namespace System.Web.ModelBinding {
    using System;

    // Returns a user-specified binder for a given open generic type.
    public sealed class GenericModelBinderProvider : ModelBinderProvider {

        private readonly Func<Type[], IModelBinder> _modelBinderFactory;
        private readonly Type _modelType;

        public GenericModelBinderProvider(Type modelType, IModelBinder modelBinder) {
            if (modelType == null) {
                throw new ArgumentNullException("modelType");
            }
            if (modelBinder == null) {
                throw new ArgumentNullException("modelBinder");
            }

            ValidateParameters(modelType, null /* modelBinderType */);

            _modelType = modelType;
            _modelBinderFactory = _ => modelBinder;
        }

        public GenericModelBinderProvider(Type modelType, Type modelBinderType) {
            // The binder can be a closed type, in which case it will be instantiated directly. If the binder
            // is an open type, the type arguments will be determined at runtime and the corresponding closed
            // type instantiated.

            if (modelType == null) {
                throw new ArgumentNullException("modelType");
            }
            if (modelBinderType == null) {
                throw new ArgumentNullException("modelBinderType");
            }

            ValidateParameters(modelType, modelBinderType);
            bool modelBinderTypeIsOpenGeneric = modelBinderType.IsGenericTypeDefinition;

            _modelType = modelType;
            _modelBinderFactory = typeArguments => {
                Type closedModelBinderType = (modelBinderTypeIsOpenGeneric) ? modelBinderType.MakeGenericType(typeArguments) : modelBinderType;
                return (IModelBinder)Activator.CreateInstance(closedModelBinderType);
            };
        }

        public GenericModelBinderProvider(Type modelType, Func<Type[], IModelBinder> modelBinderFactory) {
            if (modelType == null) {
                throw new ArgumentNullException("modelType");
            }
            if (modelBinderFactory == null) {
                throw new ArgumentNullException("modelBinderFactory");
            }

            ValidateParameters(modelType, null /* modelBinderType */);

            _modelType = modelType;
            _modelBinderFactory = modelBinderFactory;
        }

        public Type ModelType {
            get {
                return _modelType;
            }
        }

        public bool SuppressPrefixCheck {
            get;
            set;
        }

        public override IModelBinder GetBinder(ModelBindingExecutionContext modelBindingExecutionContext, ModelBindingContext bindingContext) {
            ModelBinderUtil.ValidateBindingContext(bindingContext);

            Type[] typeArguments = null;
            if (ModelType.IsInterface) {
                Type matchingClosedInterface = TypeHelpers.ExtractGenericInterface(bindingContext.ModelType, ModelType);
                if (matchingClosedInterface != null) {
                    typeArguments = matchingClosedInterface.GetGenericArguments();
                }
            }
            else {
                typeArguments = TypeHelpers.GetTypeArgumentsIfMatch(bindingContext.ModelType, ModelType);
            }

            if (typeArguments != null) {
                if (SuppressPrefixCheck || bindingContext.UnvalidatedValueProvider.ContainsPrefix(bindingContext.ModelName)) {
                    return _modelBinderFactory(typeArguments);
                }
            }

            return null;
        }

        private static void ValidateParameters(Type modelType, Type modelBinderType) {
            if (!modelType.IsGenericTypeDefinition) {
                throw Error.GenericModelBinderProvider_ParameterMustSpecifyOpenGenericType(modelType, "modelType");
            }
            if (modelBinderType != null) {
                if (!typeof(IModelBinder).IsAssignableFrom(modelBinderType)) {
                    throw Error.Common_TypeMustImplementInterface(modelBinderType, typeof(IModelBinder), "modelBinderType");
                }
                if (modelBinderType.IsGenericTypeDefinition) {
                    if (modelType.GetGenericArguments().Length != modelBinderType.GetGenericArguments().Length) {
                        throw Error.GenericModelBinderProvider_TypeArgumentCountMismatch(modelType, modelBinderType);
                    }
                }
            }
        }

    }
}