NetworkTopologyStrategy.cs

NetworkTopologyStrategy.cs

internal class NetworkTopologyStrategy : IReplicationStrategy, IEquatable<NetworkTopologyStrategy>
{
    private readonly SortedSet<DatacenterReplicationFactor> _replicationFactorsSet;
    private readonly IReadOnlyDictionary<string, int> _replicationFactorsMap;
    private readonly int _hashCode;

    public NetworkTopologyStrategy(IReadOnlyDictionary<string, int> replicationFactors)
    {
        _replicationFactorsSet = new SortedSet<DatacenterReplicationFactor>(
            replicationFactors.Select(rf => new DatacenterReplicationFactor(rf.Key, rf.Value)), 
            DatacenterReplicationFactorComparer.Instance);

        _replicationFactorsMap = replicationFactors;
        _hashCode = NetworkTopologyStrategy.ComputeHashCode(_replicationFactorsSet);
    }

    public override bool Equals(object obj)
    {
        return Equals(obj as NetworkTopologyStrategy);
    }

    public bool Equals(NetworkTopologyStrategy other)
    {
        return other != null && _replicationFactorsSet.SetEquals(other._replicationFactorsSet);
    }

    private static int ComputeHashCode(IEnumerable<DatacenterReplicationFactor> replicationFactorsSet)
    {
        return Utils.CombineHashCode(replicationFactorsSet);
    }

    public override int GetHashCode()
    {
        return _hashCode;
    }
}

internal struct DatacenterReplicationFactor : IEquatable<DatacenterReplicationFactor>
{
    private readonly int _hashCode;

    public DatacenterReplicationFactor(string datacenter, int replicationFactor)
    {
        Datacenter = datacenter ?? throw new ArgumentNullException(nameof(datacenter));
        ReplicationFactor = replicationFactor;
        _hashCode = DatacenterReplicationFactor.ComputeHashCode(Datacenter, ReplicationFactor);
    }

    public string Datacenter { get; }

    public int ReplicationFactor { get; }

    public override bool Equals(object obj)
    {
        return obj.GetType() == GetType() && Equals((DatacenterReplicationFactor)obj);
    }

    public bool Equals(DatacenterReplicationFactor other)
    {
        return Datacenter == other.Datacenter &&
               ReplicationFactor == other.ReplicationFactor;
    }

    public override int GetHashCode()
    {
        return _hashCode;
    }

    private static int ComputeHashCode(string datacenter, int replicationFactor)
    {
        return Utils.CombineHashCode(new object[] { datacenter, replicationFactor });
    }
}

internal class DatacenterReplicationFactorComparer : IComparer<DatacenterReplicationFactor>
{
    private DatacenterReplicationFactorComparer() { }

    public static DatacenterReplicationFactorComparer Instance { get; } = new DatacenterReplicationFactorComparer();
    
    public int Compare(DatacenterReplicationFactor x, DatacenterReplicationFactor y)
    {
        return string.Compare(x.Datacenter, y.Datacenter, StringComparison.Ordinal);
    }
}