# VWAP Algorithm Implementation Design

## Overview

This document details the implementation of the Volume Weighted Average Price (VWAP) algorithm in the Order Management System (OMS), which executes orders by participating in the market volume proportionally to achieve execution prices close to the volume-weighted average price over a specified period.

## VWAP Algorithm Fundamentals

### Algorithm Description
The VWAP algorithm executes orders by participating in market trading volume proportionally throughout a specified time period. The goal is to achieve an execution price close to the volume-weighted average price of the instrument over that period, making it particularly suitable for liquid instruments where volume patterns can be predicted or followed.

### Key Characteristics
1. **Volume-based Participation**: Execution is proportional to market trading volume
2. **Benchmark Tracking**: Aims to achieve VWAP benchmark for the period
3. **Market Responsiveness**: Adapts to market liquidity patterns
4. **Suitable for Liquid Instruments**: Works best with instruments that have predictable volume patterns

## VWAP Parameters

### Core Parameters
```csharp
/// <summary>
/// Parameters for VWAP algorithm execution
/// </summary>
public record VwapParameters
{
    /// <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>
    /// Target participation rate (0.0 to 1.0)
    /// </summary>
    public double ParticipationRate { get; set; } = 0.1; // 10% participation
    
    /// <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 participation rate based on remaining quantity
    /// </summary>
    public bool AdjustParticipationRate { get; set; } = true;
    
    /// <summary>
    /// Minimum order size (to avoid very small orders)
    /// </summary>
    public int MinOrderSize { get; set; } = 1;
    
    /// <summary>
    /// Maximum order size (to control individual order impact)
    /// </summary>
    public int? MaxOrderSize { get; set; }
    
    /// <summary>
    /// Interval for checking volume and placing orders (in seconds)
    /// </summary>
    public int CheckIntervalSeconds { get; set; } = 30;
    
    /// <summary>
    /// Whether to cancel remaining orders at end time
    /// </summary>
    public bool CancelAtEndTime { get; set; } = true;
    
    /// <summary>
    /// Aggressiveness factor (0.0 to 1.0) - higher values place orders more aggressively
    /// </summary>
    public double Aggressiveness { get; set; } = 0.5;
    
    /// <summary>
    /// Custom metadata for the algorithm
    /// </summary>
    public Dictionary<string, object> Metadata { get; set; } = new Dictionary<string, object>();
}
```

### VWAP Configuration
```csharp
/// <summary>
/// Configuration for VWAP algorithm behavior
/// </summary>
public record VwapConfig
{
    /// <summary>
    /// Default participation rate
    /// </summary>
    public double DefaultParticipationRate { get; set; } = 0.1;
    
    /// <summary>
    /// Default check interval (in seconds)
    /// </summary>
    public int DefaultCheckIntervalSeconds { get; set; } = 30;
    
    /// <summary>
    /// Whether to enable adaptive participation based on market conditions
    /// </summary>
    public bool EnableAdaptiveParticipation { get; set; } = false;
    
    /// <summary>
    /// Maximum participation rate to prevent excessive market impact
    /// </summary>
    public double MaxParticipationRate { get; set; } = 0.25; // 25%
    
    /// <summary>
    /// Minimum participation rate to ensure execution
    /// </summary>
    public double MinParticipationRate { get; set; } = 0.01; // 1%
    
    /// <summary>
    /// Whether to prioritize execution speed over VWAP tracking
    /// </summary>
    public bool PrioritizeSpeed { get; set; } = false;
    
    /// <summary>
    /// Retry count for failed order placements
    /// </summary>
    public int MaxRetries { get; set; } = 3;
    
    /// <summary>
    /// Delay between retries (in seconds)
    /// </summary>
    public int RetryDelaySeconds { get; set; } = 5;
    
    /// <summary>
    /// Whether to use volume prediction models
    /// </summary>
    public bool EnableVolumePrediction { get; set; } = false;
    
    /// <summary>
    /// Whether to log detailed execution information
    /// </summary>
    public bool EnableDetailedLogging { get; set; } = false;
    
    public static VwapConfig Default => new VwapConfig();
}
```

