using FluentAssertions;
using StellaOps.Signals.Models;
using StellaOps.Signals.Parsing;
using Xunit;

namespace StellaOps.Signals.Reachability.Tests;

/// <summary>
/// Unit tests for CallgraphSchemaMigrator.
/// Verifies schema migration from legacy format to stella.callgraph.v1.
/// </summary>
public class CallgraphSchemaMigratorTests
{
    #region EnsureV1 - Schema Version Tests

    [Fact]
    public void EnsureV1_SetsSchemaToV1_WhenNotSet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Schema = string.Empty
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Schema.Should().Be(CallgraphSchemaVersions.V1);
    }

    [Fact]
    public void EnsureV1_PreservesV1Schema_WhenAlreadySet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Schema = CallgraphSchemaVersions.V1
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Schema.Should().Be(CallgraphSchemaVersions.V1);
    }

    [Fact]
    public void EnsureV1_UpdatesLegacySchema_ToV1()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Schema = "legacy-schema-1.0"
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Schema.Should().Be(CallgraphSchemaVersions.V1);
    }

    #endregion

    #region EnsureV1 - Language Parsing Tests

    [Theory]
    [InlineData("dotnet", CallgraphLanguage.DotNet)]
    [InlineData(".net", CallgraphLanguage.DotNet)]
    [InlineData("csharp", CallgraphLanguage.DotNet)]
    [InlineData("c#", CallgraphLanguage.DotNet)]
    [InlineData("java", CallgraphLanguage.Java)]
    [InlineData("node", CallgraphLanguage.Node)]
    [InlineData("nodejs", CallgraphLanguage.Node)]
    [InlineData("javascript", CallgraphLanguage.Node)]
    [InlineData("typescript", CallgraphLanguage.Node)]
    [InlineData("python", CallgraphLanguage.Python)]
    [InlineData("go", CallgraphLanguage.Go)]
    [InlineData("golang", CallgraphLanguage.Go)]
    [InlineData("rust", CallgraphLanguage.Rust)]
    [InlineData("ruby", CallgraphLanguage.Ruby)]
    [InlineData("php", CallgraphLanguage.Php)]
    [InlineData("binary", CallgraphLanguage.Binary)]
    [InlineData("native", CallgraphLanguage.Binary)]
    [InlineData("elf", CallgraphLanguage.Binary)]
    [InlineData("swift", CallgraphLanguage.Swift)]
    [InlineData("kotlin", CallgraphLanguage.Kotlin)]
    public void EnsureV1_ParsesLanguageString_ToEnum(string languageString, CallgraphLanguage expected)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Language = languageString,
            LanguageType = CallgraphLanguage.Unknown
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.LanguageType.Should().Be(expected);
    }

    [Fact]
    public void EnsureV1_PreservesLanguageType_WhenAlreadySet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Language = "java",
            LanguageType = CallgraphLanguage.DotNet // Already set to something different
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.LanguageType.Should().Be(CallgraphLanguage.DotNet);
    }

    #endregion

    #region EnsureV1 - Node Visibility Inference Tests

    [Fact]
    public void EnsureV1_InfersPublicVisibility_ForStandardNames()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "ProcessOrder", Visibility = SymbolVisibility.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.Visibility.Should().Be(SymbolVisibility.Public);
    }

    [Fact]
    public void EnsureV1_InfersPrivateVisibility_ForUnderscorePrefixed()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "_privateMethod", Visibility = SymbolVisibility.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.Visibility.Should().Be(SymbolVisibility.Private);
    }

    [Fact]
    public void EnsureV1_InfersPrivateVisibility_ForAngleBracketNames()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "<Main>$", Visibility = SymbolVisibility.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.Visibility.Should().Be(SymbolVisibility.Private);
    }

    [Fact]
    public void EnsureV1_InfersInternalVisibility_ForInternalNamespace()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "Helper", Namespace = "MyApp.Internal.Utils", Visibility = SymbolVisibility.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.Visibility.Should().Be(SymbolVisibility.Internal);
    }

    [Fact]
    public void EnsureV1_PreservesVisibility_WhenAlreadySet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "_privateMethod", Visibility = SymbolVisibility.Protected }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.Visibility.Should().Be(SymbolVisibility.Protected);
    }

    #endregion

    #region EnsureV1 - Symbol Key Building Tests

    [Fact]
    public void EnsureV1_BuildsSymbolKey_FromNamespaceAndName()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "ProcessOrder", Namespace = "MyApp.Services" }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.SymbolKey.Should().Be("MyApp.Services.ProcessOrder");
    }

