import { useState } from 'react';
import {
  Title, Text, Card, Table, Group, Stack, Badge, Loader, Center,
  Button, NumberInput,
} from '@mantine/core';
import { IconPrinter } from '@tabler/icons-react';
import { useQuery } from '@tanstack/react-query';
import api from '../../services/api';

interface ProjectItem {
  id: string;
  name: string;
  description: string;
  category: string;
  estimated_cost: number;
  target_year: number | null;
  useful_life_years: number | null;
  last_replacement_date: string | null;
  fund_source: string;
  status: string;
  priority: number;
  condition_rating: number | null;
  year_amounts: Record<number, number>;
  beyond: number;
}

interface CategoryGroup {
  category: string;
  projects: ProjectItem[];
}

interface CapitalPlanningData {
  title: string;
  start_year: number;
  years: number[];
  categories: CategoryGroup[];
  year_totals: Record<number, number>;
  beyond_total: number;
  grand_total: number;
  generated_at: string;
}

const fmt = (v: number) =>
  v === 0 ? '-' : v.toLocaleString('en-US', { style: 'currency', currency: 'USD', maximumFractionDigits: 0 });

export function CapitalPlanningPage() {
  const [startYear, setStartYear] = useState(new Date().getFullYear());

  const { data, isLoading } = useQuery<CapitalPlanningData>({
    queryKey: ['capital-planning', startYear],
    queryFn: async () => {
      const { data } = await api.get(`/reports/capital-planning?startYear=${startYear}`);
      return data;
    },
  });

  if (isLoading) return <Center h={300}><Loader /></Center>;

  const years = data?.years || [];
  const hasProjects = (data?.categories || []).some((c) => c.projects.length > 0);

  return (
    <Stack>
      <Group justify="space-between">
        <div>
          <Title order={2}>Capital Planning Report</Title>
          <Text c="dimmed" size="sm">{data?.title || '5-Year Capital Project Forecast'}</Text>
        </div>
        <Group>
          <NumberInput
            size="xs"
            w={100}
            value={startYear}
            onChange={(v) => v && setStartYear(Number(v))}
            min={2020}
            max={2050}
          />
          <Button
            variant="light"
            leftSection={<IconPrinter size={16} />}
            onClick={() => window.print()}
          >
            Print / PDF
          </Button>
        </Group>
      </Group>

      {!hasProjects ? (
        <Card withBorder p="xl">
          <Text ta="center" c="dimmed" py="lg">
            No capital projects found. Add projects on the Projects page to generate this report.
          </Text>
        </Card>
      ) : (
        <Card withBorder p="lg" className="capital-planning-print">
          <Title order={3} ta="center" mb="xs">{data?.title}</Title>
          <Text ta="center" c="dimmed" size="sm" mb="md">
            Generated {new Date(data?.generated_at || '').toLocaleDateString()}
          </Text>

          <Table striped withTableBorder withColumnBorders>
            <Table.Thead>
              <Table.Tr>
                <Table.Th>Description</Table.Th>
                <Table.Th ta="center" w={60}>Life (yr)</Table.Th>
                <Table.Th ta="center" w={90}>Last Done</Table.Th>
                {years.map((y) => (
                  <Table.Th key={y} ta="right" w={100}>{y}</Table.Th>
                ))}
                <Table.Th ta="right" w={100}>Beyond</Table.Th>
              </Table.Tr>
            </Table.Thead>
            <Table.Tbody>
              {(data?.categories || []).map((cat) => {
                const catTotals: Record<number, number> = {};
                let catBeyond = 0;
                for (const y of years) catTotals[y] = 0;
                for (const p of cat.projects) {
                  for (const y of years) catTotals[y] += p.year_amounts[y] || 0;
                  catBeyond += p.beyond;
                }

                return [
                  <Table.Tr key={`cat-${cat.category}`} style={{ background: 'var(--mantine-color-blue-0)' }}>
                    <Table.Td colSpan={3 + years.length + 1}>
                      <Text fw={700} size="sm">{cat.category}</Text>
                    </Table.Td>
                  </Table.Tr>,
                  ...cat.projects.map((p) => (
                    <Table.Tr key={p.id}>
                      <Table.Td>
                        <Text size="sm">{p.name}</Text>
                        {p.status !== 'planned' && (
                          <Badge size="xs" variant="light" ml={4}
                            color={p.status === 'completed' ? 'green' : p.status === 'in_progress' ? 'blue' : 'gray'}>
                            {p.status}
                          </Badge>
                        )}
                      </Table.Td>
                      <Table.Td ta="center">
                        <Text size="sm">{p.useful_life_years || '-'}</Text>
                      </Table.Td>
                      <Table.Td ta="center">
                        <Text size="sm">
                          {p.last_replacement_date
                            ? new Date(p.last_replacement_date).getFullYear()
                            : '-'}
                        </Text>
                      </Table.Td>
                      {years.map((y) => (
                        <Table.Td key={y} ta="right" ff="monospace">
                          <Text size="sm">{fmt(p.year_amounts[y] || 0)}</Text>
                        </Table.Td>
                      ))}
                      <Table.Td ta="right" ff="monospace">
                        <Text size="sm">{fmt(p.beyond)}</Text>
                      </Table.Td>
                    </Table.Tr>
                  )),
                  <Table.Tr key={`subtotal-${cat.category}`} style={{ borderTop: '2px solid var(--mantine-color-gray-4)' }}>
                    <Table.Td colSpan={3}>
                      <Text size="sm" fw={600} fs="italic">Subtotal — {cat.category}</Text>
                    </Table.Td>
                    {years.map((y) => (
                      <Table.Td key={y} ta="right" ff="monospace">
                        <Text size="sm" fw={600}>{fmt(catTotals[y])}</Text>
                      </Table.Td>
                    ))}
                    <Table.Td ta="right" ff="monospace">
                      <Text size="sm" fw={600}>{fmt(catBeyond)}</Text>
                    </Table.Td>
                  </Table.Tr>,
                ];
              })}
            </Table.Tbody>
            <Table.Tfoot>
              <Table.Tr style={{ background: 'var(--mantine-color-dark-0)' }}>
                <Table.Td colSpan={3}>
                  <Text fw={700}>TOTAL</Text>
                </Table.Td>
                {years.map((y) => (
                  <Table.Td key={y} ta="right" ff="monospace">
                    <Text fw={700}>{fmt(data?.year_totals[y] || 0)}</Text>
                  </Table.Td>
                ))}
                <Table.Td ta="right" ff="monospace">
                  <Text fw={700}>{fmt(data?.beyond_total || 0)}</Text>
                </Table.Td>
              </Table.Tr>
            </Table.Tfoot>
          </Table>
        </Card>
      )}
    </Stack>
  );
}