import React, { useState, useEffect } from 'react'
import api from '../utils/api'
import { useAuth } from '../context/AuthContext'

function TrainingPlanningPage() {
  const { user } = useAuth()
  const [groups, setGroups] = useState([])
  const [selectedGroupId, setSelectedGroupId] = useState('')
  const [units, setUnits] = useState([])
  const [exercises, setExercises] = useState([])
  const [loading, setLoading] = useState(true)
  const [showModal, setShowModal] = useState(false)
  const [editingUnit, setEditingUnit] = useState(null)

  // Date range (default: next 30 days)
  const today = new Date().toISOString().split('T')[0]
  const thirtyDaysLater = new Date(Date.now() + 30 * 24 * 60 * 60 * 1000).toISOString().split('T')[0]

  const [startDate, setStartDate] = useState(today)
  const [endDate, setEndDate] = useState(thirtyDaysLater)

  // Form state
  const [formData, setFormData] = useState({
    group_id: '',
    planned_date: '',
    planned_time_start: '',
    planned_time_end: '',
    planned_focus: '',
    actual_date: '',
    actual_time_start: '',
    actual_time_end: '',
    attendance_count: '',
    status: 'planned',
    notes: '',
    trainer_notes: '',
    exercises: []
  })

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

  useEffect(() => {
    if (selectedGroupId) {
      loadUnits()
    }
  }, [selectedGroupId, startDate, endDate])

  const loadData = async () => {
    try {
      const [groupsData, exercisesData] = await Promise.all([
        api.listTrainingGroups({ status: 'active' }),
        api.listExercises()
      ])
      setGroups(groupsData)
      setExercises(exercisesData)

      // Auto-select first group if trainer owns it
      if (groupsData.length > 0) {
        const ownGroup = groupsData.find(g => g.trainer_id === user?.id)
        if (ownGroup) {
          setSelectedGroupId(ownGroup.id)
        } else if (groupsData.length === 1) {
          setSelectedGroupId(groupsData[0].id)
        }
      }
    } catch (err) {
      console.error('Failed to load data:', err)
      alert('Fehler beim Laden: ' + err.message)
    } finally {
      setLoading(false)
    }
  }

  const loadUnits = async () => {
    if (!selectedGroupId) return

    try {
      const unitsData = await api.listTrainingUnits({ group_id: selectedGroupId, start_date: startDate, end_date: endDate })
      setUnits(unitsData)
    } catch (err) {
      console.error('Failed to load units:', err)
    }
  }

  const handleQuickCreate = async () => {
    if (!selectedGroupId) {
      alert('Bitte wähle zuerst eine Trainingsgruppe')
      return
    }

    const date = prompt('Datum für neue Trainingseinheit (YYYY-MM-DD):', today)
    if (!date) return

    try {
      await api.quickCreateTrainingUnit({
        group_id: parseInt(selectedGroupId),
        planned_date: date
      })
      await loadUnits()
    } catch (err) {
      alert('Fehler beim Erstellen: ' + err.message)
    }
  }

  const handleCreate = () => {
    if (!selectedGroupId) {
      alert('Bitte wähle zuerst eine Trainingsgruppe')
      return
    }

    const group = groups.find(g => g.id === parseInt(selectedGroupId))

    setEditingUnit(null)
    setFormData({
      group_id: selectedGroupId,
      planned_date: today,
      planned_time_start: group?.time_start?.slice(0, 5) || '',
      planned_time_end: group?.time_end?.slice(0, 5) || '',
      planned_focus: '',
      actual_date: '',
      actual_time_start: '',
      actual_time_end: '',
      attendance_count: '',
      status: 'planned',
      notes: '',
      trainer_notes: '',
      exercises: []
    })
    setShowModal(true)
  }

  const handleEdit = async (unit) => {
    try {
      const fullUnit = await api.getTrainingUnit(unit.id)
      setEditingUnit(fullUnit)
      setFormData({
        group_id: fullUnit.group_id,
        planned_date: fullUnit.planned_date || '',
        planned_time_start: fullUnit.planned_time_start?.slice(0, 5) || '',
        planned_time_end: fullUnit.planned_time_end?.slice(0, 5) || '',
        planned_focus: fullUnit.planned_focus || '',
        actual_date: fullUnit.actual_date || '',
        actual_time_start: fullUnit.actual_time_start?.slice(0, 5) || '',
        actual_time_end: fullUnit.actual_time_end?.slice(0, 5) || '',
        attendance_count: fullUnit.attendance_count || '',
        status: fullUnit.status || 'planned',
        notes: fullUnit.notes || '',
        trainer_notes: fullUnit.trainer_notes || '',
        exercises: fullUnit.exercises || []
      })
      setShowModal(true)
    } catch (err) {
      alert('Fehler beim Laden: ' + err.message)
    }
  }

