/* ========================================================================
 * Copyright (c) 2005-2025 The OPC Foundation, Inc. All rights reserved.
 *
 * OPC Foundation MIT License 1.00
 *
 * Permission is hereby granted, free of charge, to any person
 * obtaining a copy of this software and associated documentation
 * files (the "Software"), to deal in the Software without
 * restriction, including without limitation the rights to use,
 * copy, modify, merge, publish, distribute, sublicense, and/or sell
 * copies of the Software, and to permit persons to whom the
 * Software is furnished to do so, subject to the following
 * conditions:
 *
 * The above copyright notice and this permission notice shall be
 * included in all copies or substantial portions of the Software.
 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND,
 * EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES
 * OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT
 * HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY,
 * WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING
 * FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR
 * OTHER DEALINGS IN THE SOFTWARE.
 *
 * The complete license agreement can be found here:
 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

using System;
using System.Collections.Generic;
using System.Collections.Immutable;
using System.IO;
using System.Linq;
using System.Text;
using System.Xml;
using Microsoft.Extensions.Logging;
using Moq;
using NUnit.Framework;
using Opc.Ua.Schema.Model;
using Opc.Ua.Tests;

namespace Opc.Ua.SourceGeneration.Generator.Tests
{
    /// <summary>
    /// Snapshot tests for the <see cref="FluentBuilderGenerator"/>: verify
    /// the opt-in flag, the type-and-instance wrapper shape, the typed
    /// IVariableBuilder accessors, and the typed sync/async OnCall
    /// overloads on method wrappers.
    /// </summary>
    [TestFixture]
    [Category("Generator")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [Parallelizable(ParallelScope.All)]
    public class FluentBuilderGeneratorTests
    {
        [Test]
        public void Emit_WithoutOptIn_ProducesNoFluentBuildersFile()
        {
            Dictionary<string, string> files = GenerateForTestModel(generateNodeManager: false);

            Assert.That(files.Keys, Has.None.EndsWith(".FluentBuilders.g.cs"));
        }

        [Test]
        public void Emit_WithOptIn_ProducesFluentBuildersFile()
        {
            Dictionary<string, string> files = GenerateForTestModel(generateNodeManager: true);

            Assert.That(files.Keys, Has.Some.EndsWith(".FluentBuilders.g.cs"),
                "Generator should emit a FluentBuilders file when GenerateNodeManager=true");
        }

        [Test]
        public void EmittedFluentBuilders_HasTypedManagerInterfaceAndProxy()
        {
            string fb = GetFluentBuilders();

            Assert.That(fb, Does.Match(
                @"internal\s+interface\s+I\w+NodeManagerBuilder\s*:\s*" +
                @"global::Opc\.Ua\.Server\.Fluent\.INodeManagerBuilder"),
                "A typed IBuilder interface extending INodeManagerBuilder must be emitted");

            Assert.That(fb, Does.Match(
                @"internal\s+sealed\s+class\s+\w+NodeManagerTypedBuilder\s*:\s*I\w+NodeManagerBuilder"),
                "A typed proxy implementing the IBuilder must be emitted");

            Assert.That(fb, Does.Contain("private readonly global::Opc.Ua.Server.Fluent.INodeManagerBuilder __inner"),
                "The proxy must wrap an INodeManagerBuilder");
        }

        [Test]
        public void EmittedFluentBuilders_AreAutoGenerated_AndUseGlobalQualifiedTypes()
        {
            string fb = GetFluentBuilders();

            Assert.That(fb, Does.StartWith("// <auto-generated />"),
                "FluentBuilders file must start with the auto-generated marker");
            Assert.That(fb, Does.Contain("[global::System.CodeDom.Compiler.GeneratedCodeAttribute("),
                "FluentBuilders file must carry the GeneratedCode attribute");
            Assert.That(fb, Does.Contain("#pragma warning disable"),
                "FluentBuilders file must suppress warnings to survive strict consumer projects");
        }

        [Test]
        public void EmittedFluentBuilders_WrappersAreInternalSealed()
        {
            string fb = GetFluentBuilders();

            // Per design decision #8 — wrappers are internal sealed because
            // Configure is a private partial. Public exposure would add a
            // surface that can never be called outside the assembly.
            Assert.That(fb, Does.Match(@"internal\s+sealed\s+class\s+\w+Builder\b"),
                "Wrapper classes should be 'internal sealed'");
            Assert.That(fb, Does.Not.Match(@"public\s+(sealed\s+)?class\s+\w+Builder\b"),
                "Wrapper classes must not be public");
        }

        [Test]
        public void EmittedFluentBuilders_VariableAccessorsReturnTypedIVariableBuilder()
        {
            string fb = GetFluentBuilders();

            // TestModel's RestrictedObjectType has a Mandatory variable child
            // 'Red' of type RestrictedVariableType (Int32). The wrapper for
            // the predefined TestObject instance must surface that variable
            // through a typed IVariableBuilder<int> accessor.
            Assert.That(fb, Does.Match(
                @"public\s+global::Opc\.Ua\.Server\.Fluent\.IVariableBuilder<\w+>\s+\w+\s*\{"),
                "Variable children should expose IVariableBuilder<TValue> accessors");

            // Each accessor lazily resolves the namespace index to support
            // cross-namespace browse names (NamespaceUris.GetIndexOrAppend).
            Assert.That(fb, Does.Contain("Context.NamespaceUris.GetIndexOrAppend("),
                "Variable accessors should resolve the namespace via GetIndexOrAppend");
            Assert.That(fb, Does.Match(
                @"return\s+__node\.Variable<\w+>\(new global::Opc\.Ua\.QualifiedName\("),
                "Variable accessors should fall back to INodeBuilder.Variable<T>()");
        }

        [Test]
        public void EmittedFluentBuilders_MethodWrappersExposeSyncAndAsyncOnCall()
        {
            string fb = GetFluentBuilders();

