/**
 * Trainingsablauf anzeigen, drucken und lokal auf der Matte abhaken (Fortschritt im Browser gespeichert).
 */
import React, { useCallback, useEffect, useMemo, useState } from 'react'
import { Link, useNavigate, useParams } from 'react-router-dom'
import api from '../utils/api'
import ExercisePeekModal from '../components/ExercisePeekModal'
import { itemStableKey, sortedSections, sortedItems } from '../utils/trainingPlanUtils'

function storageKey(unitId) {
  return `sj_training_run_checked_${unitId}`
}

function formatMin(m) {
  if (m === null || m === undefined || m === '') return null
  const n = Number(m)
  if (!Number.isFinite(n)) return null
  return `${n} Min.`
}

function statusLabel(s) {
  if (s === 'completed') return 'Durchgeführt'
  if (s === 'cancelled') return 'Abgesagt'
  return 'Geplant'
}

export default function TrainingUnitRunPage() {
  const { unitId } = useParams()
  const navigate = useNavigate()
  const idNum = unitId ? parseInt(unitId, 10) : NaN

  const [unit, setUnit] = useState(null)
  const [loadError, setLoadError] = useState(null)
  const [loading, setLoading] = useState(true)
  const [checked, setChecked] = useState(() => new Set())
  const [peekExerciseId, setPeekExerciseId] = useState(null)

  const loadChecked = useCallback((uid) => {
    try {
      const raw = sessionStorage.getItem(storageKey(uid))
      if (!raw) return new Set()
      const arr = JSON.parse(raw)
      if (!Array.isArray(arr)) return new Set()
      return new Set(arr.map(String))
    } catch {
      return new Set()
    }
  }, [])

  useEffect(() => {
    if (!unitId || Number.isNaN(idNum)) {
      setLoadError('Ungültige Trainingseinheit')
      setLoading(false)
      return
    }
    let cancelled = false
    ;(async () => {
      setLoading(true)
      setLoadError(null)
      try {
        const u = await api.getTrainingUnit(idNum)
        if (!cancelled) {
          setUnit(u)
          setChecked(loadChecked(idNum))
        }
      } catch (e) {
        if (!cancelled) setLoadError(e.message || 'Laden fehlgeschlagen')
      } finally {
        if (!cancelled) setLoading(false)
      }
    })()
    return () => {
      cancelled = true
    }
  }, [unitId, idNum, loadChecked])

  const persistChecked = useCallback(
    (next) => {
      setChecked(next)
      try {
        sessionStorage.setItem(storageKey(idNum), JSON.stringify([...next]))
      } catch {
        /* ignore quota */
      }
    },
    [idNum]
  )

  const toggle = useCallback(
    (key) => {
      const next = new Set(checked)
      if (next.has(key)) next.delete(key)
      else next.add(key)
      persistChecked(next)
    },
    [checked, persistChecked]
  )

  const clearProgress = useCallback(() => {
    persistChecked(new Set())
    try {
      sessionStorage.removeItem(storageKey(idNum))
    } catch {
      /* ignore */
    }
  }, [idNum, persistChecked])

  const sections = useMemo(() => sortedSections(unit), [unit])

  const totalPlannedMin = useMemo(() => {
    let t = 0
    for (const sec of sections) {
      for (const it of sortedItems(sec)) {
        if (it.item_type === 'exercise' && it.planned_duration_min != null) {
          const n = Number(it.planned_duration_min)
          if (Number.isFinite(n)) t += n
        }
      }
    }
    return t
  }, [sections])

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

  if (loadError || !unit) {
    return (
      <div className="card" style={{ margin: '1rem', padding: '1.5rem' }}>
        <p style={{ marginBottom: '1rem' }}>{loadError || 'Trainingseinheit nicht gefunden.'}</p>
        <button type="button" className="btn btn-secondary" onClick={() => navigate('/planning')}>
          Zur Planung
        </button>
      </div>
    )
  }

  return (
    <div className="training-run-page app-page app-page--constrained-sm" style={{ paddingBottom: '2rem' }}>
      <ExercisePeekModal
        open={peekExerciseId != null}
        exerciseId={peekExerciseId}
        onClose={() => setPeekExerciseId(null)}
      />

