import { useState, useEffect } from 'react'
import { Target, Plus, Pencil, Trash2, TrendingUp, Calendar } from 'lucide-react'
import { api } from '../utils/api'
import dayjs from 'dayjs'
import 'dayjs/locale/de'
dayjs.locale('de')

// Goal Mode Definitions
const GOAL_MODES = [
  {
    id: 'weight_loss',
    icon: '📉',
    label: 'Gewichtsreduktion',
    description: 'Kaloriendefizit, Fettabbau',
    color: '#D85A30'
  },
  {
    id: 'strength',
    icon: '💪',
    label: 'Kraftaufbau',
    description: 'Muskelwachstum, progressive Belastung',
    color: '#378ADD'
  },
  {
    id: 'endurance',
    icon: '🏃',
    label: 'Ausdauer',
    description: 'VO2Max, aerobe Kapazität',
    color: '#1D9E75'
  },
  {
    id: 'recomposition',
    icon: '⚖️',
    label: 'Körperkomposition',
    description: 'Gleichzeitig Fett ab- & Muskeln aufbauen',
    color: '#7B68EE'
  },
  {
    id: 'health',
    icon: '❤️',
    label: 'Allgemeine Gesundheit',
    description: 'Ausgewogen, präventiv',
    color: '#E67E22'
  }
]

// Goal Type Definitions
const GOAL_TYPES = {
  weight: { label: 'Gewicht', unit: 'kg', icon: '⚖️' },
  body_fat: { label: 'Körperfett', unit: '%', icon: '📊' },
  lean_mass: { label: 'Muskelmasse', unit: 'kg', icon: '💪' },
  vo2max: { label: 'VO2Max', unit: 'ml/kg/min', icon: '🫁' },
  strength: { label: 'Kraft', unit: 'kg', icon: '🏋️' },
  flexibility: { label: 'Beweglichkeit', unit: 'cm', icon: '🤸' },
  bp: { label: 'Blutdruck', unit: 'mmHg', icon: '❤️' },
  rhr: { label: 'Ruhepuls', unit: 'bpm', icon: '💓' }
}

export default function GoalsPage() {
  const [goalMode, setGoalMode] = useState(null)
  const [goals, setGoals] = useState([])
  const [showGoalForm, setShowGoalForm] = useState(false)
  const [editingGoal, setEditingGoal] = useState(null)
  const [loading, setLoading] = useState(true)
  const [error, setError] = useState(null)
  const [toast, setToast] = useState(null)

  // Form state
  const [formData, setFormData] = useState({
    goal_type: 'weight',
    is_primary: false,
    target_value: '',
    unit: 'kg',
    target_date: '',
    name: '',
    description: ''
  })

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

  const loadData = async () => {
    setLoading(true)
    setError(null)
    try {
      const [modeData, goalsData] = await Promise.all([
        api.getGoalMode(),
        api.listGoals()
      ])
      setGoalMode(modeData.goal_mode)
      setGoals(goalsData)
    } catch (err) {
      console.error('Failed to load goals:', err)
      setError('Fehler beim Laden der Ziele')
    } finally {
      setLoading(false)
    }
  }

  const showToast = (message, duration = 2000) => {
    setToast(message)
    setTimeout(() => setToast(null), duration)
  }

  const handleGoalModeChange = async (newMode) => {
    try {
      await api.updateGoalMode(newMode)
      setGoalMode(newMode)
      showToast('✓ Trainingsmodus aktualisiert')
    } catch (err) {
      console.error('Failed to update goal mode:', err)
      setError('Fehler beim Aktualisieren des Trainingsmodus')
    }
  }

  const handleCreateGoal = () => {
    setEditingGoal(null)
    setFormData({
      goal_type: 'weight',
      is_primary: goals.length === 0, // First goal is primary by default
      target_value: '',
      unit: GOAL_TYPES['weight'].unit,
      target_date: '',
      name: '',
      description: ''
    })
    setShowGoalForm(true)
  }