            // Every method wrapper must offer BOTH sync and async OnCall
            // overloads so user code-behind can choose the natural shape.
            Assert.That(fb, Does.Match(
                @"public\s+\w+MethodBuilder\s+OnCall\s*\(\s*global::System\.Action\s+handler\s*\)"),
                "Method wrappers should expose a sync OnCall(Action) overload");
            Assert.That(fb, Does.Match(
                @"public\s+\w+MethodBuilder\s+OnCall\s*\(\s*" +
                @"global::System\.Func<global::System\.Threading\.CancellationToken,\s*" +
                @"global::System\.Threading\.Tasks\.ValueTask>\s+handler\s*\)"),
                "Method wrappers should expose an async OnCall(Func<CT,ValueTask>) overload");
        }

        [Test]
        public void EmittedFluentBuilders_InstanceAccessorsAreLazyAndAllocateChildBuilder()
        {
            string fb = GetFluentBuilders();

            // Child accessors should never cache — each get materializes a
            // fresh wrapper around an INodeBuilder<TChildState>. Caching
            // would be unsafe because INodeBuilder identity is per-resolution.
            Assert.That(fb, Does.Not.Match(@"private\s+\w+Builder\s+__child"),
                "Child accessors must not cache the wrapper");
            Assert.That(fb, Does.Match(
                @"return\s+new\s+\w+Builder\s*\(\s*__node\.Child<\w+"),
                "Object child accessors should resolve via INodeBuilder.Child<T>()");
        }

        [Test]
        public void EmittedFluentBuilders_TopLevelInstanceWrapperLivesAtNamespaceScope()
        {
            string fb = GetFluentBuilders();

            // Top-level wrappers must sit directly under the namespace
            // body — i.e. at column 4 (one level into the namespace block
            // emitted by FluentBuilderTemplates.File). Use TestObject as
            // an exemplar — TestModel.xml declares it as a top-level
            // instance.
            Assert.That(fb, Does.Match(@"(?m)^    internal sealed class TestObjectBuilder\b"),
                "Top-level wrappers must be declared at namespace scope (column 4)");
        }

        [Test]
        public void EmittedFluentBuildersObjectWrapperUsesTypeDefinitionState()
        {
            string fb = GetFluentBuilders();

            Assert.That(
                fb,
                Does.Match(
                    @"(?ms)internal\s+sealed\s+class\s+TestObjectBuilder\b.*?" +
                    @"INodeBuilder<global::TestModel\.RestrictedObjectState>\s+__node;"),
                "An object wrapper with a resolved TypeDefinition must use its concrete generated State type");
        }

        [Test]
        public void EmittedFluentBuilders_MethodWrapperIsNestedInsideOwningObject()
        {
            string fb = GetFluentBuilders();

            // TestObject's RestrictedObjectType has a Mandatory Method
            // child 'Blue'. Its wrapper class must be nested one level
            // inside TestObjectBuilder — i.e. declared at column 8.
            Assert.That(fb, Does.Match(
                @"(?m)^        internal sealed class BlueMethodBuilder\b"),
                "Method wrappers must be nested inside the owning object's wrapper (column 8)");
        }

        [Test]
        public void EmittedFluentBuilders_ChildAccessorReturnsSimpleLeafName()
        {
            string fb = GetFluentBuilders();

            // Child accessors should return the simple leaf name only
            // (e.g. 'BlueMethodBuilder') because the wrapper is nested
            // inside the parent, not the old flat
            // 'TestObject_BlueMethodBuilder' identifier.
            Assert.That(fb, Does.Not.Match(@"public\s+TestObject_\w+Builder\s+\w+"),
                "Child accessors must reference the simple leaf-name wrapper, not a flat dotted identifier");
            Assert.That(fb, Does.Match(@"public\s+BlueMethodBuilder\s+Blue\b"),
                "Child accessor for 'Blue' should return the simple-leaf-name 'BlueMethodBuilder'");
        }

        [Test]
        public void MethodWithIntInputAndOutputEmitsTypedSyncOverload()
        {
            string fb = GetFluentBuilders();

            // TestModel's MathInstance has a Mandatory method 'Compute'
            // declared inline with InputArguments(x: Int32) and
            // OutputArguments(result: Int32). The generator must surface
            // a typed sync OnCall overload that maps Variant<-> int both
            // ways without requiring the user to touch ArrayOf<Variant>.
            Assert.That(fb, Does.Match(
                @"public\s+ComputeMethodBuilder\s+OnCall\s*\(\s*global::System\.Func<int,\s*int>\s+handler\s*\)"),
                "Compute(Int32 -> Int32) should expose a sync OnCall(Func<int,int>) overload");
        }

        [Test]
        public void MethodWithIntInputAndOutputEmitsTypedAsyncOverload()
        {
            string fb = GetFluentBuilders();

            // The async overload threads CancellationToken between the
            // unpacked inputs and the ValueTask<TResult> return type.
            Assert.That(fb, Does.Match(
                @"public\s+ComputeMethodBuilder\s+OnCall\s*\(\s*" +
                @"global::System\.Func<int,\s*" +
                @"global::System\.Threading\.CancellationToken,\s*" +
                @"global::System\.Threading\.Tasks\.ValueTask<int>>\s+handler\s*\)"),
                "Compute(Int32 -> Int32) should expose an async OnCall(Func<int,CT,ValueTask<int>>) overload");
        }

        [Test]
        public void MethodInputUnpackUsesVariantTryGetValue()
        {
            string fb = GetFluentBuilders();

            // Inputs flow through Variant.TryGetValue<T>(out T) so the
            // generated lambda short-circuits with BadInvalidArgument when
            // the caller sends the wrong wire type.
            Assert.That(fb, Does.Match(
                @"if\s*\(!__inputs\[0\]\.TryGetValue\(out\s+int\s+__a0\)\)"),
                "Input unpack should use Variant.TryGetValue<T>(out T) for primitive inputs");
            Assert.That(fb, Does.Contain(
                "return new global::Opc.Ua.ServiceResult(global::Opc.Ua.StatusCodes.BadInvalidArgument);"),
                "Failed input unpack should return BadInvalidArgument");
            Assert.That(fb, Does.Contain(
                "return new global::Opc.Ua.ServiceResult(global::Opc.Ua.StatusCodes.BadArgumentsMissing);"),
                "Missing input arg count should return BadArgumentsMissing");
        }

