# TWAP Algorithm Implementation Design

## Overview

This document details the implementation of the Time Weighted Average Price (TWAP) algorithm in the Order Management System (OMS), which executes large orders by slicing them into smaller orders over a specified time period to minimize market impact.

## TWAP Algorithm Fundamentals

### Algorithm Description
The TWAP algorithm is designed to execute large orders by dividing them into smaller, equal-sized slices and executing these slices at regular intervals throughout a specified time period. The primary goal is to minimize market impact by spreading the execution over time and participating equally in all time periods.

### Key Characteristics
1. **Time-based Slicing**: Orders are divided based on time intervals rather than volume
2. **Equal Participation**: Equal participation rate in each time interval
3. **Market Impact Reduction**: Minimizes information leakage by spreading execution
4. **Predictable Execution**: Provides consistent execution pattern

## TWAP Parameters

### Core Parameters
```csharp
/// <summary>
/// Parameters for TWAP algorithm execution
/// </summary>
public record TwapParameters
{
    /// <summary>
    /// Trading symbol
    /// </summary>
    public string Symbol { get; set; }
    
    /// <summary>
    /// Order side (Buy/Sell)
    /// </summary>
    public OrderSide Side { get; set; }
    
    /// <summary>
    /// Total quantity to execute
    /// </summary>
    public int TotalQuantity { get; set; }
    
    /// <summary>
    /// Start time for execution
    /// </summary>
    public DateTime StartTime { get; set; }
    
    /// <summary>
    /// End time for execution
    /// </summary>
    public DateTime EndTime { get; set; }
    
    /// <summary>
    /// Interval between order submissions (in seconds)
    /// </summary>
    public int IntervalSeconds { get; set; }
    
    /// <summary>
    /// Optional limit price for limit orders
    /// </summary>
    public decimal? LimitPrice { get; set; }
    
    /// <summary>
    /// Time in force for orders
    /// </summary>
    public TimeInForce TimeInForce { get; set; } = TimeInForce.Day;
    
    /// <summary>
    /// Whether to adjust slice sizes based on remaining time
    /// </summary>
    public bool AdjustForRemainingTime { get; set; } = true;
    
    /// <summary>
    /// Minimum slice size (to avoid very small orders)
    /// </summary>
    public int MinSliceSize { get; set; } = 1;
    
    /// <summary>
    /// Maximum slice size (to control individual order impact)
    /// </summary>
    public int? MaxSliceSize { get; set; }
    
    /// <summary>
    /// Whether to cancel remaining orders at end time
    /// </summary>
    public bool CancelAtEndTime { get; set; } = true;
    
    /// <summary>
    /// Custom metadata for the algorithm
    /// </summary>
    public Dictionary<string, object> Metadata { get; set; } = new Dictionary<string, object>();
}
```

### TWAP Configuration
```csharp
/// <summary>
/// Configuration for TWAP algorithm behavior
/// </summary>
public record TwapConfig
{
    /// <summary>
    /// Default execution duration
    /// </summary>
    public TimeSpan DefaultDuration { get; set; } = TimeSpan.FromMinutes(30);
    
    /// <summary>
    /// Default interval between orders
    /// </summary>
    public int DefaultIntervalSeconds { get; set; } = 60;
    
    /// <summary>
    /// Whether to enable adaptive slicing based on market conditions
    /// </summary>
    public bool EnableAdaptiveSlicing { get; set; } = false;
    
    /// <summary>
    /// Maximum deviation from scheduled execution time (in seconds)
    /// </summary>
    public int MaxTimeDeviationSeconds { get; set; } = 30;
    
    /// <summary>
    /// Whether to prioritize execution speed over impact reduction
    /// </summary>
    public bool PrioritizeSpeed { get; set; } = false;
    
    /// <summary>
    /// Retry count for failed slice executions
    /// </summary>
    public int MaxRetries { get; set; } = 3;
    
    /// <summary>
    /// Delay between retries (in seconds)
    /// </summary>
    public int RetryDelaySeconds { get; set; } = 5;
    
    /// <summary>
    /// Whether to log detailed execution information
    /// </summary>
    public bool EnableDetailedLogging { get; set; } = false;
    
    public static TwapConfig Default => new TwapConfig();
}
```

