using System;
using System.Collections.Generic;

namespace DTS.DASLib.Service
{
    // Custom comparer for the IDASCommunication class.
    public class AnalogInputDASChannelComparer : IEqualityComparer<AnalogInputDASChannel>
    {
        // GainInfo are equal if their Gain is equal.
        public bool Equals(AnalogInputDASChannel x, AnalogInputDASChannel y)
        {
            // Check whether the compared objects reference the same data.
            if (ReferenceEquals(x, y))
                return true;

            // Check whether any of the compared objects is null.
            if (x is null || y is null)
                return false;

            if (x.OwningModule == null || y.OwningModule == null)
                return false;

            if (x.OwningModule.OwningDAS == null || y.OwningModule.OwningDAS == null)
                return false;

            if (string.IsNullOrEmpty(x.OwningModule.OwningDAS.SerialNumber) ||
                string.IsNullOrEmpty(y.OwningModule.OwningDAS.SerialNumber))
                return false;

            // Check whether they are equal.
            return x.ModuleChannelNumber == y.ModuleChannelNumber &&
                   x.OwningModule.ModuleArrayIndex == y.OwningModule.ModuleArrayIndex &&
                   x.OwningModule.OwningDAS.SerialNumber == y.OwningModule.OwningDAS.SerialNumber &&
                   x.AbsoluteDisplayOrder == y.AbsoluteDisplayOrder &&
                   x.UnitConverision == y.UnitConverision;
        }

        // If Equals() returns true for a pair of objects,
        // GetHashCode must return the same value for these objects.

        public int GetHashCode(AnalogInputDASChannel analog)
        {
            // Check whether the object is null.

            if (string.IsNullOrEmpty(analog.OwningModule?.OwningDAS?.SerialNumber))
                return 0;

            // Get the hash code for the fields
            return analog.ModuleChannelNumber.GetHashCode() ^
                   analog.OwningModule.ModuleArrayIndex.GetHashCode() ^
                   analog.OwningModule.OwningDAS.SerialNumber.GetHashCode() ^
                   analog.AbsoluteDisplayOrder.GetHashCode() ^
                   analog.UnitConverision.GetHashCode();
        }
    }
}