/**
 * HistoryDiff — Visual diff table of field changes for an entity history entry.
 * Shows old value (red strikethrough) → new value (green) per field.
 */

import React from 'react';
import clsx from 'clsx';
import { ArrowRight } from 'lucide-react';
import { useTranslation } from 'react-i18next';

export interface HistoryDiffProps {
  changes: Record<string, { old: any; new: any }>;
  className?: string;
}

/**
 * Format a value for display, handling null/undefined gracefully.
 */
function formatValue(value: any): string {
  if (value === null || value === undefined) {
    return '—';
  }
  if (typeof value === 'boolean') {
    return value ? 'true' : 'false';
  }
  if (typeof value === 'object') {
    try {
      return JSON.stringify(value);
    } catch {
      return String(value);
    }
  }
  return String(value);
}

export function HistoryDiff({ changes, className }: HistoryDiffProps) {
  const { t } = useTranslation();
  const entries = Object.entries(changes);

  if (entries.length === 0) {
    return (
      <p className="text-sm text-secondary-500 italic">
        {t('entityHistory.noChanges', 'Keine Änderungen')}
      </p>
    );
  }

  return (
    <div className={clsx('overflow-x-auto', className)}>
      <table className="w-full text-sm border-collapse">
        <thead>
          <tr className="border-b border-secondary-200">
            <th className="text-left font-medium text-secondary-600 py-2 pr-4">
              {t('entityHistory.field', 'Feld')}
            </th>
            <th className="text-left font-medium text-secondary-600 py-2 pr-4">
              {t('entityHistory.oldValue', 'Alter Wert')}
            </th>
            <th className="w-8 py-2" aria-hidden="true" />
            <th className="text-left font-medium text-secondary-600 py-2">
              {t('entityHistory.newValue', 'Neuer Wert')}
            </th>
          </tr>
        </thead>
        <tbody>
          {entries.map(([field, change]) => {
            const oldDisplay = formatValue(change.old);
            const newDisplay = formatValue(change.new);
            const isOldEmpty = change.old === null || change.old === undefined;
            const isNewEmpty = change.new === null || change.new === undefined;

            return (
              <tr key={field} className="border-b border-secondary-100 last:border-0">
                <td className="py-2 pr-4 font-medium text-secondary-700">
                  {field}
                </td>
                <td
                  className={clsx(
                    'py-2 pr-4',
                    isOldEmpty
                      ? 'text-secondary-400 italic'
                      : 'text-danger-700 line-through'
                  )}
                >
                  {oldDisplay}
                </td>
                <td className="py-2 text-center text-secondary-400">
                  <ArrowRight className="inline h-3.5 w-3.5" aria-hidden="true" />
                </td>
                <td
                  className={clsx(
                    'py-2',
                    isNewEmpty
                      ? 'text-secondary-400 italic'
                      : 'text-success-700 font-medium'
                  )}
                >
                  {newDisplay}
                </td>
              </tr>
            );
          })}
        </tbody>
      </table>
    </div>
  );
}