## TWAP Execution Models

### TWAP Execution State
```csharp
/// <summary>
/// State of a TWAP execution
/// </summary>
public record TwapExecutionState
{
    /// <summary>
    /// Unique identifier for this TWAP execution
    /// </summary>
    public string ExecutionId { get; set; } = Guid.NewGuid().ToString();
    
    /// <summary>
    /// Parameters used for this execution
    /// </summary>
    public TwapParameters Parameters { get; set; }
    
    /// <summary>
    /// Current execution status
    /// </summary>
    public TwapExecutionStatus Status { get; set; } = TwapExecutionStatus.Pending;
    
    /// <summary>
    /// Total quantity to execute
    /// </summary>
    public int TotalQuantity { get; set; }
    
    /// <summary>
    /// Quantity already executed
    /// </summary>
    public int ExecutedQuantity { get; set; }
    
    /// <summary>
    /// Remaining quantity to execute
    /// </summary>
    public int RemainingQuantity => TotalQuantity - ExecutedQuantity;
    
    /// <summary>
    /// Scheduled slice executions
    /// </summary>
    public List<TwapSlice> ScheduledSlices { get; set; } = new List<TwapSlice>();
    
    /// <summary>
    /// Completed slice executions
    /// </summary>
    public List<TwapSlice> CompletedSlices { get; set; } = new List<TwapSlice>();
    
    /// <summary>
    /// Failed slice executions
    /// </summary>
    public List<TwapSlice> FailedSlices { get; set; } = new List<TwapSlice>();
    
    /// <summary>
    /// Start time of execution
    /// </summary>
    public DateTime? StartTime { get; set; }
    
    /// <summary>
    /// End time of execution
    /// </summary>
    public DateTime? EndTime { get; set; }
    
    /// <summary>
    /// When this execution was created
    /// </summary>
    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    
    /// <summary>
    /// When this execution was last updated
    /// </summary>
    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
    
    /// <summary>
    /// Error information if execution failed
    /// </summary>
    public string ErrorMessage { get; set; }
    
    /// <summary>
    /// Performance metrics for this execution
    /// </summary>
    public TwapPerformanceMetrics PerformanceMetrics { get; set; } = new TwapPerformanceMetrics();
}
```

### TWAP Slice
```csharp
/// <summary>
/// Represents a single slice of a TWAP execution
/// </summary>
public record TwapSlice
{
    /// <summary>
    /// Unique identifier for this slice
    /// </summary>
    public string SliceId { get; set; } = Guid.NewGuid().ToString();
    
    /// <summary>
    /// Reference to parent TWAP execution
    /// </summary>
    public string ExecutionId { get; set; }
    
    /// <summary>
    /// Slice number (1-based)
    /// </summary>
    public int SliceNumber { get; set; }
    
    /// <summary>
    /// Scheduled execution time
    /// </summary>
    public DateTime ScheduledTime { get; set; }
    
    /// <summary>
    /// Actual execution time
    /// </summary>
    public DateTime? ActualTime { get; set; }
    
    /// <summary>
    /// Quantity for this slice
    /// </summary>
    public int Quantity { get; set; }
    
    /// <summary>
    /// Status of this slice
    /// </summary>
    public TwapSliceStatus Status { get; set; } = TwapSliceStatus.Pending;
    
    /// <summary>
    /// Order ID for this slice (if submitted)
    /// </summary>
    public string OrderId { get; set; }
    
    /// <summary>
    /// Fills for this slice
    /// </summary>
    public List<OrderFill> Fills { get; set; } = new List<OrderFill>();
    
    /// <summary>
    /// Total filled quantity
    /// </summary>
    public int FilledQuantity => Fills?.Sum(f => f.Quantity) ?? 0;
    
    /// <summary>
    /// Average fill price
    /// </summary>
    public decimal AverageFillPrice => Fills?.Any() == true ? 
        Fills.Sum(f => f.Quantity * f.FillPrice) / FilledQuantity : 0;
    
    /// <summary>
    /// Total commission for this slice
    /// </summary>
    public decimal TotalCommission => Fills?.Sum(f => f.Commission) ?? 0;
    
    /// <summary>
    /// Error information if slice failed
    /// </summary>
    public string ErrorMessage { get; set; }
    
    /// <summary>
    /// Retry count for this slice
    /// </summary>
    public int RetryCount { get; set; }
    
    /// <summary>
    /// When this slice was created
    /// </summary>
    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    
    /// <summary>
    /// When this slice was last updated
    /// </summary>
    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
}
```

### TWAP Performance Metrics
```csharp
/// <summary>
/// Performance metrics for TWAP execution
/// </summary>
public record TwapPerformanceMetrics
{
    /// <summary>
    /// Total execution time
    /// </summary>
    public TimeSpan TotalExecutionTime { get; set; }
    
    /// <summary>
    /// Average time between slice executions
    /// </summary>
    public TimeSpan AverageIntervalTime { get; set; }
    
    /// <summary>
    /// Standard deviation of interval times
    /// </summary>
    public TimeSpan IntervalTimeStdDev { get; set; }
    
    /// <summary>
    /// Total slippage (percentage)
    /// </summary>
    public decimal TotalSlippage { get; set; }
    
    /// <summary>
    /// Average slippage per slice (percentage)
    /// </summary>
    public decimal AverageSlippage { get; set; }
    
    /// <summary>
    /// Implementation shortfall (percentage)
    /// </summary>
    public decimal ImplementationShortfall { get; set; }
    
    /// <summary>
    /// Volume participation rate
    /// </summary>
    public decimal ParticipationRate { get; set; }
    
    /// <summary>
    /// Number of successful slices
    /// </summary>
    public int SuccessfulSlices { get; set; }
    
    /// <summary>
    /// Number of failed slices
    /// </summary>
    public int FailedSlices { get; set; }
    
    /// <summary>
    /// Number of cancelled slices
    /// </summary>
    public int CancelledSlices { get; set; }
    
    /// <summary>
    /// Total commission paid
    /// </summary>
    public decimal TotalCommission { get; set; }
    
    /// <summary>
    /// When metrics were last updated
    /// </summary>
    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
}
```

