Extract PolicyBuilder base interface

Author: Matthias Gessinger

src/Abstractions/src/Asp.Versioning.Abstractions/IPolicyBuilder.cs

@@ -0,0 +1,35 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+
+namespace Asp.Versioning;
+
+/// <summary>
+/// Defines the behavior of a policy builder which applies to a single API version.
+/// </summary>
+/// <typeparam name="TPolicy">The type of policy which is built by this builder.</typeparam>
+public interface IPolicyBuilder<TPolicy>
+{
+    /// <summary>
+    /// Gets the policy name.
+    /// </summary>
+    /// <value>The policy name, if any.</value>
+    /// <remarks>The name is typically of an API.</remarks>
+    string? Name { get; }
+
+    /// <summary>
+    /// Gets the API version the policy is for.
+    /// </summary>
+    /// <value>The specific policy <see cref="ApiVersion">API version</see>, if any.</value>
+    ApiVersion? ApiVersion { get; }
+
+    /// <summary>
+    /// Configures the builder per the specified <paramref name="policy"/>.
+    /// </summary>
+    /// <param name="policy">The applied <typeparamref name="TPolicy">policy</typeparamref>.</param>
+    void Per( TPolicy policy );
+
+    /// <summary>
+    /// Builds and returns a policy.
+    /// </summary>
+    /// <returns>A new <typeparamref name="TPolicy">policy</typeparamref>.</returns>
+    TPolicy Build();
+}

src/Abstractions/src/Asp.Versioning.Abstractions/ISunsetPolicyBuilder.cs

@@ -5,26 +5,14 @@ namespace Asp.Versioning;
 /// <summary>
 /// Defines the behavior of a sunset policy builder.
 /// </summary>
-public interface ISunsetPolicyBuilder
+public interface ISunsetPolicyBuilder : IPolicyBuilder<SunsetPolicy>
 {
     /// <summary>
-    /// Gets the policy name.
-    /// </summary>
-    /// <value>The policy name, if any.</value>
-    /// <remarks>The name is typically of an API.</remarks>
-    string? Name { get; }
-
-    /// <summary>
-    /// Gets the API version the policy is for.
-    /// </summary>
-    /// <value>The specific policy <see cref="ApiVersion">API version</see>, if any.</value>
-    ApiVersion? ApiVersion { get; }
-
-    /// <summary>
-    /// Applies a sunset policy per the specified policy.
+    /// Creates and returns a new link builder.
     /// </summary>
-    /// <param name="policy">The applied <see cref="SunsetPolicy">sunset policy</see>.</param>
-    void Per( SunsetPolicy policy );
+    /// <param name="linkTarget">The link target URL.</param>
+    /// <returns>A new <see cref="ILinkBuilder">link builder</see>.</returns>
+    ILinkBuilder Link( Uri linkTarget );
 
     /// <summary>
     /// Indicates when a sunset policy is applied.
@@ -33,17 +21,4 @@ public interface ISunsetPolicyBuilder
     /// sunset policy is applied.</param>
     /// <returns>The current <see cref="ISunsetPolicyBuilder">sunset policy builder</see>.</returns>
     ISunsetPolicyBuilder Effective( DateTimeOffset sunsetDate );
-
-    /// <summary>
-    /// Creates and returns a new link builder.
-    /// </summary>
-    /// <param name="linkTarget">The link target URL.</param>
-    /// <returns>A new <see cref="ILinkBuilder">link builder</see>.</returns>
-    ILinkBuilder Link( Uri linkTarget );
-
-    /// <summary>
-    /// Builds and returns a sunset policy.
-    /// </summary>
-    /// <returns>A new <see cref="SunsetPolicy">sunset policy</see>.</returns>
-    SunsetPolicy Build();
 }

