[PM-1012] Feature access using context (#2764)

* Document online method

* Feature accessors with context

* Direct null assertion

* Establish a constants class for flag keys

src/Core/Constants.cs

@@ -22,3 +22,8 @@ public static class AuthenticationSchemes
 {
     public const string BitwardenExternalCookieAuthenticationScheme = "bw.external";
 }
+
+public static class FeatureFlagKeys
+{
+    public const string SecretsManager = "secrets-manager";
+}

src/Core/Services/IFeatureService.cs

@@ -1,6 +1,39 @@
-namespace Bit.Core.Services;
+using Bit.Core.Context;
+
+namespace Bit.Core.Services;
 
 public interface IFeatureService
 {
+    /// <summary>
+    /// Checks whether online access to feature status is available.
+    /// </summary>
+    /// <returns>True if the service is online, otherwise false.</returns>
     bool IsOnline();
+
+    /// <summary>
+    /// Checks whether a given feature is enabled.
+    /// </summary>
+    /// <param name="key">The key of the feature to check.</param>
+    /// <param name="currentContext">A context providing information that can be used to evaluate whether a feature should be on or off.</param>
+    /// <param name="defaultValue">The default value for the feature.</param>
+    /// <returns>True if the feature is enabled, otherwise false.</returns>
+    bool IsEnabled(string key, ICurrentContext currentContext, bool defaultValue = false);
+
+    /// <summary>
+    /// Gets the integer variation of a feature.
+    /// </summary>
+    /// <param name="key">The key of the feature to check.</param>
+    /// <param name="currentContext">A context providing information that can be used to evaluate the feature value.</param>
+    /// <param name="defaultValue">The default value for the feature.</param>
+    /// <returns>The feature variation value.</returns>
+    int GetIntVariation(string key, ICurrentContext currentContext, int defaultValue = 0);
+
+    /// <summary>
+    /// Gets the string variation of a feature.
+    /// </summary>
+    /// <param name="key">The key of the feature to check.</param>
+    /// <param name="currentContext">A context providing information that can be used to evaluate the feature value.</param>
+    /// <param name="defaultValue">The default value for the feature.</param>
+    /// <returns>The feature variation value.</returns>
+    string GetStringVariation(string key, ICurrentContext currentContext, string defaultValue = null);
 }

src/Core/Services/Implementations/LaunchDarklyFeatureService.cs

@@ -1,4 +1,5 @@
-using Bit.Core.Settings;
+using Bit.Core.Context;
+using Bit.Core.Settings;
 using LaunchDarkly.Sdk.Server;
 using LaunchDarkly.Sdk.Server.Integrations;
 
@@ -47,8 +48,44 @@ public class LaunchDarklyFeatureService : IFeatureService, IDisposable
         return _client.Initialized && !_client.IsOffline();
     }
 
+    public bool IsEnabled(string key, ICurrentContext currentContext, bool defaultValue = false)
+    {
+        return _client.BoolVariation(key, BuildContext(currentContext), defaultValue);
+    }
+
+    public int GetIntVariation(string key, ICurrentContext currentContext, int defaultValue = 0)
+    {
+        return _client.IntVariation(key, BuildContext(currentContext), defaultValue);
+    }
+
+    public string GetStringVariation(string key, ICurrentContext currentContext, string defaultValue = null)
+    {
+        return _client.StringVariation(key, BuildContext(currentContext), defaultValue);
+    }
+
     public void Dispose()
     {
         _client?.Dispose();
     }
+
+    private LaunchDarkly.Sdk.Context BuildContext(ICurrentContext currentContext)
+    {
+        var builder = LaunchDarkly.Sdk.Context.MultiBuilder();
+
+        if (currentContext.UserId.HasValue)
+        {
+            var user = LaunchDarkly.Sdk.Context.Builder(currentContext.UserId.Value.ToString());
+            user.Kind(LaunchDarkly.Sdk.ContextKind.Default);
+            builder.Add(user.Build());
+        }
+
+        if (currentContext.OrganizationId.HasValue)
+        {
+            var org = LaunchDarkly.Sdk.Context.Builder(currentContext.OrganizationId.Value.ToString());
+            org.Kind("org");
+            builder.Add(org.Build());
+        }
+
+        return builder.Build();
+    }
 }