---
source_files:
  - DataPRO/IService/StateMachine/States/Arm.cs
  - DataPRO/IService/StateMachine/States/Arming.cs
  - DataPRO/IService/StateMachine/States/Realtime.cs
  - DataPRO/IService/StateMachine/States/Download.cs
  - DataPRO/IService/StateMachine/States/HardwareDiscovery.cs
  - DataPRO/IService/StateMachine/States/Prepare.cs
  - DataPRO/IService/StateMachine/States/ConfigureStart.cs
  - DataPRO/IService/StateMachine/States/RealtimeStart.cs
  - DataPRO/IService/StateMachine/States/Configure.cs
  - DataPRO/IService/StateMachine/States/Diagnose.cs
  - DataPRO/IService/StateMachine/States/DownloadStart.cs
  - DataPRO/IService/StateMachine/States/HardwareDiscoveryStart.cs
generated_at: "2026-04-16T04:00:35.991960+00:00"
model: "Qwen/Qwen3-Coder-Next-FP8"
schema_version: 1
sha256: "dc1b1b8c07850591"
---

# States

## Documentation: StateMachine States Module

### 1. Purpose  
This module defines the concrete state implementations for the DAS (Data Acquisition System) service state machine. Each class represents a terminal or selector state in the state transition graph, encapsulating entry actions and transition logic. The states manage transitions between operational modes such as hardware discovery, configuration, arming, real-time acquisition, and data download. The module serves as the behavioral core of the state machine, where transitions are determined by runtime status flags and configuration parameters.

### 2. Public Interface  

All classes inherit from `DASState` (or `DASStateSelector` for selector states) in the `DTS.DASLib.Service.StateMachine` namespace. Only `Realtime`, `ConfigureStart`, `RealtimeStart`, `Configure`, `Diagnose`, `DownloadStart`, and `HardwareDiscoveryStart` are `public`; the rest are `internal`.

#### Terminal States (non-selector, inherit `DASState`)
- **`public class Realtime : DASState`**  
  Represents the active real-time acquisition state. Returns `State.Realtime` via the `State` property. No custom entry action.

- **`internal class Arm : DASState`**  
  Represents the armed (ready but not yet acquiring) state. Returns `State.Arm`.

- **`internal class Arming : DASState`**  
  Represents the transitional arming state. Returns `State.Arming`.

- **`internal class Download : DASState`**  
  Represents the data download state. Returns `State.Download`.

- **`internal class HardwareDiscovery : DASState`**  
  Represents the hardware discovery state. Returns `State.HardwareDiscovery`.

- **`internal class Prepare : DASState`**  
  Represents the prepare state. Overrides `OnEntry` to invoke `PrepareDASFactory`, which detaches all devices and clears host name arrays in `DASFactory` (if non-null). Returns `State.Prepare`.

#### Selector States (inherit `DASStateSelector`)
- **`public class ConfigureStart : DASStateSelector`**  
  Entry action: `ApplyConfig`, which calls `Status.ConfigureStatus.ApplyConfig()`.  
  Selector logic: Always returns `States.Instance.Diagnose`.  
  Returns `State.ConfigureStart`.

- **`public class RealtimeStart : DASStateSelector`**  
  Entry action: `Start`, which calls `Status.RealtimeStatus.StartRealtime()`.  
  Selector logic:  
  - If `Status.RealtimeStatus.CouldNotStartRealtime` is true → returns `States.Instance.RealtimeStart` (retry loop).  
  - Else → returns `States.Instance.Realtime`.  
  Returns `State.RealtimeStart`.

- **`public class Configure : DASStateSelector`**  
  Selector logic:  
  - `AllowApplyConfig()` currently always returns `true` (placeholder logic).  
  - If true → returns `States.Instance.ConfigureStart`.  
  - Else → returns `States.Instance.Configure` (self-loop).  
  Returns `State.Configure`.

- **`public class Diagnose : DASStateSelector`**  
  Selector logic:  
  - Returns `States.Instance.RealtimeStart` if either:  
    (a) `Status.DiagnoseParams.ProceedToRealtimeWhenDone && Status.DiagnoseParams.AllUnitsPassedDiagnostic`, or  
    (b) `Status.DiagnoseParams.ProceedToRealtimeWhenDone && !Status.DiagnoseParams.RequireAllUnitsPassDiagnostic`.  
  - Else → returns `States.Instance.Diagnose` (self-loop).  
  Returns `State.Diagnose`.

