1 ? '[Verkaufseinheit entfernen]' : '[Entfernen (min. 1 erforderlich)]' },
  { id: 'back', label: () => '[Zurück]' },
];

function errorMessage(err: unknown): string {
  return err instanceof Error ? err.message : 'Unbekannter Fehler';
}

export function ArticleDetailScreen() {
  const { params, navigate, back } = useNavigation();
  const articleId = params['articleId'] ?? '';
  const { activateArticle, deactivateArticle, removeSalesUnit } = useArticles();

  const [article, setArticle] = useState<ArticleDTO | null>(null);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [selectedAction, setSelectedAction] = useState(0);
  const [mode, setMode] = useState<Mode>('menu');
  const [actionLoading, setActionLoading] = useState(false);
  const [successMessage, setSuccessMessage] = useState<string | null>(null);
  const [selectedSuIndex, setSelectedSuIndex] = useState(0);

  const loadArticle = useCallback(() => {
    setLoading(true);
    setError(null);
    client.articles.getById(articleId)
      .then((a) => { setArticle(a); setLoading(false); })
      .catch((err: unknown) => { setError(errorMessage(err)); setLoading(false); });
  }, [articleId]);

  useEffect(() => { if (articleId) loadArticle(); }, [loadArticle, articleId]);

  useInput((_input, key) => {
    if (loading || actionLoading) return;

    if (mode === 'select-sales-unit' && article) {
      if (key.upArrow) setSelectedSuIndex((i) => Math.max(0, i - 1));
      if (key.downArrow) setSelectedSuIndex((i) => Math.min(article.salesUnits.length - 1, i + 1));
      if (key.return) {
        const su = article.salesUnits[selectedSuIndex];
        if (su && article.salesUnits.length > 1) void handleRemoveSalesUnit(su);
      }
      if (key.escape) setMode('menu');
      return;
    }

    if (mode !== 'menu') return;
    if (key.upArrow) setSelectedAction((i) => Math.max(0, i - 1));
    if (key.downArrow) setSelectedAction((i) => Math.min(MENU_ITEMS.length - 1, i + 1));
    if (key.return) void handleAction();
    if (key.backspace || key.escape) back();
  });

  const handleAction = async () => {
    if (!article) return;
    const item = MENU_ITEMS[selectedAction];
    if (!item) return;

    switch (item.id) {
      case 'toggle-status':
        setMode('confirm-status');
        break;
      case 'add-sales-unit':
        navigate('article-add-sales-unit', { articleId: article.id });
        break;
      case 'remove-sales-unit':
        if (article.salesUnits.length > 1) {
          setSelectedSuIndex(0);
          setMode('select-sales-unit');
        }
        break;
      case 'back':
        back();
        break;
    }
  };

  const handleToggleStatus = useCallback(async () => {
    if (!article) return;
    setMode('menu');
    setActionLoading(true);
    const fn = article.status === 'ACTIVE' ? deactivateArticle : activateArticle;
    const updated = await fn(article.id);
    setActionLoading(false);
    if (updated) {
      setArticle(updated);
      setSuccessMessage(article.status === 'ACTIVE' ? 'Artikel deaktiviert.' : 'Artikel aktiviert.');
    }
  }, [article, activateArticle, deactivateArticle]);

  const handleRemoveSalesUnit = useCallback(async (su: SalesUnitDTO) => {
    if (!article) return;
    setMode('menu');
    setActionLoading(true);
    const updated = await removeSalesUnit(article.id, su.id);
    setActionLoading(false);
    if (updated) {
      setArticle(updated);
      setSuccessMessage(`Verkaufseinheit "${UNIT_LABELS[su.unit as Unit]}" entfernt.`);
    }
  }, [article, removeSalesUnit]);

  if (loading) return <LoadingSpinner label="Lade Artikel..." />;
  if (error && !article) return <ErrorDisplay message={error} onDismiss={back} />;
  if (!article) return <Text color="red">Artikel nicht gefunden.</Text>;

  const statusColor = article.status === 'ACTIVE' ? 'green' : 'red';

  return (
    <Box flexDirection="column" gap={1}>
      <Text color="cyan" bold>Artikel: {article.articleNumber} – {article.name}</Text>

      {error && <ErrorDisplay message={error} onDismiss={() => setError(null)} />}
      {successMessage && <SuccessDisplay message={successMessage} onDismiss={() => setSuccessMessage(null)} />}

      {/* Info-Box */}
      <Box flexDirection="column" borderStyle="round" borderColor="gray" paddingX={2} paddingY={1}>
        <Box gap={2}>
          <Text color="gray">Status:</Text>
          <Text color={statusColor} bold>{article.status}</Text>
        </Box>
        <Box gap={2}>
          <Text color="gray">Artikelnummer:</Text>
          <Text>{article.articleNumber}</Text>
        </Box>
        <Box gap={2}>
          <Text color="gray">Kategorie-ID:</Text>
          <Text>{article.categoryId}</Text>
        </Box>
        <Box flexDirection="column" marginTop={1}>
          <Text color="gray">Verkaufseinheiten ({article.salesUnits.length}):</Text>
          {article.salesUnits.map((su) => (
            <Box key={su.id} paddingLeft={2} gap={1}>
              <Text color="yellow">•</Text>
              <Text>{UNIT_LABELS[su.unit as Unit]}</Text>
              <Text color="gray">({PRICE_MODEL_LABELS[su.priceModel as PriceModel]})</Text>
              <Text color="green">{su.price.toFixed(2)} €</Text>
            </Box>
          ))}
        </Box>
        {article.supplierIds.length > 0 && (
          <Box gap={2} marginTop={1}>
            <Text color="gray">Lieferanten:</Text>
            <Text>{article.supplierIds.length} zugewiesen</Text>
          </Box>
        )}
      </Box>

      {/* Confirm Status */}
      {mode === 'confirm-status' && (
        <ConfirmDialog
          message={article.status === 'ACTIVE' ? 'Artikel deaktivieren?' : 'Artikel aktivieren?'}
          onConfirm={() => void handleToggleStatus()}
          onCancel={() => setMode('menu')}
        />
      )}

      {/* Select Sales Unit to Remove */}
      {mode === 'select-sales-unit' && (
        <Box flexDirection="column" gap={1}>
          <Text color="yellow">Verkaufseinheit entfernen:</Text>
          {article.salesUnits.map((su, i) => (
            <Box key={su.id}>
              <Text color={i === selectedSuIndex ? 'cyan' : 'white'}>
                {i === selectedSuIndex ? '▶ ' : '  '}
                {UNIT_LABELS[su.unit as Unit]} – {su.price.toFixed(2)} €
              </Text>
            </Box>
          ))}
          <Text color="gray" dimColor>↑↓ auswählen · Enter Entfernen · Escape Abbrechen</Text>
        </Box>
      )}

      {/* Action Menu */}
      {mode === 'menu' && (
        <Box flexDirection="column">
          <Text color="gray" bold>Aktionen:</Text>
          {actionLoading && <LoadingSpinner label="Aktion wird ausgeführt..." />}
          {!actionLoading && MENU_ITEMS.map((item, index) => (
            <Box key={item.id}>
              <Text color={index === selectedAction ? 'cyan' : 'white'}>
                {index === selectedAction ? '▶ ' : '  '}{item.label(article)}
              </Text>
            </Box>
          ))}
        </Box>
      )}

      <Box marginTop={1}>
        <Text color="gray" dimColor>↑↓ navigieren · Enter ausführen · Backspace Zurück</Text>
      </Box>
    </Box>
  );
}