jtr/DevDisciples.Json.Tools/Json2CSharpTranslator.cs

using DevDisciples.Json.Parser;
using DevDisciples.Json.Parser.Syntax;
using DevDisciples.Parsing;
using DevDisciples.Parsing.Extensions;
using Humanizer;

namespace DevDisciples.Json.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.CurrentName = 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.ForEach(@class => @class.Translate(context));

        return context.Builder.ToString();
    }

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

        context.Classes.Add(@class);

        foreach (var prop in @object.Properties)
        {
            context.CurrentName = prop.Key.Lexeme;
            var visitor = Visitors[prop.Value.GetType()];
            var translation = visitor(prop.Value, context);

            switch (translation)
            {
                case ClassTranslation:
                    @class.Properties.Add(new PropertyTranslation
                    {
                        Type = translation.Name,
                        Name = translation.Name,
                    });
                    break;
                case PropertyTranslation property:
                    @class.Properties.Add(property);
                    break;
            }
        }

        return @class;
    }

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

        if (array.Elements.Length == 0)
        {
            type = "object";
        }
        else if (array.Elements.All(e => e is JsonObjectSyntax))
        {
            context.Classes.Add(SquashObjects(context.CurrentName, array.Elements, context));
            type = context.Classes.Last().Name;
        }
        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";
        }

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

    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.CurrentName,
        };
    }

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

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

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

    private static ClassTranslation SquashObjects(string className, IEnumerable<IJsonSyntax> objects, Context context)
    {
        var classes = objects
            .Select(@object => Object(@object, context))
            .ToArray();

        var squashed = new ClassTranslation
        {
            Name = className.Singularize(),
            Properties = new()
        };

        foreach (var @class in classes)
        foreach (var prop in ((ClassTranslation)@class).Properties)
            if (squashed.Properties.All(p => p.Name != prop.Name))
                squashed.Properties.Add(prop);

        return squashed;
    }
}