## VWAP Execution Models

### VWAP Execution State
```csharp
/// <summary>
/// State of a VWAP execution
/// </summary>
public record VwapExecutionState
{
    /// <summary>
    /// Unique identifier for this VWAP execution
    /// </summary>
    public string ExecutionId { get; set; } = Guid.NewGuid().ToString();
    
    /// <summary>
    /// Parameters used for this execution
    /// </summary>
    public VwapParameters Parameters { get; set; }
    
    /// <summary>
    /// Current execution status
    /// </summary>
    public VwapExecutionStatus Status { get; set; } = VwapExecutionStatus.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>
    /// Cumulative volume for the period
    /// </summary>
    public long CumulativeVolume { get; set; }
    
    /// <summary>
    /// Expected volume based on prediction models
    /// </summary>
    public long? ExpectedVolume { get; set; }
    
    /// <summary>
    /// Orders placed during execution
    /// </summary>
    public List<VwapOrder> Orders { get; set; } = new List<VwapOrder>();
    
    /// <summary>
    /// Completed orders
    /// </summary>
    public List<VwapOrder> CompletedOrders { get; set; } = new List<VwapOrder>();
    
    /// <summary>
    /// Failed orders
    /// </summary>
    public List<VwapOrder> FailedOrders { get; set; } = new List<VwapOrder>();
    
    /// <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 VwapPerformanceMetrics PerformanceMetrics { get; set; } = new VwapPerformanceMetrics();
}
```

### VWAP Order
```csharp
/// <summary>
/// Represents a single order placed as part of VWAP execution
/// </summary>
public record VwapOrder
{
    /// <summary>
    /// Unique identifier for this order
    /// </summary>
    public string OrderId { get; set; }
    
    /// <summary>
    /// Reference to parent VWAP execution
    /// </summary>
    public string ExecutionId { get; set; }
    
    /// <summary>
    /// Order number within execution (1-based)
    /// </summary>
    public int OrderNumber { get; set; }
    
    /// <summary>
    /// Scheduled placement time
    /// </summary>
    public DateTime ScheduledTime { get; set; }
    
    /// <summary>
    /// Actual placement time
    /// </summary>
    public DateTime? ActualTime { get; set; }
    
    /// <summary>
    /// Quantity for this order
    /// </summary>
    public int Quantity { get; set; }
    
    /// <summary>
    /// Status of this order
    /// </summary>
    public VwapOrderStatus Status { get; set; } = VwapOrderStatus.Pending;
    
    /// <summary>
    /// Order details
    /// </summary>
    public OrderRequest OrderDetails { get; set; }
    
    /// <summary>
    /// Fills for this order
    /// </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 order
    /// </summary>
    public decimal TotalCommission => Fills?.Sum(f => f.Commission) ?? 0;
    
    /// <summary>
    /// Error information if order failed
    /// </summary>
    public string ErrorMessage { get; set; }
    
    /// <summary>
    /// Retry count for this order
    /// </summary>
    public int RetryCount { get; set; }
    
    /// <summary>
    /// When this order was created
    /// </summary>
    public DateTime CreatedAt { get; set; } = DateTime.UtcNow;
    
    /// <summary>
    /// When this order was last updated
    /// </summary>
    public DateTime UpdatedAt { get; set; } = DateTime.UtcNow;
}
```

### VWAP Performance Metrics
```csharp
/// <summary>
/// Performance metrics for VWAP execution
/// </summary>
public record VwapPerformanceMetrics
{
    /// <summary>
    /// Total execution time
    /// </summary>
    public TimeSpan TotalExecutionTime { get; set; }
    
    /// <summary>
    /// Achieved VWAP price
    /// </summary>
    public decimal AchievedVwap { get; set; }
    
    /// <summary>
    /// Benchmark VWAP price
    /// </summary>
    public decimal BenchmarkVwap { get; set; }
    
    /// <summary>
    /// Slippage relative to VWAP (percentage)
    /// </summary>
    public decimal VwapSlippage { get; set; }
    
    /// <summary>
    /// Implementation shortfall (percentage)
    /// </summary>
    public decimal ImplementationShortfall { get; set; }
    
    /// <summary>
    /// Volume participation rate achieved
    /// </summary>
    public decimal ActualParticipationRate { get; set; }
    
    /// <summary>
    /// Target participation rate
    /// </summary>
    public decimal TargetParticipationRate { get; set; }
    
    /// <summary>
    /// Number of successful orders
    /// </summary>
    public int SuccessfulOrders { get; set; }
    
    /// <summary>
    /// Number of failed orders
    /// </summary>
    public int FailedOrders { get; set; }
    
    /// <summary>
    /// Number of cancelled orders
    /// </summary>
    public int CancelledOrders { 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 VWAP execution
/// </summary>
public enum VwapExecutionStatus
{
    Pending,
    Running,
    Completed,
    Cancelled,
    Failed
}

/// <summary>
/// Status of VWAP order
/// </summary>
public enum VwapOrderStatus
{
    Pending,
    Scheduled,
    Submitted,
    PartiallyFilled,
    Filled,
    Cancelled,
    Failed
}
```

