import { useState, useEffect, useCallback } from 'react';
import {
  Title,
  Text,
  Stack,
  Card,
  SimpleGrid,
  Group,
  Button,
  Table,
  Badge,
  Loader,
  Center,
  Alert,
  ThemeIcon,
  Divider,
  Accordion,
  Paper,
  Tabs,
  Collapse,
  ActionIcon,
} from '@mantine/core';
import {
  IconBulb,
  IconCash,
  IconBuildingBank,
  IconChartAreaLine,
  IconAlertTriangle,
  IconSparkles,
  IconRefresh,
  IconCoin,
  IconPigMoney,
  IconChevronDown,
  IconChevronUp,
} from '@tabler/icons-react';
import { useQuery } from '@tanstack/react-query';
import { notifications } from '@mantine/notifications';
import api from '../../services/api';

// ── Types ──

interface FinancialSummary {
  operating_cash: number;
  reserve_cash: number;
  operating_investments: number;
  reserve_investments: number;
  total_operating: number;
  total_reserve: number;
  total_all: number;
}

interface FinancialSnapshot {
  summary: FinancialSummary;
  investment_accounts: Array<{
    id: string;
    name: string;
    institution: string;
    investment_type: string;
    fund_type: string;
    principal: string;
    interest_rate: string;
    maturity_date: string | null;
    current_value: string;
  }>;
}

interface MarketRate {
  bank_name: string;
  apy: string;
  min_deposit: string | null;
  term: string;
  term_months: number | null;
  rate_type: string;
  fetched_at: string;
}

interface MarketRatesResponse {
  cd: MarketRate[];
  money_market: MarketRate[];
  high_yield_savings: MarketRate[];
}

interface Recommendation {
  type: string;
  priority: 'high' | 'medium' | 'low';
  title: string;
  summary: string;
  details: string;
  fund_type: string;
  suggested_amount?: number;
  suggested_term?: string;
  suggested_rate?: number;
  bank_name?: string;
  rationale: string;
}

interface AIResponse {
  recommendations: Recommendation[];
  overall_assessment: string;
  risk_notes: string[];
}

interface SavedRecommendation {
  id: string;
  recommendations: Recommendation[];
  overall_assessment: string;
  risk_notes: string[];
  response_time_ms: number;
  created_at: string;
  status: 'processing' | 'complete' | 'error';
  last_failed: boolean;
  error_message?: string;
}

// ── Helpers ──

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

const priorityColors: Record<string, string> = {
  high: 'red',
  medium: 'yellow',
  low: 'blue',
};

const typeIcons: Record<string, any> = {
  cd_ladder: IconChartAreaLine,
  new_investment: IconBuildingBank,
  reallocation: IconRefresh,
  maturity_action: IconCash,
  liquidity_warning: IconAlertTriangle,
  general: IconBulb,
};

const typeLabels: Record<string, string> = {
  cd_ladder: 'CD Ladder',
  new_investment: 'New Investment',
  reallocation: 'Reallocation',
  maturity_action: 'Maturity Action',
  liquidity_warning: 'Liquidity',
  general: 'General',
};

// ── Rate Table Component ──

function RateTable({ rates, showTerm }: { rates: MarketRate[]; showTerm: boolean }) {
  if (rates.length === 0) {
    return (
      <Text ta="center" c="dimmed" py="lg">
        No rates available. Run the market rate fetcher to populate data.
      </Text>
    );
  }

  return (
    <Table striped highlightOnHover>
      <Table.Thead>
        <Table.Tr>
          <Table.Th>Bank</Table.Th>
          <Table.Th ta="right">APY</Table.Th>
          {showTerm && <Table.Th>Term</Table.Th>}
          <Table.Th ta="right">Min Deposit</Table.Th>
        </Table.Tr>
      </Table.Thead>
      <Table.Tbody>
        {rates.map((r, i) => (
          <Table.Tr key={i}>
            <Table.Td fw={500}>{r.bank_name}</Table.Td>
            <Table.Td ta="right" fw={700} c="green">
              {parseFloat(r.apy).toFixed(2)}%
            </Table.Td>
            {showTerm && <Table.Td>{r.term}</Table.Td>}
            <Table.Td ta="right" ff="monospace">
              {r.min_deposit
                ? `$${parseFloat(r.min_deposit).toLocaleString()}`
                : '-'}
            </Table.Td>
          </Table.Tr>
        ))}
      </Table.Tbody>
    </Table>
  );
}

