#pragma warning disable RS1035 // Do not use APIs banned for analyzers - This is an MSBuild task, not an analyzer

using System;
using System.Collections.Generic;
using System.IO;
using System.Linq;
using Microsoft.Build.Framework;
using Microsoft.Build.Utilities;
using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;

namespace Svrnty.CQRS.Grpc.Generators;

/// <summary>
/// MSBuild task that generates .proto files by creating its own Roslyn compilation.
/// This runs BEFORE CoreCompile to solve the source generator timing issue.
/// </summary>
public class GenerateProtoFileTask : Task
{
    /// <summary>
    /// The project directory
    /// </summary>
    [Required]
    public string ProjectDirectory { get; set; } = string.Empty;

    /// <summary>
    /// The output directory where the proto file should be written (typically Protos/)
    /// </summary>
    [Required]
    public string OutputDirectory { get; set; } = string.Empty;

    /// <summary>
    /// The name of the proto file to generate (typically cqrs_services.proto)
    /// </summary>
    [Required]
    public string ProtoFileName { get; set; } = string.Empty;

    /// <summary>
    /// The C# source files to compile (from @(Compile) ItemGroup)
    /// </summary>
    [Required]
    public ITaskItem[] SourceFiles { get; set; } = Array.Empty<ITaskItem>();

    /// <summary>
    /// The assembly references (from @(ReferencePath) ItemGroup)
    /// </summary>
    [Required]
    public ITaskItem[] References { get; set; } = Array.Empty<ITaskItem>();

    /// <summary>
    /// The root namespace of the project
    /// </summary>
    public string RootNamespace { get; set; } = string.Empty;

    /// <summary>
    /// The assembly name of the project
    /// </summary>
    public string AssemblyName { get; set; } = string.Empty;

    public override bool Execute()
    {
        try
        {
            Log.LogMessage(MessageImportance.High,
                "Svrnty.CQRS.Grpc: Generating proto file via MSBuild task...");

            // Determine the namespace for the proto file
            var projectNamespace = !string.IsNullOrEmpty(RootNamespace) ? RootNamespace
                : !string.IsNullOrEmpty(AssemblyName) ? AssemblyName
                : "Generated";
            var grpcNamespace = $"{projectNamespace}.Grpc";
            var packageName = "cqrs";

            // Create the compilation
            var compilation = CreateCompilation();
            if (compilation == null)
            {
                Log.LogWarning("Svrnty.CQRS.Grpc: Could not create compilation. Writing placeholder proto file.");
                WritePlaceholderProto(grpcNamespace);
                return true;
            }

            // Check for compilation errors that would prevent proper analysis
            var diagnostics = compilation.GetDiagnostics()
                .Where(d => d.Severity == DiagnosticSeverity.Error)
                .ToList();

            if (diagnostics.Count > 0)
            {
                Log.LogMessage(MessageImportance.Normal,
                    $"Svrnty.CQRS.Grpc: Compilation has {diagnostics.Count} errors. Attempting to generate proto anyway...");

                // Log first few errors for debugging
                foreach (var diag in diagnostics.Take(5))
                {
                    Log.LogMessage(MessageImportance.Low, $"  {diag.GetMessage()}");
                }
            }

            // Use the ProtoFileGenerator to generate content
            var generator = new ProtoFileGenerator(compilation);
            var protoContent = generator.Generate(packageName, grpcNamespace);

            // Check if we got meaningful content
            if (string.IsNullOrWhiteSpace(protoContent) || !protoContent.Contains("rpc "))
            {
                Log.LogMessage(MessageImportance.High,
                    "Svrnty.CQRS.Grpc: No commands/queries/notifications found. Writing minimal proto file.");
                WritePlaceholderProto(grpcNamespace);
                return true;
            }

            // Ensure output directory exists
            var fullOutputPath = Path.IsPathRooted(OutputDirectory)
                ? OutputDirectory
                : Path.Combine(ProjectDirectory, OutputDirectory);
            Directory.CreateDirectory(fullOutputPath);

            // Write the proto file
            var protoFilePath = Path.Combine(fullOutputPath, ProtoFileName);
            File.WriteAllText(protoFilePath, protoContent);