  const handleDelete = async (unit) => {
    if (!confirm(`Trainingseinheit vom ${unit.planned_date} wirklich löschen?`)) return

    try {
      await api.deleteTrainingUnit(unit.id)
      await loadUnits()
    } catch (err) {
      alert('Fehler beim Löschen: ' + err.message)
    }
  }

  const handleSubmit = async (e) => {
    e.preventDefault()

    if (!formData.group_id || !formData.planned_date) {
      alert('Gruppe und Datum sind Pflichtfelder')
      return
    }

    try {
      const payload = {
        ...formData,
        group_id: parseInt(formData.group_id),
        attendance_count: formData.attendance_count ? parseInt(formData.attendance_count) : null,
        exercises: formData.exercises.map((ex, idx) => ({
          exercise_id: ex.exercise_id,
          order_index: idx,
          planned_duration_min: ex.planned_duration_min ? parseInt(ex.planned_duration_min) : null,
          actual_duration_min: ex.actual_duration_min ? parseInt(ex.actual_duration_min) : null,
          notes: ex.notes || null,
          modifications: ex.modifications || null
        }))
      }

      if (editingUnit) {
        await api.updateTrainingUnit(editingUnit.id, payload)
      } else {
        await api.createTrainingUnit(payload)
      }

      setShowModal(false)
      await loadUnits()
    } catch (err) {
      alert('Fehler beim Speichern: ' + err.message)
    }
  }

  const updateFormField = (field, value) => {
    setFormData(prev => ({ ...prev, [field]: value }))
  }

  const addExercise = () => {
    setFormData(prev => ({
      ...prev,
      exercises: [...prev.exercises, {
        exercise_id: '',
        planned_duration_min: '',
        actual_duration_min: '',
        notes: '',
        modifications: ''
      }]
    }))
  }

  const updateExercise = (index, field, value) => {
    setFormData(prev => ({
      ...prev,
      exercises: prev.exercises.map((ex, i) =>
        i === index ? { ...ex, [field]: value } : ex
      )
    }))
  }

  const removeExercise = (index) => {
    setFormData(prev => ({
      ...prev,
      exercises: prev.exercises.filter((_, i) => i !== index)
    }))
  }

  const moveExercise = (index, direction) => {
    const newExercises = [...formData.exercises]
    const target = index + direction

    if (target < 0 || target >= newExercises.length) return

    [newExercises[index], newExercises[target]] = [newExercises[target], newExercises[index]]
    setFormData(prev => ({ ...prev, exercises: newExercises }))
  }

  if (loading) {
    return (
      <div style={{ padding: '2rem', textAlign: 'center' }}>
        <div className="spinner"></div>
        <p>Laden...</p>
      </div>
    )
  }

  const selectedGroup = groups.find(g => g.id === parseInt(selectedGroupId))

  return (
    <div style={{ padding: '2rem' }}>
      <div style={{ maxWidth: '1200px', margin: '0 auto' }}>
        <h1 style={{ marginBottom: '1.5rem' }}>Trainingsplanung</h1>

        {/* Group & Date Controls */}
        <div className="card" style={{ marginBottom: '1.5rem' }}>
          <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(200px, 1fr))', gap: '1rem' }}>
            <div>
              <label className="form-label">Trainingsgruppe</label>
              <select
                className="form-input"
                value={selectedGroupId}
                onChange={(e) => setSelectedGroupId(e.target.value)}
              >
                <option value="">Bitte wählen</option>
                {groups.map(g => (
                  <option key={g.id} value={g.id}>
                    {g.name} ({g.club_name})
                  </option>
                ))}
              </select>
            </div>

            <div>
              <label className="form-label">Von</label>
              <input
                type="date"
                className="form-input"
                value={startDate}
                onChange={(e) => setStartDate(e.target.value)}
              />
            </div>

