---
phase: 05-jamtrack-implementation
plan: 02
subsystem: media
tags: [redux, thunks, websocket, react, jamclient]

# Dependency graph
requires:
  - phase: 05-01
    provides: Redux state structures (jamTrackState, downloadState, mixdown state)
provides:
  - 6 async thunks for JamTrack operations
  - 3 WebSocket handlers for real-time updates
  - JKSessionJamTrackPlayer component skeleton
affects: [05-03, 05-04, 05-05]

# Tech tracking
tech-stack:
  added: []
  patterns:
    - "Async thunks with dispatch for nested operations"
    - "Global callbacks for native client download progress"
    - "Component initialization: buildFqId → check sync → autoPlay"

key-files:
  created:
    - jam-ui/src/components/client/JKSessionJamTrackPlayer.js
  modified:
    - jam-ui/src/store/features/mediaSlice.js
    - jam-ui/src/hooks/useSessionWebSocket.js

key-decisions:
  - "Enhanced loadJamTrack checks sync state and triggers download if needed"
  - "downloadJamTrack uses global window callbacks for native client integration"
  - "seekJamTrack applies UAT-003 fix pattern (pending seek while paused)"
  - "WebSocket handlers parse messages correctly with parseInt for numbers"

patterns-established:
  - "Thunks can dispatch other thunks using dispatch().unwrap()"
  - "Global callbacks named as strings for native client callback pattern"
  - "Component cleanup on unmount with closeJamTrack thunk"

issues-created: []

# Metrics
duration: 25min
completed: 2026-01-14
---

# Phase 5 Plan 2: Async Thunks & Component Core Summary

**Complete async infrastructure with 6 thunks, 3 WebSocket handlers, and skeleton component for JamTrack player**

## Performance

- **Duration:** 25 min
- **Started:** 2026-01-14T15:58:38Z
- **Completed:** 2026-01-14T16:23:47Z
- **Tasks:** 3
- **Files modified:** 3

## Accomplishments

- **6 async thunks implemented:** Enhanced loadJamTrack with sync checking, downloadJamTrack with progress callbacks, checkJamTrackSync, loadJMEP, seekJamTrack with UAT-003 fix, closeJamTrack with cleanup
- **3 WebSocket handlers:** Extended MIXER_CHANGES for mixdowns, enhanced JAM_TRACK_CHANGES with correct parsing, added MIXDOWN_CHANGES for download progress
- **Component skeleton created:** JKSessionJamTrackPlayer with initialization pattern, cleanup on unmount, Redux connections, and placeholder render
- **All thunks use fqId format** correctly for jamClient calls
- **Global callback pattern** implemented for native client download integration

## Task Commits

Each task was committed atomically:

1. **Task 1: Implement 6 async thunks in mediaSlice** - `8a536ac62` (feat)
2. **Task 2: Add 3 WebSocket handlers** - `db06357d3` (feat)
3. **Task 3: Create JKSessionJamTrackPlayer component skeleton** - `2cf7205ff` (feat)

**Plan metadata:** (pending)

## Files Created/Modified

- `jam-ui/src/store/features/mediaSlice.js` - Added 6 async thunks (loadJamTrack enhanced, downloadJamTrack, checkJamTrackSync, loadJMEP, seekJamTrack, closeJamTrack) with extraReducers
- `jam-ui/src/hooks/useSessionWebSocket.js` - Extended MIXER_CHANGES, enhanced JAM_TRACK_CHANGES, added MIXDOWN_CHANGES handlers
- `jam-ui/src/components/client/JKSessionJamTrackPlayer.js` - Created component skeleton with initialization, cleanup, and Redux connections

## Decisions Made

**Enhanced loadJamTrack architecture:**
- Checks sync state via JamTrackGetTrackDetail before playing
- Automatically triggers downloadJamTrack if not synchronized
- Loads JMEP if available before playback
- Returns fqId for component use

**Global callback pattern for downloads:**
- Native client requires callback functions as string names (not function references)
- Set up window.jamTrackDownloadProgress, window.jamTrackDownloadSuccess, window.jamTrackDownloadFail
- Callbacks dispatch Redux actions to update downloadState
- Pattern matches legacy MediaContext implementation

**Component initialization flow:**
- Build fqId → check sync → set open in Redux → autoPlay if requested
- Uses mountedRef to prevent state updates after unmount
- Cleanup on unmount calls closeJamTrack thunk to stop playback and clear state

**WebSocket parsing:**
- parseInt applied to position values from WebSocket messages
- Null/undefined checks with fallback defaults
- Handlers dispatch to multiple Redux slices (mediaSlice, activeSessionSlice)

## Deviations from Plan

None - plan executed exactly as written.

## Issues Encountered

None

## Next Phase Readiness

- Async infrastructure complete and ready for playback controls
- Component skeleton ready for UI implementation in Plan 3
- WebSocket handlers active for real-time state updates
- All patterns follow Backing Track player conventions from Phase 3

---
*Phase: 05-jamtrack-implementation*
*Completed: 2026-01-14*
