using System.Collections.Generic;

using System.Data.Common;

using System.Linq;

using DataBoss.Linq;

namespace DataBoss.Data

{

public class MultiDataReader : DataReaderDecoratorBase

{

readonly IReadOnlyList<DbDataReader> readers;

readonly int[] nextNext;

int next;

public MultiDataReader(IReadOnlyList<DbDataReader> readers) : base(readers[0]) {

this.readers = readers;

this.nextNext = new int[readers.Count];

for(var i = 0; i != readers.Count; ++i)

this.nextNext[i] = (i + 1) % readers.Count;

this.next = readers.Count - 1;

}

public override bool IsClosed => readers.All(x => x.IsClosed);

public override void Close() => readers.ForEach(x => x.Close());

protected override void Dispose(bool disposing)

{

if(!disposing)

return;

readers.ForEach(x => x.Dispose());

}

public override bool NextResult() => false;

public override bool Read() {

for(;;) {

var current = nextNext[next];

if (readers[current].Read()) {

Inner = readers[current];

next = current;

return true;

} else {

if(current == nextNext[current])

return false;

nextNext[next] = nextNext[current];

}

}

}

}

}