c37fa6d1f6
- CommandHistory + 4 command classes + backend CRUD endpoints - Full mouse interactions: drag-place, move, resize, delete, undo/redo - Requirements TL-02, TL-03, TL-06 marked complete - Progress: 86% (12/14 plans)
148 lines
7.6 KiB
Markdown
148 lines
7.6 KiB
Markdown
---
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phase: 04-timeline-editor
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plan: 02
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subsystem: ui
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tags: [canvas, timeline, drag-drop, undo-redo, command-pattern, fastapi, crud]
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dependency_graph:
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requires:
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- phase: 04-timeline-editor/04-01
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provides: TimelineCanvas class with coordinate helpers, tracks data structure, render loop
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- phase: 03-communication-protocol
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provides: Show/Cue/Track models, show_store persistence
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provides:
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- CommandHistory with 50-step undo/redo stack
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- PlaceBlockCommand, MoveBlockCommand, ResizeBlockCommand, DeleteBlockCommand
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- Block CRUD REST endpoints (POST/PATCH/DELETE /api/shows/.../blocks)
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- Full block interaction: drag-from-palette, move, resize, delete
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- Overlap prevention on same track
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- Snap-to-beat on mouseup (100ms threshold)
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affects:
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- 04-03 (block inspector wiring will use selectedBlock and _onSelectBlock)
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- 04-04 (playback engine reads cues from tracks which are now populated)
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tech-stack:
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added: [HTML5 drag-and-drop API, crypto.randomUUID(), command pattern]
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patterns:
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- Command pattern with execute/undo/redo for all timeline mutations
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- Fire-and-forget fetch for backend sync (no await, no blocking UI)
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- Live drag preview with revert-then-command on mouseup
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- Document-level mousemove/mouseup listeners during drag (not canvas-level)
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key-files:
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created:
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- lightsync/frontend/timeline/history.js
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- lightsync/frontend/timeline/commands.js
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- lightsync/api/timeline.py
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modified:
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- lightsync/frontend/timeline/timeline.js
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- lightsync/frontend/app.js
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- lightsync/main.py
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key-decisions:
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- "_startMove revert-then-command pattern: live drag updates block.timestamp directly for visual feedback, mouseup reverts to oldTimestamp then executes MoveBlockCommand — ensures history always has the correct before/after state"
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- "Circular import with main.py is expected: timeline.py imports lightsync.main as state at module level, same as shows.py — works at runtime, breaks only on isolated python -c import (non-issue)"
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- "Resize handles drawn as 8px highlighted zones on selected block for discoverability"
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- "Ghost preview during dragover uses trackIdx + time from _dragState rather than raw pixel coordinates — decoupled from render"
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patterns-established:
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- "Timeline command: stores references to tracks array + block object, mutates block in-place, syncs to backend fire-and-forget"
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- "setCurrentShowId() module-level function for routing backend sync without coupling commands to app state"
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requirements-completed: [TL-02, TL-03, TL-06]
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duration: 9min
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completed: 2026-04-06
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---
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# Phase 04 Plan 02: Block Interactions + Command Pattern Summary
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**Command-pattern block editing with drag-from-palette, move/resize/delete interactions, undo/redo (50 steps), overlap prevention, snap-to-beat, and backend CRUD endpoints.**
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## Performance
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- **Duration:** ~9 min
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- **Started:** 2026-04-06T23:35:38Z
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- **Completed:** 2026-04-06T23:44:50Z
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- **Tasks:** 2
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- **Files modified:** 5 (3 created, 3 modified)
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## Accomplishments
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- `CommandHistory` class: 50-step max, execute/undo/redo, redo cleared on new action (branching protection)
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- 4 command classes: `PlaceBlockCommand`, `MoveBlockCommand`, `ResizeBlockCommand`, `DeleteBlockCommand` — each with backend sync via fire-and-forget fetch
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- REST API: POST/PATCH/DELETE `/api/shows/{show_id}/tracks/{device_id}/blocks` with auto-create track if missing
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- Full mouse interaction: hitTest with 8px resize zones, live drag preview, overlap rejection, snap-to-beat on release
