#!/usr/bin/env python
import subprocess
from dataclasses import dataclass
from argparse import ArgumentParser


@dataclass(frozen=True)
class ZfsProp:
    prop: str
    value: str
    source: str


D_ZFS_PROPS = dict[str, ZfsProp]


def zfs_get_all(name: str) -> D_ZFS_PROPS:
    res = dict()
    s = subprocess.run(
        f"zfs get -H -p -o property,value,source all {name}",
        shell=True,
        check=True,
        capture_output=True,
    )
    for line in s.stdout.decode().splitlines(keepends=False):
        p = ZfsProp(*line.split("\t"))
        res[p.prop] = p

    return res


def no_backups_statement(props: D_ZFS_PROPS) -> str:
    referenced = int(props["referenced"].value)
    mounted = props["mounted"] == "yes"
    mountpoint = props["mountpoint"].value
    usedbysnapshots = int(props["usedbysnapshots"].value)

    if (
        usedbysnapshots == 0
        and mounted is False
        and referenced < 175_000
        and mountpoint == "none"
    ):
        return "OK; A parent dataset, no data is actually stored"

    else:
        return "CHECK; Not really sure"


def main(pool_name: str, only_no_backups: bool) -> int:
    p = subprocess.run(
        f"zfs list -H -o name -r {pool_name}", shell=True, capture_output=True
    )
    if p.returncode == 1 and p.stdout == b"":
        print("Pool not found")
        return 1

    if p.returncode != 0:
        print("return code of zfs list was not 0")
        return 2

    print("DATASET\tBACKUP_LABEL\tVALUE\tSOURCE\tHEURISTIC")
    for ds_name in p.stdout.decode().splitlines(keepends=False):
        props = zfs_get_all(ds_name)

        autobackup_props: D_ZFS_PROPS = {
            p: props[p] for p in props.keys() if p.startswith("autobackup:")
        }

        if len(autobackup_props) > 1:
            raise RuntimeError(
                f">1 autobackup: properties on {ds_name=!r}: {autobackup_props!r}"
            )

        elif len(autobackup_props) == 0:
            msg = no_backups_statement(props)
            print(f"{ds_name}\tno\t\t\t{msg}")

        else:
            if not only_no_backups:
                autobackup_prop: ZfsProp = next(iter((autobackup_props.values())))
                print(
                    f"{ds_name}\t{autobackup_prop.prop}\t{autobackup_prop.value}\t{autobackup_prop.source}"
                )


if __name__ == "__main__":
    import sys

    try:
        parser = ArgumentParser(
            "zfs_autobackup_explorer",
            usage="It's wise to pipe output to column tool to get "
            f"formatted output: {sys.argv[0]} | column -t -s $'\\t' | less -S",
        )
        parser.add_argument("pool_name")
        parser.add_argument("--only-no-backups", action="store_true", default=False)
        args = parser.parse_args()
        exit(main(args.pool_name, args.only_no_backups))

    except KeyboardInterrupt:
        print("exiting by CTRL+C")
        exit(130)