import { useEffect, useState } from 'react';
import { ActionIcon, Alert, Button, Checkbox, Group, Loader, Stack, Text, TextInput } from '@mantine/core';
import { useTranslation } from 'react-i18next';
import { IconGripVertical, IconInfoCircle, IconPlus, IconTrash } from '@tabler/icons-react';
import { notify, useErrorHandler } from '@ema-platform/ui';
import type { BilingualValue } from '@ema-platform/ui';
import {
  useGetQuestionWithOptionsQuery,
  useSetQuestionOptionsMutation,
} from '../api/question-api';

interface DraftOption {
  text: BilingualValue;
  isCorrect: boolean;
}

/**
 * MCQ options + correct-answer editor for a CHOICE-form question (Phase 2).
 *
 * Only reachable while editing an already-created question — options attach
 * to a question id, matching the backend's `PUT /questions/:id/options`
 * full-replace endpoint. Nothing here is ever shown to a candidate; this is
 * the authoring side only.
 */
export function QuestionOptionsEditor({ questionId }: { questionId: string }) {
  const { t } = useTranslation();
  const { handleError } = useErrorHandler();
  const { data: question, isFetching } = useGetQuestionWithOptionsQuery(questionId);
  const [setOptions, { isLoading: isSaving }] = useSetQuestionOptionsMutation();
  const [draft, setDraft] = useState<DraftOption[]>([]);

  useEffect(() => {
    if (!question) return;
    const existing = question.options ?? [];
    setDraft(
      existing.length
        ? existing
            .slice()
            .sort((a, b) => a.order - b.order)
            .map((o) => ({ text: o.text, isCorrect: false }))
        : [
            { text: { en: '', am: '' }, isCorrect: false },
            { text: { en: '', am: '' }, isCorrect: false },
          ],
    );
    // isCorrect never comes back from the API by design — an examiner
    // re-editing options re-marks the correct one(s) rather than us
    // pretending to know what they were.
  }, [question]);

  const updateField = (index: number, lang: keyof BilingualValue, value: string) => {
    setDraft((prev) =>
      prev.map((o, i) => (i === index ? { ...o, text: { ...o.text, [lang]: value } } : o)),
    );
  };

  const toggleCorrect = (index: number) => {
    setDraft((prev) => prev.map((o, i) => (i === index ? { ...o, isCorrect: !o.isCorrect } : o)));
  };

  const addOption = () => {
    setDraft((prev) => [...prev, { text: { en: '', am: '' }, isCorrect: false }]);
  };

  const removeOption = (index: number) => {
    setDraft((prev) => prev.filter((_, i) => i !== index));
  };

  const handleSave = async () => {
    if (draft.length < 2) {
      notify.error(t('question.options.needAtLeastTwo'));
      return;
    }
    if (!draft.some((o) => o.isCorrect)) {
      notify.error(t('question.options.needOneCorrect'));
      return;
    }
    if (draft.some((o) => !o.text.en.trim() || !o.text.am.trim())) {
      notify.error(t('question.options.textRequired'));
      return;
    }
    try {
      await setOptions({ id: questionId, options: draft }).unwrap();
      notify.success(t('question.options.saved'));
    } catch (e) {
      handleError(e);
    }
  };

  if (isFetching) return <Loader size="sm" />;

  return (
    <Stack gap="sm">
      <Alert icon={<IconInfoCircle size={15} />} color="blue" variant="light">
        {t('question.options.hint')}
      </Alert>
      {draft.map((option, index) => (
        <Group key={index} gap="xs" wrap="nowrap" align="center">
          <IconGripVertical size={16} style={{ opacity: 0.4 }} />
          <Stack gap={6} style={{ flex: 1 }}>
            <TextInput
              label={t('question.options.optionEn', { number: index + 1 })}
              value={option.text.en}
              onChange={(e) => updateField(index, 'en', e.currentTarget.value)}
              size="sm"
              required
            />
            <TextInput
              label={t('question.options.optionAm', { number: index + 1 })}
              value={option.text.am}
              onChange={(e) => updateField(index, 'am', e.currentTarget.value)}
              size="sm"
              required
            />
          </Stack>
          <Checkbox
            label={t('question.options.correct')}
            checked={option.isCorrect}
            onChange={() => toggleCorrect(index)}
          />
          <ActionIcon
            variant="subtle"
            color="red"
            size="sm"
            disabled={draft.length <= 2}
            onClick={() => removeOption(index)}
          >
            <IconTrash size={14} />
          </ActionIcon>
        </Group>
      ))}
      <Group justify="space-between">
        <Button variant="subtle" size="xs" leftSection={<IconPlus size={14} />} onClick={addOption}>
          {t('question.options.addOption')}
        </Button>
        <Button size="sm" loading={isSaving} onClick={handleSave}>
          {t('question.options.save')}
        </Button>
      </Group>
      <Text fz="xs" c="dimmed">{t('question.options.replaceNotice')}</Text>
    </Stack>
  );
}