  const handleEditGoal = (goal) => {
    setEditingGoal(goal.id)
    setFormData({
      goal_type: goal.goal_type,
      is_primary: goal.is_primary,
      target_value: goal.target_value,
      unit: goal.unit,
      target_date: goal.target_date || '',
      name: goal.name || '',
      description: goal.description || ''
    })
    setShowGoalForm(true)
  }

  const handleGoalTypeChange = (type) => {
    setFormData(f => ({
      ...f,
      goal_type: type,
      unit: GOAL_TYPES[type].unit
    }))
  }

  const handleSaveGoal = async () => {
    if (!formData.target_value) {
      setError('Bitte Zielwert eingeben')
      return
    }

    try {
      const data = {
        goal_type: formData.goal_type,
        is_primary: formData.is_primary,
        target_value: parseFloat(formData.target_value),
        unit: formData.unit,
        target_date: formData.target_date || null,
        name: formData.name || null,
        description: formData.description || null
      }

      if (editingGoal) {
        await api.updateGoal(editingGoal, data)
        showToast('✓ Ziel aktualisiert')
      } else {
        await api.createGoal(data)
        showToast('✓ Ziel erstellt')
      }

      await loadData()
      setShowGoalForm(false)
      setEditingGoal(null)
    } catch (err) {
      console.error('Failed to save goal:', err)
      setError(err.message || 'Fehler beim Speichern')
    }
  }

  const handleDeleteGoal = async (goalId) => {
    if (!confirm('Ziel wirklich löschen?')) return

    try {
      await api.deleteGoal(goalId)
      showToast('✓ Ziel gelöscht')
      await loadData()
    } catch (err) {
      console.error('Failed to delete goal:', err)
      setError('Fehler beim Löschen')
    }
  }

  const getProgressColor = (progress) => {
    if (progress >= 100) return 'var(--accent)'
    if (progress >= 75) return '#1D9E75'
    if (progress >= 50) return '#378ADD'
    if (progress >= 25) return '#E67E22'
    return '#D85A30'
  }

  if (loading) {
    return (
      <div className="page">
        <div style={{ textAlign: 'center', padding: '40px' }}>
          <div className="spinner"></div>
        </div>
      </div>
    )
  }

  return (
    <div className="page">
      <div className="page-header">
        <h1><Target size={24} /> Ziele</h1>
      </div>

      {error && (
        <div className="card" style={{ background: '#FEF2F2', border: '1px solid #FCA5A5', marginBottom: 16 }}>
          <p style={{ color: '#DC2626', margin: 0 }}>{error}</p>
        </div>
      )}

      {toast && (
        <div style={{
          position: 'fixed',
          top: 16,
          right: 16,
          background: 'var(--accent)',
          color: 'white',
          padding: '12px 20px',
          borderRadius: 8,
          boxShadow: '0 4px 12px rgba(0,0,0,0.15)',
          zIndex: 1000
        }}>
          {toast}
        </div>
      )}

      {/* Strategic Goal Mode Selection */}
      <div className="card" style={{ marginBottom: 16 }}>
        <h2 style={{ marginTop: 0 }}>🎯 Trainingsmodus</h2>
        <p style={{ color: 'var(--text2)', fontSize: 14, marginBottom: 16 }}>
          Wähle deine grundlegende Trainingsausrichtung. Dies beeinflusst die Gewichtung
          und Interpretation aller Analysen.
        </p>

