from .structs import *
from .exceptions import ParseError


def parseDef(token, prev, tokens):
    if len(tokens) < 2:
        raise ParseError("invalid def", token.line)
    elif tokens[0].type_ != TokenType.SYMBOL:
        raise ParseError("'def' must take a symbol", token.line)
    sym, inc = parseSymbol(tokens[0], token, tokens[1:])
    return NebDef(sym), inc + 1

def parseLambda(token, prev, tokens):
    # lambda [type] ( [arg] [&] ) [(expr)]
    # func <name> [type] ( [arg] [&] ) [(expr)]
    idx = 0
    sym = None
    return_type = Type(":any")
    if token.type_ == TokenType.FUNC:
        if tokens[idx].type_ != TokenType.SYMBOL:
            raise ParseError("'func' must take a symbol", tokens[idx].line)
        sym, counter = parseSymbol(tokens[idx], token, tokens[idx+1:])
        idx += counter
    else:
        sym = Symbol("<lambda>", token.line)

    if tokens[idx].type_ == TokenType.COLON:
        return_type, counter = parseType(tokens[idx], token, tokens[idx+1:])
        idx += counter

    if tokens[idx].type_ != TokenType.OPEN_PAREN:
        raise ParseError("expecting argument list", tokens[idx].line)

    args, many, counter = parseFunctionArguments(tokens[idx:], tokens[idx-1], tokens[idx+1:])
    idx += counter

    body = []
    while tokens[idx].type_ != TokenType.CLOSE_PAREN:
        token = tokens[idx]
        counter = 1
        if token.type_ == TokenType.OPEN_PAREN:
            expr, counter = parseExpression(token, prev, tokens[idx+1:])
            body.append(expr)
        elif token.type_ in (TokenType.FALSE, TokenType.TRUE, TokenType.STRING, TokenType.INT, TokenType.FLOAT):
            lit, counter = parseLiteral(token, prev, tokens[idx+1:])
            body.append(lit)
        elif token.type_ == TokenType.COLON:
            typ, counter = parseType(token, prev, tokens[idx+1:])
            body.append(typ)
        else:
            inner_sym, counter = parseSymbol(token, prev, tokens[idx+1:])
            body.append(inner_sym)
        idx += counter
        prev = token

    return NebFuncDef(sym, return_type, args, many, body), idx + 1 

def parseFunctionArguments(token, prev, tokens):
    idx = 0
    args = []
    prev = token
    many = None
    prev_type = False
    first = True
    while tokens[idx].type_ != TokenType.CLOSE_PAREN:
        token = tokens[idx]
        if token.type_ == TokenType.SYMBOL:
            if many is not None:
                raise ParseError("& must be last argument", token.line)
            sym, counter = parseSymbol(token, prev, tokens)
            args.append(Arg(sym.name, TypeEnum.ANY))
            prev_type = False
            counter = 1
        elif token.type_ == TokenType.MANY:
            many = Arg("&", TypeEnum.ANY)
            prev_type = False
            counter = 1
        elif token.type_ == TokenType.COLON and not prev_type and not first:
            if prev_type:
                raise ParseError("can't have two types in a row", token.line) 
            if first:
                raise ParseError("type can't be first", token.line) 
            typ, counter = parseType(token, prev, tokens[idx+1:])
            if many is None:
                args[-1].type_ = typ
            else:
                many.type_ = typ
            prev_type = True
        else:
            raise ParseError("invalid function signature", token)
        first = False
        idx += counter

    # this should return function
    return args, many, idx + 2  # parens


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)
        elif token.type_ == TokenType.DEF:
            expr, inc = parseDef(token, prev, tokens[idx+1:])
            args.append(expr)
        elif token.type_ in (TokenType.LAMBDA, TokenType.FUNC):
            expr, inc = parseLambda(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):
    if token.type_ == TokenType.APOSTROPHE:
        if len(tokens) == 0 or tokens[0].type_ != TokenType.SYMBOL:
            raise ParseError("quote must be followed by a symbol", token.line)
        return Symbol(tokens[0].text, tokens[0].line, True), 2
    else:
        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 len(tokens) > 0 and 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

    elif tokens[0].type_ == TokenType.OPEN_BRACE:
        # 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_BRACE:
            raise ParseError("invalid type definition (expecting close brace)", tokens[1+counter].line)
        return Type(":{}", 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