        [Test]
        public void MethodOutputBoxUsesVariantFrom()
        {
            string fb = GetFluentBuilders();

            // Outputs are boxed back through Variant.From<T>(value) and
            // assigned by index into the __outputs list which the base
            // MethodState dispatcher pre-populates with default values
            // (one slot per declared output argument). Single-output
            // methods bind the user handler's return value to '__r'.
            Assert.That(fb, Does.Contain(
                "__outputs[0] = global::Opc.Ua.Variant.From(__r);"),
                "Single-output methods should box the handler result via __outputs[0] = Variant.From(__r)");
        }

        [Test]
        public void MethodWithMultipleInputArgsEmitsCorrectArity()
        {
            string fb = GetFluentBuilders();

            // TestModel's MathInstance.Add(a: Int32, b: Int32 -> sum: Int32)
            // must produce a sync OnCall overload whose handler arity
            // matches the input count (Func<int,int,int>) and an async
            // overload that appends CancellationToken + ValueTask<int>.
            Assert.That(fb, Does.Match(
                @"public\s+AddMethodBuilder\s+OnCall\s*\(\s*global::System\.Func<int,\s*int,\s*int>\s+handler\s*\)"),
                "Add(Int32,Int32 -> Int32) should expose a sync OnCall(Func<int,int,int>) overload");
            Assert.That(fb, Does.Match(
                @"public\s+AddMethodBuilder\s+OnCall\s*\(\s*" +
                @"global::System\.Func<int,\s*int,\s*" +
                @"global::System\.Threading\.CancellationToken,\s*" +
                @"global::System\.Threading\.Tasks\.ValueTask<int>>\s+handler\s*\)"),
                "Add(Int32,Int32 -> Int32) should expose an async OnCall(Func<int,int,CT,ValueTask<int>>) overload");
            // Unpack arity: index 0 and index 1 must both be present.
            Assert.That(fb, Does.Match(
                @"if\s*\(!__inputs\[1\]\.TryGetValue\(out\s+int\s+__a1\)\)"),
                "Multi-input methods should unpack each Variant by index (e.g. __inputs[1] -> __a1)");
        }

        [Test]
        public void DeclarationBackedInputOnlyMethodEmitsTypedOnCallOverloads()
        {
            string fb = GenerateForDeclarationBackedModel();
            const string methodWrapper = @"(?s)internal\s+sealed\s+class\s+AdjustMethodBuilder\b.*?";

            Assert.Multiple(() =>
            {
                Assert.That(fb, Does.Match(
                    methodWrapper +
                    @"public\s+AdjustMethodBuilder\s+OnCall\s*\(" +
                    @"\s*global::System\.Action<float>\s+handler\s*\)"),
                    "The declaration-backed Adjust method should expose OnCall(Action<float>).");
                Assert.That(fb, Does.Match(
                    methodWrapper +
                    @"public\s+AdjustMethodBuilder\s+OnCall\s*\(" +
                    @"\s*global::System\.Func<float,\s*" +
                    @"global::System\.Threading\.CancellationToken,\s*" +
                    @"global::System\.Threading\.Tasks\.ValueTask>\s+handler\s*\)"),
                    "The declaration-backed Adjust method should expose the async input-only OnCall overload.");
                Assert.That(fb, Does.Match(
                    methodWrapper +
                    @"if\s*\(!__inputs\[0\]\.TryGetValue\(out\s+float\s+__a0\)\)"),
                    "Generated dispatch should unpack the declaration-backed Float input from the Variant list.");
                Assert.That(fb, Does.Match(
                    methodWrapper + @"handler\(__a0\);"),
                    "Generated dispatch should pass the unpacked Float value to the sync handler.");
            });
        }

        [Test]
        public void DeclarationBackedNodeSetFixtureCarriesDeclarationInputArgument()
        {
            Dictionary<string, string> files = GenerateForDeclarationBackedNodeSet();
            string values = files.Single(
                kv => kv.Key.EndsWith(".NodeStates.ex.g.cs", StringComparison.Ordinal)).Value;

            Assert.Multiple(() =>
            {
                Assert.That(values, Does.Contain("AdjustDeclaration_InputArguments"));
                Assert.That(values, Does.Contain("Name = \"setpoint\""));
            });
        }

        /// <summary>
        /// A NodeSet2 encodes a Method's InputArguments Property as a list of Argument
        /// ExtensionObjects, so the importer's value decoder must be able to resolve the Argument
        /// encoding id. When it cannot, the arguments decode to an empty list and every generated
        /// method wrapper silently loses its parameters while still reporting HasArguments. This
        /// asserts the imported arguments actually reach the generated method surface.
        /// </summary>
        [Test]
        public void DeclarationBackedNodeSetEmitsTypedMethodArguments()
        {
            Dictionary<string, string> files = GenerateForDeclarationBackedNodeSet();
            string nodeStates = files
                .Single(kv => kv.Key.EndsWith(".NodeStates.g.cs", StringComparison.Ordinal)).Value;

            Assert.That(nodeStates, Does.Match(@"float\s+setpoint"),
                "The Float input declared by the NodeSet2 method declaration must be imported " +
                "and emitted as a typed parameter on the generated method handler.");
        }

        [Test]
        public void EmittedNodeManager_InvokesBothPlainAndTypedConfigurePartials()
        {
            Dictionary<string, string> files = GenerateForTestModel(generateNodeManager: true);
            string mgr = files.Single(kv => kv.Key.EndsWith(".NodeManager.g.cs", StringComparison.Ordinal)).Value;

            // Both partials must be declared so users can implement either.
            Assert.That(
                mgr,
                Does.Contain(
                    "partial void Configure(" +
                    "global::Opc.Ua.Server.Fluent.INodeManagerBuilder builder);"),
                "Plain Configure(INodeManagerBuilder) partial declaration must be emitted");
            Assert.That(mgr, Does.Match(@"partial\s+void\s+Configure\s*\(\s*I\w+NodeManagerBuilder\s+builder\s*\);"),
                "Typed Configure(I{Manager}NodeManagerBuilder) partial declaration must be emitted");

