open CalcLex.Internal;
open CalcLex.UserDeclarations;

datatype opNode = OP of result;

datatype synTree = 
     Empty
  |  EXP of synTree * synTree
  |  EXP1 of opNode * synTree 
  |  TERM of synTree * synTree
  |  TERM1 of opNode * synTree
  |  FACTOR of result;


fun exp tokenList =
     let val (termTree, rest1) = term tokenList in
       let val (exp1Tree, rest) = exp1 rest1 in
         (EXP(termTree, exp1Tree), rest)
       end
     end

and exp1 (PLUS::more) = 
     let val (expTree, rest) = exp more in
       (EXP1(OP(PLUS), expTree), rest)
     end
  | exp1 (SUB::more) = 
     let val (expTree, rest) = exp more in
       (EXP1(OP(SUB), expTree), rest)
     end
  | exp1 rest = (Empty, rest)

and term tokenlist =
      let val (factorTree, rest1) = factor tokenlist in
        let val (term1Tree, rest) = term1 rest1 in
          (TERM(factorTree, term1Tree), rest)
        end
      end

and term1 (DIV::more) =
     let val (termTree, rest) = term more in
       (TERM1(OP(DIV), termTree), rest)
     end
  | term1 (TIMES::more) = 
     let val (termTree, rest) = term more in
       (TERM1(OP(TIMES), termTree), rest)
     end
  | term1 rest = (Empty, rest)

and factor (ID(s)::rest) = (FACTOR(ID(s)), rest)
  | factor (NUM(n)::rest) = (FACTOR(NUM(n)), rest)
  | factor (LPAREN::more) =
      let val (expTree, (RPAREN::rest)) = exp more in
        (expTree, rest)
      end;

exception SYNTAX_ERROR of lexresult list;

fun allTokens (lexer) =
      let val token = (lexer():lexresult) in
        if token=EOF 
          then [EOF]
          else token::allTokens(lexer)
      end;

fun parse () = parse1 []
and parse1 [] =  
   let val infile = (TextIO.openIn("testfile")) in
    let val lexer = CalcLex.makeLexer(fn n => TextIO.inputLine infile ) in
     let val (parseTree, rest) = exp (allTokens(lexer)) in 
       if rest=[ EOF ] then parseTree
         else raise SYNTAX_ERROR(rest)
     end
    end
   end;