import {
  Alert,
  Badge,
  Button,
  Card,
  Table,
  Tabs,
  Text,
} from "@mantine/core";
import { IconAlertTriangle, IconSeeding } from "@tabler/icons-react";
import { useMutation, useQuery, useQueryClient } from "@tanstack/react-query";
import { useTranslation } from "react-i18next";

import { Can } from "@/auth/Can";
import { HR_PERMS } from "@/auth/permissions";
import { apiErrorMessage } from "@/auth/http";
import { PageHeader } from "@/shared/components/PageHeader";
import { localized } from "@/shared/lib/localizedName";
import {
  listComponents,
  listStatutoryRates,
  listStructures,
  listTaxBrackets,
  seedPayrollStatutory,
} from "./api";
import { money } from "./components/PayslipView";

export function PayrollSettingsPage() {
  const queryClient = useQueryClient();
  const { i18n } = useTranslation();

  const components = useQuery({
    queryKey: ["payroll-components"],
    queryFn: listComponents,
  });
  const structures = useQuery({
    queryKey: ["payroll-structures"],
    queryFn: listStructures,
  });
  const brackets = useQuery({ queryKey: ["tax-brackets"], queryFn: listTaxBrackets });
  const rates = useQuery({ queryKey: ["statutory-rates"], queryFn: listStatutoryRates });

  const seed = useMutation({
    mutationFn: seedPayrollStatutory,
    onSuccess: () => {
      queryClient.invalidateQueries({ queryKey: ["payroll-components"] });
      queryClient.invalidateQueries({ queryKey: ["tax-brackets"] });
      queryClient.invalidateQueries({ queryKey: ["statutory-rates"] });
    },
  });

  return (
    <>
      <PageHeader
        title="Payroll settings"
        description="Components, structures and the statutory tables"
        actions={
          <Can permission={HR_PERMS.payroll.manageIncomeTaxTable}>
            <Button
              variant="default"
              leftSection={<IconSeeding size={16} />}
              loading={seed.isPending}
              onClick={() => seed.mutate()}
            >
              Seed statutory configuration
            </Button>
          </Can>
        }
      />

      {seed.isError && (
        <Alert color="red" mb="md" icon={<IconAlertTriangle size={18} />}>
          {apiErrorMessage(seed.error)}
        </Alert>
      )}
      {seed.data && (
        <Alert color="green" variant="light" mb="md">
          Components: {seed.data.components.created.length || "none"} added. Tax
          bands: {seed.data.taxBands}. Rates:{" "}
          {seed.data.rates.created.join(", ") || "none added"}.
        </Alert>
      )}

      <Tabs defaultValue="tax">
        <Tabs.List mb="md">
          <Tabs.Tab value="tax">Income tax</Tabs.Tab>
          <Tabs.Tab value="components">Components</Tabs.Tab>
          <Tabs.Tab value="structures">Structures</Tabs.Tab>
        </Tabs.List>

        <Tabs.Panel value="tax">
          {/* The single most important caveat in the module. These bands decide
              every employee's tax and this codebase cannot know whether a later
              schedule has been enacted. */}
          <Alert color="yellow" variant="light" mb="md" icon={<IconAlertTriangle size={18} />}>
            <Text size="sm" fw={600}>
              Verify these bands before running real payroll.
            </Text>
            <Text size="sm">
              They are seeded from Income Tax Proclamation 979/2016 and decide
              every employee's tax. The table is effective-dated, so a newer
              schedule is added as rows with a later start date — payslips for
              earlier months keep resolving the bands that applied to them.
            </Text>
          </Alert>

          <Card withBorder radius="md" p={0}>
            <Table striped verticalSpacing="sm">
              <Table.Thead>
                <Table.Tr>
                  <Table.Th>From</Table.Th>
                  <Table.Th>To</Table.Th>
                  <Table.Th ta="right">Rate</Table.Th>
                  <Table.Th ta="right">Less deduction</Table.Th>
                  <Table.Th>In force from</Table.Th>
                </Table.Tr>
              </Table.Thead>
              <Table.Tbody>
                {(brackets.data ?? []).map((band) => (
                  <Table.Tr key={band.id}>
                    <Table.Td>{money(band.lowerBound)}</Table.Td>
                    <Table.Td>
                      {band.upperBound ? money(band.upperBound) : "and above"}
                    </Table.Td>
                    <Table.Td ta="right">
                      {(Number(band.rate) * 100).toFixed(0)}%
                    </Table.Td>
                    <Table.Td ta="right">{money(band.deduction)}</Table.Td>
                    <Table.Td>
                      <Text size="xs" c="dimmed">
                        {band.effectiveFrom} · {band.statuteReference ?? "—"}
                      </Text>
                    </Table.Td>
                  </Table.Tr>
                ))}
                {(brackets.data ?? []).length === 0 && (
                  <Table.Tr>
                    <Table.Td colSpan={5}>
                      <Text size="sm" c="dimmed" ta="center" py="lg">
                        No bands configured — payroll cannot be calculated until
                        there are.
                      </Text>
                    </Table.Td>
                  </Table.Tr>
                )}
              </Table.Tbody>
            </Table>
          </Card>

