import { Link, useNavigate } from 'react-router-dom'
import { useQuery } from '@tanstack/react-query'
import { BarChart, Bar, XAxis, YAxis, CartesianGrid, Tooltip, ResponsiveContainer, AreaChart, Area } from 'recharts'
import { startOfWeek, format, subWeeks, eachWeekOfInterval, subDays, addDays } from 'date-fns'
import api from '../utils/api'
import StatCard from '../components/ui/StatCard'
import {
  formatDuration, formatDistance, formatPace, formatHeartRate,
  formatDate, sportIcon, formatSleep,
} from '../utils/format'

function bbLevelColor(level) {
  if (level == null) return '#6b7280'
  if (level >= 75) return '#3b82f6'
  if (level >= 50) return '#22c55e'
  if (level >= 25) return '#f59e0b'
  return '#ef4444'
}

function MiniBodyBattery({ bb }) {
  if (!bb?.end_level && !bb?.charged) return null
  const { charged, drained, start_level, end_level, values } = bb
  const color = bbLevelColor(end_level)
  const sparkData = Array.isArray(values)
    ? values.map(([ts, level]) => ({ ts, level }))
    : []
  return (
    <div className="bg-gray-900 rounded-xl border border-gray-800 p-4 h-full">
      <div className="flex items-center justify-between mb-2">
        <h3 className="text-sm font-medium text-gray-300">Body Battery</h3>
        <Link to="/health" className="text-xs text-blue-400 hover:underline">View →</Link>
      </div>
      <div className="flex items-baseline gap-3 flex-wrap">
        {end_level != null && (
          <span className="text-3xl font-bold" style={{ color }}>{Math.round(end_level)}</span>
        )}
        {charged != null && (
          <span className="text-sm font-semibold text-green-400">+{charged}</span>
        )}
        {drained != null && (
          <span className="text-sm font-semibold text-orange-400">-{drained}</span>
        )}
      </div>
      {start_level != null && end_level != null && (
        <p className="text-xs text-gray-500 mt-1">{start_level} → {end_level} today</p>
      )}
      {sparkData.length >= 2 && (
        <div className="mt-3">
          <ResponsiveContainer width="100%" height={60}>
            <AreaChart data={sparkData} margin={{ top: 2, right: 0, bottom: 0, left: 0 }}>
              <defs>
                <linearGradient id="bbGrad" x1="0" y1="0" x2="0" y2="1">
                  <stop offset="5%" stopColor={color} stopOpacity={0.3} />
                  <stop offset="95%" stopColor={color} stopOpacity={0} />
                </linearGradient>
              </defs>
              <Area type="monotone" dataKey="level" stroke={color} strokeWidth={1.5}
                fill="url(#bbGrad)" dot={false} isAnimationActive={false} />
              <Tooltip
                contentStyle={{ background: '#111827', border: '1px solid #374151', borderRadius: 6, fontSize: 11 }}
                labelFormatter={ts => format(new Date(ts), 'HH:mm')}
                formatter={v => [`${Math.round(v)}`, 'Battery']}
              />
            </AreaChart>
          </ResponsiveContainer>
        </div>
      )}
    </div>
  )
}

function WeeklyChart({ activities }) {
  const navigate = useNavigate()

  if (!activities?.length) return (
    <div className="flex items-center justify-center h-36 text-gray-600 text-sm">No activities yet</div>
  )