            Log.LogMessage(MessageImportance.High,
                $"Svrnty.CQRS.Grpc: Successfully generated proto file at {protoFilePath}");

            return true;
        }
        catch (Exception ex)
        {
            Log.LogErrorFromException(ex, true);
            return false;
        }
    }

    private CSharpCompilation? CreateCompilation()
    {
        try
        {
            // Parse all source files into syntax trees
            var syntaxTrees = new List<SyntaxTree>();
            foreach (var sourceFile in SourceFiles)
            {
                var filePath = sourceFile.ItemSpec;
                if (!Path.IsPathRooted(filePath))
                {
                    filePath = Path.Combine(ProjectDirectory, filePath);
                }

                if (!File.Exists(filePath))
                {
                    Log.LogMessage(MessageImportance.Low, $"Source file not found: {filePath}");
                    continue;
                }

                try
                {
                    var sourceText = File.ReadAllText(filePath);
                    var syntaxTree = CSharpSyntaxTree.ParseText(
                        sourceText,
                        CSharpParseOptions.Default.WithLanguageVersion(LanguageVersion.Latest),
                        path: filePath);
                    syntaxTrees.Add(syntaxTree);
                }
                catch (Exception ex)
                {
                    Log.LogMessage(MessageImportance.Low, $"Failed to parse {filePath}: {ex.Message}");
                }
            }

            if (syntaxTrees.Count == 0)
            {
                Log.LogWarning("Svrnty.CQRS.Grpc: No source files could be parsed.");
                return null;
            }

            Log.LogMessage(MessageImportance.Normal,
                $"Svrnty.CQRS.Grpc: Parsed {syntaxTrees.Count} source files");

            // Create metadata references from the References
            var metadataReferences = new List<MetadataReference>();
            foreach (var reference in References)
            {
                var refPath = reference.ItemSpec;
                if (!File.Exists(refPath))
                {
                    Log.LogMessage(MessageImportance.Low, $"Reference not found: {refPath}");
                    continue;
                }

                try
                {
                    var metadataRef = MetadataReference.CreateFromFile(refPath);
                    metadataReferences.Add(metadataRef);
                }
                catch (Exception ex)
                {
                    Log.LogMessage(MessageImportance.Low, $"Failed to load reference {refPath}: {ex.Message}");
                }
            }

            Log.LogMessage(MessageImportance.Normal,
                $"Svrnty.CQRS.Grpc: Loaded {metadataReferences.Count} references");

            // Create the compilation
            var compilationOptions = new CSharpCompilationOptions(OutputKind.DynamicallyLinkedLibrary)
                .WithNullableContextOptions(NullableContextOptions.Enable);

            var assemblyName = !string.IsNullOrEmpty(AssemblyName) ? AssemblyName : "TempCompilation";
            var compilation = CSharpCompilation.Create(
                assemblyName,
                syntaxTrees,
                metadataReferences,
                compilationOptions);

            return compilation;
        }
        catch (Exception ex)
        {
            Log.LogMessage(MessageImportance.High,
                $"Svrnty.CQRS.Grpc: Failed to create compilation: {ex.Message}");
            return null;
        }
    }

    private void WritePlaceholderProto(string grpcNamespace)
    {
        var placeholderProto = $@"syntax = ""proto3"";

option csharp_namespace = ""{grpcNamespace}"";

package cqrs;

// Placeholder proto file - will be regenerated when commands/queries are available
// Using namespace: {grpcNamespace}

// Empty service definitions so Grpc.Tools generates base classes
service CommandService {{
}}

service QueryService {{
}}

service DynamicQueryService {{
}}
";
        var fullOutputPath = Path.IsPathRooted(OutputDirectory)
            ? OutputDirectory
            : Path.Combine(ProjectDirectory, OutputDirectory);
        Directory.CreateDirectory(fullOutputPath);
        var protoFilePath = Path.Combine(fullOutputPath, ProtoFileName);
        File.WriteAllText(protoFilePath, placeholderProto);

        Log.LogMessage(MessageImportance.High,
            $"Svrnty.CQRS.Grpc: Wrote placeholder proto file at {protoFilePath}");
    }
}