import { useState, useEffect, useRef, useCallback } from 'react';
import { useNavigate } from 'react-router-dom';
import { useQuery, useQueryClient } from '@tanstack/react-query';
import { format } from 'date-fns';
import { Bell, Plus, Calendar as CalIcon, ListTodo, RefreshCw } from 'lucide-react';
import api from '@/lib/api';
import type { DashboardData, UpcomingResponse, WeatherData } from '@/types';
import { useSettings } from '@/hooks/useSettings';
import { useAlerts } from '@/hooks/useAlerts';
import StatsWidget from './StatsWidget';
import TodoWidget from './TodoWidget';
import CalendarWidget from './CalendarWidget';
import UpcomingWidget from './UpcomingWidget';
import WeekTimeline from './WeekTimeline';
import DayBriefing from './DayBriefing';
import CountdownWidget from './CountdownWidget';
import TrackedProjectsWidget from './TrackedProjectsWidget';
import AlertBanner from './AlertBanner';
import EventForm from '../calendar/EventForm';
import TodoForm from '../todos/TodoForm';
import ReminderForm from '../reminders/ReminderForm';
import { Card, CardContent, CardHeader, CardTitle } from '@/components/ui/card';
import { Button } from '@/components/ui/button';
import { DashboardSkeleton } from '@/components/ui/skeleton';
import { cn } from '@/lib/utils';

function getGreeting(name?: string): string {
  const hour = new Date().getHours();
  const suffix = name ? `, ${name}.` : '.';
  if (hour < 5) return `Good night${suffix}`;
  if (hour < 12) return `Good morning${suffix}`;
  if (hour < 17) return `Good afternoon${suffix}`;
  if (hour < 21) return `Good evening${suffix}`;
  return `Good night${suffix}`;
}

export default function DashboardPage() {
  const navigate = useNavigate();
  const queryClient = useQueryClient();
  const { settings } = useSettings();
  const { alerts, dismiss: dismissAlert, snooze: snoozeAlert } = useAlerts();
  const [quickAddType, setQuickAddType] = useState<'event' | 'todo' | 'reminder' | null>(null);
  const [dropdownOpen, setDropdownOpen] = useState(false);
  const dropdownRef = useRef<HTMLDivElement>(null);
  const [clockNow, setClockNow] = useState(() => new Date());

  // Live clock — synced to the minute boundary, re-syncs after tab sleep/resume
  useEffect(() => {
    let intervalId: ReturnType<typeof setInterval>;
    let timeoutId: ReturnType<typeof setTimeout>;

    function startClock() {
      clearTimeout(timeoutId);
      clearInterval(intervalId);
      setClockNow(new Date());
      const msUntilNextMinute = (60 - new Date().getSeconds()) * 1000 - new Date().getMilliseconds();
      timeoutId = setTimeout(() => {
        setClockNow(new Date());
        intervalId = setInterval(() => setClockNow(new Date()), 60_000);
      }, msUntilNextMinute);
    }

    startClock();

    // Re-sync when tab becomes visible again (after sleep/background throttle)
    function handleVisibility() {
      if (document.visibilityState === 'visible') startClock();
    }
    document.addEventListener('visibilitychange', handleVisibility);

    return () => {
      clearTimeout(timeoutId);
      clearInterval(intervalId);
      document.removeEventListener('visibilitychange', handleVisibility);
    };
  }, []);

  // Click outside to close dropdown
  useEffect(() => {
    function handleClickOutside(e: MouseEvent) {
      if (dropdownRef.current && !dropdownRef.current.contains(e.target as Node)) {
        setDropdownOpen(false);
      }
    }
    if (dropdownOpen) document.addEventListener('mousedown', handleClickOutside);
    return () => document.removeEventListener('mousedown', handleClickOutside);
  }, [dropdownOpen]);

  // Keyboard quick-add: Ctrl+N / Cmd+N opens dropdown, e/t/r selects type
  useEffect(() => {
    function handleKeyDown(e: KeyboardEvent) {
      // Don't trigger inside inputs/textareas or when a form is open
      const tag = (e.target as HTMLElement)?.tagName;
      if (tag === 'INPUT' || tag === 'TEXTAREA' || tag === 'SELECT') return;
      if (quickAddType) return;

      if ((e.ctrlKey || e.metaKey) && e.key === 'n') {
        e.preventDefault();
        setDropdownOpen(true);
        return;
      }

      if (dropdownOpen) {
        if (e.key === 'Escape') {
          setDropdownOpen(false);
          return;
        }
        if (e.key === 'e') {
          setQuickAddType('event');
          setDropdownOpen(false);
          return;
        }
        if (e.key === 't') {
          setQuickAddType('todo');
          setDropdownOpen(false);
          return;
        }
        if (e.key === 'r') {
          setQuickAddType('reminder');
          setDropdownOpen(false);
          return;
        }
      }
    }
    document.addEventListener('keydown', handleKeyDown);
    return () => document.removeEventListener('keydown', handleKeyDown);
  }, [dropdownOpen, quickAddType]);

