import { useState, useMemo, useEffect, useCallback } from 'react';
import { useRiskStore } from '@/stores';
import { analysisApi } from '@/services/api';
import type { ExtendedAlert, RiskStats } from './types';

interface UseAlertsDataParams {
  selectedHorizon: number | 'all';
  selectedPriority: 'all' | 'P1' | 'P2';
  sortBy: 'risk' | 'time';
  debouncedRiskRange: [number, number];
  activeTab: 'list' | 'stats';
}

interface TrendPoint { date: string; cases: number; risk: number }

// 预警仪表盘的数据层：派生 extendedAlerts/filteredAlerts/riskStats、按需拉取风险趋势、
// 以及 CSV/JSON 导出辅助。角色/隐私计算保留在 orchestrator，不在此处。
export function useAlertsData({
  selectedHorizon,
  selectedPriority,
  sortBy,
  debouncedRiskRange,
  activeTab,
}: UseAlertsDataParams) {
  const alerts = useRiskStore((s) => s.alerts);

  // Risk-trend data for the 风险统计 tab, fetched on demand
  const [trendData, setTrendData] = useState<TrendPoint[]>([]);
  const [trendLoading, setTrendLoading] = useState(false);
  const [trendError, setTrendError] = useState<string | null>(null);
  const [trendLoaded, setTrendLoaded] = useState(false);

  // Fetch real risk-trend data when the 风险统计 tab is first opened
  useEffect(() => {
    if (activeTab !== 'stats' || trendLoaded) return;
    let cancelled = false;
    setTrendLoading(true);
    setTrendError(null);
    analysisApi
      .getTrend(14)
      .then((res: { dates?: string[]; values?: number[] }) => {
        if (cancelled) return;
        const dates = res?.dates ?? [];
        const values = res?.values ?? [];
        setTrendData(dates.map((date, i) => ({ date, cases: 0, risk: values[i] ?? 0 })));
        setTrendLoaded(true);
      })
      .catch((err: unknown) => {
        if (cancelled) return;
        setTrendError(err instanceof Error ? err.message : '加载风险趋势失败');
      })
      .finally(() => {
        if (!cancelled) setTrendLoading(false);
      });
    return () => { cancelled = true; };
  }, [activeTab, trendLoaded]);

  const extendedAlerts: ExtendedAlert[] = useMemo(() => {
    const now = Date.now();
    return (alerts || []).map((alert) => {
      const forecastDate = new Date(alert.forecast_time);
      const diffDays = Math.ceil((forecastDate.getTime() - now) / (1000 * 60 * 60 * 24));
      const horizon = diffDays <= 1 ? 1 : diffDays <= 3 ? 3 : 7;

      return {
        ...alert,
        latitude: alert.latitude || 0,
        longitude: alert.longitude || 0,
        forecast_horizon: horizon,
      };
    });
  }, [alerts]);

  const filteredAlerts = useMemo(() => {
    return extendedAlerts
      .filter((alert) => {
        const horizonMatch = selectedHorizon === 'all' || alert.forecast_horizon === selectedHorizon;
        const priorityMatch = selectedPriority === 'all' || alert.priority === selectedPriority;
        const riskMatch = alert.risk_value >= debouncedRiskRange[0] && alert.risk_value <= debouncedRiskRange[1];
        return horizonMatch && priorityMatch && riskMatch;
      })
      .sort((a, b) => {
        if (sortBy === 'risk') {
          return b.risk_value - a.risk_value;
        }
        return new Date(b.forecast_time).getTime() - new Date(a.forecast_time).getTime();
      });
  }, [extendedAlerts, selectedHorizon, selectedPriority, sortBy, debouncedRiskRange]);

  // Risk distribution stats (includes p1/p2 counts) — single pass over each array
  const riskStats: RiskStats = useMemo(() => {
    // p1/p2 reflect the full (unfiltered) alert set
    let p1 = 0;
    let p2 = 0;
    for (const a of extendedAlerts) {
      if (a.priority === 'P1') p1++;
      else if (a.priority === 'P2') p2++;
    }

    // Single pass over filteredAlerts: counters + sum + district map
    let high = 0;
    let mediumHigh = 0;
    let medium = 0;
    let sum = 0;
    const byDistrict: Record<string, number> = {};
    for (const a of filteredAlerts) {
      const v = a.risk_value;
      if (v >= 0.8) high++;
      else if (v >= 0.6) mediumHigh++;
      else if (v >= 0.4) medium++;
      sum += v;
      const d = a.region || '未知';
      byDistrict[d] = (byDistrict[d] || 0) + 1;
    }
    const avgRisk = filteredAlerts.length > 0 ? sum / filteredAlerts.length : 0;

    const topDistricts = Object.entries(byDistrict)
      .sort((a, b) => b[1] - a[1])
      .slice(0, 5);

    return { p1, p2, high, mediumHigh, medium, avgRisk, topDistricts };
  }, [extendedAlerts, filteredAlerts]);

  // Export utilities
  const exportToCsv = useCallback(() => {
    const headers = ['alert_id', 'grid_id', 'region', 'street', 'latitude', 'longitude', 'risk_value', 'priority', 'forecast_horizon', 'reason', 'timestamp'];
    const rows = filteredAlerts.map(a => [
      a.alert_id, a.grid_id, a.region, a.street,
      a.latitude, a.longitude, a.risk_value, a.priority,
      a.forecast_horizon, `"${a.reason}"`, a.timestamp,
    ]);
    const csv = [headers.join(','), ...rows.map(r => r.join(','))].join('\n');
    const blob = new Blob(['' + csv], { type: 'text/csv;charset=utf-8;' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `alerts_${new Date().toISOString().split('T')[0]}.csv`;
    a.click();
    URL.revokeObjectURL(url);
  }, [filteredAlerts]);

  const exportToJson = useCallback(() => {
    const json = JSON.stringify(filteredAlerts, null, 2);
    const blob = new Blob([json], { type: 'application/json' });
    const url = URL.createObjectURL(blob);
    const a = document.createElement('a');
    a.href = url;
    a.download = `alerts_${new Date().toISOString().split('T')[0]}.json`;
    a.click();
    URL.revokeObjectURL(url);
  }, [filteredAlerts]);

  return {
    extendedAlerts,
    filteredAlerts,
    riskStats,
    trendData,
    trendLoading,
    trendError,
    exportToCsv,
    exportToJson,
  };
}