module AbstractSyntaxTree where

import qualified Parser

type AST = Node

data Node = Operation Opcode Node Node
          | Scalar Int
          deriving Show

data Opcode = Add
            | Sub
            | Mult
            | Div
            deriving Show

createAST :: Parser.CST -> AST
createAST = simplifyExpr

simplifyExpr :: Parser.Expr -> Node
simplifyExpr expr = case expr of
    Parser.Add term expr2 -> Operation Add (simplifyTerm term) (simplifyExpr expr2)
    Parser.Sub term expr2 -> Operation Sub (simplifyTerm term) (simplifyExpr expr2)
    Parser.ETerm term -> simplifyTerm term

simplifyTerm :: Parser.Term -> Node
simplifyTerm term = case term of
    Parser.Mult factor term2 -> Operation Mult (simplifyFactor factor) (simplifyTerm term2)
    Parser.Div  factor term2 -> Operation Div  (simplifyFactor factor) (simplifyTerm term2)
    Parser.TFactor factor -> simplifyFactor factor

simplifyFactor :: Parser.Factor -> Node
simplifyFactor factor = case factor of
    Parser.Integer i -> Scalar i
    Parser.Parantheses expr -> simplifyExpr expr
    Parser.NegFactor (Parser.Integer i) -> Scalar (-i)  -- Shortcut to avoid storing -x as -1 * x
    Parser.NegFactor  factor2 -> Operation Mult (Scalar (-1)) (simplifyFactor factor2)