feat: Implement cache lookup value in emulator

src/Testing/Document/MockCacheLookupValueProvider.cs

@@ -35,5 +35,7 @@ internal Setup(
 
         public void WithCallback(Action<GatewayContext, CacheLookupValueConfig> callback) =>
             _handler.CallbackSetup.Add((_predicate, callback).ToTuple());
+
+        public void WithValue(object value) => _handler.ValueSetup.Add((_predicate, value).ToTuple());
     }
 }

src/Testing/Document/TestDocumentExtensions.cs

@@ -22,4 +22,7 @@ public static MockPoliciesProvider<IOnErrorContext> SetupOnError(this TestDocume
 
     public static CertificateStore SetupCertificateStore(this TestDocument document) =>
         document.Context.CertificateStore;
+
+    public static CacheStore SetupCacheStore(this TestDocument document) =>
+        document.Context.CacheStore;
 }

src/Testing/Emulator/Data/CacheStore.cs

@@ -0,0 +1,42 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+namespace Azure.ApiManagement.PolicyToolkit.Testing.Emulator.Data;
+
+public class CacheStore
+{
+    private readonly Dictionary<string, object> _internalCache = new();
+    private readonly Dictionary<string, object> _externalCache = new();
+
+    private bool _isExternalCacheSetup = false;
+
+    internal Dictionary<string, object>? GetCache(string type) =>
+        type switch
+        {
+            "internal" => _internalCache,
+            "external" => _isExternalCacheSetup ? _externalCache : null,
+            "prefer-external" => _isExternalCacheSetup ? _externalCache : _internalCache,
+            _ => throw new ArgumentException($"Unrecognized type {type}", nameof(type)),
+        };
+
+    public IReadOnlyDictionary<string, object> InternalCache => _internalCache;
+    public IReadOnlyDictionary<string, object> ExternalCache => _externalCache;
+
+    public CacheStore WithExternalCacheSetup(bool isSetup = true)
+    {
+        _isExternalCacheSetup = isSetup;
+        return this;
+    }
+
+    public CacheStore WithExternalCacheValue(string key, object value)
+    {
+        _externalCache.Add(key, value);
+        return this;
+    }
+
+    public CacheStore WithInternalCacheValue(string key, object value)
+    {
+        _internalCache.Add(key, value);
+        return this;
+    }
+}

src/Testing/Emulator/Policies/CacheLookupValueHandler.cs

@@ -13,10 +13,40 @@ namespace Azure.ApiManagement.PolicyToolkit.Testing.Emulator.Policies;
 ]
 internal class CacheLookupValueHandler : PolicyHandler<CacheLookupValueConfig>
 {
+    public List<Tuple<
+        Func<GatewayContext, CacheLookupValueConfig, bool>,
+        object
+    >> ValueSetup { get; } = new();
+
     public override string PolicyName => nameof(IInboundContext.CacheLookupValue);
 
     protected override void Handle(GatewayContext context, CacheLookupValueConfig config)
     {
-        throw new NotImplementedException();
+        var fromSetup = ValueSetup.Find(tuple => tuple.Item1(context, config))?.Item2;
+        if (fromSetup is not null)
+        {
+            context.Variables[config.VariableName] = fromSetup;
+            return;
+        }
+
+        var cachingType = config.CachingType ?? "prefer-external";
+
+
+        var store = context.CacheStore.GetCache(cachingType);
+        if (store is null)
+        {
+            return;
+        }
+
+        if (store.TryGetValue(config.Key, out var value))
+        {
+            context.Variables[config.VariableName] = value;
+            return;
+        }
+
+        if (config.DefaultValue is not null)
+        {
+            context.Variables[config.VariableName] = config.DefaultValue;
+        }
     }
 }

src/Testing/GatewayContext.cs

@@ -15,6 +15,7 @@ public class GatewayContext : MockExpressionContext
     internal readonly SectionContextProxy<IOutboundContext> OutboundProxy;
     internal readonly SectionContextProxy<IOnErrorContext> OnErrorProxy;
     internal readonly CertificateStore CertificateStore = new();
+    internal readonly CacheStore CacheStore = new();
 
