using NModbus.BasicServer.Interfaces;

using NModbus.Interfaces;

using System.Collections.Concurrent;

namespace NModbus.BasicServer

{

/// <summary>

/// Stores points using a Dictionary rather than an array.

/// </summary>

/// <remarks>

/// Rather than allocate a full array of <see cref="UInt16.MaxValue"/> values, we use a <see cref="ConcurrentDictionary{UInt16, TValue}"/>

/// to store only those addresses which have been set.

/// </remarks>

/// <typeparam name="T"></typeparam>

public class SparsePointStorage<T> : IPointStorage<T>

where T : struct

{

private readonly ConcurrentDictionary<ushort, T> values = new ConcurrentDictionary<ushort, T>();

public T this[ushort address]

{

get

{

if (values.TryGetValue(address, out var value))

return value;

return default;

}

set

{

values[address] = value;

}

}

public event EventHandler<DeviceReadArgs>? BeforeDeviceRead;

public event EventHandler<DeviceReadArgs>? AfterDeviceRead;

public event EventHandler<DeviceWriteArgs<T>>? BeforeDeviceWrite;

public event EventHandler<DeviceWriteArgs<T>>? AfterDeviceWrite;

private void VerifyPointsAreInRange(ushort startingAddress, ushort numberOfPoints)

{

if (startingAddress + numberOfPoints > ushort.MaxValue)

throw new ModbusServerException(ModbusExceptionCode.IllegalDataAddress);

}

T[] IDevicePointStorage<T>.ReadPoints(ushort startingAddress, ushort numberOfPoints)

{

VerifyPointsAreInRange(startingAddress, numberOfPoints);

var args = new DeviceReadArgs(startingAddress, numberOfPoints);

BeforeDeviceRead?.Invoke(this, args);

var points = new T[numberOfPoints];

for (var index = 0; index < numberOfPoints; index++)

{

values.TryGetValue((ushort)(startingAddress + index), out var value);

points[index] = value;

}

AfterDeviceRead?.Invoke(this, args);

return points;

}

void IDevicePointStorage<T>.WritePoints(ushort startingAddress, T[] values)

{

VerifyPointsAreInRange(startingAddress, (ushort)values.Length);

var args = new DeviceWriteArgs<T>(startingAddress, values);

BeforeDeviceWrite?.Invoke(this, args);

for (var index = 0; index < values.Length; index++)

{

this.values[(ushort)(startingAddress + index)] = values[index];

}

AfterDeviceWrite?.Invoke(this, args);

}

}

}