/// <summary>
/// Combine the specified cubes over the common axes
/// </summary>
/// <param name="cubes">The set of cubes</param>
/// <param name="axes">The set of axes to combine upon</param>
/// <typeparam name="TValueType"></typeparam>
/// <returns>A new instance of <see cref="ICube{TValueType}"/> containing all of the values from the input cubes</returns>
/// <exception cref="ArgumentNullException">Thrown if <paramref name="cubes"/> is null</exception>
/// <exception cref="InvalidOperationException">Thrown if there are no common axes between the cubes</exception>
public static ICube <TValueType> CombineCubes <TValueType>(
IEnumerable <ICube <TValueType> > cubes,
IReadOnlyList <string> axes = null) where TValueType : ICubeValue
{
if (cubes == null)
{
throw new ArgumentNullException(nameof(cubes));
}
var filteredCubes = cubes.Where(cube => cube != null).ToList();
if (!filteredCubes.Any())
{
return(null);
}
HashSet <IAxis> commonAxes = null;
foreach (var cube in filteredCubes)
{
if (commonAxes == null)
{
commonAxes = new HashSet <IAxis>(cube.AxisSet);
}
else
{
commonAxes = new HashSet <IAxis>(commonAxes.Intersect(cube.AxisSet));
}
}
if (commonAxes.Count == 0)
{
throw new InvalidOperationException("Unable to combine cubes - zero common axes");
}
IAxis [] axisList;
if (axes != null)
{
var commonAxesAsDictionary = commonAxes.ToDictionary((a) => a.Name, a => a);
var axesAsHashSet = new HashSet <string>(axes);
commonAxes = new HashSet <IAxis>(commonAxes.Where(a => axesAsHashSet.Contains(a.Name)));
foreach (var axisName in axes)
{
if (!commonAxesAsDictionary.TryGetValue(axisName, out var axis))
{
throw new InvalidOperationException($"No axis '{axisName}' found on input cubes");
}
}
axisList = axes.Select(a => commonAxesAsDictionary [a]).ToArray();
}
else
{
axisList = commonAxes.ToArray();
}
var outputCube = new Cube <TValueType>(new AxisSet(axisList));
var axisNames = new HashSet <string>(axisList.Select(axis => axis.Name));
foreach (var cube in filteredCubes)
{
int [] axisIndices = new int [axisList.Length];
for (int idx = 0; idx < axisIndices.Length; idx++)
{
axisIndices [idx] = cube.AxisSet.GetIndexOf(axisList [idx].Name);
}
object [] keys = new object [axisList.Length];
foreach (var point in cube)
{
for (int idx = 0; idx < axisIndices.Length; ++idx)
{
keys [idx] = point.GetAxisValue(axisIndices [idx]);
}
outputCube.AddItem(keys, point.CubeValue);
foreach (var error in cube.ErrorSet)
{
var filteredErrorKeys = new Dictionary <string, object>();
foreach (var axisName in error.ErrorAxes.Where(k => axisNames.Contains(k)))
{
filteredErrorKeys [axisName] = error.GetErrorKey(axisName);
}
outputCube.AddError(filteredErrorKeys, error.ErrorMessage);
}
}
}
return(outputCube);
}