### Enums
```csharp
/// <summary>
/// Status of TWAP execution
/// </summary>
public enum TwapExecutionStatus
{
    Pending,
    Running,
    Completed,
    Cancelled,
    Failed
}

/// <summary>
/// Status of TWAP slice
/// </summary>
public enum TwapSliceStatus
{
    Pending,
    Scheduled,
    Submitted,
    PartiallyFilled,
    Filled,
    Cancelled,
    Failed
}
```

## TWAP Algorithm Implementation

### TWAP Executor
```csharp
/// <summary>
/// Executes TWAP algorithms
/// </summary>
public class TwapExecutor
{
    private readonly ILogger<TwapExecutor> _logger;
    private readonly IOrderManager _orderManager;
    private readonly TwapConfig _config;
    private readonly Dictionary<string, TwapExecutionState> _executions;
    private readonly Dictionary<string, Timer> _sliceTimers;
    private readonly object _lock = new object();
    
    public TwapExecutor(
        ILogger<TwapExecutor> logger,
        IOrderManager orderManager,
        TwapConfig config = null)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _orderManager = orderManager ?? throw new ArgumentNullException(nameof(orderManager));
        _config = config ?? TwapConfig.Default;
        _executions = new Dictionary<string, TwapExecutionState>();
        _sliceTimers = new Dictionary<string, Timer>();
    }
    
    /// <summary>
    /// Execute a TWAP order
    /// </summary>
    public async Task<TwapExecutionState> ExecuteTwapAsync(TwapParameters parameters, StrategyContext context)
    {
        if (parameters == null) throw new ArgumentNullException(nameof(parameters));
        if (context == null) throw new ArgumentNullException(nameof(context));
        
        // Validate parameters
        ValidateParameters(parameters);
        
        // Create execution state
        var executionState = CreateExecutionState(parameters);
        
        lock (_lock)
        {
            _executions[executionState.ExecutionId] = executionState;
        }
        
        _logger.LogInformation("Starting TWAP execution {ExecutionId} for {Symbol} {Side} {Quantity}", 
            executionState.ExecutionId, parameters.Symbol, parameters.Side, parameters.TotalQuantity);
        
        try
        {
            // Schedule slices
            await ScheduleSlicesAsync(executionState, context);
            
            // Start execution
            await StartExecutionAsync(executionState);
            
            return executionState;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error starting TWAP execution {ExecutionId}", executionState.ExecutionId);
            
            executionState.Status = TwapExecutionStatus.Failed;
            executionState.ErrorMessage = ex.Message;
            executionState.UpdatedAt = DateTime.UtcNow;
            
            throw;
        }
    }
    
    private void ValidateParameters(TwapParameters parameters)
    {
        if (string.IsNullOrEmpty(parameters.Symbol))
            throw new ArgumentException("Symbol is required", nameof(parameters));
            
        if (parameters.TotalQuantity <= 0)
            throw new ArgumentException("Total quantity must be positive", nameof(parameters));
            
        if (parameters.StartTime >= parameters.EndTime)
            throw new ArgumentException("Start time must be before end time", nameof(parameters));
            
        if (parameters.IntervalSeconds <= 0)
            throw new ArgumentException("Interval must be positive", nameof(parameters));
            
        var duration = parameters.EndTime - parameters.StartTime;
        var minInterval = TimeSpan.FromSeconds(parameters.IntervalSeconds);
        if (duration < minInterval)
            throw new ArgumentException("Duration must be at least as long as interval", nameof(parameters));
    }
    
    private TwapExecutionState CreateExecutionState(TwapParameters parameters)
    {
        var executionState = new TwapExecutionState
        {
            Parameters = parameters,
            TotalQuantity = parameters.TotalQuantity,
            StartTime = parameters.StartTime,
            EndTime = parameters.EndTime
        };
        
        // Calculate slices
        var slices = CalculateSlices(parameters);
        executionState.ScheduledSlices.AddRange(slices);
        
        return executionState;
    }
    
    private List<TwapSlice> CalculateSlices(TwapParameters parameters)
    {
        var slices = new List<TwapSlice>();
        var duration = parameters.EndTime - parameters.StartTime;
        var totalSeconds = duration.TotalSeconds;
        var intervalSeconds = parameters.IntervalSeconds;
        
        // Calculate number of slices
        var sliceCount = (int)Math.Floor(totalSeconds / intervalSeconds);
        if (sliceCount <= 0) sliceCount = 1;
        
        // Calculate base slice size
        var baseSliceSize = parameters.TotalQuantity / sliceCount;
        var remainder = parameters.TotalQuantity % sliceCount;
        
        // Create slices
        for (int i = 0; i < sliceCount; i++)
        {
            var sliceSize = baseSliceSize;
            if (i < remainder) sliceSize++; // Distribute remainder
            
            // Apply size limits
            if (sliceSize < parameters.MinSliceSize)
                sliceSize = parameters.MinSliceSize;
                
            if (parameters.MaxSliceSize.HasValue && sliceSize > parameters.MaxSliceSize.Value)
                sliceSize = parameters.MaxSliceSize.Value;
            
