Walkthrough — ICU alarm pipeline (enhanced)

Demo: example\ICU-alarm-pipeline(enhanced)-Demo.dart
Sibling: ICU-alarm-pipeline-Demo.dart (bus + one gate only)

Adds TestCell on sensor ingress, a WARN Receptor, a ledger, ACK that resets Distinct on the same Receptor, and AsyncMapWithRetry.

Design
Parts
Implementation map
Scenarios (what the last good run showed)
Pulse path (scenario 2)
Real bay vs this file

Design

hrIn    TestCell 20–250  ─┐
spo2In  TestCell 0–100   ─┼─ set* → publishVitals → Reading(bed, hr, spo2, moving)
motionIn                 ─┘
                              │
                              ▼
                         vitalsIn
                    ┌─────────┴─────────┐
                    ▼                   ▼
              page gate            warn gate
         MapValue + Distinct     MapValue + Distinct
              + Filter(page)          + Filter(warn)
                    │                   │
                    ▼                   ▼
              pageHandle            warnHandle
                    │
                    ├─ observe → ledger PAGE + console pager
                    └─ AsyncMapWithRetry → pagerHandle
ackIn ─────────────────────────────────► resetDistinct()

Requirement	Owner
Impossible HR / SpO2	`TestCell` on ingress, not on state
One Reading per tick	`publishVitals` bus
PAGE vs WARN	two Receptors, same `severityOf`
No duplicate PAGE	Distinct before Filter; ACK clears `_pageLast`
Nurse text	`AsyncMapWithRetry` + observer print
Audit	`ledger` list (in-process)

Do not call toHandle again on ACK. A second handle stays subscribed to vitalsIn and doubles every later PAGE (Concurrent modification if you mutate synapses in the same effect).

Parts

Cell

Cell	Kind	Role
`hrIn` / `spo2In`	ingress + TestCell	reject 9 / 140
`motionIn`	ingress	bool
`vitalsIn`	ingress `<Reading>`	snapshot bus
`ackIn`	ingress `<String>`	who acknowledged
`pageHandle.cell`	`toHandle`	PAGE only
`warnHandle.cell`	`toHandle`	WARN only
`pagerHandle.cell`	`AsyncMapWithRetry`	I/O with `count: 2`

_hr / _spo2 / _moving are a Dart cache. setHr returns false and does not call publishVitals when TestCell rejects.

Instruction

Stage	Type
`MapValue<Reading, Severity>`	`severityOf`
`_distinctPage` / `_distinctWarn`	closured last-value; ACK zeroes it
`Filter<Severity>(page)` / `warn`	drop the other severities

Library DistinctUntilChanged is not used: it cannot be reset without a new handle.

Receptor

buildPageGate().toHandle(source: vitalsIn.cell) once at installGates(). Same for WARN. One lock per gate.

Flow operators

MapValue, Filter, FlowInstruction (custom Distinct), AsyncMapWithRetry (count, not retries), Cell.observe, Cell.ingress(testRule:).

Implementation map

Block in the dart file	What
Architecture / expected output comments	talk track
`Reading` / `Severity` / `LedgerEntry`	domain
`hrRange` / `spo2Range`	TestCell
`publishVitals` / `set*`	bus
`severityOf`	clinical map
`_distinctPage` + `resetDistinct`	ACK
`installGates`	two Receptors + pager + observes
`main`	seed + scenarios 1–9

installGates runs once. ACK only touches Distinct fields.

Scenarios (what the last good run showed)

#	Drive	Result	Demonstrates
Seed	still, 96, 72	three vitals, no PAGE	bus + Filter
1	repeat 72/96	no PAGE	Distinct on `none`
2	SpO2 86	PAGE + ledger + pager	first critical
3	moving then still	no page while moving; PAGE when still	artifact then Distinct `none`→`page`
4–5	SpO2 85, HR 35	no PAGE	Distinct holds `page` (header text that says PAGE here is wrong)
WARN	HR 55, SpO2 90	WARN	second Receptor
6	96 / 74 then ACK	recover; Distinct cleared	ACK ≠ new `toHandle`
7	SpO2 87	one PAGE	reset Distinct
8	HR 9, SpO2 140	TestCell lines; no vitals	ingress boundary
9	ACK, recover, SpO2 80, fail-once	one PAGE; pagerAttempts includes retry	`AsyncMapWithRetry`

Good-run counts: vitals 18, pages 4, warns 1, ledger 7 (4 PAGE + 1 WARN

2 ACK). pagerAttempts can be 5 if the first nurse-app call throws.

Pulse path (scenario 2)

setSpo2(86)
  spo2In.emit — TestCell pass
  _spo2 = 86
  publishVitals → vitalsIn
    page Receptor: MapValue page → Distinct emit → Filter pass
    warn Receptor: Filter drop
    observe PAGE → ledger
    AsyncMapWithRetry → pager cell

Scenario 8 stops at hrIn.emit / spo2In.emit.

Real bay vs this file

Still missing	Suggested next Cell/Flow piece
Snapshot is a Dart cache	bed `Nucleus` / trusted `Cell.synthesis`
No 10–15 s hold	`Debounce` / `BufferTime` in front of the gate
Ledger is a `List`	append-only ledger Cell
Two pager printers	keep `pagerHandle` or the observer Future, not both
ACK does not dispose I/O	fine; do not stack `toHandle`
No `Context`	bed/ward on Pulse
WARN unused by pager	charge-nurse Cell from `warnHandle`

Flow stays on “is this PAGE / WARN?”
TestCell stays on the sensor ingress.
ACK stays a flag on Distinct, not a second graph.

Demo · ICU Alarm Pipeline topic