import { useState } from 'react';
import { Stack, Button, Modal, Text, TextInput, Textarea, Select, Card, Switch } from '@mantine/core';
import { useDisclosure } from '@mantine/hooks';
import { useTranslation } from 'react-i18next';
import {IconPlus} from '@tabler/icons-react';
import { AdvancedTable, ErrorState, ModalFooter, notify, PageHeader, useServerTable } from '@ema-platform/ui';
import { extractErrorMessage, useGetRanksQuery, useLocalized } from '@ema-platform/api';
import {
  useGetCertificationsQuery,
  useCreateCertificationMutation,
  useUpdateCertificationMutation,
  useDeleteCertificationMutation,
} from '../../api/certification-api';
import { type Certification } from '../../types/certification';
import { certificationColumns } from './columns';
import { certificationActionsColumn } from './actions';

interface CertificationFormValues {
  nameEn: string;
  nameAm: string;
  descEn: string;
  descAm: string;
  rankKey: string | null;
  isActive: boolean;
}

function CertificationForm({
  editing,
  rankOptions,
  isSubmitting,
  onSubmit,
  onCancel,
}: {
  editing: Certification | null;
  rankOptions: { value: string; label: string }[];
  isSubmitting: boolean;
  onSubmit: (values: CertificationFormValues, isEdit: boolean) => void;
  onCancel: () => void;
}) {
  const { t } = useTranslation();
  const [nameEn, setNameEn] = useState(editing?.name?.en ?? '');
  const [nameAm, setNameAm] = useState(editing?.name?.am ?? '');
  const [descEn, setDescEn] = useState(editing?.description?.en ?? '');
  const [descAm, setDescAm] = useState(editing?.description?.am ?? '');
  const [rankKey, setRankKey] = useState<string | null>(editing?.rankKey ?? null);
  const [isActive, setIsActive] = useState(editing?.isActive ?? true);

  const handleSubmit = (e: React.FormEvent) => {
    e.preventDefault();
    if (!nameEn.trim() || !nameAm.trim()) {
      notify.error(t('certification.validation.nameRequired', 'Both English and Amharic names are required'));
      return;
    }
    onSubmit({ nameEn: nameEn.trim(), nameAm: nameAm.trim(), descEn, descAm, rankKey, isActive }, !!editing);
  };

  return (
    <Modal opened onClose={onCancel} title={editing ? t('certification.update') : t('certification.add')} size="md">
      <form onSubmit={handleSubmit}>
        <Stack gap="sm">
          <TextInput label={t('certification.form.nameEn')} placeholder={t('certification.form.nameEnPlaceholder')} value={nameEn} onChange={(e) => setNameEn(e.currentTarget.value)} size="sm" required />
          <TextInput label={t('certification.form.nameAm')} placeholder={t('certification.form.nameAmPlaceholder')} value={nameAm} onChange={(e) => setNameAm(e.currentTarget.value)} size="sm" required />
          <Textarea label={t('certification.form.descEn')} placeholder={t('certification.form.descEnPlaceholder')} value={descEn} onChange={(e) => setDescEn(e.currentTarget.value)} size="sm" autosize minRows={2} />
          <Textarea label={t('certification.form.descAm')} placeholder={t('certification.form.descAmPlaceholder')} value={descAm} onChange={(e) => setDescAm(e.currentTarget.value)} size="sm" autosize minRows={2} />
          <Select
            label={t('certification.form.rankKey', 'STCW rank (for exam scheduling)')}
            description={t('certification.form.rankKeyHint', 'Leave blank if this certification is not part of the examined CoC/CoP ladder.')}
            placeholder={t('certification.form.rankKeyPlaceholder', 'Not rank-specific')}
            data={rankOptions}
            value={rankKey}
            onChange={setRankKey}
            size="sm"
            clearable
            searchable
          />
          {editing && (
            <Switch
              label={t('certification.form.isActive', 'Active')}
              description={t(
                'certification.form.isActiveHint',
                'Inactive certifications stay on existing exams but are not offered for new ones.',
              )}
              checked={isActive}
              onChange={(e) => setIsActive(e.currentTarget.checked)}
              size="sm"
            />
          )}
          <ModalFooter>
            <Button variant="default" onClick={onCancel} size="sm">{t('certification.cancel')}</Button>
            <Button type="submit" size="sm" loading={isSubmitting}>{editing ? t('certification.update') : t('certification.create')}</Button>
          </ModalFooter>
        </Stack>
      </form>
    </Modal>
  );
}

