# Stephanie Taylor
# CS333 
# Spring 2026
# Demonstrate parser for LL language (with BNF as grammar)
# Demonstrate parser for similar language with EBNF as grammar, enforcing left-associativitys

import simple_tokenizer as tokenizer

# Whenever we enter a parseX function, we have already retrieved the first token in that statement.

class E_Node:
    def __init__( self, left, op, right ):
        self.left = left
        self.op = op
        self.right = right

    def printTree( self, spaces = "" ):
        print( spaces + "E_Node with op", self.op )
        self.left.printTree( spaces + "  " )
        self.right.printTree( spaces + "  " )
        
class T_Node:
    def __init__( self, val ):
        self.val = val
        
    def printTree( self, spaces = "" ):
        print( spaces + "T_Node", self.val )

# Parse enforcing left-associativity 
# Start Symbol: E
# Non-terminals: 0 | ... | 9, +, -
# E -> T  Op E | T
# Op -> + | -
# T -> 0 | ... | 9
class BNF_LL_Parser:
    def __init__( self, filename=None, lines=None ):
        self.tokenizer = tokenizer.Tokenizer( filename, lines )
        self.ast = None
        self.token = None
        
    def getToken(self):
        self.token = self.tokenizer.getToken()
        #print "Getting Token: ", self.token
        
    def parseT( self ):
        t = T_Node( self.token.value )
        self.getToken()
        return t
                               
    def parseE(self):
        subtree = self.parseT()
        if self.token is not None:
            op = self.token.value
            self.getToken() # move into first token of next expression
            subtree = E_Node( subtree, op, self.parseE() )
        return subtree
        
    def buildTree( self ):
        self.getToken()
        self.root = self.parseE()

# Parse enforcing left-associativity 
# Start Symbol: E
# Non-terminals: 0...9, +, -
# E -> T { Op T }
# Op -> + | -
# T -> 0 | ... | 9
class EBNF_Parser:
    def __init__( self, filename=None, lines=None ):
        self.tokenizer = tokenizer.Tokenizer( filename, lines )
        self.ast = None
        self.token = None
        
    def getToken(self):
        self.token = self.tokenizer.getToken()
        #print "Getting Token: ", self.token
        
    def parseT( self ):
        t = T_Node( self.token.value )
        self.getToken()
        return t
                               
    def parseE(self):
        subtree = self.parseT()
        while self.token is not None and self.token.value in "+-":
            op = self.token.value
            self.getToken() # move into first token of next expression
            # and return a Tree that puts any other +/- operations we have already
            # seen in the left kid, so they are evaluated first.
            subtree = E_Node( subtree, op, self.parseT() )
        return subtree
        
    def buildTree( self ):
        self.getToken()
        self.root = self.parseE()

if __name__ == "__main__":
   # p = EBNF_Parser( lines=["3-4+5"] )
    p = BNF_LL_Parser( lines=["3-4+5"] )
    p.buildTree()
    p.root.printTree( "" )