import { useEffect, useState } from 'react';
import { Button, Divider, Drawer, NumberInput, Stack, Text, TextInput } from '@mantine/core';
import { useTranslation } from 'react-i18next';
import { BilingualInput, ModalFooter } from '@ema-platform/ui';
import type { FormSchemaPalette, FormSectionConfig } from '@ema-platform/api';
import { ConditionBuilder, type ConditionValue } from './ConditionBuilder';
import type { ConditionTarget } from '../config/schema-paths';

const KEY_PATTERN = /^[A-Za-z][A-Za-z0-9_]*$/;

function emptySection(): FormSectionConfig {
  return { key: '', title: { en: '', am: '' }, fields: [] };
}

/** Adds/edits one section's own metadata — its fields are managed on the list, not here. */
export function SectionEditorDrawer({
  opened,
  onClose,
  section,
  onSave,
  palette,
  conditionTargets,
}: {
  opened: boolean;
  onClose: () => void;
  /** Null = adding a new section. */
  section: FormSectionConfig | null;
  onSave: (section: Omit<FormSectionConfig, 'fields'>) => void;
  palette: FormSchemaPalette | undefined;
  conditionTargets: ConditionTarget[];
}) {
  const { t } = useTranslation();
  const [draft, setDraft] = useState<FormSectionConfig>(emptySection());
  const [keyError, setKeyError] = useState<string | null>(null);
  const isNew = !section;

  useEffect(() => {
    if (opened) {
      setDraft(section ? { ...section, title: { ...section.title } } : emptySection());
      setKeyError(null);
    }
  }, [opened, section]);

  function save() {
    if (!draft.key.trim() || !KEY_PATTERN.test(draft.key.trim())) {
      setKeyError(t('certReq.section.keyInvalid', 'Key must start with a letter and contain only letters, numbers, underscores'));
      return;
    }
    if (!draft.title.en?.trim()) return;
    const { fields: _fields, ...meta } = draft;
    onSave({ ...meta, key: draft.key.trim() });
  }

  return (
    <Drawer
      opened={opened}
      onClose={onClose}
      position="right"
      size="md"
      title={<Text fw={700}>{isNew ? t('certReq.section.add', 'Add section') : t('certReq.section.edit', 'Edit section')}</Text>}
    >
      <Stack gap="md">
        <TextInput
          label={t('certReq.section.key', 'Section key')}
          placeholder="certificate"
          required
          value={draft.key}
          error={keyError}
          disabled={!isNew}
          description={
            isNew
              ? t('certReq.section.keyHelp', 'Letters, numbers and underscores only')
              : t('certReq.section.keyLocked', 'Key cannot change once created')
          }
          onChange={(e) => {
            const { value } = e.currentTarget;
            setDraft((d) => ({ ...d, key: value }));
          }}
        />

        <BilingualInput
          label={t('certReq.section.title', 'Title')}
          required
          value={{ en: draft.title.en ?? '', am: draft.title.am ?? '' }}
          onChange={(v) => setDraft((d) => ({ ...d, title: v }))}
        />

        <BilingualInput
          label={t('certReq.section.description', 'Description')}
          value={{ en: draft.description?.en ?? '', am: draft.description?.am ?? '' }}
          onChange={(v) => setDraft((d) => ({ ...d, description: v }))}
        />

        <TextInput
          label={t('certReq.section.group', 'Wizard step group')}
          description={t(
            'certReq.section.groupHelp',
            'Sections sharing the same group render together on one step',
          )}
          value={draft.group ?? ''}
          onChange={(e) => {
            const { value } = e.currentTarget;
            setDraft((d) => ({ ...d, group: value || undefined }));
          }}
        />

        <NumberInput
          label={t('certReq.section.groupOrder', 'Group order')}
          value={draft.groupOrder ?? ''}
          onChange={(v) => setDraft((d) => ({ ...d, groupOrder: typeof v === 'number' ? v : undefined }))}
        />

        <NumberInput
          label={t('certReq.section.sortOrder', 'Sort order')}
          value={draft.sortOrder ?? ''}
          onChange={(v) => setDraft((d) => ({ ...d, sortOrder: typeof v === 'number' ? v : undefined }))}
        />

        <Divider label={t('certReq.condition.title', 'Visibility condition')} labelPosition="left" />
        <ConditionBuilder
          value={(draft.showWhen ?? null) as ConditionValue | null}
          onChange={(v) => setDraft((d) => ({ ...d, showWhen: v ?? undefined }))}
          targets={conditionTargets}
          palette={palette}
        />

        <ModalFooter>
          <Button variant="default" onClick={onClose}>{t('certReq.cancel', 'Cancel')}</Button>
          <Button color="teal" onClick={save}>
            {isNew ? t('certReq.section.add', 'Add section') : t('certReq.saveChanges', 'Save changes')}
          </Button>
        </ModalFooter>
      </Stack>
    </Drawer>
  );
}