import React, { useState, useCallback } from 'react';
import { useTranslation } from 'react-i18next';
import { useForm } from 'react-hook-form';
import { zodResolver } from '@hookform/resolvers/zod';
import { z } from 'zod';
import { apiGet, apiPost, apiPatch, apiDelete } from '@/api/client';

interface Sequence {
  id: string;
  name: string;
  prefix: string;
  next_number: number;
  padding: number;
}

// ── Zod Schema ──
const sequenceSchema = z.object({
  name: z.string().min(1, 'required'),
  prefix: z.string().optional().default(''),
  padding: z.coerce.number().int().min(1, 'invalidNumber').max(10, 'invalidNumber'),
});

type SequenceFormData = z.infer<typeof sequenceSchema>;

export function SettingsSequencesPage() {
  const { t } = useTranslation();
  const [sequences, setSequences] = useState<Sequence[]>([]);
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState<string | null>(null);
  const [showForm, setShowForm] = useState(false);
  const [editing, setEditing] = useState<Sequence | null>(null);

  const {
    register,
    handleSubmit,
    reset,
    formState: { errors, isSubmitting },
  } = useForm<SequenceFormData>({
    resolver: zodResolver(sequenceSchema),
    defaultValues: { name: '', prefix: '', padding: 4 },
  });

  const fetchSequences = useCallback(async () => {
    setLoading(true);
    setError(null);
    try {
      const data = await apiGet<{ items: Sequence[]; total: number }>('/sequences');
      setSequences(data.items);
    } catch (err: any) {
      setError(err.message || t('common.error'));
    } finally {
      setLoading(false);
    }
  }, [t]);

  React.useEffect(() => { fetchSequences(); }, [fetchSequences]);

  const onSubmit = async (data: SequenceFormData) => {
    try {
      if (editing) {
        await apiPatch(`/sequences/${editing.id}`, data);
      } else {
        await apiPost('/sequences', data);
      }
      setShowForm(false);
      setEditing(null);
      reset({ name: '', prefix: '', padding: 4 });
      await fetchSequences();
    } catch (err: any) {
      setError(err.message || t('common.error'));
    }
  };

  const handleDelete = async (id: string) => {
    if (!window.confirm(t('sequences.confirmDelete'))) return;
    try {
      await apiDelete(`/sequences/${id}`);
      await fetchSequences();
    } catch (err: any) {
      setError(err.message || t('common.error'));
    }
  };

  const handleEdit = (seq: Sequence) => {
    setEditing(seq);
    reset({ name: seq.name, prefix: seq.prefix, padding: seq.padding });
    setShowForm(true);
  };

  const handleNew = () => {
    setEditing(null);
    reset({ name: '', prefix: '', padding: 4 });
    setShowForm(true);
  };

  const errorMsg = (key: string | undefined) => {
    if (!key) return undefined;
    if (key === 'required') return t('validation.required');
    if (key === 'invalidNumber') return t('validation.invalidNumber', 'Invalid number');
    return key;
  };

  if (loading) return <div className="text-secondary-500">{t('common.loading')}</div>;

  return (
    <div className="space-y-6" data-testid="settings-sequences">
      <div className="flex items-center justify-between">
        <h1 className="text-2xl font-bold text-secondary-900">{t('sequences.title')}</h1>
        <button
          onClick={handleNew}
          className="px-4 py-2 text-sm font-medium text-white bg-primary-600 rounded-lg hover:bg-primary-700"
        >
          {t('sequences.add')}
        </button>
      </div>

      {error && <div className="p-3 text-sm text-red-700 bg-red-50 rounded-lg">{error}</div>}

      {showForm && (
        <form onSubmit={handleSubmit(onSubmit)} className="p-4 border border-secondary-200 rounded-lg space-y-3">
          <div>
            <label className="block text-sm font-medium text-secondary-700">{t('sequences.name')}</label>
            <input type="text" {...register('name')} className="mt-1 block w-full rounded-md border border-secondary-300 px-3 py-1.5 text-sm" />
            {errors.name && <p className="text-xs text-danger-600 mt-1">{errorMsg(errors.name.message)}</p>}
          </div>
          <div className="grid grid-cols-2 gap-3">
            <div>
              <label className="block text-sm font-medium text-secondary-700">{t('sequences.prefix')}</label>
              <input type="text" {...register('prefix')} placeholder="RE-" className="mt-1 block w-full rounded-md border border-secondary-300 px-3 py-1.5 text-sm" />
              {errors.prefix && <p className="text-xs text-danger-600 mt-1">{errorMsg(errors.prefix.message)}</p>}
            </div>
            <div>
              <label className="block text-sm font-medium text-secondary-700">{t('sequences.padding')}</label>
              <input type="number" min={1} max={10} {...register('padding')} className="mt-1 block w-full rounded-md border border-secondary-300 px-3 py-1.5 text-sm" />
              {errors.padding && <p className="text-xs text-danger-600 mt-1">{errorMsg(errors.padding.message)}</p>}
            </div>
          </div>
          <div className="flex justify-end gap-2">
            <button type="button" onClick={() => { setShowForm(false); setEditing(null); }} className="px-3 py-1.5 text-sm font-medium text-secondary-700 bg-secondary-100 rounded-lg hover:bg-secondary-200">{t('common.cancel')}</button>
            <button type="submit" disabled={isSubmitting} className="px-3 py-1.5 text-sm font-medium text-white bg-primary-600 rounded-lg hover:bg-primary-700">{t('common.save')}</button>
          </div>
        </form>
      )}

      <div className="overflow-hidden border border-secondary-200 rounded-lg">
        <table className="min-w-full divide-y divide-secondary-200">
          <thead className="bg-secondary-50">
            <tr>
              <th className="px-4 py-2 text-left text-xs font-medium text-secondary-500 uppercase">{t('sequences.name')}</th>
              <th className="px-4 py-2 text-left text-xs font-medium text-secondary-500 uppercase">{t('sequences.prefix')}</th>
              <th className="px-4 py-2 text-left text-xs font-medium text-secondary-500 uppercase">{t('sequences.nextNumber')}</th>
              <th className="px-4 py-2 text-left text-xs font-medium text-secondary-500 uppercase">{t('sequences.padding')}</th>
              <th className="px-4 py-2"></th>
            </tr>
          </thead>
          <tbody className="divide-y divide-secondary-200">
            {sequences.map((seq) => (
              <tr key={seq.id}>
                <td className="px-4 py-2 text-sm text-secondary-900">{seq.name}</td>
                <td className="px-4 py-2 text-sm text-secondary-900">{seq.prefix}</td>
                <td className="px-4 py-2 text-sm text-secondary-900">{seq.next_number}</td>
                <td className="px-4 py-2 text-sm text-secondary-900">{seq.padding}</td>
                <td className="px-4 py-2 text-sm text-right">
                  <button onClick={() => handleEdit(seq)} className="text-secondary-600 hover:underline mr-3">{t('common.edit')}</button>
                  <button onClick={() => handleDelete(seq.id)} className="text-red-600 hover:underline">{t('common.delete')}</button>
                </td>
              </tr>
            ))}
          </tbody>
        </table>
      </div>
    </div>
  );
}