      <nav className="training-run-toolbar no-print" style={{ marginBottom: '1rem', display: 'flex', gap: '0.5rem', flexWrap: 'wrap', alignItems: 'center' }}>
        <button type="button" className="btn btn-secondary" onClick={() => navigate('/planning')}>
          Zur Planung
        </button>
        <Link
          to={`/planning/run/${unitId}/coach`}
          className="btn btn-primary"
          style={{ textDecoration: 'none', display: 'inline-flex', alignItems: 'center', justifyContent: 'center' }}
        >
          Im Training (Coach)
        </Link>
        <button type="button" className="btn btn-secondary" onClick={() => window.print()}>
          Drucken / PDF
        </button>
        <button type="button" className="btn btn-secondary" title="Alle Häkchen auf dieser Matte zurücksetzen" onClick={() => confirm('Fortschritt wirklich zurücksetzen?') && clearProgress()}>
          Fortschritt leeren
        </button>
      </nav>

      <header className="training-run-header card" style={{ marginBottom: '1rem', padding: '1.25rem' }}>
        <h1 style={{ fontSize: '1.35rem', marginBottom: '0.75rem', lineHeight: 1.3 }}>
          Training
          {unit.planned_date && ` · ${unit.planned_date}`}
          {unit.planned_time_start && ` · ${String(unit.planned_time_start).slice(0, 5)}`}
          {unit.planned_time_end && `–${String(unit.planned_time_end).slice(0, 5)}`}
        </h1>
        <div style={{ fontSize: '0.9rem', color: 'var(--text2)', display: 'grid', gap: '0.35rem' }}>
          {unit.group_name && (
            <span>
              <strong>Gruppe:</strong> {unit.group_name}
              {unit.club_name && ` (${unit.club_name})`}
            </span>
          )}
          {unit.group_location && (
            <span>
              <strong>Ort:</strong> {unit.group_location}
            </span>
          )}
          {unit.planned_focus && (
            <span>
              <strong>Fokus:</strong> {unit.planned_focus}
            </span>
          )}
          <span>
            <strong>Status:</strong> {statusLabel(unit.status)}
          </span>
          {totalPlannedMin > 0 && (
            <span>
              <strong>Geplante Zeit (Übungen):</strong> ca. {totalPlannedMin} Min.
            </span>
          )}
        </div>
        {unit.notes && (
          <div
            className="training-run-notes-print"
            style={{
              marginTop: '1rem',
              padding: '0.65rem 0.85rem',
              background: 'var(--accent-light)',
              borderRadius: '8px',
              fontSize: '0.92rem'
            }}
          >
            <strong>Hinweis Teilnehmer:</strong> {unit.notes}
          </div>
        )}
      </header>

      {sections.length === 0 ? (
        <p className="card" style={{ padding: '1.25rem', color: 'var(--text2)' }}>
          Noch keine Abschnitte in diesem Plan. Unter <Link to="/planning">Planung</Link> bearbeiten.
        </p>
      ) : (
        <div style={{ display: 'flex', flexDirection: 'column', gap: '1.25rem' }}>
          {sections.map((sec, si) => {
            const secOrder = sec.order_index ?? si
            const items = sortedItems(sec)
            return (
              <section key={sec.id ?? `sec-${si}`} className="card training-run-section" style={{ padding: '1.15rem 1.25rem' }}>
                <h2 style={{ fontSize: '1.05rem', marginBottom: '0.65rem', color: 'var(--accent-dark)' }}>
                  {sec.title || `Abschnitt ${si + 1}`}
                </h2>
                {sec.guidance_notes && (
                  <p style={{ fontSize: '0.88rem', color: 'var(--text2)', marginBottom: '0.85rem', whiteSpace: 'pre-wrap' }}>
                    {sec.guidance_notes}
                  </p>
                )}
                <ul style={{ listStyle: 'none', padding: 0, margin: 0, display: 'flex', flexDirection: 'column', gap: '0.65rem' }}>
                  {items.map((it, ii) => {
                    const ck = itemStableKey(it, secOrder, ii)
                    const done = checked.has(ck)

