import { useState, useEffect } from 'react'
import { Pencil, Trash2, X, TrendingUp, TrendingDown, Minus } from 'lucide-react'
import { api } from '../utils/api'
import dayjs from 'dayjs'
import 'dayjs/locale/de'
dayjs.locale('de')

function empty() {
  return {
    date: dayjs().format('YYYY-MM-DD'),
    resting_hr: '',
    hrv: '',
    note: ''
  }
}

function EntryForm({ form, setForm, onSave, onCancel, saving, saveLabel = 'Speichern' }) {
  const set = (k, v) => setForm(f => ({ ...f, [k]: v }))

  return (
    <div>
      <div className="form-row">
        <label className="form-label">Datum</label>
        <input
          type="date"
          className="form-input"
          style={{ width: 140 }}
          value={form.date}
          onChange={e => set('date', e.target.value)}
        />
        <span className="form-unit" />
      </div>

      <div className="form-row">
        <label className="form-label">Ruhepuls *</label>
        <input
          type="number"
          className="form-input"
          min={30}
          max={120}
          step={1}
          placeholder="z.B. 58"
          value={form.resting_hr || ''}
          onChange={e => set('resting_hr', e.target.value)}
        />
        <span className="form-unit">bpm</span>
      </div>

      <div className="form-row">
        <label className="form-label">HRV</label>
        <input
          type="number"
          className="form-input"
          min={1}
          max={300}
          step={1}
          placeholder="optional"
          value={form.hrv || ''}
          onChange={e => set('hrv', e.target.value)}
        />
        <span className="form-unit">ms</span>
      </div>

      <div className="form-row">
        <label className="form-label">Notiz</label>
        <input
          type="text"
          className="form-input"
          placeholder="optional"
          value={form.note || ''}
          onChange={e => set('note', e.target.value)}
        />
        <span className="form-unit" />
      </div>

      <div style={{ display: 'flex', gap: 6, marginTop: 8 }}>
        <button
          className="btn btn-primary"
          style={{ flex: 1 }}
          onClick={onSave}
          disabled={saving}
        >
          {saveLabel}
        </button>
        {onCancel && (
          <button className="btn btn-secondary" style={{ flex: 1 }} onClick={onCancel}>
            <X size={13} /> Abbrechen
          </button>
        )}
      </div>
    </div>
  )
}

export default function VitalsPage() {
  const [entries, setEntries] = useState([])
  const [stats, setStats] = useState(null)
  const [tab, setTab] = useState('list')
  const [form, setForm] = useState(empty())
  const [editing, setEditing] = useState(null)
  const [saving, setSaving] = useState(false)
  const [saved, setSaved] = useState(false)
  const [error, setError] = useState(null)

  const load = async () => {
    try {
      const [e, s] = await Promise.all([api.listVitals(90), api.getVitalsStats(30)])
      setEntries(e)
      setStats(s)
    } catch (err) {
      console.error('Load failed:', err)
      setError(err.message)
    }
  }

  useEffect(() => {
    load()
  }, [])

  const handleSave = async () => {
    setSaving(true)
    setError(null)

    try {
      const payload = { date: form.date }

      // Only include fields if they have values
      if (form.resting_hr) payload.resting_hr = parseInt(form.resting_hr)
      if (form.hrv) payload.hrv = parseInt(form.hrv)
      if (form.note) payload.note = form.note

      if (!payload.resting_hr && !payload.hrv) {
        setError('Mindestens Ruhepuls oder HRV muss angegeben werden')
        setSaving(false)
        return
      }

      await api.createVitals(payload)
      setSaved(true)
      await load()
      setTimeout(() => {
        setSaved(false)
        setForm(empty())
      }, 1500)
    } catch (err) {
      console.error('Save failed:', err)
      setError(err.message || 'Fehler beim Speichern')
      setTimeout(() => setError(null), 5000)
    } finally {
      setSaving(false)
    }
  }

  const handleUpdate = async () => {
    try {
      const payload = {}

      // Only include fields if they have values
      if (editing.date) payload.date = editing.date
      if (editing.resting_hr) payload.resting_hr = parseInt(editing.resting_hr)
      if (editing.hrv) payload.hrv = parseInt(editing.hrv)
      if (editing.note) payload.note = editing.note