// ── Recommendations Display Component ──

function RecommendationsDisplay({
  aiResult,
  lastUpdated,
  lastFailed,
}: {
  aiResult: AIResponse;
  lastUpdated?: string;
  lastFailed?: boolean;
}) {
  return (
    <Stack>
      {/* Last Updated timestamp + failure message */}
      {lastUpdated && (
        <Stack gap={0} align="flex-end">
          <Text size="xs" c="dimmed" ta="right">
            Last updated: {new Date(lastUpdated).toLocaleString()}
          </Text>
          {lastFailed && (
            <Text size="10px" c="orange" fw={500} style={{ opacity: 0.85 }}>
              last analysis failed — showing cached data
            </Text>
          )}
        </Stack>
      )}

      {/* Overall Assessment */}
      <Alert color="blue" variant="light" title="Overall Assessment">
        <Text size="sm">{aiResult.overall_assessment}</Text>
      </Alert>

      {/* Risk Notes */}
      {aiResult.risk_notes && aiResult.risk_notes.length > 0 && (
        <Alert
          color="yellow"
          variant="light"
          title="Risk Notes"
          icon={<IconAlertTriangle />}
        >
          <Stack gap={4}>
            {aiResult.risk_notes.map((note, i) => (
              <Text key={i} size="sm">
                {note}
              </Text>
            ))}
          </Stack>
        </Alert>
      )}

      {/* Recommendation Cards */}
      {aiResult.recommendations.length > 0 ? (
        <Accordion variant="separated">
          {aiResult.recommendations.map((rec, i) => {
            const Icon = typeIcons[rec.type] || IconBulb;
            return (
              <Accordion.Item key={i} value={`rec-${i}`}>
                <Accordion.Control>
                  <Group>
                    <ThemeIcon
                      variant="light"
                      color={priorityColors[rec.priority] || 'gray'}
                      size="md"
                    >
                      <Icon size={16} />
                    </ThemeIcon>
                    <div style={{ flex: 1 }}>
                      <Group gap="xs">
                        <Text fw={600}>{rec.title}</Text>
                        <Badge
                          size="xs"
                          color={priorityColors[rec.priority]}
                        >
                          {rec.priority}
                        </Badge>
                        <Badge size="xs" variant="light">
                          {typeLabels[rec.type] || rec.type}
                        </Badge>
                        <Badge
                          size="xs"
                          variant="dot"
                          color={
                            rec.fund_type === 'reserve'
                              ? 'violet'
                              : rec.fund_type === 'operating'
                                ? 'blue'
                                : 'gray'
                          }
                        >
                          {rec.fund_type}
                        </Badge>
                      </Group>
                      <Text size="sm" c="dimmed" mt={2}>
                        {rec.summary}
                      </Text>
                    </div>
                    {rec.suggested_amount != null && (
                      <Text fw={700} ff="monospace" c="green" size="lg">
                        {fmt(rec.suggested_amount)}
                      </Text>
                    )}
                  </Group>
                </Accordion.Control>
                <Accordion.Panel>
                  <Stack gap="sm">
                    <Text size="sm">{rec.details}</Text>

