From 7275214ceb59f457be439efb974960dd581f4ffc Mon Sep 17 00:00:00 2001
From: Kevin Schneider <schneider.kev@outlook.de>
Date: Fri, 23 Feb 2024 14:05:16 +0100
Subject: [PATCH] Add custom json formatter for `format: date`

---
 .../v3/DefinitionCompiler.fs                  |  4 ++++
 src/SwaggerProvider.Runtime/RuntimeHelpers.fs | 23 +++++++++++++++++++
 2 files changed, 27 insertions(+)

diff --git a/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs b/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
index a0e980d..93232cb 100644
--- a/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
+++ b/src/SwaggerProvider.DesignTime/v3/DefinitionCompiler.fs
@@ -263,6 +263,10 @@ type DefinitionCompiler(schema: OpenApiDocument, provideNullable) as this =
 
                         let pField, pProp = generateProperty propName pTy
 
+                        //
+                        if (schemaObj.Type, schemaObj.Format) = ("string", "date") then
+                            pProp.AddCustomAttribute(RuntimeHelpers.getDateTimeOffsetFullDateConverterAttribute())
+
                         if not <| String.IsNullOrWhiteSpace propSchema.Description then
                             pProp.AddXmlDoc propSchema.Description
 
diff --git a/src/SwaggerProvider.Runtime/RuntimeHelpers.fs b/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
index 07867b8..7cefc56 100644
--- a/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
+++ b/src/SwaggerProvider.Runtime/RuntimeHelpers.fs
@@ -2,6 +2,7 @@ namespace Swagger.Internal
 
 open System
 open System.Net.Http
+open System.Text.Json
 open System.Text.Json.Serialization
 open System.Threading.Tasks
 
@@ -18,6 +19,19 @@ module MediaTypes =
     [<Literal>]
     let MultipartFormData = "multipart/form-data"
 
+type DateTimeOffsetFullDateConverter() =
+
+    inherit JsonConverter<DateTimeOffset>()
+
+    override this.Read(reader: byref<Utf8JsonReader>, _typ: Type, options: JsonSerializerOptions) =
+        DateTimeOffset.Parse(reader.GetString())
+
+    override this.Write(writer: Utf8JsonWriter, value: DateTimeOffset, options: JsonSerializerOptions) =
+        writer.WriteStringValue(
+            // full-date: date-fullyear "-" date-month "-" date-mday according to https://datatracker.ietf.org/doc/html/rfc3339#section-5.6
+            // this format is required for strings with format 'date' according to https://swagger.io/docs/specification/data-models/data-types/
+            value.ToUniversalTime().ToString("yyyy-MM-dd")
+        )
 
 type AsyncExtensions() =
     static member cast<'t> asyncOp =
@@ -123,6 +137,15 @@ module RuntimeHelpers =
 
             member _.NamedArguments = [||] :> Collections.Generic.IList<_> }
 
+    let getDateTimeOffsetFullDateConverterAttribute() =
+        { new Reflection.CustomAttributeData() with
+            member _.Constructor = typeof<JsonConverterAttribute>.GetConstructor [| typeof<Type> |]
+
+            member _.ConstructorArguments =
+                [| Reflection.CustomAttributeTypedArgument(typeof<Type>, typeof<DateTimeOffsetFullDateConverter>) |] :> Collections.Generic.IList<_>
+
+            member _.NamedArguments = [||] :> Collections.Generic.IList<_> }
+
     let toStringContent(valueStr: string) =
         new StringContent(valueStr, Text.Encoding.UTF8, "application/json")