            <div>
              <label className="form-label">Bis</label>
              <input
                type="date"
                className="form-input"
                value={endDate}
                onChange={(e) => setEndDate(e.target.value)}
              />
            </div>
          </div>

          {selectedGroup && (
            <div style={{ marginTop: '1rem', padding: '1rem', background: 'var(--surface2)', borderRadius: '8px' }}>
              <p style={{ fontSize: '0.875rem', color: 'var(--text2)' }}>
                📍 {selectedGroup.location || 'Kein Ort angegeben'}
                {selectedGroup.weekday && ` · ${selectedGroup.weekday}`}
                {selectedGroup.time_start && ` · ${selectedGroup.time_start.slice(0, 5)} - ${selectedGroup.time_end?.slice(0, 5)}`}
              </p>
            </div>
          )}
        </div>

        {/* Action Buttons */}
        {selectedGroupId && (
          <div style={{ display: 'flex', gap: '0.5rem', marginBottom: '1.5rem' }}>
            <button className="btn btn-primary" onClick={handleCreate}>
              + Neue Trainingseinheit
            </button>
            <button className="btn btn-secondary" onClick={handleQuickCreate}>
              ⚡ Schnell erstellen
            </button>
          </div>
        )}

        {/* Units List */}
        {!selectedGroupId ? (
          <div className="card">
            <p style={{ color: 'var(--text2)', textAlign: 'center' }}>
              Bitte wähle eine Trainingsgruppe aus
            </p>
          </div>
        ) : units.length === 0 ? (
          <div className="card">
            <p style={{ color: 'var(--text2)', textAlign: 'center' }}>
              Keine Trainingseinheiten im gewählten Zeitraum
            </p>
          </div>
        ) : (
          <div style={{ display: 'grid', gap: '1rem' }}>
            {units.map(unit => (
              <div key={unit.id} className="card">
                <div style={{ display: 'flex', justifyContent: 'space-between', alignItems: 'start', marginBottom: '1rem' }}>
                  <div>
                    <h3 style={{ marginBottom: '0.25rem' }}>
                      {unit.planned_date}
                      {unit.planned_time_start && ` · ${unit.planned_time_start.slice(0, 5)} - ${unit.planned_time_end?.slice(0, 5)}`}
                    </h3>
                    {unit.planned_focus && (
                      <p style={{ color: 'var(--text2)', fontSize: '0.875rem', marginBottom: '0.5rem' }}>
                        🎯 {unit.planned_focus}
                      </p>
                    )}
                    <div style={{ display: 'flex', gap: '0.5rem', flexWrap: 'wrap' }}>
                      <span style={{
                        fontSize: '0.75rem',
                        padding: '0.25rem 0.5rem',
                        borderRadius: '4px',
                        background: unit.status === 'completed' ? '#2ea44f' : unit.status === 'cancelled' ? 'var(--danger)' : 'var(--surface2)',
                        color: unit.status === 'completed' || unit.status === 'cancelled' ? 'white' : 'var(--text2)'
                      }}>
                        {unit.status === 'planned' && '📅 Geplant'}
                        {unit.status === 'completed' && '✓ Durchgeführt'}
                        {unit.status === 'cancelled' && '✗ Abgesagt'}
                      </span>
                      {unit.attendance_count !== null && (
                        <span style={{
                          fontSize: '0.75rem',
                          padding: '0.25rem 0.5rem',
                          borderRadius: '4px',
                          background: 'var(--surface2)',
                          color: 'var(--text2)'
                        }}>
                          👥 {unit.attendance_count} Teilnehmer
                        </span>
                      )}
                    </div>
                  </div>

                  <div style={{ display: 'flex', gap: '0.5rem' }}>
                    <button
                      className="btn btn-secondary"
                      onClick={() => handleEdit(unit)}
                    >
                      Bearbeiten
                    </button>
                    <button
                      className="btn"
                      style={{
                        background: 'var(--danger)',
                        color: 'white',
                        border: 'none'
                      }}
                      onClick={() => handleDelete(unit)}
                    >
                      Löschen
                    </button>
                  </div>
                </div>

                {unit.notes && (
                  <p style={{ color: 'var(--text2)', fontSize: '0.875rem', marginTop: '0.5rem' }}>
                    💬 {unit.notes}
                  </p>
                )}
              </div>
            ))}
          </div>
        )}