## VWAP Algorithm Implementation

### VWAP Executor
```csharp
/// <summary>
/// Executes VWAP algorithms
/// </summary>
public class VwapExecutor
{
    private readonly ILogger<VwapExecutor> _logger;
    private readonly IOrderManager _orderManager;
    private readonly IMarketDataProvider _marketDataProvider;
    private readonly VwapConfig _config;
    private readonly Dictionary<string, VwapExecutionState> _executions;
    private readonly Dictionary<string, Timer> _executionTimers;
    private readonly object _lock = new object();
    
    public VwapExecutor(
        ILogger<VwapExecutor> logger,
        IOrderManager orderManager,
        IMarketDataProvider marketDataProvider,
        VwapConfig config = null)
    {
        _logger = logger ?? throw new ArgumentNullException(nameof(logger));
        _orderManager = orderManager ?? throw new ArgumentNullException(nameof(orderManager));
        _marketDataProvider = marketDataProvider ?? throw new ArgumentNullException(nameof(marketDataProvider));
        _config = config ?? VwapConfig.Default;
        _executions = new Dictionary<string, VwapExecutionState>();
        _executionTimers = new Dictionary<string, Timer>();
    }
    
    /// <summary>
    /// Execute a VWAP order
    /// </summary>
    public async Task<VwapExecutionState> ExecuteVwapAsync(VwapParameters 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 VWAP execution {ExecutionId} for {Symbol} {Side} {Quantity}", 
            executionState.ExecutionId, parameters.Symbol, parameters.Side, parameters.TotalQuantity);
        
        try
        {
            // Start execution monitoring
            await StartExecutionAsync(executionState, context);
            
            return executionState;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error starting VWAP execution {ExecutionId}", executionState.ExecutionId);
            
            executionState.Status = VwapExecutionStatus.Failed;
            executionState.ErrorMessage = ex.Message;
            executionState.UpdatedAt = DateTime.UtcNow;
            
            throw;
        }
    
    private void ValidateParameters(VwapParameters 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.ParticipationRate <= 0 || parameters.ParticipationRate > 1)
            throw new ArgumentException("Participation rate must be between 0 and 1", nameof(parameters));
            
        if (parameters.CheckIntervalSeconds <= 0)
            throw new ArgumentException("Check interval must be positive", nameof(parameters));
    }
    
    private VwapExecutionState CreateExecutionState(VwapParameters parameters)
    {
        var executionState = new VwapExecutionState
        {
            Parameters = parameters,
            TotalQuantity = parameters.TotalQuantity,
            StartTime = parameters.StartTime,
            EndTime = parameters.EndTime
        };
        
        return executionState;
    }
    
    private async Task StartExecutionAsync(VwapExecutionState executionState, StrategyContext context)
    {
        executionState.Status = VwapExecutionStatus.Running;
        executionState.StartTime = DateTime.UtcNow;
        executionState.UpdatedAt = DateTime.UtcNow;
        
        // Set up periodic execution monitoring
        var timer = new Timer(async _ => 
        {
            await MonitorExecutionAsync(executionState, context);
        }, null, TimeSpan.Zero, TimeSpan.FromSeconds(executionState.Parameters.CheckIntervalSeconds));
        
        lock (_lock)
        {
            _executionTimers[executionState.ExecutionId] = timer;
        }
        
        _logger.LogInformation("VWAP execution {ExecutionId} started", executionState.ExecutionId);
    }
    
    private async Task MonitorExecutionAsync(VwapExecutionState executionState, StrategyContext context)
    {
        try
        {
            // Check if execution should end
            if (DateTime.UtcNow >= executionState.EndTime)
            {
                await CompleteExecutionAsync(executionState);
                return;
            }
            
            // Get current market volume
            var currentVolume = await GetCurrentVolumeAsync(executionState.Parameters.Symbol);
            if (currentVolume <= 0)
            {
                _logger.LogWarning("Unable to get current volume for {Symbol}", executionState.Parameters.Symbol);
                return;
            }
            
            // Update cumulative volume
            executionState.CumulativeVolume += currentVolume;
            executionState.UpdatedAt = DateTime.UtcNow;
            
            // Calculate expected volume for period
            await UpdateExpectedVolumeAsync(executionState);
            
            // Calculate order size based on participation rate
            var orderSize = CalculateOrderSize(executionState, currentVolume);
            if (orderSize <= 0)
            {
                return; // No order to place
            }
            
            // Place order
            await PlaceOrderAsync(executionState, orderSize, context);
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error monitoring VWAP execution {ExecutionId}", executionState.ExecutionId);
        }
    }
    
    private async Task<long> GetCurrentVolumeAsync(string symbol)
    {
        // In a real implementation, this would get real-time volume data
        // For now, we'll simulate volume data
        var random = new Random();
        return random.Next(100, 1000); // Simulated volume between 100-1000 contracts
    }
    
    private async Task UpdateExpectedVolumeAsync(VwapExecutionState executionState)
    {
        if (!_config.EnableVolumePrediction)
            return;
            
        // Simple volume prediction based on time elapsed
        var totalTime = executionState.EndTime.Value - executionState.StartTime.Value;
        var elapsed = DateTime.UtcNow - executionState.StartTime.Value;
        var progress = elapsed.TotalMilliseconds / totalTime.TotalMilliseconds;
        
        if (progress > 0 && executionState.CumulativeVolume > 0)
        {
