#!/usr/bin/env python
"""
Analyze developer allocation across a codebase.
"""

import argparse
import datetime
import logging
import os
import re
import subprocess
import sys


def find_user(line):
    """Given 'Ben Sima <ben@bsima.me>', finds `Ben Sima'. Returns the first
    matching string."""
    return re.findall(r"^[^<]*", line)[0].strip()


def authors_for(path, active_users):
    """Return a dictionary of {author: commits} for given path. Usernames not in
    the 'active_users' list will be filtered out."""
    raw = subprocess.check_output(
        ["git", "shortlog", "--numbered", "--summary", "--email", "--", path]
    ).decode("utf-8")
    lines = [s for s in raw.split("\n") if s]
    data = {}
    for line in lines:
        parts = line.strip().split("\t")
        author = find_user(parts[1])
        commits = parts[0]
        if author in active_users:
            data[author] = commits
    return data


def mailmap_users():
    """Returns users from the .mailmap file."""
    users = []
    with open(".mailmap") as file:
        lines = file.readlines()
        for line in lines:
            users.append(find_user(line))
    return users


MAX_SCORE = 10


def score(blackhole, liability, good, total):
    "Calculate the score."
    weights = {
        "blackhole": 0.5,
        "liability": 0.7,
    }
    return (
        MAX_SCORE
        * (
            (blackhole * weights["blackhole"])
            + (liability * weights["liability"])
            + good
        )
        / total
    )


def get_args():
    "Parse CLI arguments."
    cli = argparse.ArgumentParser(description=__doc__)
    cli.add_argument("repo", default=".", help="the git repo to run on", metavar="REPO")
    cli.add_argument(
        "-b",
        "--blackholes",
        action="store_true",
        help="print the blackholes (files with one or zero active contributors)",
    )
    cli.add_argument(
        "-l",
        "--liabilities",
        action="store_true",
        help="print the liabilities (files with < 3 active contributors)",
    )
    cli.add_argument(
        "-s",
        "--stale",
        action="store_true",
        help="print stale files (haven't been touched in 6 months)",
    )
    cli.add_argument(
        "-i", "--ignored", nargs="+", default=[], help="patterns to ignore in paths",
    )
    cli.add_argument(
        "--active-users",
        nargs="+",
        default=[],
        help="list of active user emails. if not provided, this is loaded from .mailmap",
    )
    cli.add_argument(
        "-v",
        "--verbosity",
        help="set the log level verbosity",
        choices=["debug", "warning", "error"],
        default="error",
    )
    return cli.parse_args()


def guard_git(repo):
    "Guard against non-git repos."
    is_git = subprocess.run(
        ["git", "rev-parse"],
        stderr=subprocess.PIPE,
        stdout=subprocess.PIPE,
        check=False,
    ).returncode
    if is_git != 0:
        sys.exit(f"error: not a git repository: {repo}")


def staleness(path, now):
    "How long has it been since this file was touched?"
    timestamp = datetime.datetime.strptime(
        subprocess.check_output(["git", "log", "-n1", "--pretty=%aI", path])
        .decode("utf-8")
        .strip(),
        "%Y-%m-%dT%H:%M:%S%z",
    )
    delta = now - timestamp
    return delta.days


class Repo:
    "Represents a repo and stats for the repo."

    def __init__(self, ignored_paths, active_users):
        self.paths = [
            p
            for p in subprocess.check_output(["git", "ls-files", "--no-deleted"])
            .decode("utf-8")
            .split()
            if not any(i in p for i in ignored_paths)
        ]
        logging.debug("collecting stats")
        self.stats = {}
        for path in self.paths:
            self.stats[path] = authors_for(path, active_users)
        self.blackholes = [path for path, authors in self.stats.items() if not authors]
        self.liabilities = {
            path: list(authors)
            for path, authors in self.stats.items()
            if 1 <= len(authors) < 3
        }
        now = datetime.datetime.utcnow().astimezone()
        self.stale = {}
        for path, _ in self.stats.items():
            _staleness = staleness(path, now)
            if _staleness > 180:
                self.stale[path] = _staleness

    def print_blackholes(self, full):
        "Print number of blackholes, or list of all blackholes."
        # note: file renames may result in false positives
        n_blackhole = len(self.blackholes)
        print(f"Blackholes: {n_blackhole}")
        if full:
            for path in self.blackholes:
                print(f"  {path}")

    def print_liabilities(self, full):
        "Print number of liabilities, or list of all liabilities."
        n_liabilities = len(self.liabilities)
        print(f"Liabilities: {n_liabilities}")
        if full:
            for path, authors in self.liabilities.items():
                print(f"  {path}  ({', '.join(authors)})")

    def print_score(self):
        "Print the overall score."
        n_total = len(self.stats.keys())
        n_blackhole = len(self.blackholes)
        n_liabilities = len(self.liabilities)
        n_good = n_total - n_blackhole - n_liabilities
        print("Total:", n_total)
        print(
            "Score: {:.2f}/{}".format(
                score(n_blackhole, n_liabilities, n_good, n_total), MAX_SCORE
            )
        )

    def print_stale(self, full):
        "Print stale files"
        n_stale = len(self.stale)
        print(f"Stale files: {n_stale}")
        if full:
            for path, days in self.stale.items():
                print(f"  {path}  ({days} days)")


if __name__ == "__main__":
    ARGS = get_args()
    logging.basicConfig(stream=sys.stderr, level=ARGS.verbosity.upper())

    logging.debug("starting")
    os.chdir(os.path.abspath(ARGS.repo))

    guard_git(ARGS.repo)

    # if no active users provided, load from .mailmap
    if ARGS.active_users == []:
        if os.path.exists(".mailmap"):
            ARGS.active_users = mailmap_users()

    # collect data
    REPO = Repo(ARGS.ignored, ARGS.active_users)

    # print data
    REPO.print_score()
    REPO.print_blackholes(ARGS.blackholes)
    REPO.print_liabilities(ARGS.liabilities)
    REPO.print_stale(ARGS.stale)