measurement/CONTRACT.md

# measurement — Contract

Hand-maintained for Phase 3; the `## Inputs` table is generated from
`src/commands/index.js` (see Phase 9 generator). Keep ≤ 80 lines.

## Inputs (msg.topic on Port 0)

| Canonical | Aliases (deprecated) | Payload | Effect |
|---|---|---|---|
| `set.simulator` | `simulator` | none (payload ignored) | Toggles `source.toggleSimulation()` — flips `config.simulation.enabled`. |
| `set.outlier-detection` | `outlierDetection` | none (payload ignored) | Toggles `source.toggleOutlierDetection()` — flips `config.outlierDetection.enabled`. |
| `cmd.calibrate` | `calibrate` | none | Calls `source.calibrate()` — captures the current input as the zero/reference offset. |
| `data.measurement` | `measurement` | mode-dependent — see **Payload shape** below | Pushes a sensor reading into the pipeline. Analog → `source.inputValue`; digital → `source.handleDigitalPayload(<flat map>)`. Wrong shape for the configured mode logs a helpful warning suggesting the other mode. |

Aliases log a one-time deprecation warning the first time they fire.

### `data.measurement` payload shape

Both modes accept the same three forms, mirroring pumpingStation's
`set.inflow` contract:

- **Bare scalar** — `msg.payload = 12.5` (number or numeric string). The unit
  falls back to `msg.unit`, and finally to the channel's configured unit
  (the dropdown selection in the node editor).
- **Rich object** — `msg.payload = { value, unit?, timestamp? }`. Used per-
  call to declare the unit of a single sample.
- **Digital map** (digital mode only) — `msg.payload = { <channelKey>: <bare scalar | rich object>, … }`. Each entry follows the rules above independently, so different channels in one message may carry different units.

When a supplied unit differs from the channel's configured unit, the value
is converted into the channel unit via `generalFunctions.convert` before it
enters the outlier / scaling / smoothing pipeline. If the supplied unit is
unknown or belongs to a different measure (e.g. `kg` on a `pressure`
channel), the handler logs a warning and uses the raw value treated as the
channel unit — the sample is not silently dropped.

## Outputs (msg.topic on Port 0/1/2)

- **Port 0 (process):** `msg.topic = config.general.name`. Payload built by
  `outputUtils.formatMsg(..., 'process')` from `getOutput()` (analog) or
  `getDigitalOutput()` (digital). Delta-compressed — only changed fields are
  emitted.
- **Port 1 (InfluxDB telemetry):** same shape as Port 0, formatted with the
  `'influxdb'` formatter.
- **Port 2 (registration):** at startup the node sends one
  `{ topic: 'registerChild', payload: <node.id>, positionVsParent, distance }`
  to its parent.

## Events emitted by `source.measurements.emitter`

The `MeasurementContainer` fires `<type>.measured.<position>` whenever a
matching series receives a new value. The type / position labels are set
from `config.asset.type` and `config.functionality.positionVsParent`
(analog), or per-channel from `config.channels[*]` (digital). Examples:

- `pressure.measured.upstream`
- `flow.measured.atequipment`
- `level.measured.downstream`
- `temperature.measured.atequipment`

Position labels are always lowercase in the event name. Parents subscribe
through the generic `child.measurements.emitter.on(eventName, ...)` handshake
established by `childRegistrationUtils`.

In digital mode one input message can fan out into several events — one
per channel that accepted a value on that tick.

The legacy internal `source.emitter` also fires `'mAbs'` with the current
scaled absolute value (analog mode only). This is deprecated in favour of
`measurements.emitter` and kept only for the editor status badge during the
refactor window.

## Children registered by this node

None — `measurement` is a leaf in the S88 hierarchy (Control Module). It
registers itself as a child of an upstream parent (rotatingMachine,
pumpingStation, reactor, monster, …) but does not accept its own children.
Registration goes via Port 2 at startup and is keyed off
`positionVsParent` / `distance` in the node's UI config.