            // Linear projection
            executionState.ExpectedVolume = (long)(executionState.CumulativeVolume / progress);
        }
    }
    
    private int CalculateOrderSize(VwapExecutionState executionState, long currentVolume)
    {
        // Calculate target participation
        var participationRate = executionState.Parameters.ParticipationRate;
        
        // Adjust participation rate if enabled
        if (executionState.Parameters.AdjustParticipationRate)
        {
            participationRate = AdjustParticipationRate(executionState, participationRate);
        }
        
        // Calculate target order size
        var targetSize = (int)(currentVolume * participationRate);
        
        // Apply size limits
        if (targetSize < executionState.Parameters.MinOrderSize)
            targetSize = executionState.Parameters.MinOrderSize;
            
        if (executionState.Parameters.MaxOrderSize.HasValue && 
            targetSize > executionState.Parameters.MaxOrderSize.Value)
            targetSize = executionState.Parameters.MaxOrderSize.Value;
            
        // Ensure we don't exceed remaining quantity
        if (targetSize > executionState.RemainingQuantity)
            targetSize = executionState.RemainingQuantity;
            
        return targetSize;
    }
    
    private double AdjustParticipationRate(VwapExecutionState executionState, double currentRate)
    {
        // Adjust participation rate based on time remaining and quantity remaining
        var totalTime = executionState.EndTime.Value - executionState.StartTime.Value;
        var timeRemaining = executionState.EndTime.Value - DateTime.UtcNow;
        var timeProgress = 1 - (timeRemaining.TotalMilliseconds / totalTime.TotalMilliseconds);
        
        if (timeProgress > 0)
        {
            var quantityProgress = (double)executionState.ExecutedQuantity / executionState.TotalQuantity;
            
            // If we're behind schedule, increase participation rate
            if (quantityProgress < timeProgress)
            {
                var adjustmentFactor = (timeProgress - quantityProgress) * 2; // Double the deficit
                currentRate *= (1 + adjustmentFactor);
            }
            // If we're ahead of schedule, decrease participation rate
            else if (quantityProgress > timeProgress)
            {
                var adjustmentFactor = (quantityProgress - timeProgress) * 0.5; // Half the surplus
                currentRate *= (1 - adjustmentFactor);
            }
        }
        
        // Clamp to configured limits
        if (currentRate > _config.MaxParticipationRate)
            currentRate = _config.MaxParticipationRate;
            
        if (currentRate < _config.MinParticipationRate)
            currentRate = _config.MinParticipationRate;
            
        return currentRate;
    }
    
    private async Task PlaceOrderAsync(VwapExecutionState executionState, int orderSize, StrategyContext context)
    {
        var orderNumber = executionState.Orders.Count + 1;
        
        var order = new VwapOrder
        {
            ExecutionId = executionState.ExecutionId,
            OrderNumber = orderNumber,
            ScheduledTime = DateTime.UtcNow,
            Quantity = orderSize,
            OrderDetails = new OrderRequest(
                Symbol: executionState.Parameters.Symbol,
                Side: executionState.Parameters.Side,
                Type: executionState.Parameters.LimitPrice.HasValue ? OrderType.Limit : OrderType.Market,
                Quantity: orderSize,
                LimitPrice: executionState.Parameters.LimitPrice,
                StopPrice: null,
                TimeInForce: executionState.Parameters.TimeInForce,
                Algorithm: null,
                AlgorithmParameters: new Dictionary<string, object>()
            )
        };
        
        executionState.Orders.Add(order);
        
        try
        {
            order.Status = VwapOrderStatus.Submitted;
            order.ActualTime = DateTime.UtcNow;
            order.UpdatedAt = DateTime.UtcNow;
            
            _logger.LogInformation("Placing VWAP order {OrderNumber} for {Quantity}", 
                orderNumber, orderSize);
            
            // Submit order
            var orderResult = await _orderManager.SubmitOrderAsync(order.OrderDetails, context);
            
            if (orderResult.Success)
            {
                order.OrderId = orderResult.OrderId;
                order.Status = VwapOrderStatus.Submitted; // Will monitor for fills
                order.UpdatedAt = DateTime.UtcNow;
                
                _logger.LogInformation("VWAP order {OrderNumber} submitted: {OrderId}", 
                    orderNumber, orderResult.OrderId);
            }
            else
            {
                order.Status = VwapOrderStatus.Failed;
                order.ErrorMessage = orderResult.Message;
                order.UpdatedAt = DateTime.UtcNow;
                
                _logger.LogWarning("VWAP order {OrderNumber} failed: {ErrorMessage}", 
                    orderNumber, orderResult.Message);
                
                // Handle retry if configured
                if (order.RetryCount < _config.MaxRetries)
                {
                    order.RetryCount++;
                    _logger.LogInformation("Retrying VWAP order {OrderNumber} (attempt {RetryCount})", 
                        orderNumber, order.RetryCount);
                    
                    await Task.Delay(TimeSpan.FromSeconds(_config.RetryDelaySeconds));
                    await PlaceOrderAsync(executionState, orderSize, context);
                    return;
                }
            }
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error placing VWAP order {OrderNumber}", orderNumber);
            
            order.Status = VwapOrderStatus.Failed;
            order.ErrorMessage = ex.Message;
            order.UpdatedAt = DateTime.UtcNow;
        }
        
        UpdateExecutionState(executionState, order);
    }
    