            // Both must also be invoked so a user that only implements one
            // gets their wiring run; the runtime treats unimplemented
            // partials as no-ops.
            Assert.That(mgr, Does.Contain("Configure(__m_builder);"),
                "Plain Configure call must be present in CreateAddressSpaceAsync");
            Assert.That(mgr, Does.Match(@"Configure\(\s*new\s+\w+NodeManagerTypedBuilder\(__m_builder\)\s*\)"),
                "Typed Configure call must be present in CreateAddressSpaceAsync");
        }

        [Test]
        public void EmittedFluentBuilders_PublishOverloadEmittedOnSupportsEventsWrapper()
        {
            string fb = GetFluentBuilders();

            // TestModel declares NotifierObject with SupportsEvents="true"
            // (the design-XML form of EventNotifier=SubscribeToEvents). Its
            // wrapper must expose typed Publish<TEvent> overloads bound to
            // the wrapper's underlying state type and constrained to
            // BaseEventState.
            Assert.That(fb, Does.Match(
                @"internal\s+sealed\s+class\s+NotifierObjectBuilder\b"),
                "NotifierObject must produce a wrapper class");
            Assert.That(fb, Does.Match(
                @"public\s+global::Opc\.Ua\.Server\.Fluent\.INodeBuilder<" +
                @"global::Opc\.Ua\.BaseObjectState>\s+Publish<TEvent>\(\s*" +
                @"global::System\.Collections\.Generic\.IAsyncEnumerable<TEvent>\s+source"),
                "NotifierObjectBuilder must expose Publish<TEvent>(IAsyncEnumerable<TEvent>, EventPublishOptions)");
            Assert.That(fb, Does.Match(
                @"public\s+global::Opc\.Ua\.Server\.Fluent\.INodeBuilder<" +
                @"global::Opc\.Ua\.BaseObjectState>\s+Publish<TEvent>\(\s*" +
                @"global::System\.Func<global::Opc\.Ua\.BaseObjectState,\s*" +
                @"global::Opc\.Ua\.ISystemContext,\s*" +
                @"global::System\.Threading\.CancellationToken,\s*" +
                @"global::System\.Collections\.Generic\.IAsyncEnumerable<TEvent>>\s+factory"),
                "NotifierObjectBuilder must expose the factory-style Publish<TEvent> overload");
            Assert.That(fb, Does.Contain(
                "where TEvent : global::Opc.Ua.BaseEventState"),
                "Publish<TEvent> must be constrained to BaseEventState");
            Assert.That(fb, Does.Contain(
                "global::Opc.Ua.Server.Fluent.EventNotifierBuilderExtensions.Publish<" +
                "global::Opc.Ua.BaseObjectState, TEvent>(__node,"),
                "Publish overload must forward to EventNotifierBuilderExtensions.Publish " +
                "with the wrapper's state type as TNotifier");
        }

        [Test]
        public void EmittedFluentBuilders_PublishOverloadEmittedOnGeneratesEventWrapper()
        {
            string fb = GetFluentBuilders();

            // EventEmittingObject does not set SupportsEvents but declares
            // a forward GeneratesEvent reference. The wrapper must still
            // expose Publish<TEvent>; the qualification logic walks both
            // the SupportsEvents flag and outgoing GeneratesEvent /
            // AlwaysGeneratesEvent references.
            Assert.That(fb, Does.Match(
                @"(?ms)internal\s+sealed\s+class\s+EventEmittingObjectBuilder\b.*?Publish<TEvent>"),
                "EventEmittingObjectBuilder must expose Publish<TEvent> because of the GeneratesEvent reference");
        }

        [Test]
        public void EmittedFluentBuilders_PublishOverloadAbsentOnPlainObjectWrapper()
        {
            string fb = GetFluentBuilders();

            // TestObject (RestrictedObjectType) is a plain object: no
            // SupportsEvents, no GeneratesEvent. It must NOT carry a
            // typed Publish overload — the surface stays clean and only
            // notifier candidates become discoverable through intellisense.
            Assert.That(fb, Does.Not.Match(
                @"(?ms)internal\s+sealed\s+class\s+TestObjectBuilder\b" +
                @"(?:(?!internal\s+sealed\s+class).)*?Publish<TEvent>"),
                "TestObjectBuilder must not expose Publish<TEvent> — it's not a notifier");
        }

        private static string GetFluentBuilders()
        {
            Dictionary<string, string> files = GenerateForTestModel(generateNodeManager: true);
            return files.Single(kv => kv.Key.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal)).Value;
        }

        // FB-3 phase 3: per-ObjectType IComponentAccessor/IPropertyAccessor
        // extensions emitted into the same FluentBuilders file.

        [Test]
        public void EmittedFluentBuilders_HasPerObjectTypeComponentAccessorClass()
        {
            string fb = GetFluentBuilders();

            // TestModel.RestrictedObjectType has Red (Variable), Pink
            // (Variable), and Blue (Method) — all HasComponent. The
            // generator must emit one static partial class containing
            // an extension method per child on
            // IComponentAccessor<RestrictedObjectState>.
            Assert.That(fb, Does.Match(
                @"public\s+static\s+partial\s+class\s+RestrictedObjectStateComponents"),
                "Per-ObjectType component-accessor class must be emitted");

            Assert.That(fb, Does.Match(
                @"this\s+global::Opc\.Ua\.IComponentAccessor<global::[\w\.]+\.RestrictedObjectState>"),
                "Accessor extensions must hang off Opc.Ua.IComponentAccessor<TState> (Core marker)");

            Assert.That(fb, Does.Contain(
                "new global::Opc.Ua.QualifiedName(\"Red\")"),
                "Red child accessor must resolve via unqualified QualifiedName(\"Red\")");

            Assert.That(fb, Does.Contain(
                "new global::Opc.Ua.QualifiedName(\"Blue\")"),
                "Blue method accessor must resolve via unqualified QualifiedName(\"Blue\")");
        }

        [Test]
        public void EmittedFluentBuilders_AccessorMethodTypedReturnsNarrowState()
        {
            string fb = GetFluentBuilders();