        {/* Create/Edit Modal */}
        {showModal && (
          <div style={{
            position: 'fixed',
            top: 0,
            left: 0,
            right: 0,
            bottom: 0,
            background: 'rgba(0,0,0,0.5)',
            display: 'flex',
            alignItems: 'center',
            justifyContent: 'center',
            zIndex: 1000,
            padding: '1rem',
            overflowY: 'auto'
          }}>
            <div style={{
              background: 'var(--surface)',
              borderRadius: '12px',
              padding: '2rem',
              maxWidth: '900px',
              width: '100%',
              maxHeight: '90vh',
              overflowY: 'auto',
              margin: '1rem'
            }}>
              <h2 style={{ marginBottom: '1.5rem' }}>
                {editingUnit ? 'Trainingseinheit bearbeiten' : 'Neue Trainingseinheit'}
              </h2>

              <form onSubmit={handleSubmit}>
                {/* Basic Info */}
                <h3 style={{ marginBottom: '1rem' }}>Planung</h3>

                <div style={{ display: 'grid', gridTemplateColumns: '1fr 1fr 1fr', gap: '1rem', marginBottom: '1rem' }}>
                  <div className="form-row">
                    <label className="form-label">Datum *</label>
                    <input
                      type="date"
                      className="form-input"
                      value={formData.planned_date}
                      onChange={(e) => updateFormField('planned_date', e.target.value)}
                      required
                    />
                  </div>

                  <div className="form-row">
                    <label className="form-label">Von</label>
                    <input
                      type="time"
                      className="form-input"
                      value={formData.planned_time_start}
                      onChange={(e) => updateFormField('planned_time_start', e.target.value)}
                    />
                  </div>

                  <div className="form-row">
                    <label className="form-label">Bis</label>
                    <input
                      type="time"
                      className="form-input"
                      value={formData.planned_time_end}
                      onChange={(e) => updateFormField('planned_time_end', e.target.value)}
                    />
                  </div>
                </div>

                <div className="form-row">
                  <label className="form-label">Trainingsfokus</label>
                  <input
                    type="text"
                    className="form-input"
                    value={formData.planned_focus}
                    onChange={(e) => updateFormField('planned_focus', e.target.value)}
                    placeholder="z.B. Kihon Grundlagen, Kata Heian Shodan"
                  />
                </div>

                {/* Exercises */}
                <h3 style={{ marginTop: '2rem', marginBottom: '1rem' }}>Übungen</h3>

                {formData.exercises.length === 0 ? (
                  <p style={{ color: 'var(--text2)', marginBottom: '1rem' }}>
                    Noch keine Übungen hinzugefügt
                  </p>
                ) : (
                  <div style={{ display: 'flex', flexDirection: 'column', gap: '0.5rem', marginBottom: '1rem' }}>
                    {formData.exercises.map((ex, idx) => (
                      <div key={idx} style={{
                        display: 'grid',
                        gridTemplateColumns: '30px 1fr 80px auto',
                        gap: '0.5rem',
                        alignItems: 'center',
                        padding: '0.5rem',
                        background: 'var(--surface2)',
                        borderRadius: '8px'
                      }}>
                        <div style={{ display: 'flex', flexDirection: 'column', gap: '2px' }}>
                          <button
                            type="button"
                            onClick={() => moveExercise(idx, -1)}
                            disabled={idx === 0}
                            style={{
                              padding: '2px',
                              fontSize: '0.75rem',
                              background: 'none',
                              border: 'none',
                              cursor: idx === 0 ? 'not-allowed' : 'pointer',
                              opacity: idx === 0 ? 0.3 : 1
                            }}
                          >
                            ▲
                          </button>
                          <button
                            type="button"
                            onClick={() => moveExercise(idx, 1)}
                            disabled={idx === formData.exercises.length - 1}
                            style={{
                              padding: '2px',
                              fontSize: '0.75rem',
                              background: 'none',
                              border: 'none',
                              cursor: idx === formData.exercises.length - 1 ? 'not-allowed' : 'pointer',
                              opacity: idx === formData.exercises.length - 1 ? 0.3 : 1
                            }}
                          >
                            ▼
                          </button>
                        </div>

