#!/usr/bin/env python3

import argparse
import os
import os.path as op
import shutil
import subprocess
import sys

ABORT_STRING = "Not a known VCS repository."
NOTHING_TODO_STRING = "There's nothing else to do."
NOTHING_TODO_2_STRING = "Every me and every you."
ARGPARSE_DESCRIPTION = "Compares a VCS repository with a local directory, outputs modified files."
GIT_COMMAND = ['git', 'ls-files', '--full-name']
GIT_DIRECTORY = '.git'
GIT_IGNORE = '.gitignore'
HG_COMMAND = ['hg', 'locate']
HG_DIRECTORY = '.hg'
HG_IGNORE = '.hgignore'
IGNORE_FILES = {'dotfiles': ['home/wasa/.config/llpp.conf',
                             'home/wasa/.config/mcomix/preferences.conf',
                             'home/wasa/.mutt/aliases'],
                'dotemacs': ['etc/private.el',
                             'etc/custom.el']}
def main():
    parser = argparse.ArgumentParser(description=ARGPARSE_DESCRIPTION)
    subparsers = parser.add_subparsers()

    parser_diff = subparsers.add_parser('diff', help="Print different files")
    parser_diff.add_argument('repository', help="VCS repository")
    parser_diff.add_argument('directory', help="Local directory")
    parser_diff.set_defaults(call=do_diff)

    parser_copy = subparsers.add_parser('copy', help="Copy different files")
    parser_copy.add_argument('repository', help="VCS repository")
    parser_copy.add_argument('directory', help="Local directory")
    parser_copy.set_defaults(call=do_copy)

    args = parser.parse_args()
    args.call(args)

def do_diff(args):
    vcs_action(args.repository, args.directory, 'diff')

def do_copy(args):
    vcs_action(args.repository, args.directory, 'copy')

def vcs_action(repos, directory, action):
    repos = op.expanduser(repos)
    repos_type = vcs_type(repos)
    if repos_type == 'git':
        repos_files = git_files(repos)
    elif repos_type == 'hg':
        repos_files = hg_files(repos)
    else:
        sys.exit(ABORT_STRING)

    repos_basename = op.basename(op.abspath(repos))
    ignored_files = []
    if repos_basename in IGNORE_FILES:
        ignored_files = IGNORE_FILES[repos_basename]
    interesting_files = []

    for path in repos_files:
        remote, local = [op.expanduser(op.join(op.abspath(d), path))
                         for d in [repos, directory]]
        if op.exists(local) and op.isfile(local):
            remote_hash, local_hash = [md5_sum(f) for f in [remote, local]]
            if remote_hash != local_hash and path not in ignored_files:
                interesting_files.append({'path': path,
                                          'remote': remote,
                                          'local': local})

    if action == 'diff':
        paths = [f['path'] for f in interesting_files]
        if paths:
            print('\n'.join(paths))
        else:
            print(NOTHING_TODO_STRING)
    elif action == 'copy':
        if interesting_files:
            for f in interesting_files:
                shutil.copy(f['local'], f['remote'])
        else:
            print(NOTHING_TODO_2_STRING)

def vcs_type(repos):
    if op.isdir(repos):
        if op.exists(op.join(repos, GIT_DIRECTORY)):
            return 'git'
        elif op.exists(op.join(repos, HG_DIRECTORY)):
            return 'hg'
        else:
            return 'directory'
    elif op.isfile(repos):
        return 'file'

def git_files(repos):
    return vcs_files(repos, GIT_COMMAND, GIT_IGNORE)

def hg_files(repos):
    return vcs_files(repos, HG_COMMAND, HG_IGNORE)

def vcs_files(repos, command, ignore_file):
    original_directory = os.getcwd()
    os.chdir(repos)
    relative_paths = command_output(command)
    os.chdir(original_directory)
    return [path for path in relative_paths if path != ignore_file]

def md5_sum(path):
    return command_output(['md5sum', op.expanduser(path)])[0].split()[0]

def command_output(command):
    return subprocess.check_output(command, universal_newlines=True).split('\n')

if __name__ == '__main__':
    main()