import logging
import os.path
import sys
from typing import Dict
from typing import List
from typing import MutableMapping
from typing import Optional
from typing import Set
from typing import Tuple

from pre_commit.errors import FatalError
from pre_commit.util import CalledProcessError
from pre_commit.util import cmd_output
from pre_commit.util import cmd_output_b


logger = logging.getLogger(__name__)


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


def no_git_env(
        _env: Optional[MutableMapping[str, str]] = None,
) -> Dict[str, str]:
    # 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', 'GIT_SSL_CAINFO',
            'GIT_SSL_NO_VERIFY',
        }
    }


def get_root() -> str:
    # Git 2.25 introduced a change to "rev-parse --show-toplevel" that exposed
    # underlying volumes for Windows drives mapped with SUBST.  We use
    # "rev-parse --show-cdup" to get the appropriate path, but must perform
    # an extra check to see if we are in the .git directory.
    try:
        root = os.path.abspath(
            cmd_output('git', 'rev-parse', '--show-cdup')[1].strip(),
        )
        git_dir = os.path.abspath(get_git_dir())
    except CalledProcessError:
        raise FatalError(
            'git failed. Is it installed, and are you in a Git repository '
            'directory?',
        )
    if os.path.samefile(root, git_dir):
        raise FatalError(
            'git toplevel unexpectedly empty! make sure you are not '
            'inside the `.git` directory of your repository.',
        )
    return root


def get_git_dir(git_root: str = '.') -> str:
    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: str) -> str:
    _, out, _ = cmd_output('git', 'config', 'remote.origin.url', cwd=git_root)
    return out.strip()


def is_in_merge_conflict() -> bool:
    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: bytes) -> List[str]:
    # Conflicted files start with tabs
    return [
        line.lstrip(b'#').strip().decode()
        for line in merge_msg.splitlines()
        # '#\t' for git 2.4.1
        if line.startswith((b'\t', b'#\t'))
    ]


def get_conflicted_files() -> Set[str]:
    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: Optional[str] = None) -> List[str]:
    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() -> List[str]:
    _, stdout, _ = cmd_output(
        'git', 'status', '--ignore-submodules', '--porcelain', '-z',
    )
    parts = list(reversed(zsplit(stdout)))
    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() -> List[str]:
    return zsplit(cmd_output('git', 'ls-files', '-z')[1])


def get_changed_files(old: str, new: str) -> List[str]:
    diff_cmd = ('git', 'diff', '--name-only', '--no-ext-diff', '-z')
    try:
        _, out, _ = cmd_output(*diff_cmd, f'{old}...{new}')
    except CalledProcessError:  # pragma: no cover (new git)
        # on newer git where old and new do not have a merge base git fails
        # so we try a full diff (this is what old git did for us!)
        _, out, _ = cmd_output(*diff_cmd, f'{old}..{new}')

    return zsplit(out)


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


def has_diff(*args: str, repo: str = '.') -> bool:
    cmd = ('git', 'diff', '--quiet', '--no-ext-diff', *args)
    return cmd_output_b(*cmd, cwd=repo, retcode=None)[0] == 1


def has_core_hookpaths_set() -> Tuple[bool, str]:
    _, out, _ = cmd_output_b('git', 'config', 'core.hooksPath', retcode=None)
    return bool(out.strip()), out.strip().decode()


def init_repo(path: str, remote: str) -> None:
    if os.path.isdir(remote):
        remote = os.path.abspath(remote)

    env = no_git_env()
    # avoid the user's template so that hooks do not recurse
    cmd_output_b('git', 'init', '--template=', path, env=env)
    cmd_output_b('git', 'remote', 'add', 'origin', remote, cwd=path, env=env)


def commit(repo: str = '.') -> None:
    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_b(*cmd, cwd=repo, env=env)


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


def check_for_cygwin_mismatch() -> None:
    """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'
        try:
            toplevel = get_root()
        except FatalError:  # skip the check if we're not in a git repo
            return
        is_cygwin_git = toplevel.startswith('/')

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