# Service Base Classes

> Part of `Mango.Nop.Services`. See `Mango.Nop.Services/README.md` for project overview.
> For logging bridge see `docs/LOGGING/README.md`.

## MgBackgroundServiceBase

Abstract hosted background service. Inherits `Microsoft.Extensions.Hosting.BackgroundService`.

**Constructor:** `(ILogger, IServiceProvider, int executeIntervalMs)`

| Feature | Detail |
|---|---|
| Loop pattern | `ExecuteAsync` loops: `Task.Delay(ExecuteIntervalMs)` -> `OnExecuteAsync()`, with pause support |
| `OnExecuteAsync(CancellationToken)` | Abstract — subclass implements the actual work |
| `Pause(bool)` | Pauses/resumes the loop without stopping the service |
| `ExecuteIntervalMs` | Configurable interval between iterations |
| Exception handling | Catches and logs errors per iteration, never crashes the loop |
| Logging | Uses nopCommerce `Nop.Services.Logging.ILogger` (**not** `Mango.Nop.Core.Loggers.ILogger`) |

**Interface:** `IMgBackgroundService : IHostedService, IDisposable`

## MgSessionServiceBase\<TSessionItem\>

In-memory session management using `ConcurrentDictionary<string, TSessionItem>`.

| Method | Signature | Purpose |
|---|---|---|
| `GetOrCreateSessionItem` | `(string sessionId) -> TSessionItem?` | Get existing or create new via `Activator.CreateInstance` |
| `TryAddSessionItem` | `(TSessionItem) -> bool` | Add if not exists, throws if duplicate |
| `TryGetSessionItem` | `(string sessionId, out TSessionItem) -> bool` | Try-pattern lookup |
| `TryRemoveSessionItem` | `(string sessionId, out TSessionItem) -> bool` | Remove and return |
| `TryGetSessionItemBySignlaRConnectionId` | `(string connectionId, out TSessionItem?) -> bool` | Find session by SignalR connection |
| `Count` | `() -> int` | Active session count |

**Interface:** `IMgSessionService<TSessionItem> where TSessionItem : IMgSessionItem`

## MgSessionItemBase

Base session item. Primary constructor: `(string sessionKey)`.

| Property | Type | Purpose |
|---|---|---|
| `SessionId` | `string` | Unique session identifier |
| `SignaRConnectionId` | `string?` | Associated SignalR connection ID |
| `RequestCount` | `int` | Request counter |

**Interface:** `IMgSessionItem` — `SessionId`, `SignaRConnectionId`, `RequestCount`

## MgEventConsumerBase

Abstract nopCommerce event consumer. Subscribes to:

| Event | Handler |
|---|---|
| `EntityUpdatedEvent<Product>` | `HandleEventAsync(...)` — virtual, empty default |
| `EntityInsertedEvent<Product>` | `HandleEventAsync(...)` — virtual, empty default |
| `CustomerRegisteredEvent` | `HandleEventAsync(...)` — virtual, empty default |
| `OrderPlacedEvent` | `HandleEventAsync(...)` — virtual, empty default |
| `PageRenderingEvent` | `HandleEventAsync(...)` — virtual, empty default |
| `ProductSearchEvent` | `HandleEventAsync(...)` — virtual, empty default |

Built-in helper: `CheckAndUpdateProductManageInventoryMethodToManageStock(Product)` — ensures product has `ManageStock` inventory method.

**Constructor:** `(IMgDbContextBase ctx, IHttpContextAccessor, IEnumerable<IAcLogWriterBase> logWriters)`

## MgLockServiceBase

Simple in-process lock using `SemaphoreSlim(1)`. Implements `IMgLockService` (defined in `Mango.Nop.Core.Services`).

Used by `MgDbContextBase.TransactionSafe*` variants for global serialization.