  const { data, isLoading, dataUpdatedAt } = useQuery({
    queryKey: ['dashboard'],
    queryFn: async () => {
      const now = new Date();
      const today = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}-${String(now.getDate()).padStart(2, '0')}`;
      const { data } = await api.get<DashboardData>(`/dashboard?client_date=${today}`);
      return data;
    },
    staleTime: 60_000,
    refetchInterval: 120_000,
  });

  const { data: upcomingData } = useQuery({
    queryKey: ['upcoming', settings?.upcoming_days],
    queryFn: async () => {
      const days = settings?.upcoming_days || 7;
      const now = new Date();
      const clientDate = `${now.getFullYear()}-${String(now.getMonth() + 1).padStart(2, '0')}-${String(now.getDate()).padStart(2, '0')}`;
      const { data } = await api.get<UpcomingResponse>(`/upcoming?days=${days}&client_date=${clientDate}`);
      return data;
    },
    staleTime: 60_000,
    refetchInterval: 120_000,
  });

  const { data: weatherData } = useQuery<WeatherData>({
    queryKey: ['weather'],
    queryFn: async () => {
      const { data } = await api.get<WeatherData>('/weather');
      return data;
    },
    staleTime: 30 * 60 * 1000,
    retry: false,
    enabled: !!(settings?.weather_city || (settings?.weather_lat != null && settings?.weather_lon != null)),
  });

  const handleRefresh = useCallback(() => {
    queryClient.invalidateQueries({ queryKey: ['dashboard'] });
    queryClient.invalidateQueries({ queryKey: ['upcoming'] });
  }, [queryClient]);

  if (isLoading) {
    return (
      <div className="flex flex-col h-full">
        <div className="px-4 md:px-6 py-6">
          <div className="animate-pulse space-y-2">
            <div className="h-8 w-48 rounded bg-muted" />
            <div className="h-4 w-32 rounded bg-muted" />
          </div>
        </div>
        <div className="flex-1 overflow-y-auto px-4 md:px-6 pb-6">
          <DashboardSkeleton />
        </div>
      </div>
    );
  }

  if (!data) {
    return (
      <div className="flex items-center justify-center h-full">
        <div className="text-muted-foreground">Failed to load dashboard</div>
      </div>
    );
  }

  const updatedAgo = dataUpdatedAt
    ? (() => {
        const mins = Math.floor((clockNow.getTime() - dataUpdatedAt) / 60_000);
        if (mins < 1) return 'just now';
        if (mins === 1) return '1 min ago';
        return `${mins} min ago`;
      })()
    : null;

  return (
    <div className="flex flex-col h-full">
      {/* Header — greeting + date + quick add */}
      <div className="px-4 md:px-6 pt-4 sm:pt-6 pb-1 sm:pb-2 flex items-center justify-between">
        <div>
          <h1 className="font-heading text-3xl font-bold tracking-tight animate-fade-in">
            {getGreeting(settings?.preferred_name || undefined)}
          </h1>
          <div className="flex items-center gap-2 mt-1">
            <p className="text-muted-foreground text-sm">
              <span className="tabular-nums">{format(clockNow, 'h:mm a')}</span>
              <span className="mx-1.5 text-muted-foreground/30">|</span>
              {format(clockNow, 'EEEE, MMMM d, yyyy')}
            </p>
            {updatedAgo && (
              <>
                <span className="text-muted-foreground/40 text-xs">·</span>
                <span className="text-muted-foreground/60 text-xs">Updated {updatedAgo}</span>
                <button
                  onClick={handleRefresh}
                  className="p-0.5 rounded text-muted-foreground/40 hover:text-accent transition-colors"
                  title="Refresh dashboard"
                  aria-label="Refresh dashboard"
                >
                  <RefreshCw className="h-3 w-3" />
                </button>
              </>
            )}
          </div>
        </div>
        <div className="relative" ref={dropdownRef}>
          <Button
            variant="outline"
            size="icon"
            onClick={() => setDropdownOpen(!dropdownOpen)}
            className="h-9 w-9"
            aria-haspopup="menu"
            aria-expanded={dropdownOpen}
            aria-label="Quick add"
          >
            <Plus className={cn('h-4 w-4 transition-transform duration-200', dropdownOpen && 'rotate-45')} />
          </Button>
          {dropdownOpen && (
            <div role="menu" className="absolute right-0 top-full mt-1.5 w-44 rounded-lg border bg-popover shadow-xl z-50 py-1 animate-fade-in">
              <button
                role="menuitem"
                className="flex items-center gap-2.5 w-full px-3 py-2 text-sm hover:bg-card-elevated transition-colors"
                onClick={() => { setQuickAddType('event'); setDropdownOpen(false); }}
              >
                <CalIcon className="h-4 w-4 text-purple-400" />
                Event
                <kbd className="ml-auto text-[10px] text-muted-foreground/50 font-mono bg-muted rounded px-1 py-0.5">e</kbd>
              </button>
              <button
                role="menuitem"
                className="flex items-center gap-2.5 w-full px-3 py-2 text-sm hover:bg-card-elevated transition-colors"
                onClick={() => { setQuickAddType('todo'); setDropdownOpen(false); }}
              >
                <ListTodo className="h-4 w-4 text-blue-400" />
                Todo
                <kbd className="ml-auto text-[10px] text-muted-foreground/50 font-mono bg-muted rounded px-1 py-0.5">t</kbd>
              </button>
              <button
                role="menuitem"
                className="flex items-center gap-2.5 w-full px-3 py-2 text-sm hover:bg-card-elevated transition-colors"
                onClick={() => { setQuickAddType('reminder'); setDropdownOpen(false); }}
              >
                <Bell className="h-4 w-4 text-orange-400" />
                Reminder
                <kbd className="ml-auto text-[10px] text-muted-foreground/50 font-mono bg-muted rounded px-1 py-0.5">r</kbd>
              </button>
            </div>
          )}
        </div>
      </div>