                    if (it.item_type === 'note') {
                      return (
                        <li key={ck} className={`training-run-item training-run-item--note${done ? ' training-run-item--done' : ''}`}>
                          <label
                            style={{
                              display: 'flex',
                              gap: '0.75rem',
                              alignItems: 'flex-start',
                              cursor: 'pointer',
                              fontSize: '0.92rem'
                            }}
                          >
                            <input type="checkbox" className="training-run-checkbox" checked={done} onChange={() => toggle(ck)} style={{ marginTop: '4px', width: '20px', height: '20px' }} />
                            <span style={{ whiteSpace: 'pre-wrap', color: 'var(--text2)' }}>
                              <em style={{ fontStyle: 'normal', color: 'var(--text3)', fontSize: '0.8rem' }}>Notiz</em>
                              <br />
                              {it.note_body || ''}
                            </span>
                          </label>
                        </li>
                      )
                    }

                    const title =
                      it.exercise_title ||
                      (it.exercise_id ? `Übung #${it.exercise_id}` : 'Übung')
                    const variant = it.exercise_variant_name ? ` (${it.exercise_variant_name})` : ''
                    const plan = formatMin(it.planned_duration_min)
                    const extras = []
                    if (it.exercise_focus_area) extras.push(it.exercise_focus_area)
                    const metaParts = [...extras, plan].filter(Boolean)

                    return (
                      <li key={ck} className={`training-run-item training-run-item--exercise${done ? ' training-run-item--done' : ''}`}>
                        <label
                          style={{
                            display: 'flex',
                            gap: '0.75rem',
                            alignItems: 'flex-start',
                            cursor: 'pointer'
                          }}
                        >
                          <input type="checkbox" className="training-run-checkbox" checked={done} onChange={() => toggle(ck)} style={{ marginTop: '6px', width: '22px', height: '22px', flexShrink: 0 }} />
                          <span style={{ flex: 1, minWidth: 0 }}>
                            <span style={{ fontSize: '1.02rem', fontWeight: 600 }}>
                              {title}
                              {variant}
                            </span>
                            {metaParts.length > 0 && (
                              <div style={{ fontSize: '0.85rem', color: 'var(--text3)', marginTop: '3px', lineHeight: 1.35 }}>
                                {metaParts.join(' · ')}
                              </div>
                            )}
                            {(it.notes || it.modifications) && (
                              <div style={{ marginTop: '0.35rem', fontSize: '0.88rem', color: 'var(--text2)', whiteSpace: 'pre-wrap' }}>
                                {it.notes && (
                                  <>
                                    <strong style={{ fontWeight: 600 }}>Coach:</strong> {it.notes}
                                  </>
                                )}
                                {it.modifications && (
                                  <>
                                    {it.notes ? <br /> : null}
                                    <strong style={{ fontWeight: 600 }}>Anpassung:</strong> {it.modifications}
                                  </>
                                )}
                              </div>
                            )}
                            {it.exercise_id && (
                              <div className="no-print" style={{ display: 'flex', flexWrap: 'wrap', gap: '10px', marginTop: '0.55rem', alignItems: 'center' }}>
                                <button
                                  type="button"
                                  className="btn btn-secondary"
                                  style={{ fontSize: '0.82rem', margin: 0 }}
                                  onClick={() => setPeekExerciseId(it.exercise_id)}
                                >
                                  Katalog (Popup)
                                </button>
                                <Link
                                  to={`/exercises/${it.exercise_id}`}
                                  style={{ fontSize: '0.82rem', color: 'var(--accent)' }}
                                >
                                  Vollständige Seite öffnen
                                </Link>
                              </div>
                            )}
                          </span>
                        </label>
                      </li>
                    )
                  })}
                </ul>
              </section>
            )
          })}
        </div>
      )}

      {unit.trainer_notes && (
        <div className="card training-run-trainer-note no-print" style={{ marginTop: '1.25rem', padding: '1rem', borderLeft: `4px solid var(--accent)` }}>
          <div style={{ fontSize: '0.75rem', fontWeight: 700, color: 'var(--text3)', marginBottom: '0.35rem', textTransform: 'uppercase' }}>
            Nur Trainer
          </div>
          <p style={{ fontSize: '0.92rem', whiteSpace: 'pre-wrap' }}>{unit.trainer_notes}</p>
        </div>
      )}

      <footer className="no-print training-run-footer" style={{ marginTop: '1.75rem', textAlign: 'center', fontSize: '0.82rem', color: 'var(--text3)' }}>
        Haken werden nur auf diesem Gerät gespeichert (Session — Tab schließen kann sie löschen).
      </footer>
    </div>
  )
}