            // The Blue child is a MethodDesign with no TypeDefinition;
            // the generator falls back to MethodState as the lowest-
            // common-denominator return type.
            Assert.That(fb, Does.Match(
                @"global::Opc\.Ua\.Server\.Fluent\.INodeBuilder<global::Opc\.Ua\.MethodState>\s+Blue\("),
                "Method child accessor must return INodeBuilder<MethodState>");

            // Variable children (Red) sit under HasComponent in the
            // TestModel; the generator must emit them as
            // IVariableBuilder<T> on IComponentAccessor.
            Assert.That(fb, Does.Match(
                @"global::Opc\.Ua\.Server\.Fluent\.IVariableBuilder<\w+>\s+Red\("),
                "Variable HasComponent child accessor must return IVariableBuilder<T>");
        }

        /// <summary>
        /// Regression: the placeholder child Pink_Placeholder (browse name
        /// <c>&lt;Pink&gt;</c>) got an accessor walking to a child that no
        /// instance carries, so it could never resolve.
        /// </summary>
        [Test]
        public void EmittedFluentBuildersPlaceholderChildHasNoAccessor()
        {
            string fb = GetFluentBuilders();

            Assert.That(fb, Does.Not.Contain("Pink_Placeholder("));
            Assert.That(fb, Does.Match(@"\s+Red\("), "ordinary children keep their accessor");
        }

        [Test]
        public void Emit_OmitFluentApi_SuppressesAccessorEmission()
        {
            // After the FB-R3-8 relocation, accessors emit by default
            // (when GenerateNodeManager=true OR OmitFluentApi=false).
            // Model-only consumers that don't reference Opc.Ua.Server
            // explicitly opt OUT via the OmitFluentApi flag.
            Dictionary<string, string> files = GenerateForTestModel(
                generateNodeManager: false,
                omitFluentApi: true);

            KeyValuePair<string, string>? fb = files
                .Where(kv => kv.Key.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal))
                .Cast<KeyValuePair<string, string>?>()
                .FirstOrDefault();
            Assert.That(fb, Is.Null,
                "FluentBuilders file must be suppressed when OmitFluentApi=true and GenerateNodeManager=false");
        }

        [Test]
        public void Emit_DefaultOmitFluentApiFalse_EmitsAccessorsWithoutNodeManager()
        {
            // Default opt-out semantics: accessors emit even without a
            // node manager opt-in. NodeSet2-only consumers that don't
            // override OmitFluentApi=true get the typed accessors for
            // free (provided they reference Opc.Ua.Server).
            Dictionary<string, string> files = GenerateForTestModel(
                generateNodeManager: false,
                omitFluentApi: false);

            KeyValuePair<string, string> fb = files
                .Single(kv => kv.Key.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal));
            Assert.That(fb.Value, Does.Not.Match(
                @"internal\s+interface\s+I\w+NodeManagerBuilder"),
                "Manager interface must be skipped when GenerateNodeManager=false");
            Assert.That(fb.Value, Does.Match(
                @"public\s+static\s+partial\s+class\s+RestrictedObjectStateComponents"),
                "Per-type accessor must be emitted by default (OmitFluentApi=false)");
        }

        private static Dictionary<string, string> GenerateForTestModel(
            bool generateNodeManager,
            bool omitFluentApi = true)
        {
            const string designFile = "TestModel.xml";
            ITelemetryContext telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error);
            using var fileSystem = new VirtualFileSystem();
            string resources = Path.Combine(Directory.GetCurrentDirectory(), "Resources");

            Generators.GenerateCode(
                new DesignFileCollection
                {
                    Targets = [Path.Combine(resources, designFile)],
                    IdentifierFilePath = Path.Combine(
                        resources,
                        Path.GetFileNameWithoutExtension(designFile) + ".csv"),
                    Options = new DesignFileOptions
                    {
                        GenerateNodeManager = generateNodeManager
                    }
                },
                fileSystem,
                string.Empty,
                telemetry,
                options: new GeneratorOptions
                {
                    OmitFluentApi = omitFluentApi
                });

            return fileSystem.CreatedFiles
                .Where(c => Path.GetExtension(c) == ".cs")
                .ToDictionary(c => c, c => Encoding.UTF8.GetString(fileSystem.Get(c)));
        }

        /// <summary>
        /// Regression: the typed top-level accessor built the root's NodeId with the
        /// namespace of its BrowseName instead of the namespace of its NodeId. A NodeSet
        /// instance <c>ns=1;i=2000</c> whose BrowseName is in a companion namespace
        /// (<c>2:Device</c>) then resolved <c>ns=Companion;i=2000</c>, a node that does
        /// not exist.
        /// </summary>
        [Test]
        public void TopLevelAccessorUsesTheNodeIdNamespaceNotTheBrowseNameNamespace()
        {
            const string companionUri = "http://test.org/UA/Companion/";
            Dictionary<string, string> files = GenerateForDeclarationBackedNodeSet(
                xml => xml
                    .Replace(
                        "<Uri>http://test.org/UA/DeclarationBackedMethod/</Uri>",
                        "<Uri>http://test.org/UA/DeclarationBackedMethod/</Uri>" +
                            "<Uri>" + companionUri + "</Uri>",
                        StringComparison.Ordinal)
                    .Replace(
                        "BrowseName=\"1:Device\"",
                        "BrowseName=\"2:Device\"",
                        StringComparison.Ordinal)
                    .Replace(
                        "<RequiredModel ModelUri=\"http://opcfoundation.org/UA/\"",
                        "<RequiredModel ModelUri=\"" + companionUri +
                            "\" PublicationDate=\"2024-01-01T00:00:00Z\" Version=\"1.0.0\"/>" +
                            "<RequiredModel ModelUri=\"http://opcfoundation.org/UA/\"",
                        StringComparison.Ordinal),
                ("Companion.NodeSet2.xml",
                    "<?xml version=\"1.0\" encoding=\"utf-8\"?>" +
                    "<UANodeSet xmlns=\"http://opcfoundation.org/UA/2011/03/UANodeSet.xsd\">" +
                    "<NamespaceUris><Uri>" + companionUri + "</Uri></NamespaceUris>" +
                    "<Models><Model ModelUri=\"" + companionUri +
                    "\" PublicationDate=\"2024-01-01T00:00:00Z\" Version=\"1.0.0\">" +
                    "<RequiredModel ModelUri=\"http://opcfoundation.org/UA/\"" +
                    " PublicationDate=\"2024-01-01T00:00:00Z\" Version=\"1.05.03\"/>" +
                    "</Model></Models>" +
                    "<UAObjectType NodeId=\"ns=1;i=1\" BrowseName=\"1:CompanionType\">" +
                    "<DisplayName>CompanionType</DisplayName><References>" +
                    "<Reference ReferenceType=\"i=45\" IsForward=\"false\">i=58</Reference>" +
                    "</References></UAObjectType></UANodeSet>"));
            string fb = files
                .Single(kv => kv.Key.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal)).Value;

