using Microsoft.CodeAnalysis;
using Microsoft.CodeAnalysis.CSharp;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using System.Collections.Immutable;
using System.Text;
using Telegrator.RoslynExtensions;

namespace Telegrator.RoslynGenerators
{
    [Generator(LanguageNames.CSharp)]
    public class ImplicitHandlerBuilderExtensionsGenerator : IIncrementalGenerator
    {
        public void Initialize(IncrementalGeneratorInitializationContext context)
        {
            IncrementalValueProvider<ImmutableArray<ClassDeclarationSyntax>> pipeline = context.SyntaxProvider
                .CreateSyntaxProvider(SyntaxPredicate, SyntaxTransform)
                .Where(declaration => declaration != null)
                .Collect();

            context.RegisterImplementationSourceOutput(pipeline, GenerateSource);
        }

        private static bool SyntaxPredicate(SyntaxNode node, CancellationToken _)
        {
            if (node is not ClassDeclarationSyntax)
                return false;

            return true;
        }

        private static ClassDeclarationSyntax SyntaxTransform(GeneratorSyntaxContext context, CancellationToken _)
        {
            ISymbol? symbol = context.SemanticModel.GetDeclaredSymbol(context.Node);
            if (symbol is null)
                return null!;

            if (symbol is not ITypeSymbol typeSymbol)
                return null!;

            if (!typeSymbol.IsAssignableFrom("UpdateFilterAttribute"))
                return null!;

            return (ClassDeclarationSyntax)context.Node;
        }

        private static void GenerateSource(SourceProductionContext context, ImmutableArray<ClassDeclarationSyntax> declarations)
        {
            StringBuilder source = new StringBuilder();
            Dictionary<string, string> targeters = [];
            List<string> usingDirectives =
            [
                "using Telegrator.Handlers.Building;",
                "using Telegrator.Handlers.Building.Components;"
            ];

            StringBuilder sourceBuilder = new StringBuilder()
                .AppendLine("namespace Telegrator")
                .AppendLine("{")
                .Append("\t//").Append(string.Join(", ", declarations.Select(decl => decl.Identifier.ToString()))).AppendLine()
                .AppendLine("\tpublic static partial class HandlerBuilderExtensions")
                .AppendLine("\t{");

            List<ClassDeclarationSyntax> lateTargeterClasses = [];
            foreach (ClassDeclarationSyntax classDeclaration in declarations)
            {
                try
                {
                    usingDirectives.UnionAdd(classDeclaration.FindAncestor<CompilationUnitSyntax>().Usings.Select(use => use.ToString()));
                    ParseClassDeclaration(sourceBuilder, classDeclaration, targeters);
                }
                catch (TargteterNotFoundException)
                {
                    lateTargeterClasses.Add(classDeclaration);
                }
                catch (Exception exc)
                {
                    string errorFormat = string.Format("\t\t// failed to generate for {0} : {1}", classDeclaration.Identifier.ToString(), exc.GetType().Name);
                    sourceBuilder.AppendLine(errorFormat);
                }
            }

            foreach (ClassDeclarationSyntax classDeclaration in lateTargeterClasses)
            {
                try
                {
                    usingDirectives.UnionAdd(classDeclaration.FindAncestor<CompilationUnitSyntax>().Usings.Select(use => use.ToString()));
                    ParseClassDeclaration(sourceBuilder, classDeclaration, targeters);
                }
                catch (Exception exc)
                {
                    string errorFormat = string.Format("\t\t// failed to generate for {0} : {1}", classDeclaration.Identifier.ToString(), exc.GetType().Name);
                    sourceBuilder.AppendLine(errorFormat);
                }
            }

            sourceBuilder.AppendLine("\t}\n}");
            sourceBuilder.Insert(0, string.Join("\n", usingDirectives.Select(use => use.ToString()).OrderBy(use => use)) + "\n\n");
            context.AddSource("GeneratedHandlerBuilderExtensions.cs", sourceBuilder.ToString());
        }

        private static void ParseClassDeclaration(StringBuilder sourceBuilder, ClassDeclarationSyntax classDeclaration, Dictionary<string, string> targeters)
        {
            string className = classDeclaration.Identifier.ToString();
            if (className == "FilterAnnotation")
                return;