            var slice = new TwapSlice
            {
                ExecutionId = null, // Will be set when execution starts
                SliceNumber = i + 1,
                ScheduledTime = parameters.StartTime.AddSeconds(i * intervalSeconds),
                Quantity = sliceSize
            };
            
            slices.Add(slice);
        }
        
        return slices;
    }
    
    private async Task ScheduleSlicesAsync(TwapExecutionState executionState, StrategyContext context)
    {
        var now = DateTime.UtcNow;
        
        foreach (var slice in executionState.ScheduledSlices)
        {
            slice.ExecutionId = executionState.ExecutionId;
            
            // Calculate delay until scheduled time
            var delay = slice.ScheduledTime - now;
            if (delay.TotalMilliseconds <= 0)
            {
                // Execute immediately
                _ = ExecuteSliceAsync(slice, executionState, context);
            }
            else
            {
                // Schedule for later execution
                var timer = new Timer(async _ => 
                {
                    await ExecuteSliceAsync(slice, executionState, context);
                }, null, delay, Timeout.InfiniteTimeSpan);
                
                lock (_lock)
                {
                    _sliceTimers[slice.SliceId] = timer;
                }
            }
        }
    }
    
    private async Task StartExecutionAsync(TwapExecutionState executionState)
    {
        executionState.Status = TwapExecutionStatus.Running;
        executionState.StartTime = DateTime.UtcNow;
        executionState.UpdatedAt = DateTime.UtcNow;
        
        _logger.LogInformation("TWAP execution {ExecutionId} started", executionState.ExecutionId);
    }
    
    private async Task ExecuteSliceAsync(TwapSlice slice, TwapExecutionState executionState, StrategyContext context)
    {
        try
        {
            // Remove timer if it exists
            lock (_lock)
            {
                if (_sliceTimers.ContainsKey(slice.SliceId))
                {
                    _sliceTimers[slice.SliceId].Dispose();
                    _sliceTimers.Remove(slice.SliceId);
                }
            }
            
            slice.Status = TwapSliceStatus.Submitted;
            slice.ActualTime = DateTime.UtcNow;
            slice.UpdatedAt = DateTime.UtcNow;
            
            _logger.LogInformation("Executing TWAP slice {SliceId} ({SliceNumber}/{Total}) for {Quantity}", 
                slice.SliceId, slice.SliceNumber, executionState.ScheduledSlices.Count, slice.Quantity);
            
            // Create order request
            var orderRequest = new OrderRequest(
                Symbol: executionState.Parameters.Symbol,
                Side: executionState.Parameters.Side,
                Type: executionState.Parameters.LimitPrice.HasValue ? OrderType.Limit : OrderType.Market,
                Quantity: slice.Quantity,
                LimitPrice: executionState.Parameters.LimitPrice,
                StopPrice: null,
                TimeInForce: executionState.Parameters.TimeInForce,
                Algorithm: null, // This is a slice, not an algorithm
                AlgorithmParameters: new Dictionary<string, object>()
            );
            
            // Submit order
            var orderResult = await _orderManager.SubmitOrderAsync(orderRequest, context);
            
            if (orderResult.Success)
            {
                slice.OrderId = orderResult.OrderId;
                slice.Status = TwapSliceStatus.Filled; // Simplified - in reality would monitor fills
                slice.Fills = orderResult.Status?.Fills ?? new List<OrderFill>();
                slice.UpdatedAt = DateTime.UtcNow;
                
                _logger.LogInformation("TWAP slice {SliceId} executed successfully", slice.SliceId);
            }
            else
            {
                slice.Status = TwapSliceStatus.Failed;
                slice.ErrorMessage = orderResult.Message;
                slice.UpdatedAt = DateTime.UtcNow;
                
                _logger.LogWarning("TWAP slice {SliceId} failed: {ErrorMessage}", slice.SliceId, orderResult.Message);
                
                // Handle retry if configured
                if (slice.RetryCount < _config.MaxRetries)
                {
                    slice.RetryCount++;
                    _logger.LogInformation("Retrying TWAP slice {SliceId} (attempt {RetryCount})", 
                        slice.SliceId, slice.RetryCount);
                    
                    await Task.Delay(TimeSpan.FromSeconds(_config.RetryDelaySeconds));
                    await ExecuteSliceAsync(slice, executionState, context);
                    return;
                }
            
            // Update execution state
            UpdateExecutionState(executionState, slice);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error executing TWAP slice {SliceId}", slice.SliceId);
            
            slice.Status = TwapSliceStatus.Failed;
            slice.ErrorMessage = ex.Message;
            slice.UpdatedAt = DateTime.UtcNow;
            
            UpdateExecutionState(executionState, slice);
        }
    }
    
    private void UpdateExecutionState(TwapExecutionState executionState, TwapSlice slice)
    {
        lock (_lock)
        {
            // Move slice to appropriate list
            executionState.ScheduledSlices.Remove(slice);
            
