# Mandatory Coding Patterns

These patterns MUST be followed in all code you write for the NT8 SDK.

## Thread Safety - Dictionary Access

ALL access to shared dictionaries MUST use locks.

### ❌ WRONG - No Lock
```csharp
_activeOrders[orderId] = orderStatus;  // DANGEROUS!
```

### ✅ CORRECT - With Lock
```csharp
lock (_lock)
{
    _activeOrders[orderId] = orderStatus;
}
```

### Rule
Every class with shared state MUST have:
```csharp
private readonly object _lock = new object();
```

Every access to shared collections MUST be inside:
```csharp
lock (_lock)
{
    // Dictionary/List operations here
}
```

## Error Handling - Try-Catch Required

ALL public methods MUST have try-catch blocks.

### ❌ WRONG - No Error Handling
```csharp
public async Task<string> SubmitOrder(OrderRequest request)
{
    var orderId = GenerateOrderId();
    await _nt8Adapter.SubmitToNT8(orderStatus);
    return orderId;
}
```

### ✅ CORRECT - With Error Handling
```csharp
public async Task<string> SubmitOrder(OrderRequest request)
{
    if (request == null)
        throw new ArgumentNullException("request");
    
    try
    {
        request.Validate();
    }
    catch (ArgumentException ex)
    {
        _logger.LogError("Order validation failed: {0}", ex.Message);
        throw;
    }
    
    try
    {
        var orderId = GenerateOrderId();
        await _nt8Adapter.SubmitToNT8(orderStatus);
        return orderId;
    }
    catch (Exception ex)
    {
        _logger.LogError("Order submission failed: {0}", ex.Message);
        throw;
    }
}
```

### Pattern Template
```csharp
public ReturnType MethodName(Type parameter)
{
    // 1. Validate parameters (throw ArgumentNullException/ArgumentException)
    if (parameter == null)
        throw new ArgumentNullException("parameter");
    
    // 2. Try-catch for operation-specific errors
    try
    {
        // Main logic
    }
    catch (SpecificException ex)
    {
        _logger.LogError("Specific error: {0}", ex.Message);
        // Handle or re-throw
        throw;
    }
    catch (Exception ex)
    {
        _logger.LogError("Unexpected error: {0}", ex.Message);
        throw;
    }
}
```

## Logging - Structured and Consistent

Use structured logging with string.Format (NOT string interpolation).

### Log Levels

#### LogTrace - Detailed Flow
```csharp
_logger.LogTrace("Entering method {0} with parameter {1}", methodName, param);
```

#### LogDebug - Normal Operations
```csharp
_logger.LogDebug("Order {0} state is {1}", orderId, state);
```

#### LogInformation - Important Events
```csharp
_logger.LogInformation("Order {0} submitted successfully at {1}", orderId, timestamp);
_logger.LogInformation("Order {0} filled: {1} contracts @ {2:F2}", orderId, qty, price);
```

#### LogWarning - Recoverable Issues
```csharp
_logger.LogWarning("Order validation failed: {0}", validationError);
_logger.LogWarning("Maximum active orders reached: {0}", maxOrders);
```

#### LogError - Failures
```csharp
_logger.LogError("Failed to submit order {0} to NT8: {1}", orderId, ex.Message);
_logger.LogError("Invalid state transition: {0} -> {1}", fromState, toState);
```

#### LogCritical - System Integrity Issues
```csharp
_logger.LogCritical("Emergency flatten failed for {0}: {1}", symbol, ex.Message);
```

### ❌ WRONG - String Interpolation
```csharp
_logger.LogInformation($"Order {orderId} submitted");  // C# 6+ feature!
```

### ✅ CORRECT - string.Format
```csharp
_logger.LogInformation("Order {0} submitted", orderId);
```

## XML Documentation - Required

ALL public and protected members MUST have XML documentation.

### ❌ WRONG - No Documentation
```csharp
public interface IOrderManager
{
    Task<string> SubmitOrder(OrderRequest request);
}
```

### ✅ CORRECT - With Documentation
```csharp
/// <summary>
/// Order management interface - manages complete order lifecycle
/// </summary>
public interface IOrderManager
{
    /// <summary>
    /// Submit new order for execution
    /// </summary>
    /// <param name="request">Order request with all parameters</param>
    /// <returns>Unique order ID for tracking</returns>
    /// <exception cref="ArgumentNullException">Request is null</exception>
    /// <exception cref="ArgumentException">Request validation fails</exception>
    Task<string> SubmitOrder(OrderRequest request);
}
```

### Template
```csharp
/// <summary>
/// Brief description of what this does (one line)
/// </summary>
/// <param name="paramName">What this parameter represents</param>
/// <returns>What this method returns</returns>
/// <exception cref="ExceptionType">When this exception is thrown</exception>
public ReturnType MethodName(Type paramName)
{
    // Implementation
}
```

## Constructor Pattern

### ❌ WRONG - No Validation
```csharp
public BasicOrderManager(ILogger logger, INT8OrderAdapter adapter)
{
    _logger = logger;
    _adapter = adapter;
}
```

### ✅ CORRECT - Validate Dependencies
```csharp
public BasicOrderManager(ILogger<BasicOrderManager> logger, INT8OrderAdapter adapter)
{
    if (logger == null)
        throw new ArgumentNullException("logger");
    if (adapter == null)
        throw new ArgumentNullException("adapter");
    
    _logger = logger;
    _adapter = adapter;
    
    _activeOrders = new Dictionary<string, OrderStatus>();
    _completedOrders = new Dictionary<string, OrderStatus>();
    
    // Register callbacks
    _adapter.RegisterOrderCallback(OnNT8OrderUpdate);
    
    _logger.LogInformation("BasicOrderManager initialized");
}
```

## Event Raising Pattern

NEVER raise events inside locks (prevents deadlocks).

### ❌ WRONG - Event Inside Lock
```csharp
lock (_lock)
{
    order.State = newState;
    OrderStateChanged?.Invoke(this, eventArgs);  // DEADLOCK RISK!
}
```

### ✅ CORRECT - Event Outside Lock
```csharp
OrderState previousState;
OrderState newState;

lock (_lock)
{
    previousState = order.State;
    order.State = newState;
    // Update state inside lock
}

// Raise event OUTSIDE lock
RaiseOrderStateChanged(orderId, previousState, newState, reason);
```

## Verification Checklist

Before completing ANY method, verify:
- [ ] Parameter validation (ArgumentNullException/ArgumentException)
- [ ] Try-catch on operation
- [ ] Logging at appropriate level
- [ ] Lock around shared state access
- [ ] Events raised outside locks
- [ ] XML documentation on public members
- [ ] C# 5.0 syntax only (no $, ?., =>, etc.)