#!/usr/bin/env python
# coding: utf-8
#
#  Copyright 2015 by Leipzig University Library, http://ub.uni-leipzig.de
#                 by The Finc Authors, http://finc.info
#                 by Martin Czygan, <martin.czygan@uni-leipzig.de>
#
# This file is part of some open source application.
#
# Some open source application is free software: you can redistribute
# it and/or modify it under the terms of the GNU General Public
# License as published by the Free Software Foundation, either
# version 3 of the License, or (at your option) any later version.
#
# Some open source application is distributed in the hope that it will
# be useful, but WITHOUT ANY WARRANTY; without even the implied warranty
# of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with Foobar.  If not, see <http://www.gnu.org/licenses/>.
#
# @license GPL-3.0+ <http://spdx.org/licenses/GPL-3.0+>
#

import luigi
import os

__all__ = ['Executable']

def which(program):
    """
    Return `None` if no executable can be found.
    """
    def is_exe(fpath):
        """ Is `fpath` executable? ` """
        return os.path.isfile(fpath) and os.access(fpath, os.X_OK)

    fpath, fname = os.path.split(program)
    if fpath:
        if is_exe(program):
            return program
    else:
        for path in os.environ["PATH"].split(os.pathsep):
            path = path.strip('"')
            exe_file = os.path.join(path, program)
            if is_exe(exe_file):
                return exe_file

    return None

class Executable(luigi.Task):
    """
    Checks, whether an external executable is available. This task will consider
    itself complete, only if the executable `name` is found in $PATH.
    """
    name = luigi.Parameter()
    message = luigi.Parameter(default="")

    def run(self):
        """ Only run if, task is not complete. """
        raise RuntimeError('external program required: %s (%s)' % (self.name, self.message))

    def complete(self):
        return which(self.name) is not None