      <div className="flex-1 overflow-y-auto px-4 md:px-6 pb-6">
        <div className="space-y-3 sm:space-y-5 animate-content-reveal">
          {/* Week Timeline */}
          {upcomingData && (
            <div className="animate-slide-up">
              <WeekTimeline items={upcomingData.items} />
            </div>
          )}

          {/* Smart Briefing */}
          {upcomingData && (
            <DayBriefing
              upcomingItems={upcomingData.items}
              dashboardData={data}
              weatherData={weatherData || null}
            />
          )}

          {/* Stats Row */}
          <div className="animate-slide-up" style={{ animationDelay: '50ms', animationFillMode: 'backwards' }}>
            <StatsWidget
              projectStats={data.project_stats}
              totalIncompleteTodos={data.total_incomplete_todos}
              totalTodos={data.total_todos}
              weatherData={weatherData || null}
            />
          </div>

          {/* Alert Banner */}
          <AlertBanner alerts={alerts} onDismiss={dismissAlert} onSnooze={snoozeAlert} />

          {/* Main Content — 2 columns */}
          <div className="grid gap-3 sm:gap-5 lg:grid-cols-5 animate-slide-up" style={{ animationDelay: '100ms', animationFillMode: 'backwards' }}>
            {/* Left: Upcoming feed (wider) */}
            <div className="lg:col-span-3 flex flex-col">
              <UpcomingWidget items={upcomingData?.items ?? []} />
            </div>

            {/* Right: Countdown + Today's events + todos stacked */}
            <div className="lg:col-span-2 flex flex-col gap-3 sm:gap-5">
              {data.starred_events.length > 0 && (
                <CountdownWidget events={data.starred_events} />
              )}
              <CalendarWidget events={data.todays_events} />
              <div className="flex-1">
                <TodoWidget todos={data.upcoming_todos} />
              </div>
            </div>
          </div>

          {/* Active Reminders — exclude those already shown in alert banner */}
          {(() => {
            const alertIds = new Set(alerts.map((a) => a.id));
            const futureReminders = data.active_reminders.filter((r) => !alertIds.has(r.id));
            if (futureReminders.length === 0) return null;
            return (
              <Card className="animate-slide-up" style={{ animationDelay: '150ms', animationFillMode: 'backwards' }}>
                <CardHeader>
                  <CardTitle className="flex items-center gap-2">
                    <div className="p-1.5 rounded-md bg-orange-500/10">
                      <Bell className="h-4 w-4 text-orange-400" />
                    </div>
                    Active Reminders
                  </CardTitle>
                </CardHeader>
                <CardContent>
                  <div className="space-y-0.5">
                    {futureReminders.map((reminder) => (
                      <div
                        key={reminder.id}
                        onClick={() => navigate('/reminders', { state: { reminderId: reminder.id } })}
                        className="flex items-center gap-2 py-1.5 px-2 rounded-md hover:bg-card-elevated transition-colors duration-150 cursor-pointer"
                      >
                        <div className="w-1.5 h-1.5 rounded-full bg-orange-400 shrink-0" />
                        <span className="font-medium text-sm truncate flex-1 min-w-0">{reminder.title}</span>
                        <span className="text-xs text-muted-foreground shrink-0 whitespace-nowrap">
                          {reminder.remind_at ? format(new Date(reminder.remind_at), 'MMM d, h:mm a') : ''}
                        </span>
                      </div>
                    ))}
                  </div>
                </CardContent>
              </Card>
            );
          })()}

          {/* Tracked Projects */}
          <div className="animate-slide-up" style={{ animationDelay: '200ms', animationFillMode: 'backwards' }}>
            <TrackedProjectsWidget />
          </div>
        </div>
      </div>

      {/* Quick Add Forms */}
      {quickAddType === 'event' && <EventForm event={null} onClose={() => setQuickAddType(null)} />}
      {quickAddType === 'todo' && <TodoForm todo={null} onClose={() => setQuickAddType(null)} />}
      {quickAddType === 'reminder' && <ReminderForm reminder={null} onClose={() => setQuickAddType(null)} />}
    </div>
  );
}