        <div style={{
          display: 'grid',
          gridTemplateColumns: 'repeat(auto-fit, minmax(200px, 1fr))',
          gap: 12
        }}>
          {GOAL_MODES.map(mode => (
            <button
              key={mode.id}
              onClick={() => handleGoalModeChange(mode.id)}
              className={goalMode === mode.id ? 'btn-primary' : 'btn-secondary'}
              style={{
                padding: 16,
                textAlign: 'left',
                background: goalMode === mode.id ? mode.color : 'var(--surface)',
                borderColor: goalMode === mode.id ? mode.color : 'var(--border)',
                color: goalMode === mode.id ? 'white' : 'var(--text1)'
              }}
            >
              <div style={{ fontSize: 24, marginBottom: 8 }}>{mode.icon}</div>
              <div style={{ fontWeight: 600, marginBottom: 4 }}>{mode.label}</div>
              <div style={{
                fontSize: 12,
                opacity: goalMode === mode.id ? 0.9 : 0.7
              }}>
                {mode.description}
              </div>
            </button>
          ))}
        </div>
      </div>

      {/* Tactical Goals List */}
      <div className="card">
        <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'center', marginBottom: 16 }}>
          <h2 style={{ margin: 0 }}>🎯 Konkrete Ziele</h2>
          <button className="btn-primary" onClick={handleCreateGoal}>
            <Plus size={16} /> Ziel hinzufügen
          </button>
        </div>

        {goals.length === 0 ? (
          <div style={{ textAlign: 'center', padding: '40px 20px', color: 'var(--text2)' }}>
            <Target size={48} style={{ opacity: 0.3, marginBottom: 16 }} />
            <p>Noch keine Ziele definiert</p>
            <button className="btn-primary" onClick={handleCreateGoal} style={{ marginTop: 16 }}>
              Erstes Ziel erstellen
            </button>
          </div>
        ) : (
          <div style={{ display: 'flex', flexDirection: 'column', gap: 12 }}>
            {goals.map(goal => {
              const typeInfo = GOAL_TYPES[goal.goal_type] || {}
              return (
                <div
                  key={goal.id}
                  className="card"
                  style={{
                    background: 'var(--surface2)',
                    border: goal.is_primary ? '2px solid var(--accent)' : '1px solid var(--border)'
                  }}
                >
                  <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'flex-start' }}>
                    <div style={{ flex: 1 }}>
                      <div style={{ display: 'flex', alignItems: 'center', gap: 8, marginBottom: 8 }}>
                        <span style={{ fontSize: 20 }}>{typeInfo.icon}</span>
                        <span style={{ fontWeight: 600 }}>
                          {goal.name || typeInfo.label}
                        </span>
                        {goal.is_primary && (
                          <span style={{
                            background: 'var(--accent)',
                            color: 'white',
                            fontSize: 11,
                            padding: '2px 8px',
                            borderRadius: 4
                          }}>
                            PRIMÄR
                          </span>
                        )}
                        <span style={{
                          background: goal.status === 'active' ? '#E6F4F1' : '#F3F4F6',
                          color: goal.status === 'active' ? 'var(--accent)' : 'var(--text2)',
                          fontSize: 11,
                          padding: '2px 8px',
                          borderRadius: 4
                        }}>
                          {goal.status === 'active' ? 'AKTIV' : goal.status?.toUpperCase()}
                        </span>
                      </div>

                      <div style={{ display: 'flex', gap: 24, marginBottom: 12, fontSize: 14 }}>
                        <div>
                          <span style={{ color: 'var(--text2)' }}>Start:</span>{' '}
                          <strong>{goal.start_value} {goal.unit}</strong>
                        </div>
                        <div>
                          <span style={{ color: 'var(--text2)' }}>Aktuell:</span>{' '}
                          <strong>{goal.current_value || '—'} {goal.unit}</strong>
                        </div>
                        <div>
                          <span style={{ color: 'var(--text2)' }}>Ziel:</span>{' '}
                          <strong>{goal.target_value} {goal.unit}</strong>
                        </div>
                        {goal.target_date && (
                          <div>
                            <Calendar size={14} style={{ verticalAlign: 'middle', marginRight: 4 }} />
                            {dayjs(goal.target_date).format('DD.MM.YYYY')}
                          </div>
                        )}
                      </div>

