Enhance TrainingCoachPage and trainingPlanUtils with split rejoin functionality

- Updated TrainingCoachPage to implement a prompt for users to rejoin parallel phases, improving user guidance during training sessions.
- Refactored step management logic to ensure accurate navigation through the timeline, utilizing safe step calculations.
- Introduced new utility functions in trainingPlanUtils for building save payloads and determining when to prompt for split rejoin, optimizing data handling.
- Enhanced state management for split rejoin prompts, ensuring a seamless user experience during training.

frontend/src/pages/TrainingCoachPage.jsx

@@ -1,16 +1,18 @@
 /**
  * Coach-Modus: Schrittfolge mit Split-Punkten (branch_gate), Stream-Wahl pro paralleler Phase, Assistenz und Zeitnahme.
  */
-import React, { useCallback, useEffect, useMemo, useRef, useState } from 'react'
+import React, { useCallback, useEffect, useLayoutEffect, useMemo, useRef, useState } from 'react'
 import { Link, useNavigate, useParams, useSearchParams } from 'react-router-dom'
 import api from '../utils/api'
 import ExerciseFullContent from '../components/ExerciseFullContent'
 import ExercisePeekModal from '../components/ExercisePeekModal'
 import {
   COACH_ENTRY_BRANCH_GATE,
+  buildCoachSavePlanPayload,
   coachBranchPicksStepStorageSuffix,
   coachBranchPicksStorageKey,
   coachOutlineGroupsFromTimeline,
+  coachShouldPromptSplitRejoin,
   durationOverridesMapFromDeltas,
   findCoachTimelineJumpIndexForPhase,
   flattenPlanTimeline,
@@ -18,7 +20,6 @@ import {
   listCoachStreamFocusOptions,
   mergeCoachBranchPicksWithUrlFocus,
   normalizeCoachBranchPicks,
-  sectionsToPutPayload,
   summarizeTimelineEntry,
 } from '../utils/trainingPlanUtils'
 
@@ -194,6 +195,8 @@ export default function TrainingCoachPage() {
   const [timerOwningStep, setTimerOwningStep] = useState(null)
   const [, setPulse] = useState(0)
 
+  const [splitRejoinPrompt, setSplitRejoinPrompt] = useState(null)
+
   const [trainerAppend, setTrainerAppend] = useState('')
   const [saveMarkDone, setSaveMarkDone] = useState(true)
   const [saving, setSaving] = useState(false)
@@ -398,14 +401,12 @@ export default function TrainingCoachPage() {
       setStep(0)
       return
     }
-    if (coachDebriefPhase) return
+    if (coachDebriefPhase) {
-    setStep((prev) => clampStep(prev, timeline.length))
-  }, [unit, timeline.length, coachDebriefPhase])
-
-  useEffect(() => {
-    if (!coachDebriefPhase || !unit || timeline.length === 0) return
       setStep(timeline.length - 1)
-  }, [coachDebriefPhase, unit, timeline.length])
+    } else {
+      setStep((prev) => clampStep(prev, timeline.length))
+    }
+  }, [unit, timeline.length, coachDebriefPhase])
 
   useEffect(() => {
     if (!unit || Number.isNaN(idNum)) return
@@ -419,6 +420,7 @@ export default function TrainingCoachPage() {
     } else if (prev !== navigationKey) {
       coachFocusResetRef.current = navigationKey
       setCoachDebriefPhase(false)
+      setSplitRejoinPrompt(null)
       timerReset()
     } else {
       return
@@ -439,24 +441,36 @@ export default function TrainingCoachPage() {
 
   const tickDisplaySec = Math.max(0, Math.floor(elapsedMs / 1000))
 
