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using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using System.Text;
using Microsoft.Extensions.Logging;
using NUnit.Framework;
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 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 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, Pink_Placeholder) 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>");
        }

        [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)));
        }
    }
}