from lexer import TokenType

class Expr:

    def accept(self, visitor):
        raise Exception("needs to be implemented")

    class Literal:
        def __init__(self, value):
            self.value = value
        def accept(self, visitor):
            visitor.visitLiteral(self)
        def __str__(self):
            return f"{self.value}"

    class Symbol:
        def __init__(self, name):
            self.name = name
        def accept(self, visitor):
            visitor.visitSymbol(self)
        def __str__(self):
            return f"'{self.name}"

    class Nary:
        def __init__(self, symbol, args):
            self.symbol = symbol
            self.args = args
        def accept(self, visitor):
            visitor.visitNary(self)
        def __str__(self):
            out = f"[{self.symbol} => ("
            first = True
            for arg in self.args:
                if first:
                    out = f"{out} {arg}"
                    first = False
                else:
                    out = f"{out}, {arg}"
            return f"{out} )]"

    class Binary:
        def __init__(self, symbol, left, right):
            self.symbol = symbol
            self.left = left
            self.right = right
        def accept(self, visitor):
            visitor.visitBinary(self)

class Visitor:
    def visitLiteral(self, literal):
        return literal.value
    def visitBinary(self, binary):
        sym = binary.symbol.text
        left = binary.left.accept(self)
        right = binary.right.accept(self)
        return "({sym} {left} {right}"
    def visitNary(self, nary):
        sym = nary.symbol.text
        args = []
        for arg in nary.args:
            args.append(arg.accept(self))
        return "({sym} {' '.join(args)})"
    def visitSymbol(self, symbol):
        return symbol.name

def parseExpression(token, prev, tokens):
    idx = 0
    args = []
    prev = token
    while tokens[idx].type_ != TokenType.CLOSE_PAREN:
        token = tokens[idx]
        inc = 1
        if token.type_ == TokenType.OPEN_PAREN:
            expr, inc = parseExpression(token, prev, tokens[idx+1:])
            args.append(expr)
        elif token.type_ in (TokenType.STRING, TokenType.TRUE, TokenType.FALSE, TokenType.INT, TokenType.FLOAT):
            expr, inc = parseLiteral(token, prev, tokens[idx+1:])
            args.append(expr)
        else:
            expr, inc = parseSymbol(token, prev, tokens[idx+1:])
            args.append(expr)
        idx += inc
        prev = token
    
    return Expr.Nary(args[0], args[1:]), idx + 2  # parens

def parseSymbol(token, prev, tokens):
    return Expr.Symbol(token.text), 1

def parseLiteral(token, prev, tokens):
    return Expr.Literal(token.value), 1

def parse(tokens):
    idx = 0
    prev = None
    exprs = []
    while tokens[idx].type_ != TokenType.EOF:
        token = tokens[idx]
        counter = 1
        if token.type_ == TokenType.OPEN_PAREN:
            expr, counter = parseExpression(token, prev, tokens[idx+1:])
            exprs.append(expr)
        elif token.type_ in (TokenType.FALSE, TokenType.TRUE, TokenType.STRING, TokenType.INT, TokenType.FLOAT):
            lit, counter = parseLiteral(token, prev, tokens[idx+1:])
            exprs.append(lit)
        else:
            sym, counter = parseSymbol(token, prev, tokens[idx+1:])
            exprs.append(sym)
        
        idx += counter
        prev = token
    return exprs