-  const currentEntry = timeline[step]
+  const safeStep = useMemo(() => {
-  const nextEntry = timeline[step + 1] || null
+    if (!timeline.length) return 0
-  const next2Entry = timeline[step + 2] || null
+    return Math.min(Math.max(0, step), timeline.length - 1)
+  }, [step, timeline.length])
+
+  useLayoutEffect(() => {
+    if (!timeline.length) return
+    const max = timeline.length - 1
+    const s = Math.min(Math.max(0, step), max)
+    if (s !== step) setStep(s)
+  }, [step, timeline.length])
+
+  const currentEntry = timeline[safeStep] ?? null
+  const nextEntry = timeline[safeStep + 1] || null
+  const next2Entry = timeline[safeStep + 2] || null
 
   const clockStr = formatClock(tickDisplaySec)
   const roundedMinApply = elapsedMs <= 650 ? null : Math.max(1, Math.round(elapsedMs / 60000))
   const showJumpToTimerOwner =
     timerOwningStep != null &&
-    step !== timerOwningStep &&
+    safeStep !== timerOwningStep &&
     (runStartAt != null || pausedAccumMs > 0)
   const isLastCoachStep =
     timeline.length > 0 &&
-    step >= timeline.length - 1 &&
+    safeStep >= timeline.length - 1 &&
     currentEntry?.entryKind !== COACH_ENTRY_BRANCH_GATE
 
   const timerStart = () => {
     setRunStartAt(Date.now())
-    setTimerOwningStep(step)
+    setTimerOwningStep(safeStep)
   }
 
   const timerPause = () => {
@@ -467,7 +481,7 @@ export default function TrainingCoachPage() {
   }
 
   const applySuggestedDuration = () => {
-    const idx = timerOwningStep != null ? timerOwningStep : step
+    const idx = timerOwningStep != null ? timerOwningStep : safeStep
     const ent = timeline[idx]
     const item = ent?.item
     if (!item || item.item_type !== 'exercise') return
@@ -482,6 +496,7 @@ export default function TrainingCoachPage() {
     (phaseOrder, streamOrder) => {
       if (!Number.isFinite(phaseOrder) || !Number.isFinite(streamOrder)) return
       setStreamChoiceHint(null)
+      setSplitRejoinPrompt(null)
       setBranchPicks((prev) => ({ ...normalizeCoachBranchPicks(prev), [phaseOrder]: streamOrder }))
       timerReset()
       setCoachDebriefPhase(false)
@@ -496,7 +511,7 @@ export default function TrainingCoachPage() {
   const goNext = () => setStep((s) => clampStep(s + 1))
 
   const markCurrentDoneAdvance = () => {
-    const ownerIdx = timerOwningStep != null ? timerOwningStep : step
+    const ownerIdx = timerOwningStep != null ? timerOwningStep : safeStep
     const ent = timeline[ownerIdx]
     if (ent?.entryKind === COACH_ENTRY_BRANCH_GATE) return
     const item = ent?.item
@@ -508,7 +523,12 @@ export default function TrainingCoachPage() {
     timerReset()
 
     const lastIdx = timeline.length - 1
-    if (step >= lastIdx && lastIdx >= 0) {
+    if (safeStep >= lastIdx && lastIdx >= 0) {
+      const rejoin = coachShouldPromptSplitRejoin(unit, timeline[safeStep])
+      if (rejoin) {
+        setSplitRejoinPrompt(rejoin)
+        return
+      }
       setCoachDebriefPhase(true)
       try {
         sessionStorage.setItem(storageDebriefKey(idNum), '1')
@@ -575,10 +595,10 @@ export default function TrainingCoachPage() {
     setSaveOk(null)
     setSaving(true)
     try {
-      const sectionsPayload = sectionsToPutPayload(unit, durationOverridesForApi)
+      const sectionsPayloadPart = buildCoachSavePlanPayload(unit, durationOverridesForApi)
       const tn = trainerAppend.trim()
       const payload = {
-        sections: sectionsPayload,
+        ...sectionsPayloadPart,
         ...(saveMarkDone ? { status: 'completed' } : {}),
       }
       if (tn) {
@@ -667,12 +687,14 @@ export default function TrainingCoachPage() {
               style={{ minWidth: 'min(220px, 72vw)', margin: 0, padding: '6px 8px', fontSize: '0.82rem' }}
               value={streamQuickSelectValue}
               onChange={(e) => {
+                setSplitRejoinPrompt(null)
                 setCoachDebriefPhase(false)
                 timerReset()
                 const v = e.target.value
                 if (!v) {
                   setBranchPicks({})
                   setStreamChoiceHint(null)
+                  setSplitRejoinPrompt(null)
                   setSearchParams({}, { replace: true })
                 } else {
                   const [ppo, sso] = v.split('-').map((x) => parseInt(x, 10))
@@ -714,6 +736,80 @@ export default function TrainingCoachPage() {
         </p>
       ) : null}
 
