tlang-interperter-cs/tlanglib/TLangTemplateEngine.cs

using System;
using System.Collections.Generic;
using System.IO;
using System.Text;

namespace tlang {
public class TLangGenerator
{
    Lazy<(List<LexToken> Tokens,string Source)> srcCode;
    public TLangGenerator(string src)
    {
        srcCode=new Lazy<(List<LexToken> Tokens,string Source)>(()=>{
            string text = Lex(src);
            Lexer lexer=new Lexer(new StringReader(text));
        
            return (lexer.Tokens,text);
        });
    }
    public string SourceCode 
    {
        get => srcCode.Value.Source;
    }
    public string Execute(Action<RootEnvironment> parser)
    {
        
        Parser p = new Parser(srcCode.Value.Tokens);
        RootEnvironment env=new RootEnvironment();
        p.LoadEnvironment(env);
        StringBuilder builder=new StringBuilder();
        env.SetVariable("__writer",new TExternalMethod((args)=>{
            if(args.Length >= 1)
            {
                foreach(var arg in args)
                {
                    builder.Append(arg.ToString());
                }
            }
            return TObject.Null;
        }));
        parser?.Invoke(env);

        p.Execute(env);
        
        
        //
        return builder.ToString();
    }

    private string Lex(string text)
    {
        StringBuilder tlangFile = new StringBuilder();
        StringBuilder b=new StringBuilder();
        
       bool lastInCode=true;
        bool inCode=false;
        int i = 0;
        bool isDone = false;
        Action<int> appendChar = (c)=>{
          if((lastInCode != inCode || isDone) && b.Length > 0)
          {
              if(inCode ^ (isDone && !inCode))
              {     
                    tlangFile.Append("__writer(\"");
                    b.Replace("\n","\\n").Replace("\t","\\t").Replace("\r","\\r").Replace("\"","\\\"").Replace("\'","\\\'");
                    foreach(var _c in b.ToString())
                    {
                        if(_c < 32 || _c > 126)
                        {
                            tlangFile.Append($"\\x{((int)_c).ToString("X2")}");
                        }else{
                            tlangFile.Append(_c);
                        }
                    }
                    b.Clear();
                    
                    tlangFile.Append("\");");
              }
              if(!inCode ^ (isDone && inCode))
              {
                    if(b.Length > 0)
                    {
                        tlangFile.Append(b);
                    }
                    b.Clear();
              }
          }
          
          if(c != -1)
          {
            b.Append((char)c);
          }
          
          lastInCode = inCode;  
        };
        bool escapedByAt = false;
        while(i < text.Length)
        {
            char curChar = text[i++];
            int nextChar = i<text.Length ? text[i] : -1;
            switch(curChar)
            {
                case '@':
                    if(nextChar == '{') 
                    {
                        appendChar('{');
                        i++;
                    }else if(nextChar == '}') {
                        appendChar('}');
                        i++;
                    }else if(nextChar == '@')
                    {
                        appendChar('@');
                        i++;
                    }else{
                        if(!escapedByAt)
                        {
                            
                            inCode=true;
                            escapedByAt=true;
                            //we are a variable
                            
                            foreach(var c in "__writer(")
                                appendChar(c);
                            
                        }else
                        if(escapedByAt)
                        {
                            appendChar(')');
                            appendChar(';');
                            inCode = false;
                            escapedByAt = false;
                            
                            
                        }
                    }
                    break;
                case '{':
                    if(nextChar == '{')
                    {
                        
                         i++;
                        inCode = !inCode;
                        
                    }else{
                        appendChar(curChar);
                    }
                
                    break;
               
                case '}':
                    if(nextChar == '}')
                    {
                        i++;
                        inCode = !inCode;
                        
                    }else{
                        appendChar(curChar);
                    }
                break;
                default:
                    appendChar(curChar);
                    break;
            }
        }
         isDone=true;
        appendChar(-1);
        return tlangFile.ToString();
    }
}
}