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

function Stat({ label, value }) {
  return (
    <div className="bg-gray-900 px-4 py-3 flex flex-col justify-center">
      <p className="text-xs text-gray-500">{label}</p>
      <p className="text-lg font-semibold text-white">{value}</p>
    </div>
  )
}

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, hires }) {
  const data = (hires?.length ? hires : bb?.values || []).map(([ts, level]) => ({ ts, level }))
  const charged = bb?.charged, drained = bb?.drained, end_level = bb?.end_level
  const peak = data.length ? Math.max(...data.map(d => d.level)) : end_level
  const hasGraph = data.length >= 2

  return (
    <div className="bg-gray-900 rounded-xl border border-gray-800 p-4 h-full flex flex-col">
      <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">
        {peak != null && (
          <span className="text-3xl font-bold" style={{ color: bbLevelColor(peak) }}>{Math.round(peak)}</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>}
        {end_level != null && <span className="text-xs text-gray-500">now {Math.round(end_level)}</span>}
      </div>
      {hasGraph ? (
        <div className="mt-3 flex-1">
          <ResponsiveContainer width="100%" height={70}>
            <BarChart data={data} margin={{ top: 2, right: 0, bottom: 0, left: 0 }} barCategoryGap={0}>
              <YAxis domain={[0, 100]} hide />
              <Tooltip
                contentStyle={{ background: '#111827', border: '1px solid #374151', borderRadius: 6, fontSize: 11, color: '#fff' }}
                itemStyle={{ color: '#fff' }} labelStyle={{ color: '#fff' }}
                labelFormatter={ts => format(new Date(ts), 'HH:mm')}
                formatter={v => [`${Math.round(v)}%`, 'Battery']}
              />
              <Bar dataKey="level" isAnimationActive={false} radius={0}>
                {data.map((d, i) => <Cell key={i} fill={bbLevelColor(d.level)} />)}
              </Bar>
            </BarChart>
          </ResponsiveContainer>
        </div>
      ) : (
        <p className="text-xs text-gray-600 mt-3">No body battery data today</p>
      )}
    </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: recentHealth } = useQuery({
    queryKey: ['health-metrics', 'dash'],
    queryFn: () => api.get('/health-metrics/', { params: { limit: 365 } }).then(r => r.data),
  })

  // Latest available (non-null) value per metric — Garmin updates some fields
  // less often than daily, so "today" can be sparse.
  const health = useMemo(() => {
    const rows = [...(recentHealth || [])].sort((a, b) => new Date(b.date) - new Date(a.date))
    const pick = f => rows.find(d => d[f] != null)?.[f] ?? null
    return {
      date: rows[0]?.date ? rows[0].date.slice(0, 10) : null,   // intraday endpoint wants YYYY-MM-DD
      resting_hr: pick('resting_hr'),
      sleep_duration_s: pick('sleep_duration_s'),
      hrv_nightly_avg: pick('hrv_nightly_avg'),
      sleep_score: pick('sleep_score'),
      steps: pick('steps'),
      vo2max: pick('vo2max'),
      avg_stress: pick('avg_stress'),
    }
  }, [recentHealth])

  const { data: intraday } = useQuery({
    queryKey: ['health-intraday-dash', health.date],
    queryFn: () => api.get('/health-metrics/intraday', { params: { date: health.date } }).then(r => r.data),
    enabled: !!health.date,
  })

  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 featured = recentActivities?.[0]

  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(health.resting_hr)} accent="red" />
        <StatCard label="Sleep" value={formatSleep(health.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={intraday?.body_battery} hires={intraday?.body_battery_hires} />
        </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>
          {health.date ? (
            <>
              {[
                ['HRV', health.hrv_nightly_avg ? `${Math.round(health.hrv_nightly_avg)} ms` : '--'],
                ['Sleep score', health.sleep_score ? Math.round(health.sleep_score) : '--'],
                ['Steps', health.steps?.toLocaleString() ?? '--'],
                ['VO2 Max', health.vo2max ? health.vo2max.toFixed(1) : '--'],
                ['Stress', health.avg_stress ? Math.round(health.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>

      {/* Featured most-recent activity */}
      {featured && (
        <div className="bg-gray-900 rounded-xl border border-gray-800 overflow-hidden">
          <div className="flex items-center justify-between px-4 py-3 border-b border-gray-800">
            <div className="flex items-center gap-2 min-w-0">
              <span className="text-xl">{sportIcon(featured.sport_type)}</span>
              <div className="min-w-0">
                <Link to={`/activities/${featured.id}`} className="text-sm font-semibold text-white hover:text-blue-400 transition-colors truncate block">
                  {featured.name}
                </Link>
                <p className="text-xs text-gray-500">{formatDate(featured.start_time)}</p>
              </div>
            </div>
            <Link to={`/activities/${featured.id}`} className="text-xs text-blue-400 hover:underline flex-shrink-0">Open →</Link>
          </div>
          <div className="grid grid-cols-1 lg:grid-cols-3">
            <div className="lg:col-span-2 h-64 bg-gray-950">
              {featured.polyline
                ? <ActivityMap polyline={featured.polyline} sportType={featured.sport_type} colorMode="solid" />
                : <div className="flex items-center justify-center h-full text-gray-600 text-sm">No GPS track</div>}
            </div>
            <div className="grid grid-cols-2 lg:grid-cols-1 gap-px bg-gray-800/50">
              <Stat label="Distance" value={formatDistance(featured.distance_m)} />
              <Stat label="Elevation ↑" value={formatElevation(featured.elevation_gain_m)} />
              <Stat label="Moving time" value={formatDuration(featured.duration_s)} />
              <Stat label="Calories" value={featured.calories ? `${Math.round(featured.calories)} kcal` : '--'} />
            </div>
          </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>
  )
}
