from __future__ import unicode_literals

import logging
import os.path
import sys

from pre_commit.util import cmd_output


logger = logging.getLogger(__name__)


def zsplit(s):
    s = s.strip('\0')
    if s:
        return s.split('\0')
    else:
        return []


def no_git_env(_env=None):
    # Too many bugs dealing with environment variables and GIT:
    # https://github.com/pre-commit/pre-commit/issues/300
    # In git 2.6.3 (maybe others), git exports GIT_WORK_TREE while running
    # pre-commit hooks
    # In git 1.9.1 (maybe others), git exports GIT_DIR and GIT_INDEX_FILE
    # while running pre-commit hooks in submodules.
    # GIT_DIR: Causes git clone to clone wrong thing
    # GIT_INDEX_FILE: Causes 'error invalid object ...' during commit
    _env = _env if _env is not None else os.environ
    return {
        k: v for k, v in _env.items()
        if not k.startswith('GIT_') or
        k in {'GIT_EXEC_PATH', 'GIT_SSH', 'GIT_SSH_COMMAND'}
    }


def get_root():
    return cmd_output('git', 'rev-parse', '--show-toplevel')[1].strip()


def get_git_dir(git_root='.'):
    opts = ('--git-common-dir', '--git-dir')
    _, out, _ = cmd_output('git', 'rev-parse', *opts, cwd=git_root)
    for line, opt in zip(out.splitlines(), opts):
        if line != opt:  # pragma: no branch (git < 2.5)
            return os.path.normpath(os.path.join(git_root, line))
    else:
        raise AssertionError('unreachable: no git dir')


def get_remote_url(git_root):
    ret = cmd_output('git', 'config', 'remote.origin.url', cwd=git_root)[1]
    return ret.strip()


def is_in_merge_conflict():
    git_dir = get_git_dir('.')
    return (
        os.path.exists(os.path.join(git_dir, 'MERGE_MSG')) and
        os.path.exists(os.path.join(git_dir, 'MERGE_HEAD'))
    )


def parse_merge_msg_for_conflicts(merge_msg):
    # Conflicted files start with tabs
    return [
        line.lstrip(b'#').strip().decode('UTF-8')
        for line in merge_msg.splitlines()
        # '#\t' for git 2.4.1
        if line.startswith((b'\t', b'#\t'))
    ]


def get_conflicted_files():
    logger.info('Checking merge-conflict files only.')
    # Need to get the conflicted files from the MERGE_MSG because they could
    # have resolved the conflict by choosing one side or the other
    with open(os.path.join(get_git_dir('.'), 'MERGE_MSG'), 'rb') as f:
        merge_msg = f.read()
    merge_conflict_filenames = parse_merge_msg_for_conflicts(merge_msg)

    # This will get the rest of the changes made after the merge.
    # If they resolved the merge conflict by choosing a mesh of both sides
    # this will also include the conflicted files
    tree_hash = cmd_output('git', 'write-tree')[1].strip()
    merge_diff_filenames = zsplit(
        cmd_output(
            'git', 'diff', '--name-only', '--no-ext-diff', '-z',
            '-m', tree_hash, 'HEAD', 'MERGE_HEAD',
        )[1],
    )
    return set(merge_conflict_filenames) | set(merge_diff_filenames)


def get_staged_files(cwd=None):
    return zsplit(
        cmd_output(
            'git', 'diff', '--staged', '--name-only', '--no-ext-diff', '-z',
            # Everything except for D
            '--diff-filter=ACMRTUXB',
            cwd=cwd,
        )[1],
    )


def intent_to_add_files():
    _, stdout_binary, _ = cmd_output('git', 'status', '--porcelain', '-z')
    parts = list(reversed(zsplit(stdout_binary)))
    intent_to_add = []
    while parts:
        line = parts.pop()
        status, filename = line[:3], line[3:]
        if status[0] in {'C', 'R'}:  # renames / moves have an additional arg
            parts.pop()
        if status[1] == 'A':
            intent_to_add.append(filename)
    return intent_to_add


def get_all_files():
    return zsplit(cmd_output('git', 'ls-files', '-z')[1])


def get_changed_files(new, old):
    return zsplit(
        cmd_output(
            'git', 'diff', '--name-only', '--no-ext-diff', '-z',
            '{}...{}'.format(old, new),
        )[1],
    )


def head_rev(remote):
    _, out, _ = cmd_output('git', 'ls-remote', '--exit-code', remote, 'HEAD')
    return out.split()[0]


def has_diff(*args, **kwargs):
    repo = kwargs.pop('repo', '.')
    assert not kwargs, kwargs
    cmd = ('git', 'diff', '--quiet', '--no-ext-diff') + args
    return cmd_output(*cmd, cwd=repo, retcode=None)[0]


def commit(repo='.'):
    env = no_git_env()
    name, email = 'pre-commit', 'asottile+pre-commit@umich.edu'
    env['GIT_AUTHOR_NAME'] = env['GIT_COMMITTER_NAME'] = name
    env['GIT_AUTHOR_EMAIL'] = env['GIT_COMMITTER_EMAIL'] = email
    cmd = ('git', 'commit', '--no-edit', '--no-gpg-sign', '-n', '-minit')
    cmd_output(*cmd, cwd=repo, env=env)


def git_path(name, repo='.'):
    _, out, _ = cmd_output('git', 'rev-parse', '--git-path', name, cwd=repo)
    return os.path.join(repo, out.strip())


def check_for_cygwin_mismatch():
    """See https://github.com/pre-commit/pre-commit/issues/354"""
    if sys.platform in ('cygwin', 'win32'):  # pragma: no cover (windows)
        is_cygwin_python = sys.platform == 'cygwin'
        toplevel = cmd_output('git', 'rev-parse', '--show-toplevel')[1]
        is_cygwin_git = toplevel.startswith('/')

        if is_cygwin_python ^ is_cygwin_git:
            exe_type = {True: '(cygwin)', False: '(windows)'}
            logger.warn(
                'pre-commit has detected a mix of cygwin python / git\n'
                'This combination is not supported, it is likely you will '
                'receive an error later in the program.\n'
                'Make sure to use cygwin git+python while using cygwin\n'
                'These can be installed through the cygwin installer.\n'
                ' - python {}\n'
                ' - git {}\n'.format(
                    exe_type[is_cygwin_python], exe_type[is_cygwin_git],
                ),
            )
