#!/usr/bin/python
# Copyright (C) 2013  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.


''' A Morph configuration extension for adding arbitrary files to a system

It will read the manifest files specified in the environment variable
INSTALL_FILES, then use the contens of those files to determine which files
to install into the target system.

'''

import cliapp
import os
import re
import sys
import shlex
import shutil
import stat

class InstallFilesConfigureExtension(cliapp.Application):

    '''Install the files specified in the manifests listed in INSTALL_FILES

    The manifest is formatted as:

        <octal mode> <uid decimal> <gid decimal> <filename>

    Where the filename is how the file is found inside whatever directory
    the manifest is stored in, and also the path within the system to
    install to.

    Directories on the target must be created if they do not exist.
    
    This extension supports files, symlinks and directories.

    '''

    def process_args(self, args):
        if not 'INSTALL_FILES' in os.environ:
            return
        target_root = args[0]
        manifests = shlex.split(os.environ['INSTALL_FILES'])
        for manifest in manifests:
            self.install_manifest(manifest, target_root)

    def install_manifest(self, manifest, target_root):
        manifest_dir = os.path.dirname(manifest)
        with open(manifest) as f:
            entries = f.readlines()
            for entry in entries:
                self.install_entry(entry, manifest_dir, target_root)

    def install_entry(self, entry, manifest_root, target_root):
        entry_data = re.split('\W+', entry.strip(), maxsplit=3)
        mode = int(entry_data[0], 8)
        uid = int(entry_data[1])
        gid = int(entry_data[2])
        path = entry_data[3]
        dest_path = os.path.join(target_root, './' + path)
        if stat.S_ISDIR(mode):
            if os.path.exists(dest_path):
                dest_stat = os.stat(dest_path)
                if (mode != dest_stat.st_mode
                    or uid != dest_stat.st_uid
                    or gid != dest_stat.st_gid):
                        raise cliapp.AppException('"%s" exists and is not '
                                                  'identical to directory '
                                                  '"%s"' % (dest_path, entry))
            else:
                os.mkdir(dest_path, mode)
                os.chown(dest_path, uid, gid)
                os.chmod(dest_path, mode)

        elif stat.S_ISLNK(mode):
            if os.path.lexists(dest_path):
                raise cliapp.AppException('Symlink already exists at %s'
                                          % dest_path)
            else:
                linkdest = os.readlink(os.path.join(manifest_root,
                                                    './' + path))
                os.symlink(linkdest, dest_path)
                os.lchown(dest_path, uid, gid)

        elif stat.S_ISREG(mode):
            if os.path.lexists(dest_path):
                raise cliapp.AppException('File already exists at %s'
                                           % dest_path)
            else:
                shutil.copyfile(os.path.join(manifest_root, './' + path),
                                dest_path)
                os.chown(dest_path, uid, gid)
                os.chmod(dest_path, mode)

        else:
            raise cliapp.AppException('Mode given in "%s" is not a file,'
                                      ' symlink or directory' % entry)

InstallFilesConfigureExtension().run()