    private void UpdateExecutionState(VwapExecutionState executionState, VwapOrder order)
    {
        lock (_lock)
        {
            // Update execution metrics
            UpdatePerformanceMetrics(executionState);
            
            // Check if execution is complete
            if (executionState.RemainingQuantity <= 0)
            {
                _ = CompleteExecutionAsync(executionState);
            }
            
            executionState.UpdatedAt = DateTime.UtcNow;
        }
    }
    
    private void UpdatePerformanceMetrics(VwapExecutionState executionState)
    {
        var metrics = new VwapPerformanceMetrics();
        
        // Calculate basic metrics
        var allOrders = executionState.Orders;
        if (allOrders.Any())
        {
            metrics.SuccessfulOrders = executionState.CompletedOrders.Count;
            metrics.FailedOrders = executionState.FailedOrders.Count;
            metrics.TotalCommission = allOrders.Sum(o => o.TotalCommission);
            metrics.TargetParticipationRate = (decimal)executionState.Parameters.ParticipationRate;
            
            // Calculate actual participation rate
            if (executionState.CumulativeVolume > 0)
            {
                metrics.ActualParticipationRate = (decimal)(executionState.ExecutedQuantity / (double)executionState.CumulativeVolume);
            }
            
            // Calculate VWAP prices
            var totalValue = allOrders.Where(o => o.Status == VwapOrderStatus.Filled)
                .Sum(o => o.FilledQuantity * (double)o.AverageFillPrice);
            var totalQuantity = allOrders.Where(o => o.Status == VwapOrderStatus.Filled)
                .Sum(o => o.FilledQuantity);
                
            if (totalQuantity > 0)
            {
                metrics.AchievedVwap = (decimal)(totalValue / totalQuantity);
            }
        }
        
        executionState.PerformanceMetrics = metrics;
    }
    
    private async Task CompleteExecutionAsync(VwapExecutionState executionState)
    {
        if (executionState.RemainingQuantity <= 0)
        {
            executionState.Status = VwapExecutionStatus.Completed;
            _logger.LogInformation("VWAP execution {ExecutionId} completed successfully", executionState.ExecutionId);
        }
        else
        {
            executionState.Status = VwapExecutionStatus.Failed;
            _logger.LogWarning("VWAP execution {ExecutionId} completed with remaining quantity", executionState.ExecutionId);
        }
        
        executionState.EndTime = DateTime.UtcNow;
        executionState.UpdatedAt = DateTime.UtcNow;
        
        // Clean up timer
        lock (_lock)
        {
            if (_executionTimers.ContainsKey(executionState.ExecutionId))
            {
                _executionTimers[executionState.ExecutionId].Dispose();
                _executionTimers.Remove(executionState.ExecutionId);
            }
        }
        
        // Cancel any remaining orders if configured
        if (executionState.Parameters.CancelAtEndTime)
        {
            await CancelRemainingOrdersAsync(executionState);
        }
    }
    
    private async Task CancelRemainingOrdersAsync(VwapExecutionState executionState)
    {
        foreach (var order in executionState.Orders
            .Where(o => o.Status == VwapOrderStatus.Submitted))
        {
            if (!string.IsNullOrEmpty(order.OrderId))
            {
                try
                {
                    await _orderManager.CancelOrderAsync(order.OrderId);
                    order.Status = VwapOrderStatus.Cancelled;
                    order.UpdatedAt = DateTime.UtcNow;
                }
                catch (Exception ex)
                {
                    _logger.LogError(ex, "Error cancelling VWAP order {OrderId}", order.OrderId);
                }
            }
        }
    }
    
    /// <summary>
    /// Cancel a VWAP execution
    /// </summary>
    public async Task<bool> CancelExecutionAsync(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) throw new ArgumentException("Execution ID required", nameof(executionId));
        
        VwapExecutionState executionState;
        lock (_lock)
        {
            if (!_executions.ContainsKey(executionId))
                return false;
                
            executionState = _executions[executionId];
        }
        
        if (executionState.Status != VwapExecutionStatus.Running)
            return false;
        
        try
        {
            // Cancel all active orders
            await CancelRemainingOrdersAsync(executionState);
            
            // Update execution state
            executionState.Status = VwapExecutionStatus.Cancelled;
            executionState.EndTime = DateTime.UtcNow;
            executionState.UpdatedAt = DateTime.UtcNow;
            
            // Clean up timer
            lock (_lock)
            {
                if (_executionTimers.ContainsKey(executionId))
                {
                    _executionTimers[executionId].Dispose();
                    _executionTimers.Remove(executionId);
                }
            }
            
            _logger.LogInformation("VWAP execution {ExecutionId} cancelled", executionId);
            return true;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error cancelling VWAP execution {ExecutionId}", executionId);
            return false;
        }
    }
    
    /// <summary>
    /// Get execution state
    /// </summary>
    public VwapExecutionState GetExecutionState(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) return null;
        
        lock (_lock)
        {
            return _executions.ContainsKey(executionId) ? 
                new VwapExecutionState(_executions[executionId]) : null;
        }
    }
    
    /// <summary>
    /// Get all execution states
    /// </summary>
    public List<VwapExecutionState> GetAllExecutionStates()
    {
        lock (_lock)
        {
            return _executions.Values.Select(e => new VwapExecutionState(e)).ToList();
        }
    }
}
```