            int nodeId = fb.IndexOf("(new global::Opc.Ua.NodeId(2000u, __ns))", StringComparison.Ordinal);
            Assert.That(nodeId, Is.GreaterThan(0), "Typed root accessor for Device not found:\n" + fb);
            const string lookup = "__inner.Context.NamespaceUris.GetIndexOrAppend(\"";
            int start = fb.LastIndexOf(lookup, nodeId, StringComparison.Ordinal) + lookup.Length;
            string ns = fb[start..fb.IndexOf('"', start)];
            Assert.That(ns, Is.EqualTo("http://test.org/UA/DeclarationBackedMethod/"),
                "The root NodeId must use the namespace of the NodeId, not of the BrowseName.");
        }

        private static Dictionary<string, string> GenerateForDeclarationBackedNodeSet(
            Func<string, string>? transform = null,
            (string FileName, string Content)? ignoredDependency = null)
        {
            const string nodeSetFile = "DeclarationBackedMethod.NodeSet2.xml";
            const string namespaceUri = "http://test.org/UA/DeclarationBackedMethod/";
            ITelemetryContext telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error);
            using var fileSystem = new VirtualFileSystem();
            string resources = Path.Combine(Directory.GetCurrentDirectory(), "Resources");
            string path = Path.Combine(resources, nodeSetFile);
            if (transform != null)
            {
                path = Path.Combine(resources, "Transformed." + nodeSetFile);
                fileSystem.Add(
                    path,
                    Encoding.UTF8.GetBytes(transform(File.ReadAllText(
                        Path.Combine(resources, nodeSetFile)))));
            }

            ImmutableArray<(string, NodesetFileOptions)> inputs =
                [
                    (path, new NodesetFileOptions
                    {
                        ModelUri = namespaceUri,
                        Name = "DeclarationBackedMethod",
                        Prefix = "DeclarationBackedMethod"
                    })
                ];
            if (ignoredDependency is (string fileName, string content))
            {
                string dependencyPath = Path.Combine(resources, fileName);
                fileSystem.Add(dependencyPath, Encoding.UTF8.GetBytes(content));
                inputs = inputs.Add((dependencyPath, new NodesetFileOptions { Ignore = true }));
            }

            var nodesets = new NodesetFileCollection(
                inputs,
                [],
                fileSystem,
                telemetry);

            nodesets.GenerateCode(
                fileSystem,
                string.Empty,
                telemetry,
                new GeneratorOptions
                {
                    OmitFluentApi = false
                },
                nodeManagerBindings:
                [
                    new NodeManagerAttributeBinding
                    {
                        NamespaceUri = namespaceUri,
                        TargetNamespace = "DeclarationBackedMethod",
                        TargetClassName = "DeclarationBackedMethodNodeManager",
                        GenerateFactory = false
                    }
                ]);

            return fileSystem.CreatedFiles
                .Where(c => Path.GetExtension(c) == ".cs")
                .ToDictionary(c => c, c => Encoding.UTF8.GetString(fileSystem.Get(c)));
        }

        /// <summary>
        /// Regression: every generated instance wrapper declares Builder and
        /// Node itself, so a child accessor sanitizing to one of those produced
        /// a duplicate member (CS0102). The collision is reported with an
        /// actionable message instead, the same way sibling collisions are.
        /// </summary>
        [TestCase("Node")]
        [TestCase("Builder")]
        public void EmitChildNamedAfterAWrapperMember_ReportsTheCollision(string childName)
        {
            InvalidOperationException ex = Assert.Throws<InvalidOperationException>(
                () => GenerateWrapperWithChildNamed(childName));

            Assert.That(ex.Message, Does.Contain(childName));
            Assert.That(ex.Message, Does.Contain("already declares"));
        }

        /// <summary>
        /// A child whose name does not collide still generates.
        /// </summary>
        [Test]
        public void EmitChildWithANonCollidingName_Generates()
        {
            string? builders = null;
            Assert.DoesNotThrow(() => builders = GenerateWrapperWithChildNamed("Setpoint"));
            Assert.That(builders, Does.Contain("Setpoint"));
        }

        /// <summary>
        /// Regression: the wrapper collision check ran (and threw) even when no
        /// manager wrappers are emitted, failing models that only get the
        /// per-type accessors over names nothing uses.
        /// </summary>
        [Test]
        public void EmitWithoutManagerWrappersDoesNotValidateWrapperNames()
        {
            Assert.DoesNotThrow(() => GenerateWrappers(
                "Device",
                [("Node", NewObject("Node"))],
                generateManagerWrappers: false));
        }

        /// <summary>
        /// Regression: collisions that break compilation of the emitted wrappers
        /// were not detected - a nested wrapper named after its enclosing wrapper
        /// (CS0542), and a nested wrapper type colliding with a sibling accessor
        /// or another nested type (CS0102).
        /// </summary>
        [Test]
        public void EmitNestedWrapperCollisionsAreReported()
        {
            // Object Boiler inside object Boiler: nested BoilerBuilder in BoilerBuilder.
            Assert.That(
                () => GenerateWrappers("Plant", [("Boiler", NewObject("Boiler")), ("Boiler_Boiler", NewObject("Boiler"))]),
                Throws.InvalidOperationException.With.Message.Contains("BoilerBuilder"));
            // Variable FooBuilder next to object Foo: property and nested type FooBuilder.
            Assert.That(
                () => GenerateWrappers("Plant", [("Foo", NewObject("Foo")), ("FooBuilder", NewVariable("FooBuilder"))]),
                Throws.InvalidOperationException.With.Message.Contains("FooBuilder"));
            // Method Foo next to object FooMethod: both nest FooMethodBuilder.
            Assert.That(
                () => GenerateWrappers("Plant", [("Foo", NewMethod("Foo")), ("FooMethod", NewObject("FooMethod"))]),
                Throws.InvalidOperationException.With.Message.Contains("FooMethodBuilder"));
        }

