"""
Git commits data for repositories on your filesystem
"""
REQUIRES = [
    'gitpython',
]


import shutil
from pathlib import Path
from datetime import datetime, timezone
from dataclasses import dataclass, field
from typing import List, Optional, Iterator, Set, Sequence


from my.core import PathIsh, LazyLogger, make_config
from my.core.cachew import cache_dir
from my.core.common import mcachew
from my.core.warnings import high


from my.config import commits as user_config
@dataclass
class commits_cfg(user_config):
    roots: Sequence[PathIsh] = field(default_factory=list)
    emails: Optional[Sequence[str]] = None
    names: Optional[Sequence[str]] = None


# experiment to make it lazy?
# would be nice to have a nicer syntax for it... maybe make_config could return a 'lazy' object
def config() -> commits_cfg:
    res = make_config(commits_cfg)
    if res.emails is None and res.names is None:
        # todo error policy? throw/warn/ignore
        high("Set either 'emails' or 'names', otherwise you'll get no commits")
    return res

##########################

import git # type: ignore
from git.repo.fun import is_git_dir # type: ignore


log = LazyLogger(__name__, level='info')


def by_me(c: git.objects.commit.Commit) -> bool:
    actor = c.author
    if actor.email in (config().emails or ()):
        return True
    if actor.name in (config().names or ()):
        return True
    return False


@dataclass
class Commit:
    commited_dt: datetime
    authored_dt: datetime
    message: str
    repo: str # TODO put canonical name here straightaway??
    sha: str
    ref: Optional[str] = None
    # TODO filter so they are authored by me

    @property
    def dt(self) -> datetime:
        return self.commited_dt


# TODO not sure, maybe a better idea to move it to timeline?
def fix_datetime(dt: datetime) -> datetime:
    # git module got it's own tzinfo object.. and it's pretty weird
    tz = dt.tzinfo
    assert tz is not None, dt
    assert getattr(tz, '_name') == 'fixed'
    offset = getattr(tz, '_offset')
    ntz = timezone(offset)
    return dt.replace(tzinfo=ntz)


def _git_root(git_dir: PathIsh) -> Path:
    gd = Path(git_dir)
    if gd.name == '.git':
        return gd.parent
    else:
        return gd # must be bare


def _repo_commits_aux(gr: git.Repo, rev: str, emitted: Set[str]) -> Iterator[Commit]:
    # without path might not handle pull heads properly
    for c in gr.iter_commits(rev=rev):
        if not by_me(c):
            continue
        sha = c.hexsha
        if sha in emitted:
            continue
        emitted.add(sha)

        repo = str(_git_root(gr.git_dir))

        yield Commit(
            commited_dt=fix_datetime(c.committed_datetime),
            authored_dt=fix_datetime(c.authored_datetime),
            message=c.message.strip(),
            repo=repo,
            sha=sha,
            ref=rev,
        )


def repo_commits(repo: PathIsh):
    gr = git.Repo(str(repo))
    emitted: Set[str] = set()
    for r in gr.references:
        yield from _repo_commits_aux(gr=gr, rev=r.path, emitted=emitted)


def canonical_name(repo: Path) -> str:
    # TODO could determine origin?
    if repo.match('github/repositories/*/repository'):
        return repo.parent.name
    else:
        return repo.name
        # if r.name == 'repository': # 'repository' thing from github..
        #     rname = r.parent.name
        # else:
        #     rname = r.name
    # if 'backups/github' in repo:
    #     pass # TODO 


def _fd_path() -> str:
    # todo move it to core
    fd_path: Optional[str] = shutil.which("fdfind") or shutil.which("fd-find") or shutil.which("fd")
    if fd_path is None:
        high("my.coding.commits requires 'fd' to be installed, See https://github.com/sharkdp/fd#installation")
    assert fd_path is not None
    return fd_path


def git_repos_in(roots: List[Path]) -> List[Path]:
    from subprocess import check_output
    outputs = check_output([
        _fd_path(),
        # '--follow', # right, not so sure about follow... make configurable?
        '--hidden',
        '--full-path',
        '--type', 'f',
        '/HEAD', # judging by is_git_dir, it should always be here..
        *roots,
    ]).decode('utf8').splitlines()

    candidates = set(Path(o).resolve().absolute().parent for o in outputs)

    # exclude stuff within .git dirs (can happen for submodules?)
    candidates = {c for c in candidates if '.git' not in c.parts[:-1]}

    candidates = {c for c in candidates if is_git_dir(c)}

    repos = list(sorted(map(_git_root, candidates)))
    return repos


def repos() -> List[Path]:
    return git_repos_in(list(map(Path, config().roots)))


# returns modification time for an index to use as hash function
def _repo_depends_on(_repo: Path) -> int:
    for pp in {
        ".git/FETCH_HEAD",
        ".git/HEAD",
        "FETCH_HEAD",  # bare
        "HEAD",  # bare
    }:
        ff = _repo / pp
        if ff.exists():
            return int(ff.stat().st_mtime)
    else:
        raise RuntimeError(f"Could not find a FETCH_HEAD/HEAD file in {_repo}")


def _commits(_repos: List[Path]) -> Iterator[Commit]:
    for r in _repos:
        yield from _cached_commits(r)


def _cached_commits_path(p: Path) -> str:
    p = cache_dir() / 'my.coding.commits:_cached_commits' / str(p.absolute()).strip("/")
    p.mkdir(parents=True, exist_ok=True)
    return str(p)


# per-repo commits, to use cachew
@mcachew(
    depends_on=_repo_depends_on,
    logger=log,
    cache_path=_cached_commits_path,
)
def _cached_commits(repo: Path) -> Iterator[Commit]:
    log.debug('processing %s', repo)
    yield from repo_commits(repo)


def commits() -> Iterator[Commit]:
    return _commits(repos())


# TODO enforce read only? although it doesn't touch index