improvements for PR #1

src/OpenTracing.AspNetCore/HeaderDictionaryCarrier.cs

@@ -7,12 +7,12 @@
 namespace OpenTracing.AspNetCore
 {
     /// <summary>
-    /// A <see cref="ITextMapCarrier"/> which allows <see cref="IHeaderDictionary"/> implementations to be used as carrier objects.
+    /// A <see cref="ITextMap"/> which allows <see cref="IHeaderDictionary"/> implementations to be used as carrier objects.
     /// </summary>
     /// <remarks>
     /// <see cref="IHeaderDictionary"/> is a multi-value dictionary. Since most other platforms represent http headers as regular
     /// dictionaries, this carrier represents it as a regular dictionary to tracer implementations.</remarks>
-    public class HeaderDictionaryCarrier : ITextMapCarrier
+    public class HeaderDictionaryCarrier : ITextMap
     {
         private readonly IHeaderDictionary _headers;
 

src/OpenTracing.BasicTracer/Propagation/TextMapCarrierHandler.cs

@@ -3,11 +3,9 @@
 
 namespace OpenTracing.BasicTracer.Propagation
 {
-    public class TextMapCarrierHandler :
-        IInjectCarrierHandler<ITextMapCarrier>,
-        IExtractCarrierHandler<ITextMapCarrier>
+    public class TextMapCarrierHandler
     {
-        public void MapContextToCarrier(SpanContext context, ITextMapCarrier carrier)
+        public void MapContextToCarrier(SpanContext context, ITextMap carrier)
         {
             carrier.Add(BaggageKeys.TraceId, context.TraceId.ToString());
             carrier.Add(BaggageKeys.SpanId, context.SpanId.ToString());
@@ -19,7 +17,7 @@ public void MapContextToCarrier(SpanContext context, ITextMapCarrier carrier)
             }
         }
 
-        public SpanContext MapCarrierToContext(ITextMapCarrier carrier)
+        public SpanContext MapCarrierToContext(ITextMap carrier)
         {
             // we can't create a reference without a trace-id
             Guid? traceId = TryGetGuid(carrier, BaggageKeys.TraceId);
@@ -48,7 +46,7 @@ public SpanContext MapCarrierToContext(ITextMapCarrier carrier)
             return new SpanContext(traceId.Value, spanId.Value, sampled, baggage);
         }
 
-        private Guid? TryGetGuid(ITextMapCarrier carrier, string key)
+        private Guid? TryGetGuid(ITextMap carrier, string key)
         {
             string strValue = carrier.Get(key);
 

src/OpenTracing.BasicTracer/Tracer.cs

@@ -46,55 +46,32 @@ public ISpan StartSpan(string operationName, StartSpanOptions options)
             return span;
         }
 
-        public void Inject(ISpanContext spanContext, string format, IInjectCarrier carrier)
+        public void Inject<TCarrier>(ISpanContext spanContext, Format<TCarrier> format, TCarrier carrier)
         {
-            switch (format)
-            {
-                case Formats.TextMap:
-                    InjectTextMap(spanContext, carrier);
-                    break;
-                // TODO add other formats
-                default:
-                    throw new UnsupportedFormatException($"The format '{format}' is not supported.");
-            }
-        }
+            // TODO add other formats (and maybe don't use if/else :D )
 
-        private void InjectTextMap(ISpanContext spanContext, IInjectCarrier carrier)
-        {
             var typedContext = (SpanContext)spanContext;
 
-            var textMapCarrier = carrier as ITextMapCarrier;
-            if (textMapCarrier != null)
+            if (format.Equals(Formats.TextMap))
             {
-                _textMapCarrierHandler.MapContextToCarrier(typedContext, textMapCarrier);
-                return;
+                _textMapCarrierHandler.MapContextToCarrier(typedContext, (ITextMap) carrier);
             }
-
-            throw new InvalidCarrierException($"The carrier '{carrier.GetType()}' is not supported for the format '{Formats.TextMap}'.");
-        }
-
-
-        public ISpanContext Extract(string format, IExtractCarrier carrier)
-        {
-            switch (format)
+            else
             {
-                case Formats.TextMap:
-                    return ExtractTextMap(carrier);
-                // TODO add other formats
-                default:
-                    throw new UnsupportedFormatException($"The format '{format}' is not supported.");
+                throw new UnsupportedFormatException($"The format '{format}' is not supported.");
             }
         }
 