      await api.updateVitals(editing.id, payload)
      setEditing(null)
      await load()
    } catch (err) {
      console.error('Update failed:', err)
      setError(err.message)
    }
  }

  const handleDelete = async (id) => {
    if (!confirm('Eintrag löschen?')) return
    try {
      await api.deleteVitals(id)
      await load()
    } catch (err) {
      console.error('Delete failed:', err)
      setError(err.message)
    }
  }

  const getTrendIcon = (trend) => {
    if (trend === 'increasing') return <TrendingUp size={14} style={{ color: '#D85A30' }} />
    if (trend === 'decreasing') return <TrendingDown size={14} style={{ color: '#1D9E75' }} />
    return <Minus size={14} style={{ color: 'var(--text3)' }} />
  }

  return (
    <div>
      <h1 className="page-title">Vitalwerte</h1>

      <div className="tabs" style={{ overflowX: 'auto', flexWrap: 'nowrap' }}>
        <button className={'tab' + (tab === 'list' ? ' active' : '')} onClick={() => setTab('list')}>
          Verlauf
        </button>
        <button className={'tab' + (tab === 'add' ? ' active' : '')} onClick={() => setTab('add')}>
          + Erfassen
        </button>
        <button className={'tab' + (tab === 'stats' ? ' active' : '')} onClick={() => setTab('stats')}>
          Statistik
        </button>
      </div>

      {/* Stats Overview */}
      {stats && stats.total_entries > 0 && (
        <div className="card section-gap">
          <div style={{ display: 'flex', gap: 8, flexWrap: 'wrap' }}>
            <div style={{
              flex: 1,
              minWidth: 120,
              background: 'var(--surface2)',
              borderRadius: 8,
              padding: '8px 10px',
              textAlign: 'center'
            }}>
              <div style={{ fontSize: 18, fontWeight: 700, color: '#378ADD' }}>
                {stats.avg_resting_hr_7d ? Math.round(stats.avg_resting_hr_7d) : '—'}
              </div>
              <div style={{ fontSize: 10, color: 'var(--text3)' }}>Ø Ruhepuls 7d</div>
            </div>
            <div style={{
              flex: 1,
              minWidth: 120,
              background: 'var(--surface2)',
              borderRadius: 8,
              padding: '8px 10px',
              textAlign: 'center'
            }}>
              <div style={{ fontSize: 18, fontWeight: 700, color: '#1D9E75' }}>
                {stats.avg_hrv_7d ? Math.round(stats.avg_hrv_7d) : '—'}
              </div>
              <div style={{ fontSize: 10, color: 'var(--text3)' }}>Ø HRV 7d</div>
            </div>
            <div style={{
              flex: 1,
              minWidth: 120,
              background: 'var(--surface2)',
              borderRadius: 8,
              padding: '8px 10px',
              textAlign: 'center'
            }}>
              <div style={{ fontSize: 18, fontWeight: 700, color: 'var(--text2)' }}>
                {stats.total_entries}
              </div>
              <div style={{ fontSize: 10, color: 'var(--text3)' }}>Einträge</div>
            </div>
          </div>
        </div>
      )}

      {tab === 'add' && (
        <div className="card section-gap">
          <div className="card-title">Vitalwerte erfassen</div>
          <p style={{ fontSize: 13, color: 'var(--text2)', marginBottom: 10, lineHeight: 1.6 }}>
            Morgens nach dem Aufwachen, vor dem Aufstehen: Ruhepuls messen (z.B. mit Apple Watch oder Smartwatch).
            HRV ist optional.
          </p>
          {error && (
            <div style={{
              padding: '10px',
              background: '#FCEBEB',
              border: '1px solid #D85A30',
              borderRadius: 8,
              fontSize: 13,
              color: '#D85A30',
              marginBottom: 8
            }}>
              {error}
            </div>
          )}
          <EntryForm
            form={form}
            setForm={setForm}
            onSave={handleSave}
            saveLabel={saved ? '✓ Gespeichert!' : 'Speichern'}
            saving={saving}
          />
        </div>
      )}

      {tab === 'stats' && stats && (
        <div className="card section-gap">
          <div className="card-title">Trend-Analyse (14 Tage)</div>