## Integration with OrderManager

### VWAP Integration in OrderManager
```csharp
public partial class OrderManager : IOrderManager
{
    private readonly VwapExecutor _vwapExecutor;
    
    // Enhanced constructor with VWAP executor
    public OrderManager(
        IRiskManager riskManager,
        IPositionSizer positionSizer,
        ILogger<OrderManager> logger,
        RoutingConfigurationManager configManager,
        RoutingMetricsCollector metricsCollector,
        TwapExecutor twapExecutor,
        VwapExecutor vwapExecutor) : base(riskManager, positionSizer, logger, configManager, metricsCollector, twapExecutor)
    {
        _vwapExecutor = vwapExecutor ?? throw new ArgumentNullException(nameof(vwapExecutor));
        _venueManager = new VenueManager(logger);
        _omsToVenueOrderIdMap = new Dictionary<string, string>();
        _venueToOmsOrderIdMap = new Dictionary<string, string>();
        
        // Initialize with configurations
        InitializeWithConfigurationsAsync().Wait();
    }
    
    /// <summary>
    /// Execute a VWAP order
    /// </summary>
    public async Task<OrderResult> ExecuteVwapAsync(VwapParameters parameters, StrategyContext context)
    {
        if (parameters == null) throw new ArgumentNullException(nameof(parameters));
        if (context == null) throw new ArgumentNullException(nameof(context));
        
        try
        {
            _logger.LogInformation("Executing VWAP order for {Symbol} {Side} {Quantity}", 
                parameters.Symbol, parameters.Side, parameters.TotalQuantity);
            
            // Validate through risk management
            var riskDecision = await ValidateVwapOrderAsync(parameters, context);
            if (!riskDecision.Allow)
            {
                _logger.LogWarning("VWAP order rejected by risk management: {Reason}", riskDecision.RejectReason);
                return new OrderResult(false, null, $"Risk validation failed: {riskDecision.RejectReason}", null);
            }
            
            // Execute VWAP
            var executionState = await _vwapExecutor.ExecuteVwapAsync(parameters, context);
            
            // Create order result
            var orderResult = new OrderResult(
                Success: executionState.Status == VwapExecutionStatus.Completed,
                OrderId: executionState.ExecutionId,
                Message: executionState.Status == VwapExecutionStatus.Completed ? 
                    "VWAP execution completed successfully" : 
                    $"VWAP execution failed: {executionState.ErrorMessage}",
                Status: ConvertToOrderStatus(executionState)
            );
            
            _logger.LogInformation("VWAP order execution {Result}: {Message}", 
                orderResult.Success ? "succeeded" : "failed", orderResult.Message);
            
            return orderResult;
        }
        catch (Exception ex)
        {
            _logger.LogError(ex, "Error executing VWAP order for {Symbol}", parameters.Symbol);
            return new OrderResult(false, null, $"Error executing VWAP order: {ex.Message}", null);
        }
    }
    
    private async Task<RiskDecision> ValidateVwapOrderAsync(VwapParameters parameters, StrategyContext context)
    {
        // Convert VWAP 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: "VWAP 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 OrderStatus ConvertToOrderStatus(VwapExecutionState executionState)
    {
        if (executionState == null) return null;
        
        var state = executionState.Status switch
        {
            VwapExecutionStatus.Pending => OrderState.New,
            VwapExecutionStatus.Running => OrderState.Accepted,
            VwapExecutionStatus.Completed => OrderState.Filled,
            VwapExecutionStatus.Cancelled => OrderState.Cancelled,
            VwapExecutionStatus.Failed => OrderState.Rejected,
            _ => OrderState.Unknown
        };
        
        // Combine all fills from completed orders
        var allFills = executionState.Orders.SelectMany(o => o.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 VWAP execution
    /// </summary>
    public async Task<bool> CancelVwapAsync(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) throw new ArgumentException("Execution ID required", nameof(executionId));
        
        return await _vwapExecutor.CancelExecutionAsync(executionId);
    }
    
    /// <summary>
    /// Get VWAP execution state
    /// </summary>
    public VwapExecutionState GetVwapExecutionState(string executionId)
    {
        if (string.IsNullOrEmpty(executionId)) return null;
        
        return _vwapExecutor.GetExecutionState(executionId);
    }
}
```

