Support for custom serializers

Refit/Attributes.cs

@@ -70,7 +70,7 @@ public override HttpMethod Method {
     }
 
     public enum BodySerializationMethod {
-        Json, UrlEncoded
+        Json, UrlEncoded, Custom
     }
 
     [AttributeUsage(AttributeTargets.Parameter)]

Refit/RefitSettings.cs

@@ -1,4 +1,8 @@
-using System.Reflection;
+using System;
+using System.Collections.Generic;
+using System.Net.Http;
+using System.Reflection;
+using System.Threading.Tasks;
 
 namespace Refit
 {
@@ -7,9 +11,12 @@ public class RefitSettings
         public RefitSettings()
         {
             UrlParameterFormatter = new DefaultUrlParameterFormatter();
+            CustomSerializers = new Dictionary<Type, ITypeSerializer>();
         }
 
         public IUrlParameterFormatter UrlParameterFormatter { get; set; }
+
+        public Dictionary<Type, ITypeSerializer> CustomSerializers { get; private set; }
     }
 
     public interface IUrlParameterFormatter
@@ -24,4 +31,10 @@ public virtual string Format(object parameterValue, ParameterInfo parameterInfo)
             return parameterValue != null ? parameterValue.ToString() : null;
         }
     }
+
+    public interface ITypeSerializer
+    {
+        HttpContent SerializeAsHttpContent(object value);
+        Task<object> DeserializeFromHttpContent(HttpContent content);
+    }
 }

Refit/RequestBuilderImplementation.cs

@@ -92,6 +92,10 @@ public Func<object[], HttpRequestMessage> BuildRequestFactoryForMethod(string me
                             ret.Content = new StringContent(stringParam);
                         } else {
                             switch (restMethod.BodyParameterInfo.Item1) {
+                            case BodySerializationMethod.Custom:
+                                var param = paramList[i];
+                                ret.Content = settings.CustomSerializers[param.GetType()].SerializeAsHttpContent(param);
+                                break;
                             case BodySerializationMethod.UrlEncoded:
                                 ret.Content = new FormUrlEncodedContent(new FormValueDictionary(paramList[i]));
                                 break;
@@ -230,6 +234,11 @@ Func<HttpClient, CancellationToken, object[], Task<T>> buildCancellableTaskFuncF
                     throw await ApiException.Create(resp);
                 }
 
+                ITypeSerializer customSerializer;
+                if (settings.CustomSerializers.TryGetValue(restMethod.SerializedReturnType, out customSerializer)) {
+                    return (T)await customSerializer.DeserializeFromHttpContent(resp.Content);
+                }
+
                 var ms = new MemoryStream();
                 var fromStream = await resp.Content.ReadAsStreamAsync();
                 await fromStream.CopyToAsync(ms, 4096, ct);
@@ -317,6 +326,7 @@ public class RestMethodInfo
         public Dictionary<int, ParameterInfo> ParameterInfoMap { get; set; }
         public Type ReturnType { get; set; }
         public Type SerializedReturnType { get; set; }
+        public RefitSettings RefitSettings { get; set; } // Placeholder until #80 is merged. How lazy am I!
 
         static readonly Regex parameterRegex = new Regex(@"{(.*?)}");
 
@@ -413,8 +423,12 @@ string getUrlNameForParameter(ParameterInfo paramInfo)
         Tuple<BodySerializationMethod, int> findBodyParameter(List<ParameterInfo> parameterList)
         {
             var bodyParams = parameterList
-                .Select(x => new { Parameter = x, BodyAttribute = x.GetCustomAttributes(true).OfType<BodyAttribute>().FirstOrDefault() })
-                .Where(x => x.BodyAttribute != null)
+                .Select(x => new {
+                    Parameter = x, 
+                    BodyAttribute = x.GetCustomAttributes(true).OfType<BodyAttribute>().FirstOrDefault(), 
+                    HasCustomSerializer = RefitSettings.CustomSerializers.ContainsKey(x.ParameterType)
+                })
+                .Where(x => x.BodyAttribute != null || x.HasCustomSerializer)
                 .ToList();
 
             if (bodyParams.Count > 1) {
@@ -426,7 +440,10 @@ Tuple<BodySerializationMethod, int> findBodyParameter(List<ParameterInfo> parame
             }
 
             var ret = bodyParams[0];
-            return Tuple.Create(ret.BodyAttribute.SerializationMethod, parameterList.IndexOf(ret.Parameter));
+            var serializationMethod = ret.HasCustomSerializer
+                ? BodySerializationMethod.Custom
+                : ret.BodyAttribute.SerializationMethod;
+            return Tuple.Create(serializationMethod, parameterList.IndexOf(ret.Parameter));
         }
 
         Dictionary<string, string> parseHeaders(MethodInfo methodInfo)