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"""
Common functions that can be used to mark spaces, e.g. build and devel, to indicate which tools previously built the space.

This allows the tools to detect cross tool talk and avoid it where appropriate
"""


from __future__ import print_function

import os

SPACE_BUILT_BY_MARKER_FILENAME = '.built_by'


def get_previous_tool_used_on_the_space(space_path):
    """
    Return the tool used to build the space at the given path, or None.

    Returns None if the path does not exist or if there is no built by file.

    :param str space_path: path to the space in question.
    :returns: str identifying the tool used to build the space or None.
    """
    if os.path.isdir(space_path):
        marker_path = os.path.join(space_path, SPACE_BUILT_BY_MARKER_FILENAME)
        if os.path.isfile(marker_path):
            with open(marker_path, 'r') as f:
                return f.read().strip()
    return None


def mark_space_as_built_by(space_path, tool_name):
    """
    Place a marker file in the space at the given path, telling who built it.

    The path to the marker is created if necessary.

    :param str space_path: path to the space which should be marked.
    :param str tool_name: name of the tool doing the marking.
    :raises: OSError, others, when trying to create the folder.
    """
    if not os.path.isdir(space_path):
        # Might fail if it's a file already or for permissions.
        os.makedirs(space_path)
    marker_path = os.path.join(space_path, SPACE_BUILT_BY_MARKER_FILENAME)
    with open(marker_path, 'w') as f:
        f.write(tool_name)