# (c) Copyright 2013. CodeWeavers, Inc.

import os

# Portable which(1) implementation
def which(path, app):
    """Looks for an executable in the specified directory list.

    path is an os.pathsep-separated list of directories and app is the
    executable name. If app contains a path separator then path is ignored.
    If the file is not found, then None is returned.
    """
    if os.path.isabs(app):
        if os.path.isfile(app) and os.access(app, os.X_OK):
            return app
    elif os.sep in app or (os.altsep and os.altsep in app):
        app_path = os.path.join(os.getcwd(), app)
        if os.path.isfile(app_path) and os.access(app_path, os.X_OK):
            return app_path
    else:
        for directory in path.split(os.pathsep):
            if directory == "":
                continue
            app_path = os.path.join(directory, app)
            if os.path.isfile(app_path) and os.access(app_path, os.X_OK):
                return app_path
    return None