feat: Flag metadata (open-feature#223)

Signed-off-by: Artyom Tonoyan <[email protected]>

src/OpenFeature/Model/BaseMetadata.cs

@@ -0,0 +1,76 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+
+#nullable enable
+namespace OpenFeature.Model;
+
+/// <summary>
+/// Represents the base class for metadata objects.
+/// </summary>
+public abstract class BaseMetadata
+{
+    private readonly ImmutableDictionary<string, object> _metadata;
+
+    internal BaseMetadata(Dictionary<string, object> metadata)
+    {
+        this._metadata = metadata.ToImmutableDictionary();
+    }
+
+    /// <summary>
+    /// Gets the boolean value associated with the specified key.
+    /// </summary>
+    /// <param name="key">The key of the value to retrieve.</param>
+    /// <returns>The boolean value associated with the key, or null if the key is not found.</returns>
+    public virtual bool? GetBool(string key)
+    {
+        return this.GetValue<bool>(key);
+    }
+
+    /// <summary>
+    /// Gets the integer value associated with the specified key.
+    /// </summary>
+    /// <param name="key">The key of the value to retrieve.</param>
+    /// <returns>The integer value associated with the key, or null if the key is not found.</returns>
+    public virtual int? GetInt(string key)
+    {
+        return this.GetValue<int>(key);
+    }
+
+    /// <summary>
+    /// Gets the double value associated with the specified key.
+    /// </summary>
+    /// <param name="key">The key of the value to retrieve.</param>
+    /// <returns>The double value associated with the key, or null if the key is not found.</returns>
+    public virtual double? GetDouble(string key)
+    {
+        return this.GetValue<double>(key);
+    }
+
+    /// <summary>
+    /// Gets the string value associated with the specified key.
+    /// </summary>
+    /// <param name="key">The key of the value to retrieve.</param>
+    /// <returns>The string value associated with the key, or null if the key is not found.</returns>
+    public virtual string? GetString(string key)
+    {
+        var hasValue = this._metadata.TryGetValue(key, out var value);
+        if (!hasValue)
+        {
+            return null;
+        }
+
+        return value as string ?? null;
+    }
+
+    private T? GetValue<T>(string key) where T : struct
+    {
+        var hasValue = this._metadata.TryGetValue(key, out var value);
+        if (!hasValue)
+        {
+            return null;
+        }
+
+        return value is T tValue ? tValue : null;
+    }
+}

src/OpenFeature/Model/FlagEvaluationDetails.cs

@@ -6,7 +6,7 @@ namespace OpenFeature.Model
     /// The contract returned to the caller that describes the result of the flag evaluation process.
     /// </summary>
     /// <typeparam name="T">Flag value type</typeparam>
-    /// <seealso href="https://github.com/open-feature/spec/blob/v0.5.2/specification/types.md#evaluation-details"/>
+    /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#evaluation-details"/>
     public sealed class FlagEvaluationDetails<T>
     {
         /// <summary>
@@ -45,6 +45,11 @@ public sealed class FlagEvaluationDetails<T>
         /// </summary>
         public string Variant { get; }
 
+        /// <summary>
+        /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
+        /// </summary>
+        public FlagMetadata FlagMetadata { get; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="FlagEvaluationDetails{T}"/> class.
         /// </summary>
@@ -54,15 +59,17 @@ public sealed class FlagEvaluationDetails<T>
         /// <param name="reason">Reason</param>
         /// <param name="variant">Variant</param>
         /// <param name="errorMessage">Error message</param>
+        /// <param name="flagMetadata">Flag metadata</param>
         public FlagEvaluationDetails(string flagKey, T value, ErrorType errorType, string reason, string variant,
-            string errorMessage = null)
+            string errorMessage = null, FlagMetadata flagMetadata = null)
         {
             this.Value = value;
             this.FlagKey = flagKey;
             this.ErrorType = errorType;
             this.Reason = reason;
             this.Variant = variant;
             this.ErrorMessage = errorMessage;
+            this.FlagMetadata = flagMetadata;
         }
     }
 }

src/OpenFeature/Model/FlagMetadata.cs

@@ -0,0 +1,28 @@
+using System;
+using System.Collections.Generic;
+using System.Collections.Immutable;
+
+#nullable enable
+namespace OpenFeature.Model;
+
+/// <summary>
+/// Represents the metadata associated with a feature flag.
+/// </summary>
+/// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#flag-metadata"/>
+public sealed class FlagMetadata : BaseMetadata
+{
+    /// <summary>
+    /// Constructor for the <see cref="BaseMetadata"/> class.
+    /// </summary>
+    public FlagMetadata() : this([])
+    {
+    }
+
+    /// <summary>
+    /// Constructor for the <see cref="BaseMetadata"/> class.
+    /// </summary>
+    /// <param name="metadata">The dictionary containing the metadata.</param>
+    public FlagMetadata(Dictionary<string, object> metadata) : base(metadata)
+    {
+    }
+}

src/OpenFeature/Model/ProviderEvents.cs

@@ -36,6 +36,7 @@ public class ProviderEventPayload
         /// <summary>
         /// Metadata information for the event.
         /// </summary>
+        // TODO: This needs to be changed to a EventMetadata object
         public Dictionary<string, object> EventMetadata { get; set; }
     }
 }

src/OpenFeature/Model/ResolutionDetails.cs

@@ -7,7 +7,7 @@ namespace OpenFeature.Model
     /// Describes the details of the feature flag being evaluated
     /// </summary>
     /// <typeparam name="T">Flag value type</typeparam>
-    /// <seealso href="https://github.com/open-feature/spec/blob/v0.5.2/specification/types.md#resolution-details"/>
+    /// <seealso href="https://github.com/open-feature/spec/blob/v0.7.0/specification/types.md#resolution-details"/>
     public sealed class ResolutionDetails<T>
     {
         /// <summary>
@@ -44,6 +44,11 @@ public sealed class ResolutionDetails<T>
         /// </summary>
         public string Variant { get; }
 
+        /// <summary>
+        /// A structure which supports definition of arbitrary properties, with keys of type string, and values of type boolean, string, or number.
+        /// </summary>
+        public FlagMetadata FlagMetadata { get; }
+
         /// <summary>
         /// Initializes a new instance of the <see cref="ResolutionDetails{T}"/> class.
         /// </summary>
@@ -53,15 +58,17 @@ public sealed class ResolutionDetails<T>
         /// <param name="reason">Reason</param>
         /// <param name="variant">Variant</param>
         /// <param name="errorMessage">Error message</param>
+        /// <param name="flagMetadata">Flag metadata</param>
         public ResolutionDetails(string flagKey, T value, ErrorType errorType = ErrorType.None, string reason = null,
-            string variant = null, string errorMessage = null)
+            string variant = null, string errorMessage = null, FlagMetadata flagMetadata = null)
         {
             this.Value = value;
             this.FlagKey = flagKey;
             this.ErrorType = errorType;
             this.Reason = reason;
             this.Variant = variant;
             this.ErrorMessage = errorMessage;
+            this.FlagMetadata = flagMetadata;
         }
     }
 }