import sys
import os
import json
import csv
import asyncio
import platform
import subprocess
from functools import lru_cache, partial
from pathlib import Path
from typing import List, Dict, Coroutine, Union, Iterator, Tuple
from collections import Counter, defaultdict

from . import info
from . import common


# TODO: python3.9 pathlib has is_relative_to() function
def is_relative_to(kid: str, parent: str) -> bool:
    """
    Both the `kid` and `parent` should be absolute path
    """
    return parent == os.path.commonpath((kid, parent))


@lru_cache()
def get_repos(root=None) -> Dict[str, Dict[str, str]]:
    """
    Return a `dict` of repo name to repo absolute path and repo type

    @param root: Use local config if set. If None, use either global or local
                 config depending on cwd.
    """
    path_file = common.get_config_fname('repos.csv', root)
    repos = {}
    if os.path.isfile(path_file) and os.stat(path_file).st_size > 0:
        with open(path_file) as f:
            rows = csv.DictReader(f, ['path', 'name', 'type', 'flags'],
                                  restval='')  # it's actually a reader
            repos = {r['name']:
                    {'path': r['path'], 'type': r['type'],
                        'flags': r['flags'].split()}
                     for r in rows if is_git(r['path'], is_bare=True)}
    if root is None:  # detect if inside a main path
        cwd = os.getcwd()
        for prop in repos.values():
            path = prop['path']
            if prop['type'] == 'm' and is_relative_to(cwd, path):
                return get_repos(path)
    return repos


@lru_cache()
def get_context() -> Union[Path, None]:
    """
    Return the context: either a group name or 'none'
    """
    config_dir = Path(common.get_config_dir())
    matches = list(config_dir.glob('*.context'))
    if len(matches) > 1:
        print("Cannot have multiple .context file")
        sys.exit(1)
    return matches[0] if matches else None


@lru_cache()
def get_groups() -> Dict[str, List[str]]:
    """
    Return a `dict` of group name to repo names.
    """
    fname = common.get_config_fname('groups.csv')
    groups = {}
    # Each line is a repo path and repo name separated by ,
    if os.path.isfile(fname) and os.stat(fname).st_size > 0:
        with open(fname, 'r') as f:
            rows = csv.reader(f, delimiter=':')
            groups = {r[0]: r[1].split() for r in rows}
    return groups


def get_choices() -> List[Union[str, None]]:
    """
    Return all repo names, group names, and an additional empty list. The empty
    list is added as a workaround of
    argparse's problem with coexisting nargs='*' and choices.
    See https://utcc.utoronto.ca/~cks/space/blog/python/ArgparseNargsChoicesLimitation
    and
    https://bugs.python.org/issue27227
    """
    choices = list(get_repos())
    choices.extend(get_groups())
    choices.append([])
    return choices


def is_git(path: str, is_bare=False) -> bool:
    """
    Return True if the path is a git repo.
    """
    if not os.path.exists(path):
        return False
    # An alternative is to call `git rev-parse --is-inside-work-tree`
    # I don't see why that one is better yet.
    # For a regular git repo, .git is a folder, for a worktree repo, .git is a file.
    # However, git submodule repo also has .git as a file.
    # A more reliable way to differentiable regular and worktree repos is to
    # compare the result of `git rev-parse --git-dir` and
    # `git rev-parse --git-common-dir`
    loc = os.path.join(path, '.git')
    # TODO: we can display the worktree repos in a different font.
    if os.path.exists(loc):
        return True
    if not is_bare:
        return False
    # detect bare repo
    got = subprocess.run('git rev-parse --is-bare-repository'.split(),
                            stdout=subprocess.PIPE, stderr=subprocess.DEVNULL,
                            cwd=path
                            )
    if got.returncode == 0 and got.stdout == b'true\n':
        return True
    return False