                        <select
                          className="form-input"
                          value={ex.exercise_id}
                          onChange={(e) => updateExercise(idx, 'exercise_id', parseInt(e.target.value))}
                          style={{ margin: 0 }}
                        >
                          <option value="">Übung wählen</option>
                          {exercises.map(exercise => (
                            <option key={exercise.id} value={exercise.id}>
                              {exercise.title}
                            </option>
                          ))}
                        </select>

                        <input
                          type="number"
                          className="form-input"
                          value={ex.planned_duration_min}
                          onChange={(e) => updateExercise(idx, 'planned_duration_min', e.target.value)}
                          placeholder="min"
                          style={{ margin: 0 }}
                        />

                        <button
                          type="button"
                          className="btn"
                          onClick={() => removeExercise(idx)}
                          style={{
                            padding: '0.5rem',
                            background: 'var(--danger)',
                            color: 'white',
                            border: 'none'
                          }}
                        >
                          ✗
                        </button>
                      </div>
                    ))}
                  </div>
                )}

                <button
                  type="button"
                  className="btn btn-secondary"
                  onClick={addExercise}
                  style={{ marginBottom: '2rem' }}
                >
                  + Übung hinzufügen
                </button>

                {/* Durchführung (nur bei Edit) */}
                {editingUnit && (
                  <>
                    <h3 style={{ marginTop: '2rem', marginBottom: '1rem' }}>Durchführung</h3>

                    <div style={{ display: 'grid', gridTemplateColumns: '1fr 1fr 1fr 1fr', gap: '1rem', marginBottom: '1rem' }}>
                      <div className="form-row">
                        <label className="form-label">Tatsächliches Datum</label>
                        <input
                          type="date"
                          className="form-input"
                          value={formData.actual_date}
                          onChange={(e) => updateFormField('actual_date', e.target.value)}
                        />
                      </div>

                      <div className="form-row">
                        <label className="form-label">Von</label>
                        <input
                          type="time"
                          className="form-input"
                          value={formData.actual_time_start}
                          onChange={(e) => updateFormField('actual_time_start', e.target.value)}
                        />
                      </div>

                      <div className="form-row">
                        <label className="form-label">Bis</label>
                        <input
                          type="time"
                          className="form-input"
                          value={formData.actual_time_end}
                          onChange={(e) => updateFormField('actual_time_end', e.target.value)}
                        />
                      </div>

                      <div className="form-row">
                        <label className="form-label">Teilnehmer</label>
                        <input
                          type="number"
                          className="form-input"
                          value={formData.attendance_count}
                          onChange={(e) => updateFormField('attendance_count', e.target.value)}
                        />
                      </div>
                    </div>

                    <div className="form-row">
                      <label className="form-label">Status</label>
                      <select
                        className="form-input"
                        value={formData.status}
                        onChange={(e) => updateFormField('status', e.target.value)}
                      >
                        <option value="planned">Geplant</option>
                        <option value="completed">Durchgeführt</option>
                        <option value="cancelled">Abgesagt</option>
                      </select>
                    </div>
                  </>
                )}

                {/* Notes */}
                <h3 style={{ marginTop: '2rem', marginBottom: '1rem' }}>Notizen</h3>

                <div className="form-row">
                  <label className="form-label">Öffentliche Notizen</label>
                  <textarea
                    className="form-input"
                    rows={3}
                    value={formData.notes}
                    onChange={(e) => updateFormField('notes', e.target.value)}
                    placeholder="Für alle Teilnehmer sichtbar"
                  />
                </div>

                <div className="form-row">
                  <label className="form-label">Trainernotizen</label>
                  <textarea
                    className="form-input"
                    rows={3}
                    value={formData.trainer_notes}
                    onChange={(e) => updateFormField('trainer_notes', e.target.value)}
                    placeholder="Nur für Trainer sichtbar"
                  />
                </div>

                {/* Buttons */}
                <div style={{ display: 'flex', gap: '0.5rem', marginTop: '1.5rem' }}>
                  <button type="submit" className="btn btn-primary" style={{ flex: 1 }}>
                    {editingUnit ? 'Speichern' : 'Erstellen'}
                  </button>
                  <button
                    type="button"
                    className="btn btn-secondary"
                    onClick={() => setShowModal(false)}
                  >
                    Abbrechen
                  </button>
                </div>
              </form>
            </div>
          </div>
        )}
      </div>
    </div>
  )
}

export default TrainingPlanningPage