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 *
 * OPC Foundation MIT License 1.00
 *
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 * http://opcfoundation.org/License/MIT/1.00/
 * ======================================================================*/

using System;
using System.IO;
using Moq;
using NUnit.Framework;
using Opc.Ua.Schema.Model;

namespace Opc.Ua.SourceGeneration.Generator.Tests
{
    /// <summary>
    /// Unit tests for the NodeIdGenerator class.
    /// </summary>
    [TestFixture]
    [Category("Generator")]
    [SetCulture("en-us")]
    [SetUICulture("en-us")]
    [Parallelizable]
    public class NodeIdGeneratorTests
    {
        private Mock<IFileSystem> m_mockFileSystem;
        private Mock<IModelDesign> m_mockModelDesign;
        private Mock<ITelemetryContext> m_mockTelemetry;
        private GeneratorContext m_context = null!;

        [SetUp]
        public void SetUp()
        {
            m_mockFileSystem = new Mock<IFileSystem>();
            m_mockModelDesign = new Mock<IModelDesign>();
            m_mockTelemetry = new Mock<ITelemetryContext>();

            // Setup default namespace
            var targetNamespace = new Namespace
            {
                Value = "http://test.org/UA/",
                Prefix = "Test",
                Name = "TestNamespace"
            };
            m_mockModelDesign.Setup(m => m.TargetNamespace).Returns(targetNamespace);
            m_mockModelDesign.Setup(m => m.Namespaces).Returns([targetNamespace]);
        }

        /// <summary>
        /// Tests that the constructor throws ArgumentNullException when context is null.
        /// </summary>
        [Test]
        public void Constructor_NullContext_ThrowsArgumentNullException()
        {
            // Arrange
            GeneratorContext? context = null;

            // Act & Assert
            Assert.Throws<ArgumentNullException>(() => new NodeIdGenerator(context!));
        }

        /// <summary>
        /// Tests that constructor creates instance with valid context.
        /// </summary>
        [Test]
        public void Constructor_ValidContext_CreatesInstance()
        {
            // Arrange
            m_context = new GeneratorContext
            {
                FileSystem = m_mockFileSystem.Object,
                OutputFolder = "TestOutput",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            // Act
            var generator = new NodeIdGenerator(m_context);

            // Assert
            Assert.That(generator, Is.Not.Null);
        }

        /// <summary>
        /// Tests that Emit returns early without creating files when no identifiers exist.
        /// </summary>
        [Test]
        public void Emit_NoIdentifiers_ReturnsEarlyWithoutCreatingFiles()
        {
            // Arrange
            m_mockModelDesign.Setup(m => m.Nodes).Returns([]);

            m_context = new GeneratorContext
            {
                FileSystem = m_mockFileSystem.Object,
                OutputFolder = "TestOutput",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            var generator = new NodeIdGenerator(m_context);

            // Act
            generator.Emit();

            // Assert - OpenWrite should not be called when there are no identifiers
            m_mockFileSystem.Verify(
                fs => fs.OpenWrite(It.IsAny<string>()),
                Times.Never,
                "OpenWrite should not be called when there are no identifiers");
        }

        /// <summary>
        /// Tests that Emit creates a file with the correct name when nodes with identifiers exist.
        /// </summary>
        [Test]
        public void Emit_WithNodes_CreatesFileWithCorrectName()
        {
            // Arrange
            using var memoryStream = new MemoryStream();

            var objectType = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName("TestObjectType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName("TestObjectType", "http://test.org/UA/"),
                NumericId = 1001,
                NumericIdSpecified = true
            };

            m_mockModelDesign.Setup(m => m.Nodes).Returns([objectType]);
            m_mockModelDesign.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            string? capturedPath = null;
            m_mockFileSystem.Setup(fs => fs.OpenWrite(It.IsAny<string>()))
                .Callback<string>(path => capturedPath = path)
                .Returns(memoryStream);

            m_context = new GeneratorContext
            {
                FileSystem = m_mockFileSystem.Object,
                OutputFolder = "C:\\output",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            var generator = new NodeIdGenerator(m_context);

            // Act
            generator.Emit();

            // Assert
            Assert.That(capturedPath, Is.Not.Null);
            Assert.That(capturedPath, Does.Contain("Test.Identifiers.g.cs"));
            Assert.That(capturedPath, Does.StartWith("C:\\output"));
            m_mockFileSystem.Verify(fs => fs.OpenWrite(It.IsAny<string>()), Times.Once);
        }

        /// <summary>
        /// Tests that Emit handles multiple node types correctly.
        /// </summary>
        [Test]
        public void Emit_WithMultipleNodeTypes_CreatesFile()
        {
            // Arrange
            using var memoryStream = new MemoryStream();

            var objectType = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName("TestObjectType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName("TestObjectType", "http://test.org/UA/"),
                NumericId = 1001,
                NumericIdSpecified = true
            };

            var variableType = new VariableTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName("TestVariableType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName("TestVariableType", "http://test.org/UA/"),
                NumericId = 1002,
                NumericIdSpecified = true
            };

            m_mockModelDesign.Setup(m => m.Nodes).Returns([objectType, variableType]);
            m_mockModelDesign.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            m_mockFileSystem.Setup(fs => fs.OpenWrite(It.IsAny<string>()))
                .Returns(memoryStream);

            m_context = new GeneratorContext
            {
                FileSystem = m_mockFileSystem.Object,
                OutputFolder = "C:\\output",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            var generator = new NodeIdGenerator(m_context);