                      {goal.progress_pct !== null && (
                        <div>
                          <div style={{
                            display: 'flex',
                            justifyContent: 'space-between',
                            fontSize: 12,
                            marginBottom: 4
                          }}>
                            <span>Fortschritt</span>
                            <span style={{ fontWeight: 600 }}>{goal.progress_pct}%</span>
                          </div>
                          <div style={{
                            width: '100%',
                            height: 6,
                            background: 'var(--surface)',
                            borderRadius: 3,
                            overflow: 'hidden'
                          }}>
                            <div style={{
                              width: `${Math.min(100, Math.max(0, goal.progress_pct))}%`,
                              height: '100%',
                              background: getProgressColor(goal.progress_pct),
                              transition: 'width 0.3s ease'
                            }} />
                          </div>

                          {goal.on_track !== null && (
                            <div style={{ marginTop: 8, fontSize: 12 }}>
                              {goal.on_track ? (
                                <span style={{ color: 'var(--accent)' }}>
                                  ✓ Ziel voraussichtlich erreichbar bis {dayjs(goal.target_date).format('DD.MM.YYYY')}
                                </span>
                              ) : (
                                <span style={{ color: '#D85A30' }}>
                                  ⚠ Prognose: {goal.projection_date ? dayjs(goal.projection_date).format('DD.MM.YYYY') : 'Offen'}
                                  {goal.target_date && ' (später als geplant)'}
                                </span>
                              )}
                            </div>
                          )}
                        </div>
                      )}
                    </div>

                    <div style={{ display: 'flex', gap: 8 }}>
                      <button
                        className="btn-secondary"
                        onClick={() => handleEditGoal(goal)}
                        style={{ padding: '6px 12px' }}
                      >
                        <Pencil size={14} />
                      </button>
                      <button
                        className="btn-secondary"
                        onClick={() => handleDeleteGoal(goal.id)}
                        style={{ padding: '6px 12px', color: '#DC2626' }}
                      >
                        <Trash2 size={14} />
                      </button>
                    </div>
                  </div>
                </div>
              )
            })}
          </div>
        )}
      </div>

      {/* Goal Form Modal */}
      {showGoalForm && (
        <div style={{
          position: 'fixed',
          top: 0,
          left: 0,
          right: 0,
          bottom: 0,
          background: 'rgba(0,0,0,0.5)',
          display: 'flex',
          alignItems: 'flex-start',
          justifyContent: 'center',
          zIndex: 1000,
          padding: 16,
          paddingTop: 40,
          overflowY: 'auto'
        }}>
          <div className="card" style={{
            maxWidth: 500,
            width: '100%',
            marginBottom: 40
          }}>
            <div className="card-title">
              {editingGoal ? 'Ziel bearbeiten' : 'Neues Ziel'}
            </div>

            {error && (
              <div style={{
                padding: 10,
                background: '#FCEBEB',
                border: '1px solid #D85A30',
                borderRadius: 8,
                fontSize: 13,
                color: '#D85A30',
                marginBottom: 16
              }}>
                {error}
              </div>
            )}

            {/* Zieltyp */}
            <div style={{ marginBottom: 16 }}>
              <label style={{
                display: 'block',
                fontSize: 13,
                fontWeight: 600,
                marginBottom: 4,
                color: 'var(--text2)'
              }}>
                Zieltyp
              </label>
              <select
                className="form-input"
                style={{ width: '100%' }}
                value={formData.goal_type}
                onChange={e => handleGoalTypeChange(e.target.value)}
              >
                {Object.entries(GOAL_TYPES).map(([key, info]) => (
                  <option key={key} value={key}>
                    {info.icon} {info.label}
                  </option>
                ))}
              </select>
            </div>

            {/* Name */}
            <div style={{ marginBottom: 16 }}>
              <label style={{
                display: 'block',
                fontSize: 13,
                fontWeight: 500,
                marginBottom: 4,
                color: 'var(--text2)'
              }}>
                Name (optional)
              </label>
              <input
                type="text"
                className="form-input"
                style={{ width: '100%', textAlign: 'left' }}
                value={formData.name}
                onChange={e => setFormData(f => ({ ...f, name: e.target.value }))}
                placeholder="z.B. Sommerfigur 2026"
              />
            </div>

