# Copyright 2017  Lars Wirzenius
#
# 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, either version 3 of the License, or
# (at your option) any later version.
#
# 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/>.
#
# =*= License: GPL-3+ =*=



import os

import cliapp

import vmdb


class CacheRootFSPlugin(cliapp.Plugin):

    def enable(self):
        self.app.settings.string(
            ['rootfs-tarball'],
            'store rootfs cache tar archives in FILE',
            metavar='FILE')

        self.app.step_runners.add(MakeCacheStepRunner())


class MakeCacheStepRunner(vmdb.StepRunnerInterface):

    def get_key_spec(self):
        return {
            'cache-rootfs': str,
            'options': '--one-file-system',
        }

    def run(self, values, settings, state):
        fs_tag = values['cache-rootfs']
        rootdir = state.tags.get_builder_mount_point(fs_tag)
        tar_path = settings['rootfs-tarball']
        opts = values['options'].split()
        if not tar_path:
            raise Exception('--rootfs-tarball MUST be set')
        dirs = self._find_cacheable_mount_points(state.tags, rootdir)

        tags = state.tags
        for tag in tags.get_tags():
            vmdb.progress(
                'tag {} mounted {} cached {}'.format(
                    tag, tags.get_builder_mount_point(tag), tags.is_cached(tag)))

        vmdb.progress('caching rootdir {}'.format(rootdir))
        vmdb.progress('caching relative {}'.format(dirs))
        if not os.path.exists(tar_path):
            vmdb.runcmd(
                ['tar'] + opts + ['-C', rootdir, '-caf', tar_path] + dirs)

    def _find_cacheable_mount_points(self, tags, rootdir):
        return list(sorted(
            self._make_relative(rootdir, tags.get_builder_mount_point(tag))
            for tag in tags.get_tags()
            if tags.is_cached(tag)
        ))

    def _make_relative(self, rootdir, dirname):
        assert dirname == rootdir or dirname.startswith(rootdir + '/')
        if dirname == rootdir:
            return '.'
        return dirname[len(rootdir) + 1:]
