# (C) Copyright 2005-2020 Enthought, Inc., Austin, TX
# All rights reserved.
#
# This software is provided without warranty under the terms of the BSD
# license included in LICENSE.txt and may be redistributed only under
# the conditions described in the aforementioned license. The license
# is also available online at http://www.enthought.com/licenses/BSD.txt
#
# Thanks for using Enthought open source!

from pygments.token import Token, is_token_subtype


class CompletionLexer(object):
    """ Uses Pygments and some auxillary information to lex code snippets for
        symbol contexts.
    """

    # Maps Lexer names to a list of possible name separators
    separator_map = {
        "C": [".", "->"],
        "C++": [".", "->", "::"],
        "Python": ["."],
    }

    def __init__(self, lexer):
        """ Create a CompletionLexer using the specified Pygments lexer.
        """
        self.lexer = lexer

    def get_context(self, string):
        """ Assuming the cursor is at the end of the specified string, get the
            context (a list of names) for the symbol at cursor position.
        """
        context = []
        reversed_tokens = list(self._lexer.get_tokens(string))
        reversed_tokens.reverse()

        # Pygments often tacks on a newline when none is specified in the input.
        # Remove this newline.
        if (
            reversed_tokens
            and reversed_tokens[0][1].endswith("\n")
            and not string.endswith("\n")
        ):
            reversed_tokens.pop(0)

        current_op = ""
        for token, text in reversed_tokens:

            if is_token_subtype(token, Token.Name):

                # Handle a trailing separator, e.g 'foo.bar.'
                if current_op in self._name_separators:
                    if not context:
                        context.insert(0, "")

                # Handle non-separator operators and punction.
                elif current_op:
                    break

                context.insert(0, text)
                current_op = ""

            # Pygments doesn't understand that, e.g., '->' is a single operator
            # in C++. This is why we have to build up an operator from
            # potentially several tokens.
            elif token is Token.Operator or token is Token.Punctuation:
                current_op = text + current_op

            # Break on anything that is not a Operator, Punctuation, or Name.
            else:
                break

        return context

    def get_lexer(self, lexer):
        return self._lexer

    def set_lexer(self, lexer, name_separators=None):
        self._lexer = lexer
        if name_separators is None:
            self._name_separators = self.separator_map.get(lexer.name, ["."])
        else:
            self._name_separators = list(name_separators)

    lexer = property(get_lexer, set_lexer)