                    {(rec.suggested_term ||
                      rec.suggested_rate != null ||
                      rec.bank_name) && (
                      <Paper withBorder p="sm" radius="sm">
                        <SimpleGrid cols={{ base: 1, sm: 3 }}>
                          {rec.suggested_term && (
                            <div>
                              <Text size="xs" c="dimmed">
                                Suggested Term
                              </Text>
                              <Text fw={600}>{rec.suggested_term}</Text>
                            </div>
                          )}
                          {rec.suggested_rate != null && (
                            <div>
                              <Text size="xs" c="dimmed">
                                Target Rate
                              </Text>
                              <Text fw={600}>
                                {rec.suggested_rate}% APY
                              </Text>
                            </div>
                          )}
                          {rec.bank_name && (
                            <div>
                              <Text size="xs" c="dimmed">
                                Bank
                              </Text>
                              <Text fw={600}>{rec.bank_name}</Text>
                            </div>
                          )}
                        </SimpleGrid>
                      </Paper>
                    )}

                    <Alert variant="light" color="gray" title="Rationale">
                      <Text size="sm">{rec.rationale}</Text>
                    </Alert>
                  </Stack>
                </Accordion.Panel>
              </Accordion.Item>
            );
          })}
        </Accordion>
      ) : (
        <Text ta="center" c="dimmed" py="lg">
          No specific recommendations at this time.
        </Text>
      )}
    </Stack>
  );
}

// ── Main Component ──

export function InvestmentPlanningPage() {
  const [ratesExpanded, setRatesExpanded] = useState(true);
  const [isTriggering, setIsTriggering] = useState(false);

  // Load financial snapshot on mount
  const { data: snapshot, isLoading: snapshotLoading } = useQuery<FinancialSnapshot>({
    queryKey: ['investment-planning-snapshot'],
    queryFn: async () => {
      const { data } = await api.get('/investment-planning/snapshot');
      return data;
    },
  });

  // Load market rates (all types) on mount
  const { data: marketRates, isLoading: ratesLoading } = useQuery<MarketRatesResponse>({
    queryKey: ['investment-planning-market-rates'],
    queryFn: async () => {
      const { data } = await api.get('/investment-planning/market-rates');
      return data;
    },
  });

  // Load saved recommendation — polls every 3s when processing
  const { data: savedRec } = useQuery<SavedRecommendation | null>({
    queryKey: ['investment-planning-saved-recommendation'],
    queryFn: async () => {
      const { data } = await api.get('/investment-planning/saved-recommendation');
      return data;
    },
    refetchInterval: (query) => {
      const rec = query.state.data;
      // Poll every 3 seconds while processing
      if (rec?.status === 'processing') return 3000;
      // Also poll if we just triggered (status may not be 'processing' yet)
      if (isTriggering) return 3000;
      return false;
    },
  });

  // Derive display state from saved recommendation
  const isProcessing = savedRec?.status === 'processing' || isTriggering;
  const lastFailed = savedRec?.last_failed || false;
  const hasResults = savedRec && savedRec.status === 'complete' && savedRec.recommendations.length > 0;
  const hasError = savedRec?.status === 'error' && !savedRec?.recommendations?.length;

  // Clear triggering flag once backend confirms processing or completes
  useEffect(() => {
    if (isTriggering && savedRec?.status === 'processing') {
      setIsTriggering(false);
    }
    if (isTriggering && savedRec?.status === 'complete') {
      setIsTriggering(false);
    }
  }, [savedRec?.status, isTriggering]);

  // Show notification when processing completes (transition from processing)
  const prevStatusRef = useState<string | null>(null);
  useEffect(() => {
    const [prevStatus, setPrevStatus] = prevStatusRef;
    if (prevStatus === 'processing' && savedRec?.status === 'complete') {
      notifications.show({
        message: `Generated ${savedRec.recommendations.length} investment recommendations`,
        color: 'green',
      });
    }
    if (prevStatus === 'processing' && savedRec?.status === 'error') {
      notifications.show({
        message: savedRec.error_message || 'AI recommendation analysis failed',
        color: 'red',
      });
    }
    setPrevStatus(savedRec?.status || null);
  }, [savedRec?.status]); // eslint-disable-line react-hooks/exhaustive-deps