-        private ISpanContext ExtractTextMap(IExtractCarrier carrier)
+        public ISpanContext Extract<TCarrier>(Format<TCarrier> format, TCarrier carrier)
         {
-            var textMapCarrier = carrier as ITextMapCarrier;
-            if (textMapCarrier != null)
+            // TODO add other formats (and maybe don't use if/else :D )
+
+            if (format.Equals(Formats.TextMap))
             {
-                return _textMapCarrierHandler.MapCarrierToContext(textMapCarrier);
+                return _textMapCarrierHandler.MapCarrierToContext((ITextMap) carrier);
             }
-
-            throw new InvalidCarrierException($"The carrier '{carrier.GetType()}' is not supported for the format '{Formats.TextMap}'.");
+            
+            throw new UnsupportedFormatException($"The format '{format}' is not supported.");
         }
     }
 }

src/OpenTracing/Extensions/FormatBinaryExtensions.cs

@@ -35,7 +35,7 @@ public static void InjectBinary(this ITracer tracer, ISpanContext spanContext, b
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            tracer.Inject(spanContext, Formats.Binary, new BinaryCarrier(data));
+            tracer.Inject(spanContext, Formats.Binary, data);
         }
 
         /// <summary>
@@ -51,7 +51,7 @@ public static ISpanContext ExtractBinary(this ITracer tracer, byte[] data)
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            return tracer.Extract(Formats.Binary, new BinaryCarrier(data));
+            return tracer.Extract(Formats.Binary, data);
         }
     }
 }

src/OpenTracing/Extensions/FormatHttpHeadersExtensions.cs

@@ -79,7 +79,7 @@ public static void InjectHttpHeaders(this ITracer tracer, ISpanContext spanConte
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            tracer.Inject(spanContext, Formats.HttpHeaders, new TextMapCarrier(headers));
+            tracer.Inject(spanContext, Formats.HttpHeaders, new DictionaryCarrier(headers));
         }
 
         /// <summary>
@@ -122,7 +122,7 @@ public static ISpanContext ExtractHttpHeaders(this ITracer tracer, IDictionary<s
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            return tracer.Extract(Formats.HttpHeaders, new TextMapCarrier(headers));
+            return tracer.Extract(Formats.HttpHeaders, new DictionaryCarrier(headers));
         }
     }
 }

src/OpenTracing/Extensions/FormatTextMapExtensions.cs

@@ -36,23 +36,23 @@ public static void InjectTextMap(this ITracer tracer, ISpanContext spanContext,
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            tracer.Inject(spanContext, Formats.TextMap, new TextMapCarrier(data));
+            tracer.Inject(spanContext, Formats.TextMap, new DictionaryCarrier(data));
         }
 
         /// <summary>
-        /// Returns a new <see cref="ISpanContext"/> containing the baggage of the given <paramref name="dictionary"/>
+        /// Returns a new <see cref="ISpanContext"/> containing the baggage of the given <paramref name="data"/>
         /// (using the format <see cref="Formats.HttpHeaders"/>), or null if there was no baggage found.
         /// </summary>
         /// <param name="tracer">A <see cref="ITracer"/> instance.</param>
-        /// <param name="dictionary">The dictionary will be used as a carrier for the propagation.</param>
-        public static ISpanContext ExtractTextMap(this ITracer tracer, IDictionary<string, string> dictionary)
+        /// <param name="data">The dictionary will be used as a carrier for the propagation.</param>
+        public static ISpanContext ExtractTextMap(this ITracer tracer, IDictionary<string, string> data)
         {
             if (tracer == null)
             {
                 throw new ArgumentNullException(nameof(tracer));
             }
 