            if (slice.Status == TwapSliceStatus.Filled || slice.Status == TwapSliceStatus.PartiallyFilled)
            {
                executionState.CompletedSlices.Add(slice);
                executionState.ExecutedQuantity += slice.FilledQuantity;
            }
            else
            {
                executionState.FailedSlices.Add(slice);
            }
            
            // Update execution metrics
            UpdatePerformanceMetrics(executionState);
            
            // Check if execution is complete
            if (executionState.RemainingQuantity <= 0 || 
                executionState.ScheduledSlices.Count == 0)
            {
                CompleteExecution(executionState);
            }
            
            executionState.UpdatedAt = DateTime.UtcNow;
        }
    }
    
    private void UpdatePerformanceMetrics(TwapExecutionState executionState)
    {
        var metrics = new TwapPerformanceMetrics();
        
        // Calculate basic metrics
        var allSlices = executionState.CompletedSlices.Concat(executionState.FailedSlices).ToList();
        if (allSlices.Any())
        {
            metrics.SuccessfulSlices = executionState.CompletedSlices.Count;
            metrics.FailedSlices = executionState.FailedSlices.Count;
            metrics.TotalCommission = allSlices.Sum(s => s.TotalCommission);
            
            // Calculate timing metrics
            if (executionState.StartTime.HasValue)
            {
                metrics.TotalExecutionTime = DateTime.UtcNow - executionState.StartTime.Value;
            }
        }
        
        executionState.PerformanceMetrics = metrics;
    }
    
    private void CompleteExecution(TwapExecutionState executionState)
    {
        if (executionState.RemainingQuantity <= 0)
        {
            executionState.Status = TwapExecutionStatus.Completed;
            _logger.LogInformation("TWAP execution {ExecutionId} completed successfully", executionState.ExecutionId);
        }
        else
        {
            executionState.Status = TwapExecutionStatus.Failed;
            _logger.LogWarning("TWAP execution {ExecutionId} completed with remaining quantity", executionState.ExecutionId);
        }
        
        executionState.EndTime = DateTime.UtcNow;
        executionState.UpdatedAt = DateTime.UtcNow;
        
        // Clean up timers
        lock (_lock)
        {
            foreach (var timer in _sliceTimers.Values)
            {
                timer.Dispose();
            }
            _sliceTimers.Clear();
        }
    }
    
    /// <summary>
    /// Cancel a TWAP execution
    /// </summary>
    public async Task<bool> CancelExecutionAsync(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) throw new ArgumentException("Execution ID required", nameof(executionId));
        
        TwapExecutionState executionState;
        lock (_lock)
        {
            if (!_executions.ContainsKey(executionId))
                return false;
                
            executionState = _executions[executionId];
        }
        
        if (executionState.Status != TwapExecutionStatus.Running)
            return false;
        
        try
        {
            // Cancel all pending slices
            foreach (var slice in executionState.ScheduledSlices)
            {
                if (slice.Status == TwapSliceStatus.Pending || slice.Status == TwapSliceStatus.Scheduled)
                {
                    slice.Status = TwapSliceStatus.Cancelled;
                    slice.UpdatedAt = DateTime.UtcNow;
                }
            }
            
            // Cancel active orders for submitted slices
            foreach (var slice in executionState.ScheduledSlices
                .Where(s => s.Status == TwapSliceStatus.Submitted))
            {
                if (!string.IsNullOrEmpty(slice.OrderId))
                {
                    await _orderManager.CancelOrderAsync(slice.OrderId);
                }
                slice.Status = TwapSliceStatus.Cancelled;
                slice.UpdatedAt = DateTime.UtcNow;
            }
            
            // Update execution state
            executionState.Status = TwapExecutionStatus.Cancelled;
            executionState.EndTime = DateTime.UtcNow;
            executionState.UpdatedAt = DateTime.UtcNow;
            
            // Clean up timers
            lock (_lock)
            {
                foreach (var timer in _sliceTimers.Values)
                {
                    timer.Dispose();
                }
                _sliceTimers.Clear();
            }
            
            _logger.LogInformation("TWAP execution {ExecutionId} cancelled", executionId);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error cancelling TWAP execution {ExecutionId}", executionId);
            return false;
        }
    }
    
    /// <summary>
    /// Get execution state
    /// </summary>
    public TwapExecutionState GetExecutionState(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) return null;
        
        lock (_lock)
        {
            return _executions.ContainsKey(executionId) ? 
                new TwapExecutionState(_executions[executionId]) : null;
        }
    }
    
    /// <summary>
    /// Get all execution states
    /// </summary>
    public List<TwapExecutionState> GetAllExecutionStates()
    {
        lock (_lock)
        {
            return _executions.Values.Select(e => new TwapExecutionState(e)).ToList();
        }
    }
}
```