  // Trigger AI recommendations (async — returns immediately)
  const handleTriggerAI = useCallback(async () => {
    setIsTriggering(true);
    try {
      await api.post('/investment-planning/recommendations');
    } catch (err: any) {
      setIsTriggering(false);
      notifications.show({
        message: err.response?.data?.message || 'Failed to start AI analysis',
        color: 'red',
      });
    }
  }, []);

  // Build AI result from saved recommendation for display
  const aiResult: AIResponse | null = hasResults
    ? {
        recommendations: savedRec!.recommendations,
        overall_assessment: savedRec!.overall_assessment,
        risk_notes: savedRec!.risk_notes,
      }
    : (lastFailed && savedRec?.recommendations?.length)
      ? {
          recommendations: savedRec!.recommendations,
          overall_assessment: savedRec!.overall_assessment,
          risk_notes: savedRec!.risk_notes,
        }
      : null;

  if (snapshotLoading) {
    return (
      <Center h={400}>
        <Loader size="lg" />
      </Center>
    );
  }

  const s = snapshot?.summary;

  // Determine the latest fetched_at timestamp across all rate types
  const allRatesList = [
    ...(marketRates?.cd || []),
    ...(marketRates?.money_market || []),
    ...(marketRates?.high_yield_savings || []),
  ];
  const latestFetchedAt = allRatesList.length > 0
    ? allRatesList.reduce((latest, r) =>
        new Date(r.fetched_at) > new Date(latest.fetched_at) ? r : latest,
      ).fetched_at
    : null;

  const totalRateCount =
    (marketRates?.cd?.length || 0) +
    (marketRates?.money_market?.length || 0) +
    (marketRates?.high_yield_savings?.length || 0);

  return (
    <Stack>
      {/* Page Header */}
      <Group justify="space-between" align="flex-start">
        <div>
          <Title order={2}>Investment Planning</Title>
          <Text c="dimmed" size="sm">
            Account overview, market rates, and AI-powered investment recommendations
          </Text>
        </div>
      </Group>

      {/* ── Section 1: Financial Snapshot Cards ── */}
      {s && (
        <SimpleGrid cols={{ base: 1, sm: 2, lg: 4 }}>
          <Card withBorder p="md">
            <Group gap="xs" mb={4}>
              <ThemeIcon variant="light" color="blue" size="sm">
                <IconCash size={14} />
              </ThemeIcon>
              <Text size="xs" c="dimmed" tt="uppercase" fw={700}>
                Operating Cash
              </Text>
            </Group>
            <Text fw={700} size="xl" ff="monospace">
              {fmt(s.operating_cash)}
            </Text>
            <Text size="xs" c="dimmed">
              Investments: {fmt(s.operating_investments)}
            </Text>
          </Card>

          <Card withBorder p="md">
            <Group gap="xs" mb={4}>
              <ThemeIcon variant="light" color="violet" size="sm">
                <IconPigMoney size={14} />
              </ThemeIcon>
              <Text size="xs" c="dimmed" tt="uppercase" fw={700}>
                Reserve Cash
              </Text>
            </Group>
            <Text fw={700} size="xl" ff="monospace">
              {fmt(s.reserve_cash)}
            </Text>
            <Text size="xs" c="dimmed">
              Investments: {fmt(s.reserve_investments)}
            </Text>
          </Card>

          <Card withBorder p="md">
            <Group gap="xs" mb={4}>
              <ThemeIcon variant="light" color="teal" size="sm">
                <IconChartAreaLine size={14} />
              </ThemeIcon>
              <Text size="xs" c="dimmed" tt="uppercase" fw={700}>
                Total All Funds
              </Text>
            </Group>
            <Text fw={700} size="xl" ff="monospace">
              {fmt(s.total_all)}
            </Text>
            <Text size="xs" c="dimmed">
              Operating: {fmt(s.total_operating)} | Reserve: {fmt(s.total_reserve)}
            </Text>
          </Card>