            IEnumerable<MethodDeclarationSyntax> methods = classDeclaration.Members.OfType<MethodDeclarationSyntax>();
            MethodDeclarationSyntax? targeterMethod = methods.FirstOrDefault(method => method.Identifier.ToString() == "GetFilterringTarget");

            string filterName = className.Replace("Attribute", string.Empty);
            string classTargetterMethodName = filterName + "_GetFilterringTarget";

            if (targeterMethod != null)
            {
                targeters.Add(className, classTargetterMethodName);
                RenderTargeterMethod(sourceBuilder, classTargetterMethodName, targeterMethod);
                sourceBuilder.AppendLine();
            }
            else
            {
                if (classDeclaration.BaseList == null)
                    throw new Exception();

                string baseClassName = classDeclaration.BaseList.Types
                    .ElementAt(0).GetBaseTypeSyntaxName();

                if (!targeters.ContainsKey(baseClassName))
                    throw new TargteterNotFoundException();

                classTargetterMethodName = targeters[baseClassName];
            }

            if (classDeclaration.Modifiers.Any(keyword => keyword.ValueText == "abstract"))
                return;

            if (classDeclaration.ParameterList != null)
            {
                if (classDeclaration.BaseList != null)
                {
                    PrimaryConstructorBaseTypeSyntax primaryConstructor = (PrimaryConstructorBaseTypeSyntax)classDeclaration.BaseList.Types.ElementAt(0);
                    RenderExtensionMethod(sourceBuilder, filterName, classTargetterMethodName, classDeclaration.ParameterList.Parameters, primaryConstructor.ArgumentList.Arguments);
                }
                else
                {
                    RenderExtensionMethod(sourceBuilder, filterName, classTargetterMethodName, classDeclaration.ParameterList.Parameters, []);
                }

                sourceBuilder.AppendLine();
            }

            foreach (ConstructorDeclarationSyntax constructor in classDeclaration.Members.OfType<ConstructorDeclarationSyntax>())
            {
                if (constructor.Initializer == null)
                    continue;

                RenderExtensionMethod(sourceBuilder, filterName, classTargetterMethodName, constructor.ParameterList.Parameters, constructor.Initializer.ArgumentList.Arguments);
                sourceBuilder.AppendLine();
            }
        }

        private static void RenderExtensionMethod(StringBuilder sourceBuilder, string filterName, string classTargetterMethodName, SeparatedSyntaxList<ParameterSyntax> parameters, SeparatedSyntaxList<ArgumentSyntax> arguments)
        {
            if (filterName == "ChatType")
                filterName = "InChatType"; // Because it conflicting

            sourceBuilder
                .Append("\t\t/// <summary>").AppendLine()
                .Append("\t\t/// Adds ").Append(filterName).Append(" filter to implicit handler").AppendLine()
                .Append("\t\t/// </summary>").AppendLine();

            sourceBuilder.Append("\t\tpublic static TBuilder ").Append(filterName).Append("<TBuilder>(this TBuilder builder");

            if (parameters.Any())
                sourceBuilder.Append(", ").Append(parameters.ToFullString());

            sourceBuilder
                .Append(") where TBuilder : IHandlerBuilder").AppendLine()
                .Append("\t\t{").AppendLine()
                .Append("\t\t\tbuilder.AddTargetedFilter");

            if (arguments.Count > 1)
                sourceBuilder.Append("s");

            sourceBuilder.Append("(").Append(classTargetterMethodName);

            if (arguments.Any())
                sourceBuilder.Append(", ").Append(arguments.ToFullString());

            sourceBuilder
                .Append(");").AppendLine()
                .Append("\t\t\treturn builder;").AppendLine()
                .Append("\t\t}").AppendLine();
        }

        private static void RenderTargeterMethod(StringBuilder sourceBuilder, string classTargetterMethodName, MethodDeclarationSyntax targeterMethod)
        {
            sourceBuilder.Append("\t\tprivate static ").Append(targeterMethod.ReturnType.ToString()).Append(" ").Append(classTargetterMethodName).Append(targeterMethod.ParameterList.ToFullString());

            if (targeterMethod.ExpressionBody != null)
            {
                sourceBuilder.Append(targeterMethod.ExpressionBody.ToFullString()).Append(";").AppendLine();
            }
            else if (targeterMethod.Body != null)
            {
                sourceBuilder.Append(targeterMethod.Body.ToFullString());
            }
        }
    }
}