## VWAP Configuration Management

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

## Testing Considerations

### Unit Tests for VWAP Algorithm
1. **Order Size Calculation**: Test calculation of order sizes based on volume and participation rate
2. **Parameter Validation**: Test validation of VWAP parameters
3. **Execution Monitoring**: Test monitoring of execution and order placement
4. **Order Placement**: Test placement of individual orders
5. **Error Handling**: Test handling of execution errors and retries
6. **Cancellation**: Test cancellation of VWAP executions
7. **Metrics Collection**: Test collection of performance metrics
8. **Participation Rate Adjustment**: Test adjustment of participation rate based on progress

### Integration Tests
1. **End-to-End Execution**: Test complete VWAP execution from start to finish
2. **Order Manager Integration**: Test integration with OrderManager
3. **Risk Management Integration**: Test risk validation for VWAP orders
4. **Market Data Integration**: Test integration with market data providers
5. **Performance Testing**: Test performance with high volume market data
6. **Concurrent Executions**: Test multiple concurrent VWAP executions

## Performance Considerations

### Memory Management
```csharp
/// <summary>
/// Manages memory usage for VWAP executions
/// </summary>
public class VwapMemoryManager
{
    private readonly int _maxExecutions;
    private readonly TimeSpan _executionRetentionTime;
    private readonly Dictionary<string, DateTime> _executionAccessTimes;
    private readonly object _lock = new object();
    
    public VwapMemoryManager(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 VWAP
```csharp
/// <summary>
/// Adaptive VWAP that adjusts based on market conditions
/// </summary>
public class AdaptiveVwapExecutor : VwapExecutor
{
    private readonly IVolumePredictor _volumePredictor;
    
    public AdaptiveVwapExecutor(
        ILogger<VwapExecutor> logger,
        IOrderManager orderManager,
        IMarketDataProvider marketDataProvider,
        IVolumePredictor volumePredictor,
        VwapConfig config = null) : base(logger, orderManager, marketDataProvider, config)
    {
        _volumePredictor = volumePredictor ?? throw new ArgumentNullException(nameof(volumePredictor));
    }
    
    protected override async Task UpdateExpectedVolumeAsync(VwapExecutionState executionState)
    {
        if (_config.EnableVolumePrediction && _volumePredictor != null)
        {
            try
            {
                var prediction = await _volumePredictor.PredictVolumeAsync(
                    executionState.Parameters.Symbol,
                    executionState.StartTime.Value,
                    executionState.EndTime.Value);
                    
                executionState.ExpectedVolume = prediction.TotalVolume;
            }
            catch (Exception ex)
            {
                _logger.LogError(ex, "Error getting volume prediction for {Symbol}", 
                    executionState.Parameters.Symbol);
                // Fall back to linear projection
                await base.UpdateExpectedVolumeAsync(executionState);
            }
        }
        else
        {
            await base.UpdateExpectedVolumeAsync(executionState);
        }
    }
    
    protected override double AdjustParticipationRate(VwapExecutionState executionState, double currentRate)
    {
        var adjustedRate = base.AdjustParticipationRate(executionState, currentRate);
        
