# Copyright (C) 2018 Avatao.com Innovative Learning Kft.
# All Rights Reserved. See LICENSE file for details.

from subprocess import run
from getpass import getuser


class SnapshotProvider:
    def __init__(self, directory, git_dir):
        author = f'{getuser()} via TFW {self.__class__.__name__}'
        self.gitenv = {
            'GIT_DIR': git_dir,
            'GIT_WORK_TREE': directory,
            'GIT_AUTHOR_NAME': author,
            'GIT_AUTHOR_EMAIL': '',
            'GIT_COMMITTER_NAME': author,
            'GIT_COMMITTER_EMAIL': ''
        }

        self._head_detached = False
        self._branch = 'master'
        self._branches = [self._branch]

        self._init_repo()

    def _init_repo(self):
        self._run(('git', 'init'))

    def take_snapshot(self):
        if self._head_detached:
            self._checkout_branch_from_head()
        self._run(('git', 'add', '-A'))
        self._run(('git', 'commit', '-m', 'Snapshot'))

    def _checkout_branch_from_head(self):
        head_hash = self._get_head_hash()
        self._run((
            'git', 'checkout',
            '-b', head_hash, head_hash
        ))
        self._branches.append(head_hash)
        self._branch = head_hash
        self._head_detached = False

    def _get_head_hash(self):
        return self._get_stdout(('git', 'rev-parse', 'HEAD'))

    def restore_snapshot(self, date):
        commit = self._get_commit_from_timestamp(date)
        self._checkout_commit(commit)
        self._head_detached = True

    def _get_commit_from_timestamp(self, date):
        return self._get_stdout((
            'git', 'rev-list',
            '--date=iso',
            '-n', '1',
            f'--before="{date.isoformat()}"',
            self._branch
        ))

    def _checkout_commit(self, commit):
        self._run((
            'git', 'checkout',
            commit
        ))

    def _get_stdout(self, *args, **kwargs):
        kwargs['capture_output'] = True
        stdout_bytes = self._run(*args, **kwargs).stdout
        return stdout_bytes.decode().rstrip('\n')

    def _run(self, *args, **kwargs):
        if 'env' not in kwargs:
            kwargs['env'] = self.gitenv
        return run(*args, **kwargs)