/// <summary>
/// Returns all permutations in the collections of available items.
/// </summary>
public static T[][] Permute <T>(IEnumerable <IEnumerable <T> > availableItems)
{
Debug.Assert(availableItems != null);
var listedItems = availableItems
.Select((itemCollection) => itemCollection.ToLinkList( ))
.ToLinkList( );
return(Permuter.Permute(listedItems, LinkList <T> .Empty).ToArray( ));
}
public void Permute_returns_expected_permutation(int[][] items, int[][] expectedPermutations)
{
var permutations = Permuter.Permute(items);
Assert.NotNull(permutations);
Assert.Equal(expectedPermutations.Length, permutations.Length);
foreach (var permutation in permutations)
{
Assert.Contains(permutation, expectedPermutations, ArrayComparer <int> .Instance);
}
}
private static IEnumerable <IInstanceCreator> GetMethodCreators(Type targetType, MethodBase method)
{
Debug.Assert(targetType != null);
Debug.Assert(method != null);
Debug.Assert(method.IsGenericMethod || !targetType.ContainsGenericParameters);
// Ignore recursive parameters.
var parameters = method.GetParameters( );
if (parameters.Any(p => p.ParameterType.Is(targetType) || p.ParameterType.Is(method.DeclaringType)))
{
yield break;
}
// Retrieve creators for each parameter.
var availableArguments = parameters.Select((p) => TypeCreator.GetInstanceCreators(p.ParameterType).AsEnumerable( ));
// Call constructor with all argument permutations.
foreach (var arguments in Permuter.Permute(availableArguments))
{
// If method is concrete, use it.
if (!method.IsGenericMethod)
{
yield return(WeakInstanceCreator.ForMethod(targetType, method, arguments));
}
// Otherwise, try to resolve generic arguments on method.
else if (method is MethodInfo)
{
var methodInfo = (MethodInfo)method;
var bindings = new BindingCollection(Binding.EmptyBindings);
for (int i = 0; i < parameters.Length; ++i)
{
ParameterInfo parameter = parameters[i];
IInstanceCreator argument = arguments[i];
if (parameter.ParameterType.ContainsGenericParameters)
{
GenericTypeResolver.GetAssignedGenericArguments(bindings, argument.InstanceType, parameter.ParameterType);
}
}
foreach (LinkList <Binding> b in bindings)
{
var concreteMethod = GenericTypeResolver.MakeConcreteMethod(methodInfo, b);
if (concreteMethod != null)
{
targetType = concreteMethod.ReturnType;
yield return(WeakInstanceCreator.ForMethod(targetType, concreteMethod, arguments));
}
}
}
}
}
private static ICollection <MethodInfo> GetConcreteMethods(MethodInfo method, LinkList <Binding> bindings)
{
Debug.Assert(method != null);
Debug.Assert(bindings != null);
// Try to resolve generic arguments on method.
var openArguments = GenericTypeResolver.GetOpenGenericArguments(method.GetGenericArguments( ));
var concreteBindings = new BindingCollection(bindings);
GenericTypeResolver.BindGenericArguments(concreteBindings, openArguments);
var concreteMethods = concreteBindings.Transform((b) => MakeConcreteMethod(method, openArguments, b));
// If generic arguments cannot be resolved statically, try to bind method arguments by searching for creatable parameter types.
if (concreteMethods.Count == 0)
{
var genericParameterTypes = method.GetParameters( )
.Select(p => p.ParameterType)
.Where(t => t.IsGenericType)
.ToArray( );
Debug.Assert(genericParameterTypes.All(t => !t.IsGenericParameter));
var creatableParameterTypes = genericParameterTypes
.Select(t => TypeCreator.GetCreators(t)
.Select(c => c.InstanceType)
.Distinct( )
);
var parameterBindings = new BindingCollection(bindings);
parameterBindings.Expand(Permuter.Permute(creatableParameterTypes), (b, permutation) => {
for (int i = 0; i < permutation.Length; ++i)
{
Type permutationType = permutation[i];
Type genericParameterType = genericParameterTypes[i];
GenericTypeResolver.GetAssignedGenericArguments(b, permutationType, genericParameterType);
}
});
concreteMethods = parameterBindings.Transform((b) => MakeConcreteMethod(method, openArguments, b));
}
return(concreteMethods);
}
private static IEnumerable <T[]> Permute <T>(LinkList <LinkList <T> > availableItems, LinkList <T> currentPermutation)
{
// If there are no remaining available items, return current permutation.
if (availableItems.IsEmpty)
{
return(currentPermutation.ToArray( ).MakeEnumerable( ));
}
// Otherwise, loop through all of the current available items,
// returning permutations of the remaining items.
var currentAvailableItems = availableItems.Value;
var remainingAvailableItems = availableItems.Tail;
Debug.Assert(currentAvailableItems != null);
return
(from item in currentAvailableItems
let nextPermutation = currentPermutation.Add(item)
from permutation in Permuter.Permute(remainingAvailableItems, nextPermutation)
select permutation);
}
