#!/usr/bin/python2
# Copyright (C) 2013-2015  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, see <http://www.gnu.org/licenses/>.


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

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

'''

import errno
import os
import re
import sys
import shlex
import shutil
import stat

try:
    import jinja2
    jinja_available = True
except ImportError:
    jinja_available = False

import writeexts

class InstallFilesConfigureExtension(writeexts.Extension):

    def process_args(self, args):
        if not any(var.startswith('INSTALL_FILES') for var in os.environ):
            return
        target_root = args[0]
        for manifest_var in sorted((var for var in os.environ
                                    if var.startswith('INSTALL_FILES'))):
            manifests = shlex.split(os.environ[manifest_var])
            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 force_symlink(self, source, link_name):
        try:
            os.symlink(source, link_name)
        except OSError as e:
            if e.errno == errno.EEXIST:
                os.remove(link_name)
                os.symlink(source, link_name)

    def install_entry(self, entry, manifest_root, target_root):
        m = re.match('(template )?(overwrite )?'
                     '([0-7]+) ([0-9]+) ([0-9]+) (\S+)', entry)

        if m:
            template = m.group(1)
            overwrite = m.group(2)
            mode = int(m.group(3), 8)   # mode is octal
            uid = int(m.group(4))
            gid = int(m.group(5))
            path = m.group(6)
        else:
            raise writeexts.ExtensionError(
                'Invalid manifest entry, '
                'format: [template] [overwrite] '
                '<octal mode> <uid decimal> <gid decimal> <filename>')

        dest_path = os.path.join(target_root, './' + path)
        if stat.S_ISDIR(mode):
            if os.path.exists(dest_path) and not overwrite:
                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 writeexts.ExtensionError(
                            '"%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) and not overwrite:
                raise writeexts.ExtensionError('Symlink already exists at %s'
                                               % dest_path)
            else:
                linkdest = os.readlink(os.path.join(manifest_root,
                                                    './' + path))
                self.force_symlink(linkdest, dest_path)
                os.lchown(dest_path, uid, gid)

        elif stat.S_ISREG(mode):
            if os.path.lexists(dest_path) and not overwrite:
                raise writeexts.ExtensionError('File already exists at %s'
                                               % dest_path)
            else:
                if template:
                    if not jinja_available:
                        raise writeexts.ExtensionError(
                            "Failed to install template file `%s': "
                            'install-files templates require jinja2'
                            % path)

                    loader = jinja2.FileSystemLoader(manifest_root)
                    env = jinja2.Environment(loader=loader,
                                             keep_trailing_newline=True)

                    env.get_template(path).stream(os.environ).dump(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 writeexts.ExtensionError('Mode given in "%s" is not a file,'
                                           ' symlink or directory' % entry)

InstallFilesConfigureExtension().run()