#!/usr/bin/python3

import collections
import datetime
import logging
import os
import subprocess
import textwrap

import pygit2

_log = logging.getLogger(__name__)


def register_subcommand(subparsers):
    subcmd_name = "generate-changelog"

    gen_changelog_parser = subparsers.add_parser(
        subcmd_name, help="Generate changelog entries from git commit logs",
    )

    gen_changelog_parser.add_argument("worktree_path", help="Path to the dist-git worktree")

    return subcmd_name


def run_command(command, cwd=None):
    """ Run the specified command in a specific working directory if one
    is specified.
    """
    output = None
    try:
        output = subprocess.check_output(command, cwd=cwd, stderr=subprocess.PIPE)
    except subprocess.CalledProcessError as e:
        _log.error("Command `{}` return code: `{}`".format(" ".join(command), e.returncode))
        _log.error("stdout:\n-------\n{}".format(e.stdout))
        _log.error("stderr:\n-------\n{}".format(e.stderr))
        raise Exception("Command failed to run")

    return output


def main(args):
    """ Main method. """
    repopath = args.worktree_path

    repo_obj = pygit2.Repository(repopath)
    name = os.path.basename(repopath)

    branch = repo_obj.lookup_branch(repo_obj.head.shorthand)
    commit = branch.peel(pygit2.Commit)
    data = collections.defaultdict(list)
    for commit in repo_obj.walk(commit.hex, pygit2.GIT_SORT_TIME):
        if len(commit.parents) > 1:
            # Ignore merge commits
            continue

        commit_dt = datetime.datetime.utcfromtimestamp(commit.commit_time)
        if commit_dt < (datetime.datetime.utcnow() - datetime.timedelta(days=730)):
            # Ignore all commits older than 2 years
            break

        repo_obj.checkout_tree(
            commit, strategy=pygit2.GIT_CHECKOUT_FORCE | pygit2.GIT_CHECKOUT_RECREATE_MISSING,
        )
        if os.path.exists(os.path.join(repopath, f"{name}.spec")):
            try:
                output = run_command(
                    [
                        "rpm",
                        "--qf",
                        "%{name}  %{version}  %{release}\n",
                        "--specfile",
                        f"{name}.spec",
                    ],
                    cwd=repopath,
                )
            except Exception:
                continue
            output = tuple(
                output.decode("utf-8").strip().split("\n")[0].rsplit(".", 1)[0].split("  ")
            )
            nvr = "-".join(output)

            if commit.parents:
                diff = repo_obj.diff(commit.parents[0], commit)
            else:
                # First commit in the repo
                diff = commit.tree.diff_to_tree(swap=True)

            if diff.stats.files_changed:
                files_changed = [d.new_file.path for d in diff.deltas]
                ignore = True
                for filename in files_changed:
                    if filename.endswith((".spec", ".patch")):
                        ignore = False
                if not ignore:
                    data[output].append(commit)
        else:
            print("No more spec file, bailing")
            break

    for nvr, commits in data.items():
        for idx, commit in enumerate(reversed(commits)):
            last_commit = idx + 1 == len(commits)
            commit_dt = datetime.datetime.utcfromtimestamp(commit.commit_time)
            wrapper = textwrap.TextWrapper(width=75, subsequent_indent="  ")
            message = wrapper.fill(commit.message.split("\n")[0].strip("- "))

            if last_commit:
                print(
                    f"* {commit_dt.strftime('%a %b %d %Y')} {commit.author.name}"
                    f" <{commit.author.email}> - {nvr[1]}-{nvr[2]}"
                )
            else:
                print(
                    f"* {commit_dt.strftime('%a %b %d %Y')} {commit.author.name}"
                    f" <{commit.author.email}>"
                )
            print("- %s" % message)
            print()