84 lines
2.7 KiB
Markdown
84 lines
2.7 KiB
Markdown
# Server Handoff: TV Power Coordination
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## Purpose
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Implement server-side MQTT power intent publishing so clients can keep TVs on across adjacent events and power off safely after schedules end.
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## Source of Truth
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- Shared full plan: TV_POWER_COORDINATION_TASKLIST.md
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## Scope (Server Team)
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- Scheduler-to-intent mapping
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- MQTT publishing semantics (retain, QoS, expiry)
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- Conflict handling (group vs client)
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- Observability for intent lifecycle
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## MQTT Contract (Server Responsibilities)
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### Topics
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- Primary (per-client): infoscreen/{client_id}/power/intent
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- Optional (group-level): infoscreen/groups/{group_id}/power/intent
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### Delivery Semantics
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- QoS: 1
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- retained: true
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- Always publish UTC timestamps (ISO 8601 with Z)
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### Intent Payload (v1)
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```json
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{
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"schema_version": "1.0",
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"intent_id": "uuid-or-monotonic-id",
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"issued_at": "2026-03-31T12:00:00Z",
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"expires_at": "2026-03-31T12:10:00Z",
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"target": {
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"client_id": "optional-if-group-topic",
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"group_id": "optional"
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},
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"power": {
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"desired_state": "on",
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"reason": "event_window_active",
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"grace_seconds": 30
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},
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"event_window": {
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"start": "2026-03-31T12:00:00Z",
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"end": "2026-03-31T13:00:00Z"
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}
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}
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```
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## Required Behavior
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### Adjacent/Overlapping Events
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- Never publish an intermediate off intent when windows are contiguous/overlapping.
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- Maintain continuous desired_state=on coverage across adjacent windows.
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### Reconnect/Restart
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- On scheduler restart, republish effective retained intent.
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- On event edits/cancellations, replace retained intent with a fresh intent_id.
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### Conflict Policy
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- If both group and client intent exist: per-client overrides group.
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### Expiry Safety
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- expires_at must be set for every intent.
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- Server should avoid publishing already-expired intents.
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## Implementation Tasks
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1. Add scheduler mapping layer that computes effective desired_state per client timeline.
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2. Add intent publisher with retained QoS1 delivery.
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3. Generate unique intent_id for each semantic transition.
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4. Emit issued_at/expires_at and event_window consistently in UTC.
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5. Add group-vs-client precedence logic.
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6. Add logs/metrics for publish success, retained payload age, and transition count.
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7. Add integration tests for adjacent events and reconnect replay.
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## Acceptance Criteria
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1. Adjacent events do not create OFF gap intents.
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2. Fresh client receives retained intent after reconnect and gets correct desired state.
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3. Intent payloads are schema-valid, UTC-formatted, and include expiry.
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4. Publish logs and metrics allow intent timeline reconstruction.
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## Operational Notes
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- Keep intent publishing idempotent and deterministic.
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- Preserve backward compatibility while clients run in hybrid mode.
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