+      {splitRejoinPrompt && !coachDebriefPhase ? (
+        <div
+          className="card no-print"
+          style={{
+            flexShrink: 0,
+            marginBottom: '10px',
+            padding: '16px 14px',
+            borderRadius: '12px',
+            border: '2px solid var(--accent)',
+            background: 'linear-gradient(135deg, var(--accent-light), var(--surface))',
+          }}
+        >
+          <div style={{ fontSize: '0.72rem', fontWeight: 700, color: 'var(--accent-dark)', marginBottom: '6px' }}>
+            Parallelphase · Abschluss
+          </div>
+          <p style={{ fontSize: '0.95rem', fontWeight: 700, margin: '0 0 8px', color: 'var(--text1)' }}>
+            {splitRejoinPrompt.phaseTitle != null && String(splitRejoinPrompt.phaseTitle).trim()
+              ? String(splitRejoinPrompt.phaseTitle).trim()
+              : `Phase ${splitRejoinPrompt.phaseOrderIndex}`}
+            {' — '}
+            alle Gruppen fertig?
+          </p>
+          <p style={{ fontSize: '0.84rem', color: 'var(--text2)', margin: '0 0 12px', lineHeight: 1.45 }}>
+            Diese Phase hat mehrere Streams. Kurz mit dem anderen Trainer klären, dann gemeinsam Ist-Zeiten und Speichern
+            (gilt auch, wenn danach kein weiterer Block mehr kommt).
+          </p>
+          <ul style={{ margin: '0 0 14px', paddingLeft: '1.2rem', fontSize: '0.82rem', color: 'var(--text2)' }}>
+            {splitRejoinPrompt.streams.map((st) => (
+              <li key={st.printStreamId || `s-${st.streamOrder}`}>
+                {st.streamTitle?.trim() ? String(st.streamTitle).trim() : `Gruppe ${st.streamOrder + 1}`}{' '}
+                <span style={{ color: 'var(--text3)' }}>(ca. {st.minutes} Min. Üb.)</span>
+              </li>
+            ))}
+          </ul>
+          <div style={{ display: 'flex', flexDirection: 'column', gap: '8px' }}>
+            <button
+              type="button"
+              className="btn btn-primary"
+              style={{ minHeight: '48px', fontWeight: 700 }}
+              onClick={() => {
+                setSplitRejoinPrompt(null)
+                setCoachDebriefPhase(true)
+                try {
+                  sessionStorage.setItem(storageDebriefKey(idNum), '1')
+                } catch {
+                  /* ignore */
+                }
+              }}
+            >
+              Alle Gruppen fertig — zur Nachbereitung
+            </button>
+            <button type="button" className="btn btn-secondary" style={{ minHeight: '44px' }} onClick={() => setSplitRejoinPrompt(null)}>
+              Zurück — andere Gruppe läuft noch
+            </button>
+            <button
+              type="button"
+              className="btn btn-secondary"
+              style={{ minHeight: '44px', fontSize: '0.82rem' }}
+              onClick={() => {
+                setSplitRejoinPrompt(null)
+                setCoachDebriefPhase(true)
+                try {
+                  sessionStorage.setItem(storageDebriefKey(idNum), '1')
+                } catch {
+                  /* ignore */
+                }
+              }}
+            >
+              Ausnahme: trotzdem zur Nachbereitung
+            </button>
+          </div>
+        </div>
+      ) : null}
+
       <header
         className="card training-coach-hero training-coach-hero--compact"
         style={{
@@ -727,7 +823,7 @@ export default function TrainingCoachPage() {
       >
         <div style={{ fontSize: '0.7rem', color: 'var(--text3)', textTransform: 'uppercase', letterSpacing: '0.06em' }}>
           Coach ·{' '}
-          {coachDebriefPhase ? 'Nachbereitung · abschließend speichern' : `Schritt ${(step || 0) + 1} / ${Math.max(timeline.length, 1)}`}
+          {coachDebriefPhase ? 'Nachbereitung · abschließend speichern' : `Schritt ${(safeStep || 0) + 1} / ${Math.max(timeline.length, 1)}`}
         </div>
         <h1 style={{ fontSize: '1.1rem', margin: '4px 0 0', lineHeight: 1.28 }}>
           {unit.planned_date}
@@ -781,7 +877,7 @@ export default function TrainingCoachPage() {
                   {grp.entries.map(({ ix, ent }) => {
                     const lbl = summarizeTimelineEntry(ent)
                     const ctx = ent.coachContext || ''
-                    const active = coachDebriefPhase ? ix === timeline.length - 1 : ix === step
+                    const active = coachDebriefPhase ? ix === timeline.length - 1 : ix === safeStep
                     const rowKey =
                       ent.entryKind === COACH_ENTRY_BRANCH_GATE
                         ? `gate-${ix}`
@@ -904,6 +1000,8 @@ export default function TrainingCoachPage() {
           ) : null}
         </div>
       ) : (
+        <>
+          {!splitRejoinPrompt ? (
             <>
           <div
             className="training-coach-assist training-coach-assist--compact"
@@ -942,7 +1040,7 @@ export default function TrainingCoachPage() {
           </div>
 
