import { useEffect, useState } from 'react';
import { Link } from 'react-router-dom';
import { apiClient, errorMessage, HealthDay } from '../services/api';
import Chart from '../components/charts/Chart';
import StatTile, { Status } from '../components/charts/StatTile';
import './Pages.css';

const DAYS = 30;

/** MM-DD keeps the axis readable at 30 points. */
const short = (iso: string) => iso.slice(5);

function avg(values: Array<number | null | undefined>): number | null {
  const present = values.filter((v): v is number => v != null);
  if (!present.length) return null;
  return present.reduce((a, b) => a + b, 0) / present.length;
}

/* Thresholds follow the same rules the recommendation engine uses, so the
   dashboard and the advice never disagree about what counts as low. */
function sleepStatus(hours: number | null): [Status, string] | [] {
  if (hours == null) return [];
  if (hours < 6) return ['critical', '偏少'];
  if (hours < 7) return ['warning', '略少'];
  return ['good', '充足'];
}

function rhrStatus(bpm: number | null): [Status, string] | [] {
  if (bpm == null) return [];
  if (bpm > 70) return ['serious', '偏高'];
  if (bpm > 65) return ['warning', '略高'];
  return ['good', '正常'];
}

function Dashboard() {
  const [loading, setLoading] = useState(true);
  const [error, setError] = useState('');
  const [days, setDays] = useState<HealthDay[]>([]);

  useEffect(() => {
    const load = async () => {
      try {
        const end = new Date();
        const start = new Date(end.getTime() - (DAYS - 1) * 86400000);
        setDays(
          await apiClient.getHealthSummary(
            start.toISOString().slice(0, 10),
            end.toISOString().slice(0, 10)
          )
        );
      } catch (err: any) {
        setError(errorMessage(err, '加载数据失败'));
      } finally {
        setLoading(false);
      }
    };
    load();
  }, []);

  if (loading) return <div className="page-loading">加载中…</div>;

  if (error) {
    return (
      <div className="page">
        <h2>今日概览</h2>
        <div className="error-message">{error}</div>
      </div>
    );
  }

  if (days.length === 0) {
    return (
      <div className="page">
        <h2>今日概览</h2>
        <div className="empty-state">
          <p>还没有任何健康数据。</p>
          <Link to="/sync" className="btn btn-primary">去同步 Garmin 数据</Link>
        </div>
      </div>
    );
  }

  const today = days[days.length - 1];
  const rows = days.map((d) => ({ ...d, date: short(d.date) }));

  const avgSteps = avg(days.map((d) => d.steps));
  const avgSleep = avg(days.map((d) => d.sleepDuration));
  const avgRhr = avg(days.map((d) => d.heartRate));
  const avgHrv = avg(days.map((d) => d.heartRateVariability));

  const [sleepTone, sleepWord] = sleepStatus(today.sleepDuration);
  const [rhrTone, rhrWord] = rhrStatus(today.heartRate);

  const round = (v: number | null, d = 0) =>
    v == null ? null : Math.round(v * 10 ** d) / 10 ** d;

  return (
    <div className="page">
      <header className="page-head">
        <div>
          <h2>今日概览</h2>
          <p className="subtitle">{today.date} · 近 {days.length} 天数据</p>
        </div>
        <Link to="/trends" className="btn btn-plain">查看全部趋势 →</Link>
      </header>

      {/* Activity ---------------------------------------------------------- */}
      <section className="section">
        <h3 className="section-title">活动</h3>
        <div className="tile-grid">
          <StatTile
            label="步数"
            value={today.steps}
            detail={today.stepGoal ? `目标 ${today.stepGoal.toLocaleString()}` : undefined}
            progress={
              today.steps != null && today.stepGoal ? today.steps / today.stepGoal : null
            }
          />
          <StatTile
            label="距离"
            value={round(today.distanceMeters != null ? today.distanceMeters / 1000 : null, 2)}
            unit="km"
          />
          <StatTile label="爬楼" value={round(today.floorsAscended)} unit="层" />
          <StatTile
            label="强度分钟"
            value={today.intensityMinutes}
            unit="分钟"
            detail="中等以上强度"
          />
          <StatTile
            label="总消耗"
            value={round(today.caloriesBurned)}
            unit="kcal"
            detail={
              today.activeCalories != null
                ? `其中活动 ${Math.round(today.activeCalories)}`
                : undefined
            }
          />
          <StatTile
            label="久坐"
            value={round(
              today.sedentarySeconds != null ? today.sedentarySeconds / 3600 : null, 1
            )}
            unit="小时"
          />
        </div>
      </section>