            {/* Zielwert */}
            <div style={{ fontSize: 14, fontWeight: 600, marginBottom: 8, marginTop: 20, color: 'var(--text1)' }}>
              🎯 Zielwert
            </div>
            <div style={{ marginBottom: 16 }}>
              <label style={{
                display: 'block',
                fontSize: 13,
                fontWeight: 500,
                marginBottom: 4,
                color: 'var(--text2)'
              }}>
                Wert *
              </label>
              <div style={{ display: 'flex', gap: 8 }}>
                <input
                  type="number"
                  step="0.01"
                  className="form-input"
                  style={{ flex: 1 }}
                  value={formData.target_value}
                  onChange={e => setFormData(f => ({ ...f, target_value: e.target.value }))}
                  placeholder="Zielwert eingeben"
                />
                <div style={{
                  padding: '8px 16px',
                  background: 'var(--surface2)',
                  border: '1px solid var(--border)',
                  borderRadius: 8,
                  fontSize: 14,
                  fontWeight: 600,
                  color: 'var(--text2)',
                  minWidth: 70,
                  display: 'flex',
                  alignItems: 'center',
                  justifyContent: 'center'
                }}>
                  {formData.unit}
                </div>
              </div>
            </div>

            {/* Zieldatum */}
            <div style={{ marginBottom: 16 }}>
              <label style={{
                display: 'block',
                fontSize: 13,
                fontWeight: 500,
                marginBottom: 4,
                color: 'var(--text2)'
              }}>
                Zieldatum (optional)
              </label>
              <input
                type="date"
                className="form-input"
                style={{ width: '100%', textAlign: 'left' }}
                value={formData.target_date}
                onChange={e => setFormData(f => ({ ...f, target_date: e.target.value }))}
              />
            </div>

            {/* Beschreibung */}
            <div style={{ marginBottom: 16 }}>
              <label style={{
                display: 'block',
                fontSize: 13,
                fontWeight: 500,
                marginBottom: 4,
                color: 'var(--text2)'
              }}>
                Beschreibung (optional)
              </label>
              <textarea
                className="form-input"
                style={{ width: '100%', minHeight: 80, textAlign: 'left' }}
                value={formData.description}
                onChange={e => setFormData(f => ({ ...f, description: e.target.value }))}
                rows={3}
                placeholder="Warum ist dir dieses Ziel wichtig?"
              />
            </div>

            {/* Primärziel */}
            <div style={{
              padding: 12,
              background: 'var(--surface2)',
              borderRadius: 8,
              marginBottom: 20
            }}>
              <label style={{
                display: 'flex',
                alignItems: 'flex-start',
                gap: 10,
                cursor: 'pointer'
              }}>
                <input
                  type="checkbox"
                  checked={formData.is_primary}
                  onChange={e => setFormData(f => ({ ...f, is_primary: e.target.checked }))}
                  style={{ marginTop: 2 }}
                />
                <div>
                  <div style={{ fontSize: 13, fontWeight: 600, marginBottom: 2 }}>
                    Als Primärziel setzen
                  </div>
                  <div style={{ fontSize: 12, color: 'var(--text2)' }}>
                    Dein Primärziel hat höchste Priorität in Analysen und Charts
                  </div>
                </div>
              </label>
            </div>

            {/* Buttons */}
            <button
              className="btn btn-primary btn-full"
              onClick={handleSaveGoal}
              style={{ marginBottom: 8 }}
            >
              {editingGoal ? 'Aktualisieren' : 'Ziel erstellen'}
            </button>
            <button
              className="btn btn-secondary btn-full"
              onClick={() => {
                setShowGoalForm(false)
                setEditingGoal(null)
                setError(null)
              }}
            >
              Abbrechen
            </button>
          </div>
        </div>
      )}
    </div>
  )
}