           <CoachControlsBand
-            step={step}
+            step={safeStep}
             timelineLength={timeline.length}
             onPrev={goPrev}
             onNext={goNext}
@@ -958,7 +1056,7 @@ export default function TrainingCoachPage() {
             isLastCoachStep={isLastCoachStep}
             showJumpToTimerOwner={showJumpToTimerOwner}
             showJumpToTimerOwnerRow
-            onJumpToTimerOwner={() => setStep(timerOwningStep ?? step)}
+            onJumpToTimerOwner={() => setStep(timerOwningStep ?? safeStep)}
             timerOwnerLabelIndex={timerOwningStep ?? 0}
             branchGateMode={atBranchGate}
           />
@@ -968,54 +1066,77 @@ export default function TrainingCoachPage() {
               <div
                 className="card"
                 style={{
-                  padding: '16px 14px',
+                  padding: '18px 16px',
                   marginBottom: '12px',
-                  borderRadius: '12px',
+                  borderRadius: '14px',
-                  borderLeft: '4px solid var(--accent)',
+                  border: '2px solid var(--accent)',
-                  background: 'var(--surface)',
+                  background: 'linear-gradient(180deg, var(--accent-light) 0%, var(--surface) 38%)',
+                  boxShadow: '0 2px 12px rgba(0,0,0,0.06)',
                 }}
               >
-                <div style={{ fontSize: '0.72rem', fontWeight: 700, color: 'var(--text3)', marginBottom: '8px' }}>
+                <div style={{ fontSize: '0.74rem', fontWeight: 800, color: 'var(--accent-dark)', marginBottom: '6px', letterSpacing: '0.04em' }}>
-                  Parallele Phase · Coaching-Zweig
+                  ⑂ SPLIT — GRUPPE WÄHLEN
                 </div>
-                <p style={{ fontSize: '1.02rem', fontWeight: 700, margin: '0 0 8px', color: 'var(--accent-dark)' }}>
+                <p style={{ fontSize: '1.05rem', fontWeight: 800, margin: '0 0 8px', color: 'var(--text1)' }}>
                   {currentEntry.branchMeta.phaseTitle != null && String(currentEntry.branchMeta.phaseTitle).trim()
                     ? String(currentEntry.branchMeta.phaseTitle).trim()
                     : `Phase ${currentEntry.branchMeta.phaseOrderIndex}`}
                 </p>
-                <p style={{ fontSize: '0.86rem', color: 'var(--text2)', margin: '0 0 14px', lineHeight: 1.45 }}>
+                <p style={{ fontSize: '0.88rem', color: 'var(--text2)', margin: '0 0 16px', lineHeight: 1.45 }}>
-                  Welchen Stream coachen Sie jetzt? Jeder Trainer kann auf seinem Gerät eine andere Gruppe wählen. Sobald Sie
+                  Tippen Sie auf eine Kachel, um <strong>diese Gruppe</strong> zu coachen. Andere Trainer:innen wählen auf
-                  wählen, folgen nacheinander die Übungen genau dieser Spalte (ohne Verschränkung mit den anderen Streams).
+                  ihrem Gerät parallel eine andere Kachel.
                 </p>
-                <div style={{ display: 'flex', flexDirection: 'column', gap: '10px' }}>
+                <div style={{ display: 'grid', gridTemplateColumns: 'repeat(auto-fit, minmax(240px, 1fr))', gap: '12px' }}>
                   {(currentEntry.branchMeta.streams || []).map((st) => {
                     const hinted =
                       streamChoiceHint?.phaseOrder === currentEntry.branchMeta.phaseOrderIndex &&
                       streamChoiceHint?.streamOrder === st.streamOrder
                     const label = st.streamTitle?.trim() ? String(st.streamTitle).trim() : `Gruppe ${st.streamOrder + 1}`
+                    const baseBg = hinted ? 'var(--accent)' : 'var(--surface2)'
+                    const baseColor = hinted ? '#fff' : 'var(--text1)'
+                    const borderCol = hinted ? 'var(--accent-dark)' : 'var(--border)'
                     return (
                       <button
                         key={st.printStreamId || `s-${st.streamOrder}`}
                         type="button"
-                        className={hinted ? 'btn btn-primary' : 'btn btn-secondary'}
+                        className="btn"
-                        style={{ textAlign: 'left', justifyContent: 'flex-start', padding: '12px 14px', fontWeight: 600 }}
+                        style={{
+                          textAlign: 'left',