  // Build last 8 weeks in chronological order
  const now = new Date()
  const weeks = eachWeekOfInterval({
    start: subWeeks(startOfWeek(now), 7),
    end: startOfWeek(now),
  })

  const data = weeks.map(weekStart => {
    const weekKey = format(weekStart, 'MMM d')
    const weekEnd = addDays(weekStart, 7)
    const km = activities
      .filter(a => {
        const t = new Date(a.start_time)
        return t >= weekStart && t < weekEnd
      })
      .reduce((s, a) => s + (a.distance_m || 0) / 1000, 0)
    return {
      week: weekKey,
      km: parseFloat(km.toFixed(2)),
      weekStartISO: format(weekStart, 'yyyy-MM-dd'),
      weekEndISO: format(weekEnd, 'yyyy-MM-dd'),
    }
  })

  const handleBarClick = (entry) => {
    if (entry?.activePayload?.[0]?.payload) {
      const { weekStartISO, weekEndISO } = entry.activePayload[0].payload
      navigate(`/activities?from=${weekStartISO}&to=${weekEndISO}`)
    }
  }

  return (
    <ResponsiveContainer width="100%" height={140}>
      <BarChart data={data} margin={{ top: 4, right: 4, bottom: 4, left: 0 }} barSize={20}
        onClick={handleBarClick} style={{ cursor: 'pointer' }}>
        <CartesianGrid strokeDasharray="3 3" stroke="#1f2937" vertical={false} />
        <XAxis dataKey="week" tick={{ fontSize: 10, fill: '#6b7280' }} axisLine={false} tickLine={false} />
        <YAxis tick={{ fontSize: 10, fill: '#6b7280' }} axisLine={false} tickLine={false} width={28}
          tickFormatter={v => `${v.toFixed(0)}`} />
        <Tooltip contentStyle={{ background: '#111827', border: '1px solid #374151', borderRadius: 8, fontSize: 12 }}
          formatter={(v) => [`${v.toFixed(1)} km`, 'Distance']}
          cursor={{ fill: 'rgba(59,130,246,0.1)' }} />
        <Bar dataKey="km" fill="#3b82f6" radius={[3, 3, 0, 0]} isAnimationActive={false} />
      </BarChart>
    </ResponsiveContainer>
  )
}

export default function DashboardPage() {
  const { data: recentActivities } = useQuery({
    queryKey: ['activities-recent'],
    queryFn: () => api.get('/activities/', { params: { per_page: 10 } }).then(r => r.data),
  })

  const { data: allActivities } = useQuery({
    queryKey: ['activities-all-chart'],
    queryFn: () =>
      api.get('/activities/', {
        params: { per_page: 100, from_date: subDays(new Date(), 60).toISOString() },
      }).then(r => r.data),
  })

  const { data: healthSummary } = useQuery({
    queryKey: ['health-summary'],
    queryFn: () => api.get('/health-metrics/summary').then(r => r.data),
  })

  const { data: records } = useQuery({
    queryKey: ['records-running'],
    queryFn: () => api.get('/records/', { params: { sport_type: 'running' } }).then(r => r.data),
  })

  const { data: ytdStats } = useQuery({
    queryKey: ['ytd-stats'],
    queryFn: () => api.get('/activities/stats/ytd').then(r => r.data),
  })

  const latest = healthSummary?.latest

  return (
    <div className="p-6 space-y-6">
      <div className="flex items-center justify-between">
        <h1 className="text-2xl font-bold text-white">Dashboard</h1>
        <Link to="/upload" className="text-sm text-blue-400 hover:text-blue-300 transition-colors">+ Import data</Link>
      </div>

      <div className="grid grid-cols-2 lg:grid-cols-4 gap-3">
        <StatCard label="Running this year" value={ytdStats ? `${ytdStats.running_km.toFixed(0)} km` : '--'} accent="blue" />
        <StatCard label="Cycling this year" value={ytdStats ? `${ytdStats.cycling_km.toFixed(0)} km` : '--'} accent="orange" />
        <StatCard label="Resting HR" value={formatHeartRate(latest?.resting_hr)} accent="red" />
        <StatCard label="Sleep" value={formatSleep(latest?.sleep_duration_s)} />
      </div>

      <div className="grid grid-cols-1 lg:grid-cols-4 gap-6">
        <div className="lg:col-span-2 bg-gray-900 rounded-xl border border-gray-800 p-4">
          <h3 className="text-sm font-medium text-gray-300 mb-3">Weekly distance (km)</h3>
          <WeeklyChart activities={allActivities} />
        </div>