          <div style={{ marginBottom: 16 }}>
            <div style={{
              display: 'flex',
              justifyContent: 'space-between',
              alignItems: 'center',
              padding: '8px 0',
              borderBottom: '1px solid var(--border)'
            }}>
              <div style={{ fontSize: 13, fontWeight: 600 }}>Ruhepuls</div>
              <div style={{ display: 'flex', alignItems: 'center', gap: 6 }}>
                {getTrendIcon(stats.trend_resting_hr)}
                <span style={{ fontSize: 13, color: 'var(--text2)' }}>
                  {stats.trend_resting_hr === 'increasing' ? 'Steigend' :
                   stats.trend_resting_hr === 'decreasing' ? 'Sinkend' : 'Stabil'}
                </span>
              </div>
            </div>

            <div style={{
              display: 'flex',
              justifyContent: 'space-between',
              alignItems: 'center',
              padding: '8px 0'
            }}>
              <div style={{ fontSize: 13, fontWeight: 600 }}>HRV</div>
              <div style={{ display: 'flex', alignItems: 'center', gap: 6 }}>
                {getTrendIcon(stats.trend_hrv)}
                <span style={{ fontSize: 13, color: 'var(--text2)' }}>
                  {stats.trend_hrv === 'increasing' ? 'Steigend' :
                   stats.trend_hrv === 'decreasing' ? 'Sinkend' : 'Stabil'}
                </span>
              </div>
            </div>
          </div>

          <div style={{
            padding: 12,
            background: 'var(--surface2)',
            borderRadius: 8,
            fontSize: 12,
            color: 'var(--text2)',
            lineHeight: 1.6
          }}>
            <strong>Interpretation:</strong><br />
            • Ruhepuls sinkend = bessere Fitness 💪<br />
            • HRV steigend = bessere Erholung ✨<br />
            • Ruhepuls steigend + HRV sinkend = Übertraining-Signal ⚠️
          </div>
        </div>
      )}

      {tab === 'list' && (
        <div>
          {entries.length === 0 && (
            <div className="empty-state">
              <h3>Keine Einträge</h3>
              <p>Erfasse deine ersten Vitalwerte im Tab "Erfassen".</p>
            </div>
          )}
          {entries.map(e => {
            const isEd = editing?.id === e.id
            return (
              <div key={e.id} className="card" style={{ marginBottom: 8 }}>
                {isEd ? (
                  <EntryForm
                    form={editing}
                    setForm={setEditing}
                    onSave={handleUpdate}
                    onCancel={() => setEditing(null)}
                    saveLabel="Speichern"
                  />
                ) : (
                  <div>
                    <div style={{
                      display: 'flex',
                      justifyContent: 'space-between',
                      alignItems: 'flex-start'
                    }}>
                      <div style={{ flex: 1 }}>
                        <div style={{ fontSize: 14, fontWeight: 600, marginBottom: 2 }}>
                          {dayjs(e.date).format('dd, DD. MMMM YYYY')}
                        </div>
                        <div style={{ display: 'flex', gap: 10, flexWrap: 'wrap', marginTop: 6 }}>
                          {e.resting_hr && (
                            <span style={{ fontSize: 12, color: 'var(--text2)' }}>
                              ❤️ {e.resting_hr} bpm
                            </span>
                          )}
                          {e.hrv && (
                            <span style={{ fontSize: 12, color: 'var(--text2)' }}>
                              📊 HRV {e.hrv} ms
                            </span>
                          )}
                          {e.source !== 'manual' && (
                            <span style={{ fontSize: 10, color: 'var(--text3)' }}>
                              {e.source === 'apple_health' ? 'Apple Health' : e.source}
                            </span>
                          )}
                        </div>
                        {e.note && (
                          <p style={{
                            fontSize: 12,
                            color: 'var(--text2)',
                            fontStyle: 'italic',
                            marginTop: 4
                          }}>
                            "{e.note}"
                          </p>
                        )}
                      </div>
                      <div style={{ display: 'flex', gap: 6, marginLeft: 8 }}>
                        <button
                          className="btn btn-secondary"
                          style={{ padding: '5px 8px' }}
                          onClick={() => setEditing({ ...e })}
                        >
                          <Pencil size={13} />
                        </button>
                        <button
                          className="btn btn-danger"
                          style={{ padding: '5px 8px' }}
                          onClick={() => handleDelete(e.id)}
                        >
                          <Trash2 size={13} />
                        </button>
                      </div>
                    </div>
                  </div>
                )}
              </div>
            )
          })}
        </div>
      )}
    </div>
  )
}