+                          justifyContent: 'flex-start',
+                          flexDirection: 'column',
+                          alignItems: 'stretch',
+                          padding: '14px 16px',
+                          minHeight: '96px',
+                          fontWeight: 700,
+                          background: baseBg,
+                          color: baseColor,
+                          border: `2px solid ${borderCol}`,
+                          borderRadius: '12px',
+                          boxShadow: hinted ? '0 4px 0 var(--accent-dark)' : '0 3px 0 hsl(200 20% 78%)',
+                          transition: 'transform 0.08s ease, box-shadow 0.08s ease',
+                        }}
                         onClick={() => pickStreamForPhase(currentEntry.branchMeta.phaseOrderIndex, st.streamOrder)}
                       >
-                        <span style={{ display: 'block' }}>{label}</span>
+                        <span style={{ display: 'flex', alignItems: 'center', gap: '8px', fontSize: '1rem' }}>
+                          <span style={{ fontSize: '1.35rem', lineHeight: 1 }} aria-hidden="true">
+                            {hinted ? '◉' : '○'}
+                          </span>
+                          <span>{label}</span>
+                        </span>
                         <span
                           style={{
                             display: 'block',
                             fontSize: '0.82rem',
-                            fontWeight: 500,
+                            fontWeight: 600,
-                            opacity: 0.9,
+                            opacity: hinted ? 0.95 : 0.88,
-                            marginTop: '4px',
+                            marginTop: '8px',
                           }}
                         >
-                          ca. {st.minutes} Min. (Üb.) · Antippen zum Fortfahren
+                          ≈ {st.minutes} Min. Üb. · Jetzt aktivieren
                         </span>
                         {hinted ? (
-                          <span style={{ display: 'block', fontSize: '0.75rem', marginTop: '6px', opacity: 0.95 }}>
+                          <span style={{ display: 'block', fontSize: '0.74rem', fontWeight: 600, marginTop: '8px', opacity: 0.92 }}>
-                            Hinweis aus Planansicht — bei Bedarf andere Gruppe wählen.
+                            Vorschlag aus Planansicht — trotzdem andere Kachel möglich
                           </span>
                         ) : null}
                       </button>
@@ -1026,8 +1147,8 @@ export default function TrainingCoachPage() {
             ) : currentEntry?.item?.item_type === 'note' ? (
               <div className="card" style={{ padding: '16px 14px' }}>
                 <div style={{ fontSize: '0.74rem', color: 'var(--text3)', marginBottom: '8px' }}>
-                  {currentEntry.coachContext || currentEntry.sec.title || 'Abschnitt'} · Coach-Notiz · Teil{' '}
+                  {currentEntry?.coachContext || currentEntry?.sec?.title || 'Abschnitt'} · Coach-Notiz · Teil{' '}
-                  {step + 1}
+                  {safeStep + 1}
                 </div>
                 <div style={{ fontSize: '0.78rem', color: 'var(--text3)', marginBottom: '6px' }}>Coach-Notiz</div>
                 <p style={{ fontSize: '1.05rem', lineHeight: 1.52, whiteSpace: 'pre-wrap', margin: 0 }}>{currentEntry.item.note_body || ''}</p>
@@ -1036,8 +1157,8 @@ export default function TrainingCoachPage() {
               <>
                 <div className="card training-coach-plan-strip" style={{ padding: '12px 14px', marginBottom: '12px', borderRadius: '12px', borderLeft: `3px solid var(--accent)` }}>
                   <div style={{ fontSize: '0.74rem', color: 'var(--text3)', marginBottom: '6px' }}>
-                    In diesem Training · {currentEntry.coachContext || currentEntry?.sec.title || 'Abschnitt'} · Teil{' '}
+                    In diesem Training · {currentEntry?.coachContext || currentEntry?.sec?.title || 'Abschnitt'} · Teil{' '}
-                    {step + 1}
+                    {safeStep + 1}
                   </div>
                   {currentEntry?.item && (
                     <>
@@ -1180,7 +1301,7 @@ export default function TrainingCoachPage() {
           </div>
 
