Collapse the DefaultApiVersionGroupDescriptionProvider into the GroupedApiVersionDescriptionProvider and remove it

Author: commonsensesoftware

src/AspNetCore/WebApi/src/Asp.Versioning.Mvc.ApiExplorer/GroupedApiVersionDescriptionProvider.cs

@@ -2,16 +2,18 @@
 
 namespace Asp.Versioning.ApiExplorer;
 
-using Asp.Versioning.ApiExplorer.Internal;
 using Microsoft.Extensions.Options;
+using static Asp.Versioning.ApiVersionMapping;
+using static System.Globalization.CultureInfo;
 
 /// <summary>
-/// Represents the default implementation of an object that discovers and describes the API version information within an application.
+/// Represents the default implementation of an object that discovers and describes the API version information within
+/// an application.
 /// </summary>
 [CLSCompliant( false )]
 public class GroupedApiVersionDescriptionProvider : IApiVersionDescriptionProvider
 {
-    private readonly ApiVersionDescriptionCollection<GroupedApiVersionMetadata> collection;
+    private readonly ApiVersionDescriptionCollection collection;
     private readonly IOptions<ApiExplorerOptions> options;
 
     /// <summary>
@@ -72,11 +74,7 @@ protected virtual IReadOnlyList<ApiVersionDescription> Describe( IReadOnlyList<G
     /// <summary>
     /// Represents the API version metadata applied to an endpoint with an optional group name.
     /// </summary>
-    protected class GroupedApiVersionMetadata :
-        ApiVersionMetadata,
-        IEquatable<GroupedApiVersionMetadata>,
-        IGroupedApiVersionMetadata,
-        IGroupedApiVersionMetadataFactory<GroupedApiVersionMetadata>
+    protected class GroupedApiVersionMetadata : ApiVersionMetadata, IEquatable<GroupedApiVersionMetadata>
     {
         /// <summary>
         /// Initializes a new instance of the <see cref="GroupedApiVersionMetadata"/> class.
@@ -92,10 +90,6 @@ public GroupedApiVersionMetadata( string? groupName, ApiVersionMetadata metadata
         /// <value>The associated group name, if any.</value>
         public string? GroupName { get; }
 
