diff_packages/diff_packages.py

#!/usr/bin/env python
import json
import tempfile
import subprocess
import datetime
from pathlib import Path


def get_last_boot():
    with subprocess.Popen(
        ["journalctl", "--list-boots"], stdout=subprocess.PIPE
    ) as proc:
        for line in proc.stdout.read().decode().split("\n"):
            info, end_time = line.split(chr(8212))
            info = list(filter(bool, info.split(" ")))
            bootnum = info[0]
            if bootnum == "0":
                start_date_string = " ".join(info[3:5])
                return datetime.datetime.fromisoformat(start_date_string).replace(
                    tzinfo=datetime.timezone.utc
                )


def get_snapshot__after_datetime(start: datetime.datetime):
    with subprocess.Popen(
        ["snapper", "--utc", "--iso", "--jsonout", "list", "-t", "pre-post"],
        stdout=subprocess.PIPE,
    ) as proc:
        if proc.wait() != 0:
            raise PermissionError("Snapper needs root privileges to read snapshots")
        data = json.loads(proc.stdout.read().decode())
        # ten years
        td = 3153600000
        ret = None
        for snapshot in data["root"]:
            snapshot_date = datetime.datetime.fromisoformat(snapshot["date"]).replace(
                tzinfo=datetime.timezone.utc
            )
            d = (snapshot_date - start).total_seconds()
            if 0 < d < td:
                td = d
                ret = snapshot
        return ret


def get_snapshot_path(snapshot):
    return (
        Path(snapshot["subvolume"])
        / ".snapshots"
        / Path(str(snapshot["number"]))
        / "snapshot"
    )


def write_pacman_output(path):
    out_file = tempfile.NamedTemporaryFile("wt")
    proc = subprocess.Popen(["pacman", "-Q", "--dbpath", str(path)], stdout=out_file)
    proc.wait()
    return out_file


def diff_tempfiles(old, new):
    subprocess.Popen(["diff", old.name, new.name, "--color=always", "--minimal"])


if __name__ == "__main__":
    snapshot_data = get_snapshot__after_datetime(get_last_boot())
    snapshot_root = get_snapshot_path(snapshot_data)
    db_root = "var/lib/pacman"
    old = write_pacman_output(snapshot_root / db_root)
    new = write_pacman_output(Path(snapshot_data["subvolume"]) / db_root)
    diff_tempfiles(old, new)