    [Fact]
    public void EnsureV1_BuildsSymbolKey_FromNameOnly_WhenNoNamespace()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "GlobalMethod" }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.SymbolKey.Should().Be("GlobalMethod");
    }

    [Fact]
    public void EnsureV1_PreservesSymbolKey_WhenAlreadySet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = "Method", Namespace = "Ns", SymbolKey = "Custom.Key" }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.SymbolKey.Should().Be("Custom.Key");
    }

    #endregion

    #region EnsureV1 - Entrypoint Candidate Detection Tests

    [Theory]
    [InlineData("Main")]
    [InlineData("main")]
    [InlineData("MAIN")]
    public void EnsureV1_DetectsEntrypointCandidate_ForMainMethod(string methodName)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = methodName }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.IsEntrypointCandidate.Should().BeTrue();
    }

    [Theory]
    [InlineData("OrdersController")]
    [InlineData("UserController")]
    public void EnsureV1_DetectsEntrypointCandidate_ForControllerNames(string name)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = name }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.IsEntrypointCandidate.Should().BeTrue();
    }

    [Theory]
    [InlineData("RequestHandler")]
    [InlineData("EventHandler")]
    public void EnsureV1_DetectsEntrypointCandidate_ForHandlerNames(string name)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = name }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.IsEntrypointCandidate.Should().BeTrue();
    }

    [Theory]
    [InlineData(".cctor")]
    [InlineData("ModuleInitializer")]
    public void EnsureV1_DetectsEntrypointCandidate_ForModuleInitializers(string name)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "node1", Name = name }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().ContainSingle()
            .Which.IsEntrypointCandidate.Should().BeTrue();
    }

    #endregion

    #region EnsureV1 - Edge Reason Inference Tests

    [Theory]
    [InlineData("call", EdgeReason.DirectCall)]
    [InlineData("direct", EdgeReason.DirectCall)]
    [InlineData("virtual", EdgeReason.VirtualCall)]
    [InlineData("callvirt", EdgeReason.VirtualCall)]
    [InlineData("newobj", EdgeReason.NewObj)]
    [InlineData("new", EdgeReason.NewObj)]
    [InlineData("ldftn", EdgeReason.DelegateCreate)]
    [InlineData("delegate", EdgeReason.DelegateCreate)]
    [InlineData("reflection", EdgeReason.ReflectionString)]
    [InlineData("di", EdgeReason.DiBinding)]
    [InlineData("injection", EdgeReason.DiBinding)]
    [InlineData("async", EdgeReason.AsyncContinuation)]
    [InlineData("continuation", EdgeReason.AsyncContinuation)]
    [InlineData("event", EdgeReason.EventHandler)]
    [InlineData("generic", EdgeReason.GenericInstantiation)]
    [InlineData("native", EdgeReason.NativeInterop)]
    [InlineData("pinvoke", EdgeReason.NativeInterop)]
    [InlineData("ffi", EdgeReason.NativeInterop)]
    public void EnsureV1_InfersEdgeReason_FromLegacyType(string legacyType, EdgeReason expected)
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>
            {
                new() { SourceId = "n1", TargetId = "n2", Type = legacyType, Reason = EdgeReason.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Edges.Should().ContainSingle()
            .Which.Reason.Should().Be(expected);
    }

    [Fact]
    public void EnsureV1_InfersRuntimeMinted_ForRuntimeKind()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>
            {
                new() { SourceId = "n1", TargetId = "n2", Type = "unknown", Kind = EdgeKind.Runtime, Reason = EdgeReason.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Edges.Should().ContainSingle()
            .Which.Reason.Should().Be(EdgeReason.RuntimeMinted);
    }

    [Fact]
    public void EnsureV1_InfersDynamicImport_ForHeuristicKind()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>
            {
                new() { SourceId = "n1", TargetId = "n2", Type = "unknown", Kind = EdgeKind.Heuristic, Reason = EdgeReason.Unknown }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Edges.Should().ContainSingle()
            .Which.Reason.Should().Be(EdgeReason.DynamicImport);
    }

    [Fact]
    public void EnsureV1_PreservesEdgeReason_WhenAlreadySet()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>
            {
                new() { SourceId = "n1", TargetId = "n2", Type = "call", Reason = EdgeReason.VirtualCall }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Edges.Should().ContainSingle()
            .Which.Reason.Should().Be(EdgeReason.VirtualCall);
    }

    #endregion

    #region EnsureV1 - Entrypoint Inference Tests

    [Fact]
    public void EnsureV1_InfersEntrypoints_FromEntrypointCandidateNodes()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            LanguageType = CallgraphLanguage.DotNet,
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "main", Name = "Main", IsEntrypointCandidate = true },
                new() { Id = "helper", Name = "Helper", IsEntrypointCandidate = false }
            },
            Entrypoints = new List<CallgraphEntrypoint>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().ContainSingle()
            .Which.NodeId.Should().Be("main");
    }