## Integration with OrderManager

### TWAP Integration in OrderManager
```csharp
public partial class OrderManager : IOrderManager
{
    private readonly TwapExecutor _twapExecutor;
    
    // Enhanced constructor with TWAP executor
    public OrderManager(
        IRiskManager riskManager,
        IPositionSizer positionSizer,
        ILogger<OrderManager> logger,
        RoutingConfigurationManager configManager,
        RoutingMetricsCollector metricsCollector,
        TwapExecutor twapExecutor) : base(riskManager, positionSizer, logger, configManager, metricsCollector)
    {
        _twapExecutor = twapExecutor ?? throw new ArgumentNullException(nameof(twapExecutor));
        _venueManager = new VenueManager(logger);
        _omsToVenueOrderIdMap = new Dictionary<string, string>();
        _venueToOmsOrderIdMap = new Dictionary<string, string>();
        
        // Initialize with configurations
        InitializeWithConfigurationsAsync().Wait();
    }
    
    /// <summary>
    /// Execute a TWAP order
    /// </summary>
    public async Task<OrderResult> ExecuteTwapAsync(TwapParameters parameters, StrategyContext context)
    {
        if (parameters == null) throw new ArgumentNullException(nameof(parameters));
        if (context == null) throw new ArgumentNullException(nameof(context));
        
        try
        {
            _logger.LogInformation("Executing TWAP order for {Symbol} {Side} {Quantity}", 
                parameters.Symbol, parameters.Side, parameters.TotalQuantity);
            
            // Validate through risk management
            var riskDecision = await ValidateTwapOrderAsync(parameters, context);
            if (!riskDecision.Allow)
            {
                _logger.LogWarning("TWAP order rejected by risk management: {Reason}", riskDecision.RejectReason);
                return new OrderResult(false, null, $"Risk validation failed: {riskDecision.RejectReason}", null);
            }
            
            // Execute TWAP
            var executionState = await _twapExecutor.ExecuteTwapAsync(parameters, context);
            
            // Create order result
            var orderResult = new OrderResult(
                Success: executionState.Status == TwapExecutionStatus.Completed,
                OrderId: executionState.ExecutionId,
                Message: executionState.Status == TwapExecutionStatus.Completed ? 
                    "TWAP execution completed successfully" : 
                    $"TWAP execution failed: {executionState.ErrorMessage}",
                Status: ConvertToOrderStatus(executionState)
            );
            
            _logger.LogInformation("TWAP order execution {Result}: {Message}", 
                orderResult.Success ? "succeeded" : "failed", orderResult.Message);
            
            return orderResult;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error executing TWAP order for {Symbol}", parameters.Symbol);
            return new OrderResult(false, null, $"Error executing TWAP order: {ex.Message}", null);
        }
    }
    
    private async Task<RiskDecision> ValidateTwapOrderAsync(TwapParameters parameters, StrategyContext context)
    {
        // Convert TWAP parameters to strategy intent for risk validation
        var intent = new StrategyIntent(
            Symbol: parameters.Symbol,
            Side: ConvertOrderSide(parameters.Side),
            EntryType: parameters.LimitPrice.HasValue ? OrderType.Limit : OrderType.Market,
            LimitPrice: (double?)parameters.LimitPrice,
            StopTicks: 10, // Placeholder - would calculate based on stop price
            TargetTicks: null,
            Confidence: 1.0,
            Reason: "TWAP Algorithm Order",
            Metadata: parameters.Metadata
        );
        
        // Get risk configuration
        var config = new RiskConfig(1000, 200, 10, true); // Placeholder - would get from configuration
        
        return _riskManager.ValidateOrder(intent, context, config);
    }
    
    private OrderSide ConvertOrderSide(NT8.Core.Orders.OrderSide side)
    {
        return side switch
        {
            NT8.Core.Orders.OrderSide.Buy => OrderSide.Buy,
            NT8.Core.Orders.OrderSide.Sell => OrderSide.Sell,
            _ => throw new ArgumentException($"Unsupported order side: {side}")
        };
    }
    
    private OrderStatus ConvertToOrderStatus(TwapExecutionState executionState)
    {
        if (executionState == null) return null;
        
        var state = executionState.Status switch
        {
            TwapExecutionStatus.Pending => OrderState.New,
            TwapExecutionStatus.Running => OrderState.Accepted,
            TwapExecutionStatus.Completed => OrderState.Filled,
            TwapExecutionStatus.Cancelled => OrderState.Cancelled,
            TwapExecutionStatus.Failed => OrderState.Rejected,
            _ => OrderState.Unknown
        };
        
        // Combine all fills from completed slices
        var allFills = executionState.CompletedSlices.SelectMany(s => s.Fills).ToList();
        
        return new OrderStatus(
            OrderId: executionState.ExecutionId,
            Symbol: executionState.Parameters.Symbol,
            Side: executionState.Parameters.Side,
            Type: executionState.Parameters.LimitPrice.HasValue ? OrderType.Limit : OrderType.Market,
            Quantity: executionState.TotalQuantity,
            FilledQuantity: executionState.ExecutedQuantity,
            LimitPrice: executionState.Parameters.LimitPrice,
            StopPrice: null,
            State: state,
            CreatedTime: executionState.CreatedAt,
            FilledTime: executionState.EndTime,
            Fills: allFills
        );
    }
    
    /// <summary>
    /// Cancel a TWAP execution
    /// </summary>
    public async Task<bool> CancelTwapAsync(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) throw new ArgumentException("Execution ID required", nameof(executionId));
        
        return await _twapExecutor.CancelExecutionAsync(executionId);
    }
    
    /// <summary>
    /// Get TWAP execution state
    /// </summary>
    public TwapExecutionState GetTwapExecutionState(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) return null;
        
        return _twapExecutor.GetExecutionState(executionId);
    }
}
```