          <Text size="sm" fw={600} mt="lg" mb="xs">
            Statutory rates
          </Text>
          <Card withBorder radius="md" p={0}>
            <Table striped verticalSpacing="sm">
              <Table.Tbody>
                {(rates.data ?? []).map((rate) => (
                  <Table.Tr key={rate.id}>
                    <Table.Td>
                      <Text size="sm">
                        {localized(rate.name, i18n.language) || rate.code}
                      </Text>
                    </Table.Td>
                    <Table.Td ta="right">
                      <Text size="sm" fw={600}>
                        {(Number(rate.rate) * 100).toFixed(0)}%
                      </Text>
                    </Table.Td>
                    <Table.Td>
                      <Text size="xs" c="dimmed">
                        {rate.statuteReference ?? "—"}
                      </Text>
                    </Table.Td>
                  </Table.Tr>
                ))}
              </Table.Tbody>
            </Table>
          </Card>
        </Tabs.Panel>

        <Tabs.Panel value="components">
          <Card withBorder radius="md" p={0}>
            <Table.ScrollContainer minWidth={860}>
              <Table striped verticalSpacing="sm">
                <Table.Thead>
                  <Table.Tr>
                    <Table.Th>Component</Table.Th>
                    <Table.Th>Type</Table.Th>
                    <Table.Th>How it is computed</Table.Th>
                    <Table.Th>Taxable</Table.Th>
                    <Table.Th>Pensionable</Table.Th>
                  </Table.Tr>
                </Table.Thead>
                <Table.Tbody>
                  {(components.data ?? []).map((component) => (
                    <Table.Tr key={component.id}>
                      <Table.Td>
                        <Text size="sm" fw={500}>
                          {localized(component.name, i18n.language) || component.code}
                        </Text>
                        <Text size="xs" c="dimmed">
                          {component.code}
                          {component.statuteReference && ` · ${component.statuteReference}`}
                        </Text>
                      </Table.Td>
                      <Table.Td>
                        <Badge
                          size="sm"
                          variant="light"
                          color={
                            component.componentType === "DEDUCTION"
                              ? "red"
                              : component.componentType === "EMPLOYER_CONTRIBUTION"
                                ? "gray"
                                : "green"
                          }
                        >
                          {component.componentType.replace("_", " ").toLowerCase()}
                        </Badge>
                      </Table.Td>
                      <Table.Td>
                        <Text size="xs">
                          {component.calculation === "STATUTORY"
                            ? "from the statutory table"
                            : component.calculation.replace(/_/g, " ").toLowerCase()}
                        </Text>
                        {component.taxExemptAmount && (
                          <Text size="xs" c="dimmed">
                            exempt to the lower of {money(component.taxExemptAmount)} and{" "}
                            {component.taxExemptRateOfBasic
                              ? `${(Number(component.taxExemptRateOfBasic) * 100).toFixed(0)}% of basic`
                              : "—"}
                          </Text>
                        )}
                      </Table.Td>
                      <Table.Td>
                        <Text size="sm">{component.isTaxable ? "yes" : "no"}</Text>
                      </Table.Td>
                      <Table.Td>
                        <Text size="sm">{component.isPensionable ? "yes" : "no"}</Text>
                      </Table.Td>
                    </Table.Tr>
                  ))}
                </Table.Tbody>
              </Table>
            </Table.ScrollContainer>
          </Card>
        </Tabs.Panel>

        <Tabs.Panel value="structures">
          <Card withBorder radius="md" p={0}>
            <Table striped verticalSpacing="sm">
              <Table.Thead>
                <Table.Tr>
                  <Table.Th>Structure</Table.Th>
                  <Table.Th>Lines</Table.Th>
                  <Table.Th>Active</Table.Th>
                </Table.Tr>
              </Table.Thead>
              <Table.Tbody>
                {(structures.data ?? []).map((structure) => (
                  <Table.Tr key={structure.id}>
                    <Table.Td>
                      <Text size="sm" fw={500}>
                        {localized(structure.name, i18n.language) || structure.code}
                      </Text>
                      <Text size="xs" c="dimmed">
                        {structure.code}
                      </Text>
                    </Table.Td>
                    <Table.Td>
                      <Text size="sm">{structure.lines?.length ?? "—"}</Text>
                    </Table.Td>
                    <Table.Td>
                      <Text size="sm">{structure.isActive ? "yes" : "no"}</Text>
                    </Table.Td>
                  </Table.Tr>
                ))}
                {(structures.data ?? []).length === 0 && (
                  <Table.Tr>
                    <Table.Td colSpan={3}>
                      <Text size="sm" c="dimmed" ta="center" py="lg">
                        No structures yet. Without one an employee is paid basic
                        plus the statutory lines only.
                      </Text>
                    </Table.Td>
                  </Table.Tr>
                )}
              </Table.Tbody>
            </Table>
          </Card>
        </Tabs.Panel>
      </Tabs>
    </>
  );
}