           <CoachControlsBand
-            step={step}
+            step={safeStep}
             timelineLength={timeline.length}
             onPrev={goPrev}
             onNext={goNext}
@@ -1196,11 +1317,13 @@ export default function TrainingCoachPage() {
             isLastCoachStep={isLastCoachStep}
             showJumpToTimerOwner={showJumpToTimerOwner}
             showJumpToTimerOwnerRow={false}
-            onJumpToTimerOwner={() => setStep(timerOwningStep ?? step)}
+            onJumpToTimerOwner={() => setStep(timerOwningStep ?? safeStep)}
             timerOwnerLabelIndex={timerOwningStep ?? 0}
             branchGateMode={atBranchGate}
           />
             </>
+          ) : null}
+        </>
       )}
     </div>
   )

frontend/src/utils/trainingPlanUtils.js

@@ -3,6 +3,7 @@
  */
 
 import {
+  buildPlanPayloadForSave,
   cloneJsonSerializablePlanningProfile,
   inheritPlanLocForPhasedSave,
   phaseRunsFromSections,
@@ -455,6 +456,40 @@ export function durationOverridesMapFromDeltas(unit, deltas) {
   return out
 }
 
+/** PUT-Body für Coach-Speichern: `phases` wenn Plan Phasen hat, sonst `sections` (wie Planungseditor). */
+export function buildCoachSavePlanPayload(unit, durationOverridesByItemId = {}) {
+  const withLoc = sectionsWithPlanLocForDisplay(unit)
+  const withDur = withLoc.map((sec) => ({
+    ...sec,
+    items: sortedItems(sec).map((it) => {
+      if (it.item_type !== 'exercise' || it.id == null) return it
+      const o = durationOverridesByItemId[String(it.id)]
+      const av = o?.actual_duration_min
+      if (av !== undefined && av !== '' && av !== null && Number.isFinite(Number(av))) {
+        return { ...it, actual_duration_min: Number(av) }
+      }
+      return it
+    }),
+  }))
+  return buildPlanPayloadForSave(withDur)
+}
+
+/**
+ * Nach dem letzten Block eines Streams: Rückfrage, wenn die parallele Phase mehrere Gruppen hat.
+ */
+export function coachShouldPromptSplitRejoin(unit, lastTimelineEntry) {
+  const rm = lastTimelineEntry?.runMeta
+  if (!rm || rm.kind !== 'parallel' || rm.streamOrder == null) return null
+  const model = buildPlanRunViewModelFromSections(sectionsWithPlanLocForDisplay(unit))
+  const run = model.runs.find((r) => r.kind === 'parallel' && r.phaseOrderIndex === rm.phaseOrderIndex)
+  if (!run?.streams || run.streams.length <= 1) return null
+  return {
+    phaseOrderIndex: run.phaseOrderIndex,
+    phaseTitle: run.phaseTitle,
+    streams: run.streams,
+  }
+}
+
 export function summarizeTimelineEntry(ent) {
   if (!ent) return ''
   if (ent.entryKind === COACH_ENTRY_BRANCH_GATE) {