          <Card withBorder p="md">
            <Group gap="xs" mb={4}>
              <ThemeIcon variant="light" color="green" size="sm">
                <IconCoin size={14} />
              </ThemeIcon>
              <Text size="xs" c="dimmed" tt="uppercase" fw={700}>
                Total Invested
              </Text>
            </Group>
            <Text fw={700} size="xl" ff="monospace">
              {fmt(s.operating_investments + s.reserve_investments)}
            </Text>
            <Text size="xs" c="dimmed">
              Earning interest across all accounts
            </Text>
          </Card>
        </SimpleGrid>
      )}

      {/* ── Section 2: Current Investments Table ── */}
      {snapshot?.investment_accounts && snapshot.investment_accounts.length > 0 && (
        <Card withBorder p="lg">
          <Title order={4} mb="md">
            Current Investments
          </Title>
          <Table striped highlightOnHover>
            <Table.Thead>
              <Table.Tr>
                <Table.Th>Name</Table.Th>
                <Table.Th>Institution</Table.Th>
                <Table.Th>Type</Table.Th>
                <Table.Th>Fund</Table.Th>
                <Table.Th ta="right">Principal</Table.Th>
                <Table.Th ta="right">Rate</Table.Th>
                <Table.Th>Maturity</Table.Th>
              </Table.Tr>
            </Table.Thead>
            <Table.Tbody>
              {snapshot.investment_accounts.map((inv) => (
                <Table.Tr key={inv.id}>
                  <Table.Td fw={500}>{inv.name}</Table.Td>
                  <Table.Td>{inv.institution || '-'}</Table.Td>
                  <Table.Td>
                    <Badge size="sm" variant="light">
                      {inv.investment_type}
                    </Badge>
                  </Table.Td>
                  <Table.Td>
                    <Badge
                      size="sm"
                      color={inv.fund_type === 'reserve' ? 'violet' : 'blue'}
                    >
                      {inv.fund_type}
                    </Badge>
                  </Table.Td>
                  <Table.Td ta="right" ff="monospace">
                    {fmt(parseFloat(inv.principal))}
                  </Table.Td>
                  <Table.Td ta="right">
                    {parseFloat(inv.interest_rate || '0').toFixed(2)}%
                  </Table.Td>
                  <Table.Td>
                    {inv.maturity_date
                      ? new Date(inv.maturity_date).toLocaleDateString()
                      : '-'}
                  </Table.Td>
                </Table.Tr>
              ))}
            </Table.Tbody>
          </Table>
        </Card>
      )}

      {/* ── Section 3: Today's Market Rates (Collapsible with Tabs) ── */}
      <Card withBorder p="lg">
        <Group justify="space-between" mb={ratesExpanded ? 'md' : 0}>
          <Group gap="xs">
            <Title order={4}>Today&apos;s Market Rates</Title>
            {totalRateCount > 0 && (
              <Badge size="sm" variant="light" color="gray">
                {totalRateCount} rates
              </Badge>
            )}
          </Group>
          <Group gap="xs">
            {latestFetchedAt && (
              <Text size="xs" c="dimmed">
                Last fetched: {new Date(latestFetchedAt).toLocaleString()}
              </Text>
            )}
            <ActionIcon
              variant="subtle"
              color="gray"
              onClick={() => setRatesExpanded((v) => !v)}
              title={ratesExpanded ? 'Collapse rates' : 'Expand rates'}
            >
              {ratesExpanded ? <IconChevronUp size={16} /> : <IconChevronDown size={16} />}
            </ActionIcon>
          </Group>
        </Group>

