nub-lang/compiler/NubLang.LSP/HoverHandler.cs

using System.Globalization;
using NubLang.Ast;
using NubLang.Modules;
using NubLang.Types;
using OmniSharp.Extensions.LanguageServer.Protocol.Client.Capabilities;
using OmniSharp.Extensions.LanguageServer.Protocol.Document;
using OmniSharp.Extensions.LanguageServer.Protocol.Models;

namespace NubLang.LSP;

internal class HoverHandler(WorkspaceManager workspaceManager) : HoverHandlerBase
{
    protected override HoverRegistrationOptions CreateRegistrationOptions(HoverCapability capability, ClientCapabilities clientCapabilities)
    {
        return new HoverRegistrationOptions
        {
            DocumentSelector = TextDocumentSelector.ForLanguage("nub")
        };
    }

    public override Task<Hover?> Handle(HoverParams request, CancellationToken cancellationToken)
    {
        return Task.FromResult(HandleSync(request, cancellationToken));
    }

    private Hover? HandleSync(HoverParams request, CancellationToken cancellationToken)
    {
        var topLevelNodes = workspaceManager.GetTopLevelNodes(request.TextDocument.Uri.GetFileSystemPath());

        var moduleDecl = topLevelNodes.OfType<ModuleNode>().FirstOrDefault();
        if (moduleDecl == null)
        {
            return null;
        }

        var moduleRepository = workspaceManager.GetModuleRepository();
        if (!moduleRepository.TryGet(moduleDecl.NameToken, out var module))
        {
            return null;
        }

        var line = request.Position.Line;
        var character = request.Position.Character;

        var hoveredNode = topLevelNodes.DeepestNodeAtPosition(line, character);

        if (hoveredNode == null)
        {
            return null;
        }

        var message = CreateMessage(hoveredNode, moduleRepository, module, line, character);
        if (message == null)
        {
            return null;
        }

        return new Hover
        {
            Contents = new MarkedStringsOrMarkupContent(new MarkupContent
            {
                Value = message,
                Kind = MarkupKind.Markdown,
            })
        };
    }

    private static string? CreateMessage(Node hoveredNode, ModuleRepository repository, ModuleRepository.Module currentModule, int line, int character)
    {
        return hoveredNode switch
        {
            FuncNode funcNode => CreateFuncPrototypeMessage(funcNode.Prototype),
            FuncPrototypeNode funcPrototypeNode => CreateFuncPrototypeMessage(funcPrototypeNode),
            LocalFuncIdentifierNode funcIdentifierNode => CreateLocalFuncIdentifierMessage(funcIdentifierNode, currentModule),
            ModuleFuncIdentifierNode funcIdentifierNode => CreateModuleFuncIdentifierMessage(funcIdentifierNode, repository),
            FuncParameterNode funcParameterNode => CreateTypeNameMessage("Function parameter", funcParameterNode.NameToken.Value, funcParameterNode.Type),
            VariableIdentifierNode variableIdentifierNode => CreateTypeNameMessage("Variable", variableIdentifierNode.NameToken.Value, variableIdentifierNode.Type),
            VariableDeclarationNode variableDeclarationNode => CreateTypeNameMessage("Variable declaration", variableDeclarationNode.NameToken.Value, variableDeclarationNode.Type),
            StructFieldAccessNode structFieldAccessNode => CreateTypeNameMessage("Struct field", $"{structFieldAccessNode.Target.Type}.{structFieldAccessNode.FieldToken.Value}", structFieldAccessNode.Type),
            CStringLiteralNode cStringLiteralNode => CreateLiteralMessage(cStringLiteralNode.Type, '"' + cStringLiteralNode.Value + '"'),
            StringLiteralNode stringLiteralNode => CreateLiteralMessage(stringLiteralNode.Type, '"' + stringLiteralNode.Value + '"'),
            BoolLiteralNode boolLiteralNode => CreateLiteralMessage(boolLiteralNode.Type, boolLiteralNode.Value.ToString()),
            Float32LiteralNode float32LiteralNode => CreateLiteralMessage(float32LiteralNode.Type, float32LiteralNode.Value.ToString(CultureInfo.InvariantCulture)),
            Float64LiteralNode float64LiteralNode => CreateLiteralMessage(float64LiteralNode.Type, float64LiteralNode.Value.ToString(CultureInfo.InvariantCulture)),
            I8LiteralNode i8LiteralNode => CreateLiteralMessage(i8LiteralNode.Type, i8LiteralNode.Value.ToString()),
            I16LiteralNode i16LiteralNode => CreateLiteralMessage(i16LiteralNode.Type, i16LiteralNode.Value.ToString()),
            I32LiteralNode i32LiteralNode => CreateLiteralMessage(i32LiteralNode.Type, i32LiteralNode.Value.ToString()),
            I64LiteralNode i64LiteralNode => CreateLiteralMessage(i64LiteralNode.Type, i64LiteralNode.Value.ToString()),
            U8LiteralNode u8LiteralNode => CreateLiteralMessage(u8LiteralNode.Type, u8LiteralNode.Value.ToString()),
            U16LiteralNode u16LiteralNode => CreateLiteralMessage(u16LiteralNode.Type, u16LiteralNode.Value.ToString()),
            U32LiteralNode u32LiteralNode => CreateLiteralMessage(u32LiteralNode.Type, u32LiteralNode.Value.ToString()),
            U64LiteralNode u64LiteralNode => CreateLiteralMessage(u64LiteralNode.Type, u64LiteralNode.Value.ToString()),
            StructInitializerNode structInitializerNode => CreateStructInitializerMessage(structInitializerNode, line, character),
            // Expressions can have a generic fallback showing the resulting type
            ExpressionNode expressionNode => $"""
                                              **Expression** `{expressionNode.GetType().Name}`
                                              ```nub
                                              {expressionNode.Type}
                                              ```
                                              """,
            BlockNode => null,
            _ => hoveredNode.GetType().Name
        };
    }

