56 lines
3.6 KiB
Markdown
56 lines
3.6 KiB
Markdown
---
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source_files:
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- Common/DTS.Common/Events/Diagnostics/CheckDataToDownloadEvent.cs
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generated_at: "2026-04-16T03:24:51.174525+00:00"
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model: "Qwen/Qwen3-Coder-Next-FP8"
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schema_version: 1
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sha256: "99f81a50a8d987c0"
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---
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# Diagnostics
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### 1. **Purpose**
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This module defines a Prism-based event (`CheckDataToDownloadEvent`) used to signal and coordinate a check for data that needs to be downloaded in the DTS system. It enables decoupled communication between components—typically a producer (e.g., a service or view model) initiating a download readiness check—and subscribers (e.g., a download manager or UI component) responsible for evaluating and acting on whether a download is necessary. The event supports bypassing the check (e.g., for forced or manual downloads) via the `BypassCheck` flag, and carries a reference to the originating producer for context or audit purposes.
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---
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### 2. **Public Interface**
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- **`CheckDataToDownloadEvent`**
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- *Type*: `class` inheriting from `PubSubEvent<CheckDataToDownloadEventArgs>`
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- *Behavior*: A Prism `PubSubEvent` used to publish and subscribe to download-check requests. Subscribers receive an instance of `CheckDataToDownloadEventArgs` when the event is published.
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- **`CheckDataToDownloadEventArgs`**
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- *Type*: `class`
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- *Properties*:
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- `bool BypassCheck { get; }` — Indicates whether the caller requests skipping the normal data existence/validity check (e.g., proceed directly to download).
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- `object Producer { get; }` — The object that triggered the event (e.g., a view model, service, or UI element). Used for identification or logging.
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- *Constructor*:
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- `CheckDataToDownloadEventArgs(bool bypassCheck, object o)` — Initializes the args with the bypass flag and producer reference. Both values are immutable after construction.
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---
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### 3. **Invariants**
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- `BypassCheck` is set at construction and **never modified** afterward (due to `private set`).
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- `Producer` is set at construction and **never modified** afterward (due to `private set`).
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- The `Producer` reference may be `null` (no validation is performed in the constructor), so consumers must handle null cases.
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- The event is strictly for *initiating* a check—not for reporting results. The event itself does not carry download status or payload; subscribers are expected to handle side effects (e.g., triggering downloads) based on their own logic.
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---
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### 4. **Dependencies**
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- **Depends on**:
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- `Prism.Events` (specifically `PubSubEvent<T>` from the Prism library).
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- **Used by**:
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- Any component needing to request a data-downloads check (e.g., `DownloadService`, `MainViewModel`, or UI controls).
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- Subscribers (e.g., `DownloadManager`) that react to this event to determine whether to proceed with downloading data.
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- **No other internal dependencies** are evident from this file alone.
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---
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### 5. **Gotchas**
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- **No validation on `Producer`**: The constructor accepts any `object`, including `null`. Consumers must defensively check `Producer` before use (e.g., for logging or routing).
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- **Event semantics are ambiguous**: The name `CheckDataToDownloadEvent` implies a *request*, but the event does not provide a way to *return* a result (e.g., whether download is needed). Subscribers must act asynchronously or via side effects (e.g., publishing a follow-up event).
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- **No cancellation support**: There is no mechanism for subscribers to cancel or delay the check (e.g., via a token).
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- **No versioning or schema evolution**: If `BypassCheck` or `Producer` semantics change in the future, this event type offers no backward/forward compatibility.
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- **None identified from source alone.** |