     public GatewayContext()
     {

test/Test.Testing/Emulator/Policies/CacheLookupValueTests.cs

@@ -0,0 +1,157 @@
+// Copyright (c) Microsoft Corporation.
+// Licensed under the MIT License.
+
+using Azure.ApiManagement.PolicyToolkit.Authoring;
+using Azure.ApiManagement.PolicyToolkit.Testing;
+using Azure.ApiManagement.PolicyToolkit.Testing.Document;
+
+namespace Test.Emulator.Emulator.Policies;
+
+[TestClass]
+public class CacheLookupValueTests
+{
+    class SimpleCacheLookupValuePreferExternal : IDocument
+    {
+        public void Inbound(IInboundContext context)
+        {
+            context.CacheLookupValue(new CacheLookupValueConfig()
+            {
+                Key = "key", VariableName = "variable", CachingType = "prefer-external"
+            });
+        }
+    }
+
+    class SimpleCacheLookupValueFromInternal : IDocument
+    {
+        public void Inbound(IInboundContext context)
+        {
+            context.CacheLookupValue(new CacheLookupValueConfig()
+            {
+                Key = "key", VariableName = "variable", CachingType = "internal"
+            });
+        }
+    }
+
+    class SimpleCacheLookupValueFromExternal : IDocument
+    {
+        public void Inbound(IInboundContext context)
+        {
+            context.CacheLookupValue(new CacheLookupValueConfig()
+            {
+                Key = "key", VariableName = "variable", CachingType = "external"
+            });
+        }
+    }
+
+    class SimpleCacheLookupValueWithDefaultValue : IDocument
+    {
+        public void Inbound(IInboundContext context)
+        {
+            context.CacheLookupValue(new CacheLookupValueConfig()
+            {
+                Key = "key", VariableName = "variable", DefaultValue = "test-value"
+            });
+        }
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_Callback()
+    {
+        var test = new SimpleCacheLookupValuePreferExternal().AsTestDocument();
+        var executedCallback = false;
+        test.SetupInbound().CacheLookupValue().WithCallback((_, _) =>
+        {
+            executedCallback = true;
+        });
+
+        test.RunInbound();
+
+        executedCallback.Should().BeTrue();
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_WithValueCallback()
+    {
+        var test = new SimpleCacheLookupValuePreferExternal().AsTestDocument();
+        test.SetupInbound().CacheLookupValue().WithValue("test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().ContainKey("variable").WhoseValue.Should().Be("test");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_PreferExternal_SetupCacheStore_WithInternalValue()
+    {
+        var test = new SimpleCacheLookupValuePreferExternal().AsTestDocument();
+        test.SetupCacheStore().WithInternalCacheValue("key", "test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().ContainKey("variable").WhoseValue.Should().Be("test");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_PreferExternal_SetupCacheStore_WithExternalCacheSetup()
+    {
+        var test = new SimpleCacheLookupValuePreferExternal().AsTestDocument();
+        test.SetupCacheStore().WithExternalCacheSetup().WithExternalCacheValue("key", "test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().ContainKey("variable").WhoseValue.Should().Be("test");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_WithDefaultValue()
+    {
+        var test = new SimpleCacheLookupValueWithDefaultValue().AsTestDocument();
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().ContainKey("variable").WhoseValue.Should().Be("test-value");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_InternalCache_WillNotFindValueFromExternalCache()
+    {
+        var test = new SimpleCacheLookupValueFromInternal().AsTestDocument();
+        test.SetupCacheStore().WithExternalCacheSetup().WithExternalCacheValue("key", "test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().NotContainKey("variable");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_Internal_WillNotFindValueInInternalCache()
+    {
+        var test = new SimpleCacheLookupValueFromInternal().AsTestDocument();
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().NotContainKey("variable");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_ExternalCache_WillNotFindValueInInternalCache()
+    {
+        var test = new SimpleCacheLookupValueFromExternal().AsTestDocument();
+        test.SetupCacheStore().WithInternalCacheValue("key", "test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().NotContainKey("variable");
+    }
+
+    [TestMethod]
+    public void CacheLookupValue_ExternalCache_WillNotFindValue_WhenExternalCacheNotSetup()
+    {
+        var test = new SimpleCacheLookupValueFromExternal().AsTestDocument();
+        test.SetupCacheStore().WithExternalCacheValue("key", "test");
+
+        test.RunInbound();
+
+        test.Context.Variables.Should().NotContainKey("variable");
+    }
+}