-            return tracer.Extract(Formats.TextMap, new TextMapCarrier(dictionary));
+            return tracer.Extract(Formats.TextMap, new DictionaryCarrier(data));
         }
     }
 }

src/OpenTracing/ITracer.cs

@@ -18,14 +18,14 @@ public interface ITracer
         /// <param name="spanContext">The <see cref="ISpanContext"/> instance to inject into the carrier.</param>
         /// <param name="format">The format which should be used.</param>
         /// <param name="carrier">See the documentation for the chosen <paramref name="format"/> for a description of the carrier object.</param>
-        void Inject(ISpanContext spanContext, string format, IInjectCarrier carrier);
+        void Inject<TCarrier>(ISpanContext spanContext, Format<TCarrier> format, TCarrier carrier);
 
         /// <summary>
         /// Returns a new <see cref="ISpanContext"/> containing the baggage of the given <paramref name="carrier"/>,
         /// or null if there was no baggage found.
         /// </summary>
         /// <param name="format">The format which should be used.</param>
         /// <param name="carrier">See the documentation for the chosen <paramref name="format"/> for a description of the carrier object</param>
-        ISpanContext Extract(string format, IExtractCarrier carrier);
+        ISpanContext Extract<TCarrier>(Format<TCarrier> format, TCarrier carrier);
     }
 }

src/OpenTracing/NullTracer/NullTracer.cs

@@ -15,11 +15,11 @@ public ISpan StartSpan(string operationName, StartSpanOptions options = null)
             return NullSpan.Instance;
         }
 
-        public void Inject(ISpanContext spanContext, string format, IInjectCarrier carrier)
+        public void Inject<TCarrier>(ISpanContext spanContext, Format<TCarrier> format, TCarrier carrier)
         {
         }
 
-        public ISpanContext Extract(string format, IExtractCarrier carrier)
+        public ISpanContext Extract<TCarrier>(Format<TCarrier> format, TCarrier carrier)
         {
             return null;
         }

src/OpenTracing/Propagation/TextMapCarrier.cs → src/OpenTracing/Propagation/DictionaryCarrier.cs

@@ -4,13 +4,13 @@
 namespace OpenTracing.Propagation
 {
     /// <summary>
-    /// The default <see cref="ITextMapCarrier"/> implementation which wraps an arbitrary <see cref="IDictionary{TKey,TValue}"/>.
+    /// The default <see cref="ITextMap"/> implementation which wraps an arbitrary <see cref="IDictionary{TKey,TValue}"/>.
     /// </summary>
-    public class TextMapCarrier : ITextMapCarrier
+    public class DictionaryCarrier : ITextMap
     {
         private readonly IDictionary<string, string> _payload;
 
-        public TextMapCarrier(IDictionary<string, string> payload)
+        public DictionaryCarrier(IDictionary<string, string> payload)
         {
             if (payload == null)
             {

src/OpenTracing/Propagation/Format.cs

@@ -0,0 +1,59 @@
+using System;
+
+namespace OpenTracing.Propagation
+{
+    /// <summary>
+    /// Format instances control the behavior of <see cref="ITracer.Inject" /> and <see cref="ITracer.Extract" /> 
+    /// (and also constrain the type of the carrier parameter to same).
+    /// </summary>
+    public class Format<TCarrier> : IEquatable<Format<TCarrier>>
+    {
+        /// <summary>
+        /// The unique name for this format.
+        /// </summary>
+        public string Name { get; }
+
+        public Format(string name)
+        {
+            if (string.IsNullOrWhiteSpace(name))
+            {
+                throw new ArgumentNullException(nameof(name));
+            }
+
+            Name = name;
+        }
+
+        /// <summary>
+        /// Two format instances are equal when they have the same <see cref="Name" />.
+        /// </summary>
+        public override bool Equals(object obj)
+        {
+            if (ReferenceEquals(null, obj)) return false;
+            if (ReferenceEquals(this, obj)) return true;
+            if (obj.GetType() != GetType()) return false;
+
+            return Equals(obj as Format<TCarrier>);
+        }
+
+        /// <summary>
+        /// Two format instances are equal when they have the same <see cref="Name" />.
+        /// </summary>
+        public bool Equals(Format<TCarrier> other)
+        {
+            if (other == null)
+            {
+                return false;
+            }
+
+            return string.Equals(Name, other.Name);
+        }
+
+        /// <summary>
+        /// Two format instances are equal when they have the same <see cref="Name" />.
+        /// </summary>
+        public override int GetHashCode()
+        {
+            return Name.GetHashCode();
+        }
+    }
+}