"""# Git-based Time Tracker.

Quick and dirty time tracker on git histories.

Uses the simple heuristics that each commit takes precisely one hour of work.
It will automatically trim commits below one hour if another commit occurred
less than an hour ago.

Usage:

```
python -m git_time_tracker REPO1 REPO2...
```

# Obligatory

This tool reports:

```
project    Jmaa/git-time-tracker.git                    3h 33m  (2024)
```

And the ([Hamster](https://github.com/projecthamster/hamster)) manual time tracker reports:

![](docs/obligatory-hamster.png)
"""

import argparse
import dataclasses
import datetime
import logging
import sys
import time
from collections.abc import Iterator, Sequence
from pathlib import Path

import git

logger = logging.getLogger(__name__)


@dataclasses.dataclass(frozen=True, order=True)
class WorkSample:
    registered_at: datetime.datetime
    labels: Sequence[str]


def determine_default(repo: git.Repo):
    try:
        repo.commit('main')
        return 'main'
    except:
        return 'master'


HIDDEN_LABEL_PREFIX = '__'
HIDDEN_LABEL_TOTAL = HIDDEN_LABEL_PREFIX + 'TOTAL'


def determine_project_name(repo: git.Repo) -> str:
    remotes = repo.remotes
    if len(remotes) > 0:
        return remotes.origin.url.removeprefix('git@gitfub.space:')
    return Path(repo.working_tree_dir).name


def get_samples_from_project(repo: git.Repo) -> Iterator[WorkSample]:
    project_name = determine_project_name(repo)
    assert project_name is not None

    # TODO: Branch on main or master or default

    repo.commit()

    for commit in repo.iter_commits(determine_default(repo)):
        labels = [HIDDEN_LABEL_TOTAL]
        labels.append('project:' + project_name)
        labels.append('author:' + commit.author.email)
        yield WorkSample(
            datetime.datetime.fromtimestamp(commit.authored_date, tz=datetime.UTC),
            tuple(labels),
        )
        yield WorkSample(
            datetime.datetime.fromtimestamp(commit.committed_date, tz=datetime.UTC),
            tuple(labels),
        )
        del labels


DEFAULT_EST_TIME = datetime.timedelta(hours=1)

ZERO_DURATION = datetime.timedelta(seconds=0)
HOUR = datetime.timedelta(hours=1)
MINUTE = datetime.timedelta(minutes=1)


def fmt_year_ranges_internal(years: list[int]) -> Iterator[str]:
    years = sorted(years)
    for idx, year in enumerate(years):
        at_end = idx == len(years) - 1
        range_before = idx > 0 and years[idx-1] == year - 1
        range_after = not at_end and years[idx+1] == year + 1

        if not range_before or not range_after:
            yield str(year)

        if not at_end:
            if not range_before and range_after:
                yield '-'
            elif not range_after:
                yield ','

def fmt_year_ranges(years: list[int]) -> str:
    return ''.join(list(fmt_year_ranges_internal(years)))

def fmt_line(label_type: str, label: str, total_time: datetime.timedelta) -> str:
    hours = int(total_time / HOUR)
    minutes = int((total_time - hours*HOUR)/MINUTE)
    return f'  {label_type:10} {label:40}  {hours:-4d}h {minutes:-2d}m'

def generate_report(samples: list[WorkSample], sample_filter = frozenset()) -> Iterator[str]:
    LABEL_FILTER = {}

    # Time spent per label
    time_per_label: dict[str, datetime.timedelta] = {}
    years_per_label: dict[str, set[int]] = {}
    prev_time = datetime.datetime.fromtimestamp(0, datetime.UTC)
    for sample in samples:
        est_time: datetime.timedelta = DEFAULT_EST_TIME
        est_time = min(sample.registered_at - prev_time, est_time)

        if len(sample_filter) == 0:
            pass
        elif not set(sample.labels).intersection(sample_filter):
            continue

        for label in sample.labels:
            time_per_label.setdefault(label, ZERO_DURATION)
            time_per_label[label] += est_time
            years_per_label.setdefault(label,set()).add(sample.registered_at.year)

        prev_time = sample.registered_at
        del sample, est_time

    time_and_label = [(duration, label) for label, duration in time_per_label.items()]
    time_and_label.sort(reverse=True)

    #
    yield '-' * 66
    yield '\n'
    for total_time, label_and_type in time_and_label:
        if label_and_type.startswith(HIDDEN_LABEL_PREFIX):
            continue

        label_type, label = label_and_type.split(':', 1)

        if len(LABEL_FILTER) > 0 and label_type not in LABEL_FILTER:
            continue

        yield fmt_line(label_type, label, total_time)
        yield '  ('
        yield fmt_year_ranges(years_per_label.get(label_and_type,[]))
        yield ')'
        yield '\n'
        del label, total_time

    yield '-' * 66
    yield '\n'

    yield fmt_line('', 'TOTAL', time_per_label.get(HIDDEN_LABEL_TOTAL, ZERO_DURATION))
    yield '\n'


def parse_arguments():
    parser = argparse.ArgumentParser()
    parser.add_argument('repositories', action='extend', nargs='+', type=Path)
    parser.add_argument('--filter', action='extend', nargs='+', type=str, dest='sample_filter', default=[])
    return parser.parse_args()


def main():
    logging.basicConfig()

    args = parse_arguments()

    shared_time_stamps: set[WorkSample] = set()
    for repo_path in args.repositories:
        try:
            repo = git.Repo(repo_path)
        except git.exc.InvalidGitRepositoryError:
            logger.warning('Ignoring non-repo %s', repo_path)
            continue
        logger.warning('Visit %s', repo_path)
        shared_time_stamps |= set(get_samples_from_project(repo))

    shared_time_stamps = sorted(shared_time_stamps)

    for t in generate_report(shared_time_stamps, sample_filter=args.sample_filter):
        sys.stdout.write(t)