-        static GroupedApiVersionMetadata IGroupedApiVersionMetadataFactory<GroupedApiVersionMetadata>.New(
-            string? groupName,
-            ApiVersionMetadata metadata ) => new( groupName, metadata );
-
         /// <inheritdoc />
         public bool Equals( GroupedApiVersionMetadata? other ) =>
             other is not null && other.GetHashCode() == GetHashCode();
@@ -121,4 +115,202 @@ public override int GetHashCode()
             return hash.ToHashCode();
         }
     }
+
+    private record struct GroupedApiVersion( string? GroupName, ApiVersion ApiVersion );
+
+    private sealed class ApiVersionDescriptionCollection(
+        Func<IReadOnlyList<GroupedApiVersionMetadata>, IReadOnlyList<ApiVersionDescription>> describe,
+        IEnumerable<IApiVersionMetadataCollationProvider> collators )
+    {
+        private readonly Lock syncRoot = new();
+        private readonly Func<IReadOnlyList<GroupedApiVersionMetadata>, IReadOnlyList<ApiVersionDescription>> describe = describe;
+        private readonly IApiVersionMetadataCollationProvider[] collators = [.. collators];
+        private IReadOnlyList<ApiVersionDescription>? items;
+        private int version;
+
+        public IReadOnlyList<ApiVersionDescription> Items
+        {
+            get
+            {
+                if ( items is not null && version == ComputeVersion() )
+                {
+                    return items;
+                }
+
+                using ( syncRoot.EnterScope() )
+                {
+                    var currentVersion = ComputeVersion();
+
+                    if ( items is not null && version == currentVersion )
+                    {
+                        return items;
+                    }
+
+                    var context = new ApiVersionMetadataCollationContext();
+
+                    for ( var i = 0; i < collators.Length; i++ )
+                    {
+                        collators[i].Execute( context );
+                    }
+
+                    var results = context.Results;
+                    var metadata = new GroupedApiVersionMetadata[results.Count];
+
+                    for ( var i = 0; i < metadata.Length; i++ )
+                    {
+                        metadata[i] = new GroupedApiVersionMetadata( context.Results.GroupName( i ), results[i] );
+                    }
+
+                    items = describe( metadata );
+                    version = currentVersion;
+                }
+
+                return items;
+            }
+        }
+
+        private int ComputeVersion() =>
+            collators.Length switch
+            {
+                0 => 0,
+                1 => collators[0].Version,
+                _ => ComputeVersion( collators ),
+            };
+
+        private static int ComputeVersion( IApiVersionMetadataCollationProvider[] providers )
+        {
+            var hash = default( HashCode );
+
+            for ( var i = 0; i < providers.Length; i++ )
+            {
+                hash.Add( providers[i].Version );
+            }
+
+            return hash.ToHashCode();
+        }
+    }
+
+    private sealed class ApiVersionDescriptionComparer : IComparer<ApiVersionDescription>
+    {
+        public int Compare( ApiVersionDescription? x, ApiVersionDescription? y )
+        {
+            if ( x is null )
+            {
+                return y is null ? 0 : -1;
+            }
+
+            if ( y is null )
+            {
+                return 1;
+            }
+
+            var result = x.ApiVersion.CompareTo( y.ApiVersion );
+
+            if ( result == 0 )
+            {
+                result = StringComparer.Ordinal.Compare( x.GroupName, y.GroupName );
+            }
+
+            return result;
+        }
+    }
+
+    private static class DescriptionProvider
+    {
+        internal static ApiVersionDescription[] Describe(
+            IReadOnlyList<GroupedApiVersionMetadata> metadata,
+            ISunsetPolicyManager sunsetPolicyManager,
+            ApiExplorerOptions options )
+        {
+            var descriptions = new SortedSet<ApiVersionDescription>( new ApiVersionDescriptionComparer() );
+            var supported = new HashSet<GroupedApiVersion>();
+            var deprecated = new HashSet<GroupedApiVersion>();
+
+            BucketizeApiVersions( metadata, supported, deprecated, options );
+            AppendDescriptions( descriptions, supported, sunsetPolicyManager, options, deprecated: false );
+            AppendDescriptions( descriptions, deprecated, sunsetPolicyManager, options, deprecated: true );
+
+            return [.. descriptions];
+        }
+
+        private static void BucketizeApiVersions(
+            IReadOnlyList<GroupedApiVersionMetadata> list,
+            HashSet<GroupedApiVersion> supported,
+            HashSet<GroupedApiVersion> deprecated,
+            ApiExplorerOptions options )
+        {
+            var declared = new HashSet<GroupedApiVersion>();
+            var advertisedSupported = new HashSet<GroupedApiVersion>();
+            var advertisedDeprecated = new HashSet<GroupedApiVersion>();
+
+            for ( var i = 0; i < list.Count; i++ )
+            {
+                var metadata = list[i];
+                var groupName = metadata.GroupName;
+                var model = metadata.Map( Explicit | Implicit );
+                var versions = model.DeclaredApiVersions;
+
+                for ( var j = 0; j < versions.Count; j++ )
+                {
+                    declared.Add( new( groupName, versions[j] ) );
+                }
+
+                versions = model.SupportedApiVersions;
+
+                for ( var j = 0; j < versions.Count; j++ )
+                {
+                    var version = versions[j];
+                    supported.Add( new( groupName, version ) );
+                    advertisedSupported.Add( new( groupName, version ) );
+                }
+
+                versions = model.DeprecatedApiVersions;
+
+                for ( var j = 0; j < versions.Count; j++ )
+                {
+                    var version = versions[j];
+                    deprecated.Add( new( groupName, version ) );
+                    advertisedDeprecated.Add( new( groupName, version ) );
+                }
+            }
+
+            advertisedSupported.ExceptWith( declared );
+            advertisedDeprecated.ExceptWith( declared );
+            supported.ExceptWith( advertisedSupported );
+            deprecated.ExceptWith( supported.Concat( advertisedDeprecated ) );
+
+            if ( supported.Count == 0 && deprecated.Count == 0 )
+            {
+                supported.Add( new( default, options.DefaultApiVersion ) );
+            }
+        }
+
+        private static void AppendDescriptions(
+            SortedSet<ApiVersionDescription> descriptions,
+            HashSet<GroupedApiVersion> versions,
+            ISunsetPolicyManager sunsetPolicyManager,
+            ApiExplorerOptions options,
+            bool deprecated )
+        {
+            var format = options.GroupNameFormat;
+            var formatGroupName = options.FormatGroupName;
+
+            foreach ( var (groupName, version) in versions )
+            {
+                var formattedGroupName = groupName;
+
+                if ( string.IsNullOrEmpty( formattedGroupName ) )
+                {
+                    formattedGroupName = version.ToString( format, CurrentCulture );
+                }
+                else if ( formatGroupName is not null )
+                {
+                    formattedGroupName = formatGroupName( formattedGroupName, version.ToString( format, CurrentCulture ) );
+                }
+
+                var sunsetPolicy = sunsetPolicyManager.TryGetPolicy( version, out var policy ) ? policy : default;
+                descriptions.Add( new( version, formattedGroupName, deprecated, sunsetPolicy ) );
+            }
+        }
+    }
 }