            // Act
            generator.Emit();

            // Assert
            m_mockFileSystem.Verify(fs => fs.OpenWrite(It.IsAny<string>()), Times.Once);
        }

        /// <summary>
        /// Regression: the string identifier was interpolated straight into a C#
        /// string literal, so a PLC style id containing a backslash or a quote -
        /// common in vendor NodeSets - produced source that does not compile
        /// (CS1009). The literal must be escaped.
        /// </summary>
        [Test]
        public void Emit_StringIdWithBackslashAndQuote_EscapesTheLiteral()
        {
            var node = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName(
                    "PlcTagType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName(
                    "PlcTagType", "http://test.org/UA/"),
                StringId = "PLC1\\DB10.\"Tag\""
            };

            m_mockModelDesign.Setup(m => m.Nodes).Returns([node]);
            m_mockModelDesign.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            m_context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = "out",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            new NodeIdGenerator(m_context).Emit();

            string output = ReadOnlyGeneratedFile(fileSystem);

            Assert.That(
                output,
                Does.Contain("\"PLC1\\\\DB10.\\\"Tag\\\"\""),
                "the string identifier must be emitted as an escaped C# literal");
            Assert.That(
                output,
                Does.Not.Contain("\"PLC1\\DB10.\"Tag\"\""),
                "the raw identifier would not compile");
        }

        /// <summary>
        /// A node without any identifier falls back to its symbolic name, which
        /// is escaped through the same path.
        /// </summary>
        [Test]
        public void Emit_NodeWithoutIdentifier_EmitsEscapedSymbolicName()
        {
            var node = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName(
                    "PlainType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName(
                    "PlainType", "http://test.org/UA/")
            };

            m_mockModelDesign.Setup(m => m.Nodes).Returns([node]);
            m_mockModelDesign.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            m_context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = "out",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            new NodeIdGenerator(m_context).Emit();

            Assert.That(
                ReadOnlyGeneratedFile(fileSystem),
                Does.Contain("public const string PlainType = \"PlainType\";"));
        }

        /// <summary>
        /// A Guid identifier cannot be a C# constant, so it is emitted as a
        /// static readonly field initialized from its canonical literal.
        /// </summary>
        [Test]
        public void EmitGuidIdEmitsStaticReadonlyField()
        {
            var node = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName(
                    "GuidType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName(
                    "GuidType", "http://test.org/UA/"),
                GuidId = new Guid("09087e75-8e5e-499b-954f-f2a9603db28a"),
                GuidIdSpecified = true
            };

            Assert.That(
                EmitSingleNode(node),
                Does.Contain(
                    "public static readonly global::System.Guid GuidType = " +
                    "new global::System.Guid(\"09087e75-8e5e-499b-954f-f2a9603db28a\");"));
        }

        /// <summary>
        /// An opaque identifier is emitted as a static readonly ByteString built
        /// from its base64 representation.
        /// </summary>
        [Test]
        public void EmitOpaqueIdEmitsStaticReadonlyField()
        {
            var node = new ObjectTypeDesign
            {
                SymbolicId = new System.Xml.XmlQualifiedName(
                    "OpaqueType", "http://test.org/UA/"),
                SymbolicName = new System.Xml.XmlQualifiedName(
                    "OpaqueType", "http://test.org/UA/"),
                OpaqueId = Convert.FromBase64String("M/RbKBsRVkePCePcx24oRA==")
            };

            Assert.That(
                EmitSingleNode(node),
                Does.Contain(
                    "public static readonly global::Opc.Ua.ByteString OpaqueType = " +
                    "global::Opc.Ua.ByteString.FromBase64(\"M/RbKBsRVkePCePcx24oRA==\");"));
        }

        private string EmitSingleNode(NodeDesign node)
        {
            m_mockModelDesign.Setup(m => m.Nodes).Returns([node]);
            m_mockModelDesign.Setup(m => m.IsExcluded(It.IsAny<NodeDesign>())).Returns(false);

            using var fileSystem = new VirtualFileSystem();
            m_context = new GeneratorContext
            {
                FileSystem = fileSystem,
                OutputFolder = "out",
                ModelDesign = m_mockModelDesign.Object,
                Telemetry = m_mockTelemetry.Object,
                Options = new GeneratorOptions()
            };

            new NodeIdGenerator(m_context).Emit();

            return ReadOnlyGeneratedFile(fileSystem);
        }

        private static string ReadOnlyGeneratedFile(VirtualFileSystem fileSystem)
        {
            var buffer = new System.Text.StringBuilder();
            foreach (string file in fileSystem.CreatedFiles)
            {
                buffer.AppendLine(System.Text.Encoding.UTF8.GetString(fileSystem.Get(file)));
            }
            return buffer.ToString();
        }
    }
}