        // Further adjust based on volume prediction accuracy
        if (executionState.ExpectedVolume.HasValue && executionState.CumulativeVolume > 0)
        {
            var predictionAccuracy = (double)executionState.CumulativeVolume / executionState.ExpectedVolume.Value;
            
            if (predictionAccuracy > 1.2) // Actual volume is 20% higher than predicted
            {
                adjustedRate *= 1.1; // Increase participation rate
            }
            else if (predictionAccuracy < 0.8) // Actual volume is 20% lower than predicted
            {
                adjustedRate *= 0.9; // Decrease participation rate
            }
        }
        
        return adjustedRate;
    }
}

/// <summary>
/// Interface for volume prediction
/// </summary>
public interface IVolumePredictor
{
    /// <summary>
    /// Predict volume for a symbol over a time period
    /// </summary>
    Task<VolumePrediction> PredictVolumeAsync(string symbol, DateTime startTime, DateTime endTime);
}

/// <summary>
/// Volume prediction result
/// </summary>
public record VolumePrediction
{
    public string Symbol { get; set; }
    public DateTime StartTime { get; set; }
    public DateTime EndTime { get; set; }
    public long TotalVolume { get; set; }
    public Dictionary<DateTime, long> VolumeProfile { get; set; } = new Dictionary<DateTime, long>();
    public double Confidence { get; set; } // 0.0 to 1.0
}
```

## Monitoring and Alerting

### VWAP Metrics Export
```csharp
/// <summary>
/// Exports VWAP metrics for monitoring
/// </summary>
public class VwapMetricsExporter
{
    private readonly VwapExecutor _vwapExecutor;
    
    public VwapMetricsExporter(VwapExecutor vwapExecutor)
    {
        _vwapExecutor = vwapExecutor ?? throw new ArgumentNullException(nameof(vwapExecutor));
    }
    
    public string ExportToPrometheus()
    {
        var executions = _vwapExecutor.GetAllExecutionStates();
        var sb = new StringBuilder();
        
        // Overall VWAP metrics
        var activeExecutions = executions.Count(e => e.Status == VwapExecutionStatus.Running);
        var completedExecutions = executions.Count(e => e.Status == VwapExecutionStatus.Completed);
        var failedExecutions = executions.Count(e => e.Status == VwapExecutionStatus.Failed);
        
        sb.AppendLine($"# HELP vwap_active_executions Number of active VWAP executions");
        sb.AppendLine($"# TYPE vwap_active_executions gauge");
        sb.AppendLine($"vwap_active_executions {activeExecutions}");
        
        sb.AppendLine($"# HELP vwap_completed_executions Total number of completed VWAP executions");
        sb.AppendLine($"# TYPE vwap_completed_executions counter");
        sb.AppendLine($"vwap_completed_executions {completedExecutions}");
        
        sb.AppendLine($"# HELP vwap_failed_executions Total number of failed VWAP executions");
        sb.AppendLine($"# TYPE vwap_failed_executions counter");
        sb.AppendLine($"vwap_failed_executions {failedExecutions}");
        
        // Performance metrics for completed executions
        var completed = executions.Where(e => e.Status == VwapExecutionStatus.Completed).ToList();
        if (completed.Any())
        {
            var avgSlippage = completed.Average(e => (double)e.PerformanceMetrics.VwapSlippage);
            var avgCommission = (double)completed.Average(e => e.PerformanceMetrics.TotalCommission);
            var avgParticipation = completed.Average(e => (double)e.PerformanceMetrics.ActualParticipationRate);
            
            sb.AppendLine($"# HELP vwap_average_slippage Average slippage for completed executions");
            sb.AppendLine($"# TYPE vwap_average_slippage gauge");
            sb.AppendLine($"vwap_average_slippage {avgSlippage:F4}");
            
            sb.AppendLine($"# HELP vwap_average_commission Average commission for completed executions");
            sb.AppendLine($"# TYPE vwap_average_commission gauge");
            sb.AppendLine($"vwap_average_commission {avgCommission:F2}");
            
            sb.AppendLine($"# HELP vwap_average_participation Average participation rate for completed executions");
            sb.AppendLine($"# TYPE vwap_average_participation gauge");
            sb.AppendLine($"vwap_average_participation {avgParticipation:F4}");
        }
        
        return sb.ToString();
    }
}
```

## Future Enhancements

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