def rename_repo(repos: Dict[str, Dict[str, str]], repo: str, new_name: str):
    """
    Write new repo name to file
    """
    if new_name in repos:
        print(f"{new_name} is already in use!")
        return
    prop = repos[repo]
    del repos[repo]
    repos[new_name] = prop
    # write to local config if inside a main path
    main_paths = (prop['path'] for prop in repos.values() if prop['type'] == 'm')
    cwd = os.getcwd()
    is_local_config = True
    for p in main_paths:
        if is_relative_to(cwd, p):
            write_to_repo_file(repos, 'w', p)
            break
    else:  # global config
        write_to_repo_file(repos, 'w')
        is_local_config = False
    # update groups only when outside any main repos
    if is_local_config:
        return
    groups = get_groups()
    for g, members in groups.items():
        if repo in members:
            members.remove(repo)
            members.append(new_name)
            groups[g] = sorted(members)
    write_to_groups_file(groups, 'w')


def write_to_repo_file(repos: Dict[str, Dict[str, str]], mode: str, root=None):
    """
    @param repos: each repo is {name: {properties}}
    """
    data = [(prop['path'], name, prop['type'], ' '.join(prop['flags']))
                for name, prop in repos.items()]
    fname = common.get_config_fname('repos.csv', root)
    os.makedirs(os.path.dirname(fname), exist_ok=True)
    with open(fname, mode, newline='') as f:
        writer = csv.writer(f, delimiter=',', quotechar='"', quoting=csv.QUOTE_MINIMAL)
        writer.writerows(data)


def write_to_groups_file(groups: Dict[str, List[str]], mode: str):
    """

    """
    fname = common.get_config_fname('groups.csv')
    os.makedirs(os.path.dirname(fname), exist_ok=True)
    if not groups:  # all groups are deleted
        open(fname, 'w').close()
    else:
        with open(fname, mode, newline='') as f:
            data = [
                    (group, ' '.join(repos))
                    for group, repos in groups.items()
                    ]
            writer = csv.writer(f, delimiter=':', quotechar='"', quoting=csv.QUOTE_MINIMAL)
            writer.writerows(data)


def _make_name(path: str, repos: Dict[str, Dict[str, str]],
                name_counts: Counter) -> str:
    """
    Given a new repo `path`, create a repo name. By default, basename is used.
    If name collision exists, further include parent path name.

    @param path: It should not be in `repos` and is absolute
    """
    name = os.path.basename(os.path.normpath(path))
    if name in repos or name_counts[name] > 1:
        par_name = os.path.basename(os.path.dirname(os.path.dirname(path)))
        return os.path.join(par_name, name)
    return name


def _get_repo_type(path, repo_type, root) -> str:
    """

    """
    if repo_type != '':  # explicitly set
        return repo_type
    if root is not None and os.path.normpath(root) == os.path.normpath(path):
        return 'm'
    return ''


def add_repos(repos: Dict[str, Dict[str, str]], new_paths: List[str],
              repo_type='', root=None, is_bare=False) -> Dict[str, Dict[str, str]]:
    """
    Write new repo paths to file; return the added repos.

    @param repos: name -> path
    """
    existing_paths = {prop['path'] for prop in repos.values()}
    new_paths = {p for p in new_paths if is_git(p, is_bare)}
    new_paths = new_paths - existing_paths
    new_repos = {}
    if new_paths:
        print(f"Found {len(new_paths)} new repo(s).")
        name_counts = Counter(
            os.path.basename(os.path.normpath(p)) for p in new_paths
                )
        new_repos = {_make_name(path, repos, name_counts): {
            'path': path,
            'type': _get_repo_type(path, repo_type, root),
            'flags': '',
            } for path in new_paths}
        # When root is not None, we could optionally set its type to 'm', i.e.,
        # main repo.
        write_to_repo_file(new_repos, 'a+', root)
    else:
        print('No new repos found!')
    return new_repos


def _generate_dir_hash(repo_path: str, paths: List[str]) -> Tuple[str, ...]:
    """
    Return relative parent strings

    For example, if `repo_path` is /a/b/c/d/here, and one of `paths` is /a/b/
    then return (b, c, d)
    """
    for p in paths:
        if is_relative_to(repo_path, p):
            break
    else:
        return ()
    return (os.path.basename(p),
            *os.path.normpath(os.path.relpath(repo_path, p)).split(os.sep)[:-1])


def auto_group(repos: Dict[str, Dict[str, str]], paths: List[str]
        ) -> Dict[str, List[str]]:
    """