src/Common/src/Common/PolicyBuilder.cs

@@ -0,0 +1,48 @@
+// Copyright (c) .NET Foundation and contributors. All rights reserved.
+
+namespace Asp.Versioning;
+
+using System.Globalization;
+
+/// <summary>
+/// Represents the default policy builder.
+/// </summary>
+/// <typeparam name="TPolicy">The type of policy.</typeparam>
+public abstract class PolicyBuilder<TPolicy> : IPolicyBuilder<TPolicy>
+{
+    /// <summary>
+    /// Gets a pre-built policy.
+    /// </summary>
+    /// <value>The pre-built policy, if it exists.</value>
+    protected TPolicy? Policy { get; private set; }
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="PolicyBuilder{T}"/> class.
+    /// </summary>
+    /// <param name="name">The name of the API the policy is for.</param>
+    /// <param name="apiVersion">The <see cref="ApiVersion">API version</see> the policy is for.</param>
+    public PolicyBuilder( string? name, ApiVersion? apiVersion )
+    {
+        if ( string.IsNullOrEmpty( name ) && apiVersion == null )
+        {
+            var message = string.Format( CultureInfo.CurrentCulture, Format.InvalidPolicyKey, nameof( name ), nameof( apiVersion ) );
+            throw new System.ArgumentException( message );
+        }
+
+        Name = name;
+        ApiVersion = apiVersion;
+    }
+
+    /// <inheritdoc />
+    public string? Name { get; }
+
+    /// <inheritdoc />
+    public ApiVersion? ApiVersion { get; }
+
+    /// <inheritdoc />
+    public virtual void Per( TPolicy policy ) =>
+        Policy = policy ?? throw new System.ArgumentNullException( nameof( policy ) );
+
+    /// <inheritdoc />
+    public abstract TPolicy Build();
+}

src/Common/src/Common/SunsetPolicyBuilder.cs

@@ -2,14 +2,11 @@
 
 namespace Asp.Versioning;
 
-using System.Globalization;
-
 /// <summary>
 /// Represents the default sunset policy builder.
 /// </summary>
-public class SunsetPolicyBuilder : ISunsetPolicyBuilder
+public class SunsetPolicyBuilder : PolicyBuilder<SunsetPolicy>, ISunsetPolicyBuilder
 {
-    private SunsetPolicy? sunsetPolicy;
     private DateTimeOffset? date;
     private SunsetLinkBuilder? linkBuilder;
     private Dictionary<Uri, SunsetLinkBuilder>? linkBuilders;
@@ -20,26 +17,7 @@ public class SunsetPolicyBuilder : ISunsetPolicyBuilder
     /// <param name="name">The name of the API the policy is for.</param>
     /// <param name="apiVersion">The <see cref="ApiVersion">API version</see> the policy is for.</param>
     public SunsetPolicyBuilder( string? name, ApiVersion? apiVersion )
-    {
-        if ( string.IsNullOrEmpty( name ) && apiVersion == null )
-        {
-            var message = string.Format( CultureInfo.CurrentCulture, Format.InvalidPolicyKey, nameof( name ), nameof( apiVersion ) );
-            throw new System.ArgumentException( message );
-        }
-
-        Name = name;
-        ApiVersion = apiVersion;
-    }
-
-    /// <inheritdoc />
-    public string? Name { get; }
-
-    /// <inheritdoc />
-    public ApiVersion? ApiVersion { get; }
-
-    /// <inheritdoc />
-    public virtual void Per( SunsetPolicy policy ) =>
-        sunsetPolicy = policy ?? throw new System.ArgumentNullException( nameof( policy ) );
+        : base( name, apiVersion ) { }
 
     /// <inheritdoc />
     public virtual ISunsetPolicyBuilder Effective( DateTimeOffset sunsetDate )
@@ -78,11 +56,11 @@ public virtual ILinkBuilder Link( Uri linkTarget )
     }
 
     /// <inheritdoc />
-    public virtual SunsetPolicy Build()
+    public override SunsetPolicy Build()
     {
-        if ( sunsetPolicy is not null )
+        if ( Policy is not null )
         {
-            return sunsetPolicy;
+            return Policy;
         }
 
         SunsetPolicy policy = date is null ? new() : new( date.Value );