from .structs import *
from .exceptions import ParseError


def parseExpression(token, prev, tokens):
    idx = 0
    args = []
    prev = token
    while tokens[idx].type_ != TokenType.CLOSE_PAREN:
        token = tokens[idx]
        if token.type_ == TokenType.EOF:
            raise ParseError("uneven parens: not enough closing!", token.line)
        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)
        elif token.type_ == TokenType.COLON:
            expr, inc = parseType(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(args), idx + 2  # parens

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

def parseLiteral(token, prev, tokens):
    if token.type_ == TokenType.STRING:
        return String(token.value), 1
    elif token.type_ == TokenType.INT:
        return Int(token.value), 1
    elif token.type_ == TokenType.FLOAT:
        return Float(token.value), 1
    elif token.type_ in (TokenType.TRUE, TokenType.FALSE):
        return Bool(token.value), 1
    else:
        return Literal(token.value), 1

def parseType(token, prev, tokens):
    # if the next token is a symbol, combine for a type
    if tokens[0].type_ == TokenType.SYMBOL:
        return Type(f":{tokens[0].text}"), 2
    elif tokens[0].type_ == TokenType.OPEN_BRACKET:
        # only format currently supported:
        # [ <type> ]
        if tokens[1].type_ != TokenType.COLON:
            raise ParseError("invalid type definition (expecting colon)", tokens[1].line)
        typ, counter = parseType(tokens[1], tokens[0], tokens[2:])
        if tokens[1+counter].type_ != TokenType.CLOSE_BRACKET:
            raise ParseError("invalid type definition (expecting close bracket)", tokens[1+counter].line)
        return Type(f":[]", typ), counter + 3
    else:
        raise ParseError("invalid type definition!", tokens[0].line)

def parse(tokens):
    idx = 0
    prev = None
    exprs = []
    while tokens[idx].type_ != TokenType.EOF:
        token = tokens[idx]
        counter = 1
        if token.type_ == TokenType.CLOSE_PAREN:
            raise ParseError("uneven parens: too many closing!", token.line)
        elif 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)
        elif token.type_ == TokenType.COLON:
            typ, counter = parseType(token, prev, tokens[idx+1:])
            exprs.append(typ)
        else:
            sym, counter = parseSymbol(token, prev, tokens[idx+1:])
            exprs.append(sym)
        
        idx += counter
        prev = token
    return exprs