# Copyright (C) 2014  Codethink Limited
#
# This program 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; version 2 of the License.
#
# This program 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 this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.

import cliapp
import morphlib
import glob
import os
import sysbranchdir
import stat
import tempfile

def _get_root_repo(build_ref_prefix):
    system_branch = morphlib.sysbranchdir.open_from_within('.')
    root_repo_dir = morphlib.gitdir.GitDirectory(
            system_branch.get_git_directory_name(
                system_branch.root_repository_url))
    build_branch = morphlib.buildbranch.BuildBranch(system_branch,
                                                    build_ref_prefix,
                                                    push_temporary=False)
    ref = build_branch.root_ref

    return (build_branch.root_ref, root_repo_dir)

def _get_morph_extension_directory():
    code_dir = os.path.dirname(morphlib.__file__)
    return os.path.join(code_dir, 'exts')

def _list_repo_extension_filenames(build_ref_prefix,
                                   kind): #pragma: no cover
    (ref, repo_dir) = _get_root_repo(build_ref_prefix)
    files = repo_dir.list_files(ref)
    return (f for f in files if os.path.splitext(f)[1] == kind)

def _list_morph_extension_filenames(kind):
    return glob.glob(os.path.join(_get_morph_extension_directory(),
                                  '*' + kind))

def _get_extension_name(filename):
    return os.path.basename(filename)

def _get_repo_extension_contents(build_ref_prefix, name, kind):
    (ref, repo_dir) = _get_root_repo(build_ref_prefix)
    return repo_dir.get_file_from_ref(ref, name + kind)

def _get_morph_extension_filename(name, kind):
    return os.path.join(_get_morph_extension_directory(), name + kind)

def _is_executable(filename):
    st = os.stat(filename)
    mask = stat.S_IXUSR | stat.S_IXGRP | stat.S_IXOTH
    return (stat.S_IMODE(st.st_mode) & mask) != 0

def _list_extensions(build_ref_prefix, kind):
    repo_extension_filenames = []
    try:
        repo_extension_filenames = \
                _list_repo_extension_filenames(build_ref_prefix, kind)
    except (sysbranchdir.NotInSystemBranch):
        # Squash this and just return no system branch extensions
        pass
    morph_extension_filenames = _list_morph_extension_filenames(kind)

    repo_extension_names = \
            (_get_extension_name(f) for f in repo_extension_filenames)
    morph_extension_names = \
            (_get_extension_name(f) for f in morph_extension_filenames)

    extension_names = set(repo_extension_names)
    extension_names.update(set(morph_extension_names))
    return list(extension_names)

def list_extensions(build_ref_prefix, kind=None):
    """
    List all available extensions by 'kind'.

    'kind' should be one of '.write' or '.configure'.
    If 'kind' is not provided available extensions of both
    types will be returned.
    """
    if kind:
        return _list_extensions(build_ref_prefix, kind)
    else:
        configure_extensions = _list_extensions(build_ref_prefix, '.configure')
        write_extensions = _list_extensions(build_ref_prefix, '.write')

        return configure_extensions + write_extensions

class get_extension_filename():
    """
    Find the filename of an extension by its 'name' and 'kind'.

    'kind' should be one of '.configure' or '.write'. 

    If the extension is in the build repository then a temporary
    file will be created, which will be deleted on exting the with block.
    """
    def __init__(self, build_ref_prefix, name, kind):
        self.build_ref_prefix = build_ref_prefix
        self.name = name
        self.kind = kind
        self.delete = False

    def __enter__(self):
        ext_filename = None
        try:
            ext_contents = _get_repo_extension_contents(self.build_ref_prefix,
                                                        self.name,
                                                        self.kind)
        except cliapp.AppException, sysbranchdir.NotInSystemBranch:
            # Not found: look for it in the Morph code.
            ext_filename = _get_morph_extension_filename(self.name, self.kind)
            if not os.path.exists(ext_filename):
                raise morphlib.Error(
                    'Could not find extension %s%s' % (self.name, self.kind))
            if not _is_executable(ext_filename):
                raise morphlib.Error(
                    'Extension not executable: %s' % ext_filename)
        else:
            # Found it in the system morphology's repository.
            fd, ext_filename = tempfile.mkstemp()
            os.write(fd, ext_contents)
            os.close(fd)
            os.chmod(ext_filename, 0700)
            self.delete = True

        self.ext_filename = ext_filename
        return ext_filename

    def __exit__(self, type, value, trace):
        if self.delete:
            os.remove(self.ext_filename)