    private static string CreateStructInitializerMessage(StructInitializerNode structInitializerNode, int line, int character)
    {
        var hoveredInitializerName = structInitializerNode
            .Initializers
            .Select(x => x.Key)
            .FirstOrDefault(x => x.ContainsPosition(line, character));

        var structType = (NubStructType)structInitializerNode.Type;

        if (hoveredInitializerName != null)
        {
            var field = structType.Fields.FirstOrDefault(x => x.Name == hoveredInitializerName.Value);
            if (field != null)
            {
                return $"""
                        **Field** in `{structType}`
                        ```nub
                        {hoveredInitializerName.Value}: {field.Type}
                        ```
                        """;
            }
            else
            {
                return $"""
                        **Field** in `{structType}`
                        ```nub
                        // Field not found
                        ```
                        """;
            }
        }

        return $"**Struct initializer** `{structType}`";
    }

    private static string CreateLiteralMessage(NubType type, string value)
    {
        return $"""
                **Literal** `{type}`
                ```nub
                {value}: {type}
                ```
                """;
    }

    private static string CreateTypeNameMessage(string description, string name, NubType type)
    {
        return $"""
                **{description}** `{name}`
                ```nub
                {name}: {type}
                ```
                """;
    }

    private static string CreateLocalFuncIdentifierMessage(LocalFuncIdentifierNode funcIdentifierNode, ModuleRepository.Module currentModule)
    {
        if (!currentModule.TryResolveFunc(funcIdentifierNode.NameToken, out var func, out _))
        {
            return $"""
                    **Function** `{funcIdentifierNode.NameToken.Value}`
                    ```nub
                    // Declaration not found
                    ```
                    """;
        }

        return CreateFuncPrototypeMessage(func);
    }

    private static string CreateModuleFuncIdentifierMessage(ModuleFuncIdentifierNode funcIdentifierNode, ModuleRepository repository)
    {
        if (!repository.TryGet(funcIdentifierNode.ModuleToken, out var module) || !module.TryResolveFunc(funcIdentifierNode.NameToken, out var func, out _))
        {
            return $"""
                    **Function** `{funcIdentifierNode.ModuleToken.Value}::{funcIdentifierNode.NameToken.Value}`
                    ```nub
                    // Declaration not found
                    ```
                    """;
        }

        return CreateFuncPrototypeMessage(func);
    }

    private static string CreateFuncPrototypeMessage(FuncPrototypeNode funcPrototypeNode)
    {
        var parameterText = string.Join(", ", funcPrototypeNode.Parameters.Select(x => $"{x.NameToken.Value}: {x.Type}"));
        var externText = funcPrototypeNode.ExternSymbolToken != null ? $"extern \"{funcPrototypeNode.ExternSymbolToken.Value}\" " : "";

        return $"""
                **Function** `{funcPrototypeNode.NameToken.Value}`
                ```nub
                {externText}func {funcPrototypeNode.NameToken.Value}({parameterText}): {funcPrototypeNode.ReturnType}
                ```
                """;
    }
}