        <div className="lg:col-span-1">
          <MiniBodyBattery bb={latest?.body_battery} />
        </div>

        <div className="lg:col-span-1 bg-gray-900 rounded-xl border border-gray-800 p-4 space-y-3">
          <h3 className="text-sm font-medium text-gray-300">Health today</h3>
          {latest ? (
            <>
              {[
                ['HRV', latest.hrv_nightly_avg ? `${Math.round(latest.hrv_nightly_avg)} ms` : '--'],
                ['Sleep score', latest.sleep_score ? Math.round(latest.sleep_score) : '--'],
                ['Steps', latest.steps?.toLocaleString() ?? '--'],
                ['VO2 Max', latest.vo2max ? latest.vo2max.toFixed(1) : '--'],
                ['Stress', latest.avg_stress ? Math.round(latest.avg_stress) : '--'],
              ].map(([label, val]) => (
                <div key={label} className="flex justify-between text-sm">
                  <span className="text-gray-500">{label}</span>
                  <span className="text-white">{val}</span>
                </div>
              ))}
              <Link to="/health" className="block text-xs text-blue-400 hover:underline mt-2">View full health dashboard →</Link>
            </>
          ) : (
            <p className="text-xs text-gray-600">No health data. Import a Garmin export.</p>
          )}
        </div>
      </div>

      {/* Recent activities */}
      <div className="bg-gray-900 rounded-xl border border-gray-800 p-4">
        <div className="flex items-center justify-between mb-4">
          <h3 className="text-sm font-medium text-gray-300">Recent activities</h3>
          <Link to="/activities" className="text-xs text-blue-400 hover:underline">View all →</Link>
        </div>
        <div className="space-y-2">
          {recentActivities?.slice(0, 5).map(activity => (
            <Link key={activity.id} to={`/activities/${activity.id}`}
              className="flex items-center gap-3 py-2 border-b border-gray-800/50 hover:bg-gray-800/30 rounded-lg px-2 -mx-2 transition-colors">
              <span className="text-lg">{sportIcon(activity.sport_type)}</span>
              <div className="flex-1 min-w-0">
                <p className="text-sm font-medium text-white truncate">{activity.name}</p>
                <p className="text-xs text-gray-500">{formatDate(activity.start_time)}</p>
              </div>
              <div className="flex gap-4 text-sm text-right">
                <div><p className="text-gray-200">{formatDistance(activity.distance_m)}</p><p className="text-xs text-gray-600">dist</p></div>
                <div><p className="text-gray-200">{formatDuration(activity.duration_s)}</p><p className="text-xs text-gray-600">time</p></div>
                <div><p className="text-red-400">{formatHeartRate(activity.avg_heart_rate)}</p><p className="text-xs text-gray-600">HR</p></div>
              </div>
            </Link>
          ))}
          {!recentActivities?.length && (
            <p className="text-gray-600 text-sm text-center py-8">
              No activities yet — <Link to="/upload" className="text-blue-400 hover:underline">import some data</Link>
            </p>
          )}
        </div>
      </div>

      {records?.length > 0 && (
        <div className="bg-gray-900 rounded-xl border border-gray-800 p-4">
          <div className="flex items-center justify-between mb-4">
            <h3 className="text-sm font-medium text-gray-300">Running PRs</h3>
            <Link to="/records" className="text-xs text-blue-400 hover:underline">View all →</Link>
          </div>
          <div className="grid grid-cols-2 sm:grid-cols-3 lg:grid-cols-5 gap-3">
            {records.slice(0, 5).map(rec => (
              <div key={rec.id} className="bg-gray-800/60 rounded-lg p-3 text-center">
                <p className="text-xs text-gray-500 mb-1">{rec.distance_label}</p>
                <p className="font-mono font-semibold text-yellow-400">{formatDuration(rec.duration_s)}</p>
              </div>
            ))}
          </div>
        </div>
      )}
    </div>
  )
}
