Honestly designing a parser is easy: just start using ANTLR and perhaps add later an AST layer. However if you do not want to go that I suggest looking in proje

Honestly designing a parser is easy: just start using ANTLR and perhaps add later an AST layer. However if you do not want to go that I suggest looking in projectional editing, for example JetBrains MPS or Freon by Jos Warmer