- **`public class DownloadStart : DASStateSelector`**  
  Entry action: `Start`, which calls `Status.DownloadStatusInfo.Download()`.  
  Selector logic:  
  - Returns `States.Instance.Prepare` if `CanTransitToPrepare()` is true:  
    `Status.DownloadParams.ProceedWhenDone && (Status.DownloadStatusInfo.AllDASFinished || !Status.DownloadParams.RequireAllDASFinish)`.  
  - Else → returns `States.Instance.Download` (self-loop).  
  Returns `State.DownloadStart`.

- **`public class HardwareDiscoveryStart : DASStateSelector`**  
  Entry action: `Start`, which calls either `RequeryDevice()` or `Ping()` on `Status.HardwareDiscoveryStatusInfo`, depending on whether `Status.HardwareDiscoveryParams.RequeryDevice` is non-null.  
  Selector logic (evaluated in order):  
  - `CanTransitToDownload()` → returns `States.Instance.Download`  
  - `CanTransitToConfigure()` → returns `States.Instance.Configure`  
  - `CanTransitToArm()` → returns `States.Instance.Arm`  
  - Else → returns `States.Instance.HardwareDiscovery` (self-loop)  
  Where:  
  - `CanTransitToConfigure()`: `Status.HardwareDiscoveryParams.ProceedWhenDone && (Status.HardwareDiscoveryStatusInfo.AllDASFound || !Status.HardwareDiscoveryParams.RequireAllDASFound)`  
  - `CanTransitToArm()`: `Status.HardwareDiscoveryParams.ProceedWhenDone && Status.HardwareDiscoveryStatusInfo.SomeUnitsInArmState`  
  - `CanTransitToDownload()`: `CanTransitToConfigure() && Status.HardwareDiscoveryParams.GoToDownload`  
  Returns `State.HardwareDiscoveryStart`.

### 3. Invariants  
- Every state class must override the `State` property to return its corresponding `State` enum value (e.g., `State.Prepare`, `State.Realtime`).  
- Selector states (`DASStateSelector` subclasses) must implement `StateSelector()` to return an `IDASState` (typically via `States.Instance.<StateName>`).  
- Terminal states (`DASState` subclasses) may optionally override `OnEntry` to define entry behavior; if not overridden, no entry action is executed.  
- The `OnEntry` action (if present) must call `OnEnterState()` as its first operation (observed in `Prepare`, `ConfigureStart`, `RealtimeStart`, `DownloadStart`, `HardwareDiscoveryStart`).  
- Transition decisions in selector states are based solely on `Status.*` properties and `Status.*Params` configuration objects.  
- No state class performs side effects outside of `OnEntry` or `StateSelector()`.

### 4. Dependencies  
- **Internal dependencies (from source):**  
  - `DASState` and `DASStateSelector` base classes (not shown, but implied by inheritance).  
  - `State` enum (used in `State` property overrides).  
  - `States.Instance` singleton (used to reference other states, e.g., `States.Instance.Diagnose`).  
  - `Status` object with nested properties:  
    - `ConfigureStatus`, `RealtimeStatus`, `DiagnoseParams`, `DownloadStatusInfo`, `DownloadParams`, `HardwareDiscoveryParams`, `HardwareDiscoveryStatusInfo`.  
  - `DASFactory` (used in `Prepare.PrepareDASFactory()`; assumed to be a member of the base `DASState` class or accessible via `this`).  

- **External dependencies (inferred):**  
  - `System` and related namespaces (e.g., `System.Threading.Tasks`).  
  - Likely depends on a larger `DTS.DASLib.Service` assembly containing `Status`, `States`, and base state classes.

### 5. Gotchas  
- **Incomplete logic in `Configure.AllowApplyConfig()`**: Currently always returns `true`; no actual validation of channel resolution or placement is implemented despite comments indicating intent.  
- **Selector state ordering matters**: In `HardwareDiscoveryStart`, transitions are evaluated in a specific order (Download → Configure → Arm → self-loop). Changing this order could alter behavior.  
- **Self-loops may cause infinite loops**: States like `Configure`, `Diagnose`, `Download`, and `HardwareDiscovery` can loop to themselves if conditions are not met; external triggers or status changes are required to exit.  
- **Ambiguous `DASFactory` usage**: `PrepareDASFactory()` references `DASFactory` without clear scoping—assumed to be a member of the base class, but not declared in the provided source.  
- **No explicit error handling**: Entry actions (e.g., `StartRealtime()`, `Download()`) may throw exceptions; no try/catch is visible in the source.  
- **`RealtimeStart` selector logic may retry indefinitely**: If `CouldNotStartRealtime` remains true, the state machine will loop back to `RealtimeStart` without backoff or failure reporting.  
- **`RequeryDevice()` vs `Ping()` behavior**: The condition `null != Status.HardwareDiscoveryParams.RequeryDevice` suggests `RequeryDevice` is a delegate or method group, but its type and semantics are not evident from this file.