    """
    # FIXME: the upstream code should make sure that paths are all independent
    #        i.e., each repo should be contained in one and only one path
    new_groups = defaultdict(list)
    for repo_name, prop in repos.items():
        hash = _generate_dir_hash(prop['path'], paths)
        if not hash:
            continue
        for i in range(1, len(hash)+1):
            group_name = '-'.join(hash[:i])
            new_groups[group_name].append(repo_name)
    # FIXME: need to make sure the new group names don't clash with old ones
    #        or repo names
    return new_groups


def parse_clone_config(fname: str) -> Iterator[List[str]]:
    """
    Return the url, name, and path of all repos in `fname`.
    """
    with open(fname) as f:
        for line in f:
            yield line.strip().split(',')


async def run_async(repo_name: str, path: str, cmds: List[str]) -> Union[None, str]:
    """
    Run `cmds` asynchronously in `path` directory. Return the `path` if
    execution fails.
    """
    # TODO: deprecated since 3.8, will be removed in 3.10
    process = await asyncio.create_subprocess_exec(
        *cmds,
        stdin=asyncio.subprocess.DEVNULL,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
        start_new_session=True,
        cwd=path)
    stdout, stderr = await process.communicate()
    for pipe in (stdout, stderr):
        if pipe:
            print(format_output(pipe.decode(), repo_name))
    # The existence of stderr is not good indicator since git sometimes write
    # to stderr even if the execution is successful, e.g. git fetch
    if process.returncode != 0:
        return path


def format_output(s: str, prefix: str):
    """
    Prepends every line in given string with the given prefix.
    """
    return ''.join([f'{prefix}: {line}' for line in s.splitlines(keepends=True)])


def exec_async_tasks(tasks: List[Coroutine]) -> List[Union[None, str]]:
    """
    Execute tasks asynchronously
    """
    # TODO: asyncio API is nicer in python 3.7
    if platform.system() == 'Windows':
        loop = asyncio.ProactorEventLoop()
        asyncio.set_event_loop(loop)
    else:
        loop = asyncio.get_event_loop()

    try:
        errors = loop.run_until_complete(asyncio.gather(*tasks))
    finally:
        loop.close()
    return errors


def describe(repos: Dict[str, Dict[str, str]], no_colors: bool = False) -> str:
    """
    Return the status of all repos
    """
    if repos:
        name_width = max(len(n) for n in repos) + 1
    funcs = info.get_info_funcs()

    get_repo_status = info.get_repo_status
    if get_repo_status in funcs and no_colors:
        idx = funcs.index(get_repo_status)
        funcs[idx] = partial(get_repo_status, no_colors=True)

    for name in sorted(repos):
        info_items = ' '.join(f(repos[name]) for f in funcs)
        if repos[name]['type'] == 'm':
            # ANSI color code also takes length in Python
            name = f'{info.Color.underline}{name}{info.Color.end}'
            width = name_width + 8
            yield f'{name:<{width}}{info_items}'
        else:
            yield f'{name:<{name_width}}{info_items}'


def get_cmds_from_files() -> Dict[str, Dict[str, str]]:
    """
    Parse delegated git commands from default config file
    and custom config file.

    Example return
    {
      'branch': {'help': 'show local branches'},
      'clean': {'cmd': 'clean -dfx',
                'help': 'remove all untracked files/folders'},
    }
    """
    # default config file
    fname = os.path.join(os.path.dirname(__file__), "cmds.json")
    with open(fname, 'r') as f:
        cmds = json.load(f)

    # custom config file
    root = common.get_config_dir()
    fname = os.path.join(root, 'cmds.json')
    custom_cmds = {}
    if os.path.isfile(fname) and os.path.getsize(fname):
        with open(fname, 'r') as f:
            custom_cmds = json.load(f)

    # custom commands shadow default ones
    cmds.update(custom_cmds)
    return cmds
