# -*- coding: utf-8 -*-
# Copyright (c) 2015 LOGILAB S.A. (Paris, FRANCE) <contact@logilab.fr>
# Copyright (c) 2016-2017 Claudiu Popa <pcmanticore@gmail.com>
# Copyright (c) 2016 Glenn Matthews <glmatthe@cisco.com>
# Copyright (c) 2018 Ville Skyttä <ville.skytta@upcloud.com>

# Licensed under the GPL: https://www.gnu.org/licenses/old-licenses/gpl-2.0.html
# For details: https://github.com/PyCQA/pylint/blob/master/COPYING

import astroid
from pylint.checkers import BaseTokenChecker
from pylint.checkers.utils import check_messages
from pylint.interfaces import ITokenChecker, IAstroidChecker


class ElseifUsedChecker(BaseTokenChecker):
    """Checks for use of "else if" when an "elif" could be used
    """

    __implements__ = (ITokenChecker, IAstroidChecker)
    name = "else_if_used"
    msgs = {
        "R5501": (
            'Consider using "elif" instead of "else if"',
            "else-if-used",
            "Used when an else statement is immediately followed by "
            "an if statement and does not contain statements that "
            "would be unrelated to it.",
        )
    }

    def __init__(self, linter=None):
        BaseTokenChecker.__init__(self, linter)
        self._init()

    def _init(self):
        self._elifs = []
        self._if_counter = 0

    def process_tokens(self, tokens):
        # Process tokens and look for 'if' or 'elif'
        for _, token, _, _, _ in tokens:
            if token == "elif":
                self._elifs.append(True)
            elif token == "if":
                self._elifs.append(False)

    def leave_module(self, _):
        self._init()

    def visit_ifexp(self, _):
        self._if_counter += 1

    def visit_comprehension(self, node):
        self._if_counter += len(node.ifs)

    @check_messages("else-if-used")
    def visit_if(self, node):
        if isinstance(node.parent, astroid.If):
            orelse = node.parent.orelse
            # current if node must directly follow an "else"
            if orelse and orelse == [node]:
                if not self._elifs[self._if_counter]:
                    self.add_message("else-if-used", node=node)
        self._if_counter += 1


def register(linter):
    """Required method to auto register this checker.

    :param linter: Main interface object for Pylint plugins
    :type linter: Pylint object
    """
    linter.register_checker(ElseifUsedChecker(linter))