        /// <summary>
        /// Regression: a predefined instance named after a member the typed
        /// manager builder forwards (e.g. <c>Context</c>) produced two members of
        /// that name in the typed builder (CS0102).
        /// </summary>
        [TestCase("Context")]
        [TestCase("AddObject")]
        public void EmitRootNamedAfterATypedBuilderMemberReportsTheCollision(string rootName)
        {
            Assert.That(
                () => GenerateWrappers(rootName, []),
                Throws.InvalidOperationException.With.Message.Contains(rootName));
        }

        [Test]
        public void EmitDistinctNestedWrappersGenerates()
        {
            string builders = GenerateWrappers(
                "Plant",
                [("Boiler", NewObject("Boiler")), ("Boiler_Pump", NewObject("Pump")), ("Start", NewMethod("Start"))]);

            Assert.That(builders, Does.Contain("class PumpBuilder"));
            Assert.That(builders, Does.Contain("class StartMethodBuilder"));
        }

        private const string kWrapperNamespaceUri = "http://test.org/UA/Wrappers/";

        private static ObjectDesign NewObject(string name)
        {
            return new ObjectDesign
            {
                SymbolicName = new XmlQualifiedName(name, kWrapperNamespaceUri),
                SymbolicId = new XmlQualifiedName("Id_" + name, kWrapperNamespaceUri),
                BrowseName = name
            };
        }

        private static MethodDesign NewMethod(string name)
        {
            return new MethodDesign
            {
                SymbolicName = new XmlQualifiedName(name, kWrapperNamespaceUri),
                SymbolicId = new XmlQualifiedName("Id_" + name, kWrapperNamespaceUri),
                BrowseName = name,
                InputArguments = [],
                OutputArguments = []
            };
        }

        private static VariableDesign NewVariable(string name)
        {
            var floatType = new DataTypeDesign
            {
                SymbolicName = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                SymbolicId = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                BasicDataType = BasicDataType.Float
            };
            return new VariableDesign
            {
                SymbolicName = new XmlQualifiedName(name, kWrapperNamespaceUri),
                SymbolicId = new XmlQualifiedName("Id_" + name, kWrapperNamespaceUri),
                BrowseName = name,
                DataTypeNode = floatType,
                DataType = floatType.SymbolicId,
                ValueRank = ValueRank.Scalar
            };
        }

        private static string GenerateWrappers(
            string rootName,
            (string Path, NodeDesign Node)[] children,
            bool generateManagerWrappers = true)
        {
            var targetNamespace = new Namespace
            {
                Value = kWrapperNamespaceUri,
                Prefix = "Wrappers",
                Name = "Wrappers"
            };
            var root = new ObjectDesign
            {
                SymbolicName = new XmlQualifiedName(rootName, kWrapperNamespaceUri),
                SymbolicId = new XmlQualifiedName(rootName, kWrapperNamespaceUri),
                BrowseName = rootName,
                Hierarchy = new Hierarchy()
            };
            root.Hierarchy.Nodes[string.Empty] = new HierarchyNode
            {
                RelativePath = string.Empty,
                Instance = root
            };
            foreach ((string path, NodeDesign node) in children)
            {
                root.Hierarchy.Nodes[path] = new HierarchyNode
                {
                    RelativePath = path,
                    Instance = node
                };
            }

            var model = new Mock<IModelDesign>();
            model.Setup(m => m.TargetNamespace).Returns(targetNamespace);
            model.Setup(m => m.Namespaces).Returns([targetNamespace]);
            model.Setup(m => m.GetNodeDesigns()).Returns([root]);
            model.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            var context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = string.Empty,
                ModelDesign = model.Object,
                Telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error),
                Options = new GeneratorOptions()
            };
            new FluentBuilderGenerator(context)
            {
                GenerateManagerWrappers = generateManagerWrappers,
                EmitFluentAccessors = false
            }.Emit();

            return fileSystem.CreatedFiles
                .Where(c => c.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal))
                .Select(c => Encoding.UTF8.GetString(fileSystem.Get(c)))
                .Single();
        }

        private static string GenerateWrapperWithChildNamed(string childName)
        {
            const string namespaceUri = "http://test.org/UA/WrapperCollision/";
            var targetNamespace = new Namespace
            {
                Value = namespaceUri,
                Prefix = "WrapperCollision",
                Name = "WrapperCollision"
            };
            var floatType = new DataTypeDesign
            {
                SymbolicName = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                SymbolicId = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                BasicDataType = BasicDataType.Float
            };
            var child = new VariableDesign
            {
                SymbolicName = new XmlQualifiedName(childName, namespaceUri),
                SymbolicId = new XmlQualifiedName("Device_" + childName, namespaceUri),
                BrowseName = childName,
                DataTypeNode = floatType,
                DataType = floatType.SymbolicId,
                ValueRank = ValueRank.Scalar
            };
            var root = new ObjectDesign
            {
                SymbolicName = new XmlQualifiedName("Device", namespaceUri),
                SymbolicId = new XmlQualifiedName("Device", namespaceUri),
                Hierarchy = new Hierarchy()
            };
            root.Hierarchy.Nodes[string.Empty] = new HierarchyNode
            {
                RelativePath = string.Empty,
                Instance = root
            };
            root.Hierarchy.Nodes[childName] = new HierarchyNode
            {
                RelativePath = childName,
                Instance = child
            };

            var model = new Mock<IModelDesign>();
            model.Setup(m => m.TargetNamespace).Returns(targetNamespace);
            model.Setup(m => m.Namespaces).Returns([targetNamespace]);
            model.Setup(m => m.GetNodeDesigns()).Returns([root]);
            model.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            var context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = string.Empty,
                ModelDesign = model.Object,
                Telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error),
                Options = new GeneratorOptions()
            };
            new FluentBuilderGenerator(context)
            {
                GenerateManagerWrappers = true,
                EmitFluentAccessors = false
            }.Emit();

            return fileSystem.CreatedFiles
                .Where(c => c.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal))
                .Select(c => Encoding.UTF8.GetString(fileSystem.Get(c)))
                .Single();
        }