    [Fact]
    public void EnsureV1_InfersEntrypoints_FromExplicitRoots()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            LanguageType = CallgraphLanguage.DotNet,
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "init", Name = "Initialize" }
            },
            Roots = new List<CallgraphRoot>
            {
                new("init", "init", "module_init")
            },
            Entrypoints = new List<CallgraphEntrypoint>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().ContainSingle()
            .Which.NodeId.Should().Be("init");
    }

    [Fact]
    public void EnsureV1_PreservesEntrypoints_WhenAlreadyPresent()
    {
        // Arrange
        var existingEntrypoint = new CallgraphEntrypoint
        {
            NodeId = "existing",
            Kind = EntrypointKind.Http,
            Route = "/api/test"
        };

        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "main", Name = "Main", IsEntrypointCandidate = true }
            },
            Entrypoints = new List<CallgraphEntrypoint> { existingEntrypoint }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().ContainSingle()
            .Which.NodeId.Should().Be("existing");
    }

    #endregion

    #region EnsureV1 - Ordering Tests

    [Fact]
    public void EnsureV1_SortsNodes_ByIdAlphabetically()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "z-node", Name = "Z" },
                new() { Id = "a-node", Name = "A" },
                new() { Id = "m-node", Name = "M" }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Select(n => n.Id).Should().BeInAscendingOrder();
    }

    [Fact]
    public void EnsureV1_SortsEdges_BySourceThenTargetThenTypeThenOffset()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>
            {
                new() { SourceId = "b", TargetId = "x", Type = "call", Offset = 10 },
                new() { SourceId = "a", TargetId = "y", Type = "call", Offset = 5 },
                new() { SourceId = "a", TargetId = "x", Type = "virtual", Offset = 0 },
                new() { SourceId = "a", TargetId = "x", Type = "call", Offset = 20 }
            }
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        var sortedEdges = result.Edges.ToList();
        sortedEdges[0].SourceId.Should().Be("a");
        sortedEdges[0].TargetId.Should().Be("x");
        sortedEdges[0].Type.Should().Be("call");
    }

    [Fact]
    public void EnsureV1_SortsEntrypoints_ByPhaseThenOrder()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            LanguageType = CallgraphLanguage.DotNet,
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "main", Name = "Main", IsEntrypointCandidate = true },
                new() { Id = "init", Name = ".cctor", IsEntrypointCandidate = true }
            },
            Entrypoints = new List<CallgraphEntrypoint>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().HaveCount(2);
        // ModuleInit phase should come before Runtime
        result.Entrypoints.First().NodeId.Should().Be("init");
    }

    #endregion

    #region EnsureV1 - Null Handling Tests

    [Fact]
    public void EnsureV1_ThrowsArgumentNullException_ForNullDocument()
    {
        // Act & Assert
        Assert.Throws<ArgumentNullException>(() => CallgraphSchemaMigrator.EnsureV1(null!));
    }

    [Fact]
    public void EnsureV1_HandlesEmptyNodes_Gracefully()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Nodes = new List<CallgraphNode>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Nodes.Should().BeEmpty();
    }

    [Fact]
    public void EnsureV1_HandlesEmptyEdges_Gracefully()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            Edges = new List<CallgraphEdge>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Edges.Should().BeEmpty();
    }

    #endregion

    #region Framework Inference Tests

    [Fact]
    public void EnsureV1_InfersAspNetCoreFramework_ForDotNetController()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            LanguageType = CallgraphLanguage.DotNet,
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "ctrl", Name = "OrdersController", IsEntrypointCandidate = true }
            },
            Entrypoints = new List<CallgraphEntrypoint>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().ContainSingle()
            .Which.Framework.Should().Be(EntrypointFramework.AspNetCore);
    }

    [Fact]
    public void EnsureV1_InfersSpringFramework_ForJavaController()
    {
        // Arrange
        var document = new CallgraphDocument
        {
            LanguageType = CallgraphLanguage.Java,
            Nodes = new List<CallgraphNode>
            {
                new() { Id = "ctrl", Name = "OrderController", IsEntrypointCandidate = true }
            },
            Entrypoints = new List<CallgraphEntrypoint>()
        };

        // Act
        var result = CallgraphSchemaMigrator.EnsureV1(document);

        // Assert
        result.Entrypoints.Should().ContainSingle()
            .Which.Framework.Should().Be(EntrypointFramework.Spring);
    }

    #endregion
}