## TWAP Configuration Management

### TWAP Configuration Integration
```csharp
public partial class RoutingConfigurationManager
{
    /// <summary>
    /// Get TWAP configuration
    /// </summary>
    public async Task<TwapConfig> GetTwapConfigAsync()
    {
        var config = await GetConfigurationAsync<TwapConfig>("twap-config");
        return config ?? TwapConfig.Default;
    }
    
    /// <summary>
    /// Update TWAP configuration
    /// </summary>
    public async Task UpdateTwapConfigAsync(TwapConfig config)
    {
        if (config == null) throw new ArgumentNullException(nameof(config));
        
        config.Id = "twap-config";
        config.Name = "TWAP Configuration";
        config.Description = "Configuration for TWAP algorithm behavior";
        
        await UpdateConfigurationAsync(config);
        _logger.LogInformation("TWAP configuration updated");
    }
}
```

## Testing Considerations

### Unit Tests for TWAP Algorithm
1. **Slice Calculation**: Test calculation of slices for different parameters
2. **Parameter Validation**: Test validation of TWAP parameters
3. **Execution Scheduling**: Test scheduling of slice executions
4. **Slice Execution**: Test execution of individual slices
5. **Error Handling**: Test handling of execution errors and retries
6. **Cancellation**: Test cancellation of TWAP executions
7. **Metrics Collection**: Test collection of performance metrics

### Integration Tests
1. **End-to-End Execution**: Test complete TWAP execution from start to finish
2. **Order Manager Integration**: Test integration with OrderManager
3. **Risk Management Integration**: Test risk validation for TWAP orders
4. **Performance Testing**: Test performance with large numbers of slices
5. **Concurrent Executions**: Test multiple concurrent TWAP executions

## Performance Considerations

### Memory Management
```csharp
/// <summary>
/// Manages memory usage for TWAP executions
/// </summary>
public class TwapMemoryManager
{
    private readonly int _maxExecutions;
    private readonly TimeSpan _executionRetentionTime;
    private readonly Dictionary<string, DateTime> _executionAccessTimes;
    private readonly object _lock = new object();
    
    public TwapMemoryManager(int maxExecutions = 1000, TimeSpan retentionTime = default)
    {
        _maxExecutions = maxExecutions;
        _executionRetentionTime = retentionTime == default ? 
            TimeSpan.FromHours(24) : retentionTime;
        _executionAccessTimes = new Dictionary<string, DateTime>();
    }
    
    public void RecordExecutionAccess(string executionId)
    {
        lock (_lock)
        {
            _executionAccessTimes[executionId] = DateTime.UtcNow;
        }
    }
    
    public List<string> GetExpiredExecutions()
    {
        var cutoffTime = DateTime.UtcNow.Subtract(_executionRetentionTime);
        
        lock (_lock)
        {
            return _executionAccessTimes
                .Where(kvp => kvp.Value < cutoffTime)
                .Select(kvp => kvp.Key)
                .ToList();
        }
    }
    
    public bool IsMemoryPressureHigh(int currentExecutionCount)
    {
        return currentExecutionCount > (_maxExecutions * 0.8); // 80% threshold
    }
}
```

