Generalize Codec to admit 'Format instead of forcing byte[] (#24)

jet · Oct 26, 2019 · 2a3787c · 2a3787c
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diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -13,9 +13,14 @@ The `Unreleased` section name is replaced by the expected version of next releas
 - `FsCodec.Box.Codec.Create`: an API equivalent substitute for `FsCodec.NewtonsoftJson.Codec.Create` for use in unit and integration tests [#25](https://github.com/jet/FsCodec/pull/25)
 
 ### Changed
+
+- Generalized `Codec.Create` to no longer presume `Data` and `Metadata` should always be `byte[]` [#24](https://github.com/jet/FsCodec/pull/24)
+
 ### Removed
 ### Fixed
 
+- Removed accidentally pasted `setting` and `allowNullaryCases` in `Codec.Create`  [#23](https://github.com/jet/FsCodec/pull/23)
+
 <a name="1.1.0"></a>
 ## [1.1.0] - 2019-09-19
 

diff --git a/src/FsCodec/Codec.fs b/src/FsCodec/Codec.fs
@@ -1,58 +1,55 @@
 namespace FsCodec
+
 open System
 
-/// Provides Codecs that render to a UTF-8 array suitable for storage in Event Stores, based on explicit functions you supply
+/// Provides Codecs that render to store-supported form (e.g., a UTF-8 byte array) suitable for storage in Event Stores, based on explicit functions you supply
 /// Does not involve conventions / Type Shapes / Reflection or specific Json processing libraries - see FsCodec.*.Codec for batteries-included Coding/Decoding
 type Codec =
 
     /// Generate a <code>IUnionEncoder</code> Codec suitable using the supplied pair of <c>encode</c> and <c>tryDecode</code> functions.
     // Leaving this helper private until we have a real use case which will e.g. enable us to decide whether to align the signature with the up/down functions
     //   employed in the convention-based Codec
     // (IME, while many systems have some code touching the metadata, it's not something one typically wants to encourage)
-    static member private Create<'Union,'Context>
-        (   /// Maps a 'Union to an Event Type Name with UTF-8 arrays representing the <c>Data</c> and <c>Meta</c> together with the correlationId, causationId and timestamp.
-            encode : 'Context option * 'Union -> string * byte[] * byte[] * string * string * System.DateTimeOffset option,
-            /// Attempts to map from an Event's Data to a <c>'Union</c> case, or <c>None</c> if not mappable.
-            tryDecode : ITimelineEvent<byte[]> -> 'Union option)
-        : IUnionEncoder<'Union, byte[], 'Context> =
-        { new IUnionEncoder<'Union, byte[], 'Context> with
+    static member private Create<'Union,'Format,'Context>
+        (   /// Maps a 'Union to an Event Type Name, a pair of <>'Format</c>'s representing the  <c>Data</c> and <c>Meta</c> together with the <c>correlationId</c>, <c>causationId</c> and <c>timestamp</c>.
+            encode : 'Context option * 'Union -> string * 'Format * 'Format * string * string * System.DateTimeOffset option,
+            /// Attempts to map from an Event's stored data to a <c>'Union</c> case, or <c>None</c> if not mappable.
+            tryDecode : ITimelineEvent<'Format> -> 'Union option)
+        : IUnionEncoder<'Union, 'Format, 'Context> =
+        { new IUnionEncoder<'Union, 'Format, 'Context> with
             member __.Encode(context, union) =
                 let eventType, data, metadata, correlationId, causationId, timestamp = encode (context,union)
                 Core.EventData.Create(eventType, data, metadata, correlationId, causationId, ?timestamp=timestamp) :> _
             member __.TryDecode encoded =
                 tryDecode encoded }
 
-    /// Generate a <code>IUnionEncoder</code> Codec suitable using the supplied <c>encode</c> and <c>tryDecode</code> functions to map to/from UTF8.
-    /// <c>mapCausation</c> provides metadata generation and correlation/causationId mapping based on the Context passed to the encoder
-    static member Create<'Context,'Union>
+    /// Generate a <code>IUnionEncoder</code> Codec suitable using the supplied <c>encode</c> and <c>tryDecode</code> functions to map to/from the stored form.
+    /// <c>mapCausation</c> provides metadata generation and correlation/causationId mapping based on the <c>context</c> passed to the encoder
+    static member Create<'Context,'Union,'Format>
         (   /// Maps from the TypeShape <c>UnionConverter</c> <c>'Contract</c> case the Event has been mapped to (with the raw event data as context)
             /// to the representation (typically a Discriminated Union) that is to be presented to the programming model.
-            tryDecode : FsCodec.ITimelineEvent<byte[]> -> 'Union option,
+            tryDecode : FsCodec.ITimelineEvent<'Format> -> 'Union option,
             /// Maps a fresh Event resulting from a Decision in the Domain representation type down to the TypeShape <c>UnionConverter</c> <c>'Contract</c>
             /// The function is also expected to derive
             ///   a <c>meta</c> object that will be serialized with the same settings (if it's not <c>None</c>)
             ///   and an Event Creation <c>timestamp</c>.
-            encode : 'Union -> string * byte[] * DateTimeOffset option,
+            encode : 'Union -> string * 'Format * DateTimeOffset option,
             /// Uses the 'Context passed to the Encode call and the 'Meta emitted by <c>down</c> to a) the final metadata b) the <c>correlationId</c> and c) the correlationId
-            mapCausation : 'Context option * 'Union -> byte[] * string * string,
-            /// Configuration to be used by the underlying <c>Newtonsoft.Json</c> Serializer when encoding/decoding. Defaults to same as <c>Settings.Create()</c>
-            ?settings,
-            /// Enables one to fail encoder generation if union contains nullary cases. Defaults to <c>false</c>, i.e. permitting them
-            ?rejectNullaryCases)
-        : FsCodec.IUnionEncoder<'Union,byte[],'Context> =
+            mapCausation : 'Context option * 'Union -> 'Format * string * string)
+        : FsCodec.IUnionEncoder<'Union,'Format,'Context> =
         let encode (context,union) =
             let et, d, t = encode union
             let m, correlationId, causationId = mapCausation (context, union)
             et, d, m, correlationId, causationId, t
         Codec.Create(encode,tryDecode)
 
     /// Generate a <code>IUnionEncoder</code> Codec using the supplied pair of <c>encode</c> and <c>tryDecode</code> functions.
-    static member Create<'Union>
+    static member Create<'Union,'Format when 'Format : null>
         (   /// Maps a <c>'Union</c> to an Event Type Name and a UTF-8 array representing the <c>Data</c>.
-            encode : 'Union -> string * byte[],
+            encode : 'Union -> string * 'Format,
             /// Attempts to map an Event Type Name and a UTF-8 <c>Data</c> array to a <c>'Union</c> case, or <c>None</c> if not mappable.
-            tryDecode : string * byte[] -> 'Union option)
-        : IUnionEncoder<'Union, byte[], obj> =
-        let encode' (_context,union) = let et, d = encode union in et, d, null, null, null, None
-        let tryDecode' (encoded : FsCodec.ITimelineEvent<_>) = tryDecode (encoded.EventType,encoded.Data)
+            tryDecode : string * 'Format -> 'Union option)
+        : IUnionEncoder<'Union, 'Format, obj> =
+        let encode' (_context : obj,union) = let (et, d : 'Format) = encode union in et, d, null, null, null, None
+        let tryDecode' (encoded : FsCodec.ITimelineEvent<'Format>) = tryDecode (encoded.EventType,encoded.Data)
         Codec.Create(encode', tryDecode')