        <Collapse in={ratesExpanded}>
          {ratesLoading ? (
            <Center py="lg">
              <Loader />
            </Center>
          ) : (
            <Tabs defaultValue="cd">
              <Tabs.List>
                <Tabs.Tab value="cd">
                  CDs {(marketRates?.cd?.length || 0) > 0 && (
                    <Badge size="xs" variant="light" ml={4}>{marketRates?.cd?.length}</Badge>
                  )}
                </Tabs.Tab>
                <Tabs.Tab value="money_market">
                  Money Market {(marketRates?.money_market?.length || 0) > 0 && (
                    <Badge size="xs" variant="light" ml={4}>{marketRates?.money_market?.length}</Badge>
                  )}
                </Tabs.Tab>
                <Tabs.Tab value="high_yield_savings">
                  High Yield Savings {(marketRates?.high_yield_savings?.length || 0) > 0 && (
                    <Badge size="xs" variant="light" ml={4}>{marketRates?.high_yield_savings?.length}</Badge>
                  )}
                </Tabs.Tab>
              </Tabs.List>

              <Tabs.Panel value="cd" pt="sm">
                <RateTable rates={marketRates?.cd || []} showTerm={true} />
              </Tabs.Panel>
              <Tabs.Panel value="money_market" pt="sm">
                <RateTable rates={marketRates?.money_market || []} showTerm={false} />
              </Tabs.Panel>
              <Tabs.Panel value="high_yield_savings" pt="sm">
                <RateTable rates={marketRates?.high_yield_savings || []} showTerm={false} />
              </Tabs.Panel>
            </Tabs>
          )}
        </Collapse>
      </Card>

      <Divider />

      {/* ── Section 4: AI Investment Recommendations ── */}
      <Card withBorder p="lg">
        <Group justify="space-between" mb="md">
          <Group gap="xs">
            <ThemeIcon variant="light" color="grape" size="md">
              <IconSparkles size={18} />
            </ThemeIcon>
            <div>
              <Title order={4}>AI Investment Recommendations</Title>
              <Text size="xs" c="dimmed">
                Powered by AI analysis of your complete financial picture
              </Text>
            </div>
          </Group>
          <Button
            leftSection={<IconSparkles size={16} />}
            onClick={handleTriggerAI}
            loading={isProcessing}
            variant="gradient"
            gradient={{ from: 'grape', to: 'violet' }}
          >
            {aiResult ? 'Refresh Recommendations' : 'Get AI Recommendations'}
          </Button>
        </Group>

        {/* Processing State */}
        {isProcessing && (
          <Center py="xl">
            <Stack align="center" gap="sm">
              <Loader size="lg" type="dots" />
              <Text c="dimmed" size="sm">
                Analyzing your financial data and market rates...
              </Text>
              <Text c="dimmed" size="xs">
                You can navigate away — results will appear when ready
              </Text>
            </Stack>
          </Center>
        )}

        {/* Error State (no cached data) */}
        {hasError && !isProcessing && (
          <Alert color="red" variant="light" title="Analysis Failed" mb="md">
            <Text size="sm">
              {savedRec?.error_message || 'The last AI analysis failed. Please try again.'}
            </Text>
          </Alert>
        )}

        {/* Results (with optional failure watermark) */}
        {aiResult && !isProcessing && (
          <RecommendationsDisplay
            aiResult={aiResult}
            lastUpdated={savedRec?.created_at || undefined}
            lastFailed={lastFailed}
          />
        )}

        {/* Empty State */}
        {!aiResult && !isProcessing && !hasError && (
          <Paper p="xl" radius="sm" style={{ textAlign: 'center' }}>
            <ThemeIcon variant="light" color="grape" size={48} mx="auto" mb="md">
              <IconSparkles size={28} />
            </ThemeIcon>
            <Text fw={500} mb={4}>
              AI-Powered Investment Analysis
            </Text>
            <Text c="dimmed" size="sm" maw={500} mx="auto">
              Click &quot;Get AI Recommendations&quot; to analyze your accounts, cash flow,
              budget, and capital projects against current market rates. The AI will
              suggest specific investment moves to maximize interest income while
              maintaining adequate liquidity.
            </Text>
          </Paper>
        )}
      </Card>
    </Stack>
  );
}