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- Keyboard: Delete key removes selected block, Ctrl+Z undo, Ctrl+Shift+Z / Ctrl+Y redo
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- Drag-and-drop from animation palette to canvas with ghost block preview
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## Task Commits
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1. **Task 1: Command pattern + history + backend block CRUD** - `658c92f` (feat)
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2. **Task 2: Wire mouse interactions into TimelineCanvas** - `7e18ac6` (feat)
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## Files Created/Modified
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- `lightsync/frontend/timeline/history.js` — CommandHistory class (execute, undo, redo, canUndo, canRedo, maxSteps=50)
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- `lightsync/frontend/timeline/commands.js` — PlaceBlockCommand, MoveBlockCommand, ResizeBlockCommand, DeleteBlockCommand + setCurrentShowId() + syncBlock()
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- `lightsync/api/timeline.py` — Block CRUD FastAPI router (POST/PATCH/DELETE)
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- `lightsync/frontend/timeline/timeline.js` — hitTest, _hasOverlap, snapToBeat, _setupInteractions, _startMove, _startResize, handleDrop added; CommandHistory + 4 command imports wired
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- `lightsync/frontend/app.js` — dragstart/dragover/dragleave/drop listeners for palette-to-canvas drag
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- `lightsync/main.py` — timeline router registered with prefix="/api"
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## Decisions Made
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| Decision | Rationale |
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|----------|-----------|
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| Revert-then-command pattern in _startMove | Live drag updates block.timestamp for visual feedback; mouseup reverts to oldTimestamp, then MoveBlockCommand.execute() sets final value — history always has correct before/after state |
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| Document-level mousemove/mouseup during drag | Canvas-only listeners lose events when mouse moves fast outside canvas bounds |
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| Ghost preview via _dragState.trackIdx + time | Decoupled from raw pixels — render() computes screen position, maintaining coordinate abstraction |
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| setCurrentShowId() module-level function | Commands need showId for backend sync but shouldn't be coupled to app state — module-level var injected by app.js |
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## Deviations from Plan
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### Auto-fixed Issues
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**1. [Rule 1 - Bug] Plan's _startMove had duplicated/contradictory draft code**
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- **Found during:** Task 2 implementation
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- **Issue:** The plan's `_startMove` action block contained two conflicting implementations (onDrag/onUp followed by onDrag2/onUp2) with a comment "IMPORTANT: The executor MUST implement it cleanly as a single version"
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- **Fix:** Implemented clean single version following the stated logic: record old, live-update during drag, revert + command on mouseup
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- **Files modified:** `lightsync/frontend/timeline/timeline.js`
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- **Committed in:** 7e18ac6
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---
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**Total deviations:** 1 auto-fixed (Rule 1 - Bug)
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**Impact on plan:** Fix was necessary — the draft code in the plan would not compile/run correctly as-is. Clean implementation follows exact logic specified in the IMPORTANT note.
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## Issues Encountered
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- Circular import warning during `python -c "from lightsync.api.timeline import router"` — same pattern as existing `shows.py`. Not a bug: `import lightsync.main as state` at module level causes partially-initialized module error on isolated import, but works correctly at runtime when app bootstraps normally. Docker build and startup confirmed clean.
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## Known Stubs
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None — block placement, move, resize, delete are all fully wired. Backend CRUD endpoints accept and persist mutations. Undo/redo history tracks all operations.
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## Self-Check
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- `lightsync/frontend/timeline/history.js` exists: YES (658c92f)
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- `lightsync/frontend/timeline/commands.js` exports 4 command classes: YES (658c92f)
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- `lightsync/api/timeline.py` has POST/PATCH/DELETE routes: YES (658c92f)
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- `lightsync/main.py` includes timeline router: YES (658c92f)
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- `lightsync/frontend/timeline/timeline.js` has hitTest, _startMove, _startResize, handleDrop: YES (7e18ac6)
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- `lightsync/frontend/app.js` has dragstart/dragover/drop: YES (7e18ac6)
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- Docker build: SUCCESS (fa66387)
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- App startup: CLEAN (no errors, uvicorn running)
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## Self-Check: PASSED
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## Next Phase Readiness
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- Block placement and editing is fully functional — timeline is now interactive
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- Plan 04-03 (block inspector panel) can wire into `timeline._onSelectBlock` callback and `timeline.selectedBlock`
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- Plan 04-04 (playback/live engine) reads cues from `timeline.tracks[*].cues` which are now populated by user interactions
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- No blockers
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---
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*Phase: 04-timeline-editor*
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*Completed: 2026-04-06*
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