regex for url match, means annoying constructor ocelot configuration object but cant work out a better way to do this at the moment

src/Ocelot.Library/Infrastructure/Configuration/Yaml/ConfigurationValidationResult.cs

@@ -0,0 +1,24 @@
+using System.Collections.Generic;
+using Ocelot.Library.Infrastructure.Responses;
+
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public class ConfigurationValidationResult
+    {
+        public ConfigurationValidationResult(bool isError)
+        {
+            IsError = isError;
+            Errors = new List<Error>();
+        }
+
+        public ConfigurationValidationResult(bool isError, List<Error> errors)
+        {
+            IsError = isError;
+            Errors = errors;
+        }
+
+        public bool IsError { get; private set; }
+
+        public List<Error> Errors { get; private set; } 
+    }
+}

src/Ocelot.Library/Infrastructure/Configuration/Yaml/ConfigurationValidator.cs

@@ -0,0 +1,35 @@
+using System.Collections.Generic;
+using System.Linq;
+using Ocelot.Library.Infrastructure.Responses;
+
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public class ConfigurationValidator : IConfigurationValidator
+    {
+        public Response<ConfigurationValidationResult> IsValid(YamlConfiguration configuration)
+        {
+            var duplicateUpstreamTemplates = configuration.ReRoutes
+                .Select(r => r.DownstreamTemplate)
+                .GroupBy(r => r)
+                .Where(r => r.Count() > 1)
+                .Select(r => r.Key)
+                .ToList();
+
+            if (duplicateUpstreamTemplates.Count <= 0)
+            {
+                return new OkResponse<ConfigurationValidationResult>(new ConfigurationValidationResult(false));
+            }
+                
+            var errors = new List<Error>();
+
+            foreach (var duplicateUpstreamTemplate in duplicateUpstreamTemplates)
+            {
+                var error = new DownstreamTemplateAlreadyUsedError(string.Format("Duplicate DownstreamTemplate: {0}", 
+                    duplicateUpstreamTemplate));
+                errors.Add(error);
+            }
+
+            return new OkResponse<ConfigurationValidationResult>(new ConfigurationValidationResult(true, errors));
+        }
+    }
+}

src/Ocelot.Library/Infrastructure/Configuration/Yaml/DownstreamTemplateAlreadyUsedError.cs

@@ -0,0 +1,11 @@
+using Ocelot.Library.Infrastructure.Responses;
+
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public class DownstreamTemplateAlreadyUsedError : Error
+    {
+        public DownstreamTemplateAlreadyUsedError(string message) : base(message)
+        {
+        }
+    }
+}

src/Ocelot.Library/Infrastructure/Configuration/Yaml/IConfigurationValidator.cs

@@ -0,0 +1,9 @@
+using Ocelot.Library.Infrastructure.Responses;
+
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public interface IConfigurationValidator
+    {
+        Response<ConfigurationValidationResult> IsValid(YamlConfiguration configuration);
+    }
+}

src/Ocelot.Library/Infrastructure/Configuration/Yaml/YamlConfiguration.cs

@@ -0,0 +1,14 @@
+using System.Collections.Generic;
+
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public class YamlConfiguration
+    {
+        public YamlConfiguration()
+        {
+            ReRoutes = new List<YamlReRoute>();
+        }
+
+        public List<YamlReRoute> ReRoutes { get; set; }
+    }
+}

src/Ocelot.Library/Infrastructure/Configuration/Yaml/YamlReRoute.cs

@@ -0,0 +1,9 @@
+namespace Ocelot.Library.Infrastructure.Configuration.Yaml
+{
+    public class YamlReRoute
+    {
+        public string DownstreamTemplate { get; set; }
+        public string UpstreamTemplate { get; set; }
+        public string UpstreamHttpMethod { get; set; }
+    }
+}