jtr/Jtr.Tools/Json2CSharpTranslator.cs

using Jtr.Parsing.Json;
using Jtr.Parsing.Json.Syntax;
using Jtr.Tools.Extensions;
using Jtr.Parsing;
using Jtr.Parsing.Extensions;

namespace Jtr.Tools;

public static partial class Json2CSharpTranslator
{
    private static readonly VisitorContainer<IJsonSyntax, Context, ITranslation> Visitors = new();

    static Json2CSharpTranslator()
    {
        Visitors.Register<JsonObjectSyntax>(Object);
        Visitors.Register<JsonArraySyntax>(Array);
        Visitors.Register<JsonStringSyntax>(String);
        Visitors.Register<JsonNumberSyntax>(Number);
        Visitors.Register<JsonBoolSyntax>(Bool);
        Visitors.Register<JsonNullSyntax>(Null);
    }

    public static string Translate(string input, Context? context = null)
    {
        if (JsonParser.Parse("<input>", input) is not JsonObjectSyntax root)
            throw new SyntaxException("Expected a JSON object.");

        context ??= new();
        context.Name.Push(context.RootClassName);

        var visitor = Visitors[typeof(JsonObjectSyntax)];
        visitor(root, context);

        context.Builder.Append("//using System;\n");
        context.Builder.Append("//using System.Collections.Generic;\n");
        context.Builder.Append('\n');
        context.Builder.Append($"namespace {context.Namespace};\n\n");
        context.Classes.Reverse();
        context.Classes.ForEach(@class => @class.Translate(context));

        context.Name.Pop();

        return context.Builder.ToString();
    }

    private static ITranslation Translate(IJsonSyntax visitee, Context context)
    {
        return Visitors[visitee.GetType()](visitee, context);
    }

    private static ITranslation Object(IJsonSyntax visitee, Context context)
    {
        var @object = visitee.As<JsonObjectSyntax>();
        var @class = new ClassTranslation { Name = context.CurrentClassName, Properties = new() };

        context.Class.Push(@class);

        context.Scope.Push(Context.TranslationScope.Object);

        foreach (var prop in @object.Properties)
        {
            context.Name.Push(prop.Key.Lexeme);

            var translation = Translate(prop.Value, context);

            switch (translation)
            {
                case ClassTranslation:
                    // TODO: Handle class exists
                    context.Class.Peek().Properties.Add(new PropertyTranslation
                    {
                        Type = translation.Name,
                        Name = prop.Key.Lexeme,
                    });
                    break;

                case PropertyTranslation property:
                    // TODO: Handle property exists
                    context.Class.Peek().Properties.Add(property);
                    break;
            }

            context.Name.Pop();
        }

        if (!context.Scope.IsChildOf(Context.TranslationScope.Array))
        {
            context.Classes.Add(@class);
        }

        context.Scope.Pop();

        return context.Class.Pop();
    }

    private static ITranslation Array(IJsonSyntax visitee, Context context)
    {
        var array = visitee.As<JsonArraySyntax>();

        var type = "object";

        context.Scope.Push(Context.TranslationScope.Array);

        if (array.Elements.Length == 0)
        {
            type = "object";
        }
        else if (array.Elements.All(e => e is JsonObjectSyntax))
        {
            type = context.CurrentClassName;

            var composite = array.Elements
                .Select(el => Translate(el, context))
                .Cast<ClassTranslation>();

            var @class = new ClassTranslation
            {
                Name = type,
                Properties = composite
                    .SelectMany(cls => cls.Properties)
                    .ToList(),
            };

            context.Classes.Add(@class);
        }
        else if (array.Elements.All(e => e is JsonStringSyntax es && DateTime.TryParse(es.Value, out _)))
        {
            type = "DateTime";
        }
        else if (array.Elements.All(e => e is JsonStringSyntax))
        {
            type = "string";
        }
        else if (array.Elements.All(e => e is JsonNumberSyntax))
        {
            type = array.Elements.Any(e => ((JsonNumberSyntax)e).Token.Lexeme.Contains('.')) ? "double" : "int";
        }

        context.Scope.Pop();

        return new PropertyTranslation
        {
            Type = $"List<{type}>",
            Name = context.Name.Peek(),
        };
    }

    private static ITranslation String(IJsonSyntax visitee, Context context)
    {
        var @string = visitee.As<JsonStringSyntax>();
        var type = DateTime.TryParse(@string.Value, out _) ? "DateTime" : "string";

        return new PropertyTranslation
        {
            Type = type,
            Name = context.Name.Peek(),
        };
    }

    private static ITranslation Number(IJsonSyntax visitee, Context context)
    {
        return new PropertyTranslation
        {
            Type = visitee.As<JsonNumberSyntax>().Token.Lexeme.Contains('.') ? "double" : "int",
            Name = context.Name.Peek(),
        };
    }

    private static ITranslation Bool(IJsonSyntax visitee, Context context)
    {
        return new PropertyTranslation
        {
            Type = "bool",
            Name = context.Name.Peek(),
        };
    }

    private static ITranslation Null(IJsonSyntax visitee, Context context)
    {
        return new PropertyTranslation
        {
            Type = "object",
            Name = context.Name.Peek(),
        };
    }
}