# coding=utf-8
# Copyright 2015 Pants project contributors (see CONTRIBUTORS.md).
# Licensed under the Apache License, Version 2.0 (see LICENSE).

from __future__ import absolute_import, division, print_function, unicode_literals

import sys
import tokenize
from collections import defaultdict

from six.moves import range

from pants.contrib.python.checks.checker.common import CheckstylePlugin


class TrailingWhitespace(CheckstylePlugin):
    """Warn on invalid trailing whitespace."""

    @classmethod
    def name(cls):
        return "trailing-whitespace"

    @classmethod
    def build_exception_map(cls, tokens):
        """Generates a set of ranges where we accept trailing slashes, specifically within comments
        and strings."""
        exception_ranges = defaultdict(list)
        for token in tokens:
            token_type, _, token_start, token_end = token[0:4]
            if token_type in (tokenize.COMMENT, tokenize.STRING):
                if token_start[0] == token_end[0]:
                    exception_ranges[token_start[0]].append((token_start[1], token_end[1]))
                else:
                    exception_ranges[token_start[0]].append((token_start[1], sys.maxsize))
                    for line in range(token_start[0] + 1, token_end[0]):
                        exception_ranges[line].append((0, sys.maxsize))
                    exception_ranges[token_end[0]].append((0, token_end[1]))
        return exception_ranges

    def __init__(self, *args, **kw):
        super(TrailingWhitespace, self).__init__(*args, **kw)
        self._exception_map = self.build_exception_map(self.python_file.tokens)

    def has_exception(self, line_number, exception_start, exception_end=None):
        exception_end = exception_end or exception_start
        for start, end in self._exception_map.get(line_number, ()):
            if start <= exception_start and exception_end <= end:
                return True
        return False

    def nits(self):
        for line_number, line in self.python_file.enumerate():
            stripped_line = line.rstrip()
            if stripped_line != line and not self.has_exception(
                line_number, len(stripped_line), len(line)
            ):
                yield self.error("T200", "Line has trailing whitespace.", line_number)
            if line.rstrip().endswith("\\"):
                if not self.has_exception(line_number, len(line.rstrip()) - 1):
                    yield self.error("T201", "Line has trailing slashes.", line_number)