        /// <summary>
        /// Regression: a per-type accessor was emitted for an Object child whose
        /// TypeDefinition is excluded (e.g. a Draft type), returning
        /// <c>INodeBuilder&lt;DiagnosticsState&gt;</c> for a state class that is
        /// never generated (CS0246).
        /// </summary>
        [Test]
        public void EmitTypeAccessorsChildOfExcludedTypeIsSkipped()
        {
            const string namespaceUri = "http://test.org/UA/Excluded/";
            var targetNamespace = new Namespace
            {
                Value = namespaceUri,
                Prefix = "Excluded",
                Name = "Excluded"
            };
            ObjectTypeDesign NewType(string name) => new()
            {
                SymbolicName = new XmlQualifiedName(name, namespaceUri),
                SymbolicId = new XmlQualifiedName(name, namespaceUri)
            };
            ObjectDesign NewChild(string name, ObjectTypeDesign type) => new()
            {
                SymbolicName = new XmlQualifiedName(name, namespaceUri),
                SymbolicId = new XmlQualifiedName("MachineType_" + name, namespaceUri),
                BrowseName = name,
                TypeDefinition = type.SymbolicName,
                TypeDefinitionNode = type,
                ModellingRule = ModellingRule.Mandatory
            };
            ObjectTypeDesign draftType = NewType("DiagnosticsType");
            ObjectTypeDesign motorType = NewType("MotorType");
            ObjectTypeDesign machineType = NewType("MachineType");
            machineType.Children = new ListOfChildren
            {
                Items = [NewChild("Diagnostics", draftType), NewChild("Motor", motorType)]
            };

            var model = new Mock<IModelDesign>();
            model.Setup(m => m.TargetNamespace).Returns(targetNamespace);
            model.Setup(m => m.Namespaces).Returns([targetNamespace]);
            model.Setup(m => m.GetNodeDesigns()).Returns([draftType, motorType, machineType]);
            model.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);
            model.Setup(m => m.IsExcluded(draftType)).Returns(true);

            using var fileSystem = new VirtualFileSystem();
            var context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = string.Empty,
                ModelDesign = model.Object,
                Telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error),
                Options = new GeneratorOptions()
            };
            new FluentBuilderGenerator(context)
            {
                GenerateManagerWrappers = false,
                EmitFluentAccessors = true
            }.Emit();
            string fb = fileSystem.CreatedFiles
                .Where(c => c.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal))
                .Select(c => Encoding.UTF8.GetString(fileSystem.Get(c)))
                .Single();

            Assert.Multiple(() =>
            {
                Assert.That(fb, Does.Not.Contain("DiagnosticsState"));
                Assert.That(fb, Does.Contain("INodeBuilder<global::Excluded.MotorState> Motor("));
            });
        }

        private static string GenerateForDeclarationBackedModel()
        {
            const string namespaceUri = "http://test.org/UA/DeclarationBackedMethod/";
            var targetNamespace = new Namespace
            {
                Value = namespaceUri,
                Prefix = "DeclarationBackedMethod",
                Name = "DeclarationBackedMethod"
            };
            var floatType = new DataTypeDesign
            {
                SymbolicName = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                SymbolicId = new XmlQualifiedName("Float", "http://opcfoundation.org/UA/"),
                BasicDataType = BasicDataType.Float
            };
            var declaration = new MethodDesign
            {
                SymbolicName = new XmlQualifiedName("AdjustDeclaration", namespaceUri),
                SymbolicId = new XmlQualifiedName("AdjustDeclaration", namespaceUri),
                InputArguments =
                [
                    new Parameter
                    {
                        Name = "setpoint",
                        DataTypeNode = floatType,
                        DataType = floatType.SymbolicId,
                        ValueRank = ValueRank.Scalar
                    }
                ],
                OutputArguments = []
            };
            var method = new MethodDesign
            {
                SymbolicName = new XmlQualifiedName("Adjust", namespaceUri),
                SymbolicId = new XmlQualifiedName("Device_Adjust", namespaceUri),
                InputArguments = [],
                OutputArguments = [],
                MethodDeclarationNode = declaration
            };
            var root = new ObjectDesign
            {
                SymbolicName = new XmlQualifiedName("Device", namespaceUri),
                SymbolicId = new XmlQualifiedName("Device", namespaceUri),
                Hierarchy = new Hierarchy()
            };
            root.Hierarchy.Nodes[string.Empty] = new HierarchyNode
            {
                RelativePath = string.Empty,
                Instance = root
            };
            root.Hierarchy.Nodes["Adjust"] = new HierarchyNode
            {
                RelativePath = "Adjust",
                Instance = method
            };

            var model = new Mock<IModelDesign>();
            model.Setup(m => m.TargetNamespace).Returns(targetNamespace);
            model.Setup(m => m.Namespaces).Returns([targetNamespace]);
            model.Setup(m => m.GetNodeDesigns()).Returns([root, declaration]);
            model.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            var context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = string.Empty,
                ModelDesign = model.Object,
                Telemetry = NUnitTelemetryContext.Create(logLevel: LogLevel.Error),
                Options = new GeneratorOptions()
            };
            new FluentBuilderGenerator(context)
            {
                GenerateManagerWrappers = true,
                EmitFluentAccessors = false
            }.Emit();

            return fileSystem.CreatedFiles
                .Where(c => c.EndsWith(".FluentBuilders.g.cs", StringComparison.Ordinal))
                .Select(c => Encoding.UTF8.GetString(fileSystem.Get(c)))
                .Single();
        }
    }
}