      {/* Heart & stress ---------------------------------------------------- */}
      <section className="section">
        <h3 className="section-title">心率与压力</h3>
        <div className="tile-grid">
          <StatTile
            label="静息心率"
            value={today.heartRate}
            unit="bpm"
            status={rhrTone}
            statusLabel={rhrWord}
            detail={avgRhr != null ? `30 日均 ${Math.round(avgRhr)}` : undefined}
          />
          <StatTile
            label="心率区间"
            value={
              today.heartRateMin != null && today.heartRateMax != null
                ? `${today.heartRateMin}–${today.heartRateMax}`
                : null
            }
            unit="bpm"
          />
          <StatTile
            label="心率变异性"
            value={round(today.heartRateVariability)}
            unit="ms"
            detail={avgHrv != null ? `30 日均 ${Math.round(avgHrv)}` : undefined}
          />
          <StatTile
            label="平均压力"
            value={today.stress}
            detail={today.stressMax != null ? `峰值 ${today.stressMax}` : undefined}
          />
          <StatTile
            label="身体电量"
            value={
              today.bodyBatteryLow != null && today.bodyBatteryHigh != null
                ? `${today.bodyBatteryLow}–${today.bodyBatteryHigh}`
                : null
            }
            detail={
              today.bodyBatteryCharged != null
                ? `充 ${today.bodyBatteryCharged} / 耗 ${today.bodyBatteryDrained}`
                : undefined
            }
          />
          <StatTile label="训练准备度" value={today.trainingReadiness} unit="/100" />
        </div>
      </section>

      {/* Sleep & breathing -------------------------------------------------- */}
      <section className="section">
        <h3 className="section-title">睡眠与呼吸</h3>
        <div className="tile-grid">
          <StatTile
            label="睡眠时长"
            value={today.sleepDuration}
            unit="小时"
            status={sleepTone}
            statusLabel={sleepWord}
            detail={avgSleep != null ? `30 日均 ${avgSleep.toFixed(1)}` : undefined}
          />
          <StatTile label="睡眠评分" value={round(today.sleepQuality)} unit="/100" />
          <StatTile
            label="血氧"
            value={round(today.spo2Avg)}
            unit="%"
            detail={today.spo2Min != null ? `最低 ${today.spo2Min}%` : undefined}
          />
          <StatTile
            label="呼吸频率"
            value={round(today.respirationAvg)}
            unit="次/分"
            detail={
              today.respirationMin != null && today.respirationMax != null
                ? `${today.respirationMin}–${today.respirationMax}`
                : undefined
            }
          />
        </div>
        <p className="section-link">
          <Link to="/sleep">查看睡眠分期详情 →</Link>
        </p>
      </section>

      {/* Trends ------------------------------------------------------------- */}
      <section className="section">
        <h3 className="section-title">近 {days.length} 天趋势</h3>
        <div className="chart-grid">
          <Chart
            title="步数"
            subtitle={avgSteps != null ? `日均 ${Math.round(avgSteps).toLocaleString()} 步` : undefined}
            data={rows}
            type="bar"
            series={[{ key: 'steps', label: '步数', slot: 1, unit: '步' }]}
          />
          <Chart
            title="心率"
            unit="bpm"
            data={rows}
            type="line"
            series={[
              { key: 'heartRate', label: '静息', slot: 1, unit: 'bpm' },
              { key: 'heartRateMax', label: '最高', slot: 2, unit: 'bpm' },
            ]}
          />
          <Chart
            title="睡眠时长"
            unit="小时"
            data={rows}
            type="area"
            series={[{ key: 'sleepDuration', label: '睡眠', slot: 1, unit: '小时', decimals: 1 }]}
          />
          <Chart
            title="身体电量"
            data={rows}
            type="line"
            series={[
              { key: 'bodyBatteryHigh', label: '最高', slot: 1 },
              { key: 'bodyBatteryLow', label: '最低', slot: 2 },
            ]}
          />
        </div>
      </section>
    </div>
  );
}

export default Dashboard;