#!/usr/bin/env python3
# Author: Joshua Chen
# Date: 2015-12-26
# Location: Shenzhen
# Desc: clone a repository, initialize the shadow git,
# decrypt the cipher branches.

import os, sys
prog_path = os.path.realpath(__file__)
prog_dir  = os.path.dirname(prog_path)
sys.path.insert(0, prog_dir)
import lib

class Clone:
    def __init__(self, argv):
        argv = argv[1:]
        repo = argv.pop(0)
        dir  = argv[0] if len(argv) else self.determ_dir(repo)
        self.clone(repo, dir)
        orig_dir = os.getcwd()
        os.chdir(dir)
        self.initialize()
        self.decrypt_branches()
        os.chdir(orig_dir)

    def determ_dir(self, repo):
        """ Return a directory name appropriate for the repo.
        repo for /path/to/repo.git and foo for host.xz:foo/.git
        """
        dir = repo
        if dir.endswith('.git'):    # remove trailing .git
            dir = dir[:-4]
        dir = dir.strip('/')        # remove trailing /
        dir = os.path.basename(dir) # basename only
        dir = dir.split(':')[-1]    # part after colon
        return dir

    def clone(self, repo, dir):
        cmd = 'git clone -n %s %s' % (repo, dir)
        if os.system(cmd) != 0:
            raise lib.ShellCmdErrorException

    def initialize(self):
        """ Initialize shadow git for the new local repository
        """
        print('Initializing shadow git...')
        cmd = 'git shadow-init'
        if os.system(cmd) != 0:
            raise lib.ShellCmdErrorException

    def decrypt_branches(self):
        """ Decrypt all cipher branches of the repository,
        update the 'plain_position' and 'cipher_position' of
        the position record, create local cipher branch for
        every remote-tracking cipher branch, checkout the
        master branch if there is one.
        """
        print('Decrypting cipher branches...')
        cb_prefix = lib.cipher_branch_prefix
        fb_prefix = 'refs/remotes/'
        brs       = lib.get_all_branches(remote=True)
        cbrs      = []
        for branch in brs:
            # ignore this form: origin/HEAD -> origin/cipher-master
            if ' -> ' in branch:
                continue
            branch = branch[2:]
            parts  = branch.split('/')
            # only decrypt branches of the 'origin'
            if parts[0] == 'origin' and parts[-1].startswith(cb_prefix):
                plain_name = parts[-1][len(cb_prefix):]
                cbrs.append((fb_prefix + branch, plain_name))
        if not cbrs:
            print('No cipher branch found.')
        for c_branch, p_branch in cbrs:
            if not p_branch:
                print('Ignoring %s' % c_branch, file=sys.stderr)
                continue
            print('Decrypting %s' % c_branch)
            tip = lib.decrypt_branch(c_branch)
            sha1 = lib.revision_parse(c_branch)
            reason = "move to the tip after decrypted branch %s (%s)" % (c_branch, sha1)
            lib.update_branch(p_branch, tip, reason)
            reason = "move to %s (%s)" % (c_branch, sha1)
            lib.update_branch(cb_prefix + 'origin-' + p_branch, c_branch, reason)
            lib.update_position_record('origin', p_branch, tip, c_branch)
        if lib.rev_valid('master'):
            os.system('git checkout -q master')
        print('Decryption done.')


def help(ofile=sys.stdout):
    """ Show help message
    """
    msg = 'Usage: %s repository [directory]' % os.path.basename(sys.argv[0])
    print(msg, file=ofile)


if __name__ == '__main__':
    try:
        Clone(sys.argv)
    except IndexError as e:
        help(sys.stderr)
        exit(1)
    except KeyboardInterrupt:
        exit(1)
    except:
        exit(1)
    else:
        exit(0)