export function CertificationPage() {
  const { t, i18n } = useTranslation();
  const locale = i18n.language as 'en' | 'am';
  const localized = useLocalized();
  // Server refusals (`rank_not_found`, `certification_in_use`) arrive as
  // codes; this maps them to the sentences the administrator can act on.
  const showError = (e: unknown) => notify.error(extractErrorMessage(e, t('certification.error')));
  const { data, isFetching, isError, refetch } = useGetCertificationsQuery();
  const { data: rankRes } = useGetRanksQuery();
  const rankOptions = (rankRes?.items ?? []).map((r) => ({ value: r.key, label: localized(r.name) }));
  const { setPageIndex, pageSize, setPageSize, paginate } = useServerTable();
  const [createCert, { isLoading: isCreating }] = useCreateCertificationMutation();
  const [updateCert, { isLoading: isUpdating }] = useUpdateCertificationMutation();
  const [deleteCert] = useDeleteCertificationMutation();

  const certifications = data?.items ?? [];

  const [editing, setEditing] = useState<Certification | null>(null);
  const [showForm, setShowForm] = useState(false);
  const [deleteTarget, setDeleteTarget] = useState<Certification | null>(null);
  const [deleteOpened, { open: openDelete, close: closeDelete }] = useDisclosure(false);

  const resetForm = () => {
    setEditing(null);
    setShowForm(false);
  };

  const handleSubmit = async (values: CertificationFormValues, isEdit: boolean) => {
    const name = { en: values.nameEn, am: values.nameAm };
    const description = { en: values.descEn, am: values.descAm };
    try {
      if (isEdit && editing) {
        // null clears a previously-set rank; undefined would leave it
        // untouched server-side, so the two are not interchangeable here.
        await updateCert({ id: editing.id, name, description, rankKey: values.rankKey, isActive: values.isActive }).unwrap();
        notify.success(t('certification.updated'));
      } else {
        await createCert({ name, description, rankKey: values.rankKey ?? undefined }).unwrap();
        notify.success(t('certification.created'));
      }
      resetForm();
    } catch (e) {
      showError(e);
    }
  };

  const handleDelete = async () => {
    if (!deleteTarget) return;
    try {
      await deleteCert(deleteTarget.id).unwrap();
      notify.success(t('certification.deleted'));
      closeDelete();
      setDeleteTarget(null);
    } catch (e) {
      showError(e);
    }
  };

  if (isError)
    return <ErrorState title={t('certification.loadError')} onRetry={refetch} />;

  const columns = [
    ...certificationColumns(t, locale),
    certificationActionsColumn(t, {
      onEdit: (cert) => { setEditing(cert); setShowForm(true); },
      onDelete: (cert) => { setDeleteTarget(cert); openDelete(); },
    }),
  ];

  const page = paginate(certifications);

  return (
    <Stack gap="lg">
      <PageHeader
        title={t('certification.title')}
        subtitle={t('certification.subtitle')}
        noMargin
        action={
          !showForm && (
            <Button variant="light" leftSection={<IconPlus size={16} />} onClick={() => setShowForm(true)} size="sm">
              {t('certification.add')}
            </Button>
          )
        }
      />

      {showForm && (
        <CertificationForm
          editing={editing}
          rankOptions={rankOptions}
          isSubmitting={isCreating || isUpdating}
          onSubmit={handleSubmit}
          onCancel={resetForm}
        />
      )}

      <Card withBorder padding={0}>
        <AdvancedTable
          columns={columns}
          data={page.rows}
          tableName={t('certification.title')}
          itemCount={page.itemCount}
          pageIndex={page.pageIndex}
          onPageChange={setPageIndex}
          pageSize={pageSize}
          onPageSizeChange={setPageSize}
          refresh={refetch}
          isLoading={isFetching}
          emptyText={t('certification.noItems')}
        />
      </Card>

      <Modal opened={deleteOpened} onClose={closeDelete} title={t('certification.confirmDelete')} size="sm">
        <Text mb="md">{t('certification.deleteConfirmText', { name: deleteTarget ? localized(deleteTarget.name) : '' })}</Text>
        <ModalFooter>
          <Button variant="default" onClick={closeDelete} size="sm">{t('certification.cancel')}</Button>
          <Button color="red" onClick={handleDelete} size="sm">{t('certification.delete')}</Button>
        </ModalFooter>
      </Modal>
    </Stack>
  );
}