using System;
using System.Data;
using System.Data.SqlClient;
using System.Data.SqlTypes;
using Microsoft.SqlServer.Server;
using System.Text;

[Serializable]
[SqlUserDefinedAggregate(
Format.UserDefined,
IsInvariantToOrder = false,
IsInvariantToNulls = true,
IsInvariantToDuplicates = false,
MaxByteSize = -1
)]
public struct Concatenate : IBinarySerialize
{
private StringBuilder _accumulator;
private string _delimiter;

public Boolean IsNull;

public void Init()
{
_accumulator = new StringBuilder();
_delimiter = string.Empty;
}

public void Accumulate(SqlChars item, SqlString delimiter)
{
// if we have an actual delimiter
if ((!delimiter.IsNull) && (delimiter.Value.Length > 0))
{
_delimiter = delimiter.Value;
// accumulate delimiter if we have something already
if (_accumulator.Length > 0)
_accumulator.Append(delimiter.Value);
}

// if value is null, just add delimiter (above) and return
if (item.IsNull)
return;
else
{
_accumulator.Append(item.Value);
this.IsNull = false;
}

}

public void Merge(Concatenate Group)
{

if (_accumulator.Length > 0 && Group._accumulator.Length > 0)
_accumulator.Append(_delimiter);

_accumulator.Append(Group._accumulator.ToString());

}

public SqlChars Terminate()
{

return new SqlChars(_accumulator.ToString());

}

void IBinarySerialize.Read(System.IO.BinaryReader r)
{

_delimiter = r.ReadString();
_accumulator = new StringBuilder(r.ReadString());

if (_accumulator.Length != 0)
this.IsNull = false;

}

void IBinarySerialize.Write(System.IO.BinaryWriter w)
{

w.Write(_delimiter);
w.Write(_accumulator.ToString());

}

}