### Adaptive TWAP
```csharp
/// <summary>
/// Adaptive TWAP that adjusts based on market conditions
/// </summary>
public class AdaptiveTwapExecutor : TwapExecutor
{
    private readonly IMarketDataProvider _marketDataProvider;
    
    public AdaptiveTwapExecutor(
        ILogger<TwapExecutor> logger,
        IOrderManager orderManager,
        IMarketDataProvider marketDataProvider,
        TwapConfig config = null) : base(logger, orderManager, config)
    {
        _marketDataProvider = marketDataProvider ?? throw new ArgumentNullException(nameof(marketDataProvider));
    }
    
    protected override List<TwapSlice> CalculateSlices(TwapParameters parameters)
    {
        // Get current market data
        var marketData = _marketDataProvider.GetCurrentPrice(parameters.Symbol);
        
        if (marketData.HasValue && _config.EnableAdaptiveSlicing)
        {
            // Adjust slice sizes based on volatility
            var volatility = CalculateVolatility(parameters.Symbol);
            return CalculateAdaptiveSlices(parameters, volatility);
        }
        
        // Fall back to standard calculation
        return base.CalculateSlices(parameters);
    }
    
    private decimal CalculateVolatility(string symbol)
    {
        // Simplified volatility calculation
        // In a real implementation, this would use historical price data
        return 0.01m; // 1% volatility
    }
    
    private List<TwapSlice> CalculateAdaptiveSlices(TwapParameters parameters, decimal volatility)
    {
        // Adjust slice frequency based on volatility
        // Higher volatility = more frequent, smaller slices
        var adjustedInterval = (int)(parameters.IntervalSeconds * (1 - (double)volatility)));
        if (adjustedInterval < 10) adjustedInterval = 10; // Minimum 10 seconds
        
        // Create adjusted parameters
        var adjustedParameters = new TwapParameters
        {
            Symbol = parameters.Symbol,
            Side = parameters.Side,
            TotalQuantity = parameters.TotalQuantity,
            StartTime = parameters.StartTime,
            EndTime = parameters.EndTime,
            IntervalSeconds = adjustedInterval,
            LimitPrice = parameters.LimitPrice,
            TimeInForce = parameters.TimeInForce,
            MinSliceSize = parameters.MinSliceSize,
            MaxSliceSize = parameters.MaxSliceSize
        };
        
        return base.CalculateSlices(adjustedParameters);
    }
}
```

## Monitoring and Alerting

### TWAP Metrics Export
```csharp
/// <summary>
/// Exports TWAP metrics for monitoring
/// </summary>
public class TwapMetricsExporter
{
    private readonly TwapExecutor _twapExecutor;
    
    public TwapMetricsExporter(TwapExecutor twapExecutor)
    {
        _twapExecutor = twapExecutor ?? throw new ArgumentNullException(nameof(twapExecutor));
    }
    
    public string ExportToPrometheus()
    {
        var executions = _twapExecutor.GetAllExecutionStates();
        var sb = new StringBuilder();
        
        // Overall TWAP metrics
        var activeExecutions = executions.Count(e => e.Status == TwapExecutionStatus.Running);
        var completedExecutions = executions.Count(e => e.Status == TwapExecutionStatus.Completed);
        var failedExecutions = executions.Count(e => e.Status == TwapExecutionStatus.Failed);
        
        sb.AppendLine($"# HELP twap_active_executions Number of active TWAP executions");
        sb.AppendLine($"# TYPE twap_active_executions gauge");
        sb.AppendLine($"twap_active_executions {activeExecutions}");
        
        sb.AppendLine($"# HELP twap_completed_executions Total number of completed TWAP executions");
        sb.AppendLine($"# TYPE twap_completed_executions counter");
        sb.AppendLine($"twap_completed_executions {completedExecutions}");
        
        sb.AppendLine($"# HELP twap_failed_executions Total number of failed TWAP executions");
        sb.AppendLine($"# TYPE twap_failed_executions counter");
        sb.AppendLine($"twap_failed_executions {failedExecutions}");
        
        // Performance metrics for completed executions
        var completed = executions.Where(e => e.Status == TwapExecutionStatus.Completed).ToList();
        if (completed.Any())
        {
            var avgSlippage = completed.Average(e => (double)e.PerformanceMetrics.AverageSlippage);
            var avgCommission = (double)completed.Average(e => e.PerformanceMetrics.TotalCommission);
            
            sb.AppendLine($"# HELP twap_average_slippage Average slippage for completed executions");
            sb.AppendLine($"# TYPE twap_average_slippage gauge");
            sb.AppendLine($"twap_average_slippage {avgSlippage:F4}");
            
            sb.AppendLine($"# HELP twap_average_commission Average commission for completed executions");
            sb.AppendLine($"# TYPE twap_average_commission gauge");
            sb.AppendLine($"twap_average_commission {avgCommission:F2}");
        }
        
        return sb.ToString();
    }
}
```

## Future Enhancements

1. **Machine Learning Optimization**: Use ML to optimize TWAP parameters based on historical performance
2. **Real-time Market Adaptation**: Adjust TWAP execution based on real-time market conditions
3. **Cross-Venue TWAP**: Execute TWAP orders across multiple venues simultaneously
4. **TWAP Analytics**: Advanced analytics and reporting on TWAP performance
5. **TWAP Strategy Builder**: Visual tools for building and testing TWAP strategies
6. **TWAP Benchmarking**: Compare TWAP performance against other execution algorithms
7. **TWAP Risk Controls**: Enhanced risk controls specific to algorithmic execution
8. **TWAP Compliance**: Ensure TWAP execution complies with regulatory requirements
