#!/usr/bin/python3

import contextlib
import glob
import json
import os
import subprocess
import sys
import tempfile


image = sys.argv[1]

subprocess.run(["modprobe", "nbd"], check=True)


@contextlib.contextmanager
def nbd_connect(image):
    for device in glob.glob("/dev/nbd*"):
        r = subprocess.run(["qemu-nbd", "--connect", device, "--read-only", image], check=False).returncode
        if r == 0:
            try:
                yield device
            finally:
                subprocess.run(["qemu-nbd", "--disconnect", device], check=True, stdout=subprocess.DEVNULL)
            break
    else:
        raise RuntimeError("no free network block device")


@contextlib.contextmanager
def mount(device):
    with tempfile.TemporaryDirectory() as mountpoint:
        subprocess.run(["mount", "-o", "ro", device, mountpoint], check=True)
        try:
            yield mountpoint
        finally:
            subprocess.run(["umount", "--lazy", mountpoint], check=True)


def subprocess_check_output(argv, parse_fn=None):
    output = subprocess.check_output(argv, encoding="utf-8")
    return parse_fn(output) if parse_fn else output


def read_partition_table(device):
    sfdisk = subprocess_check_output(["sfdisk", "--json", device], json.loads)
    ptable = sfdisk["partitiontable"]
    assert ptable["unit"] == "sectors"

    partitions = []
    for p in ptable["partitions"]:
        partitions.append({
            "type": p["type"],
            "bootable": p.get("bootable", False),
            "start": p["start"] * 512,
            "size": p["size"] * 512
        })

    return ptable["label"], partitions


def read_bootloader_type(device):
    with open(device, "rb") as f:
        if b"GRUB" in f.read(512):
            return "grub"
        else:
            return "unknown"


def read_os_release(tree):
    r = {}
    with open(f"{tree}/etc/os-release") as f:
        for line in f:
            key, value = line.strip().split("=")
            r[key] = value.strip('"')
    return r


def read_bls_conf(filename):
    with open(filename) as f:
        return dict(line.strip().split(" ", 1) for line in f)


report = {}
with nbd_connect(image) as device:
    report["bootloader"] = read_bootloader_type(device)
    report["partition_table"], report["partitions"] = read_partition_table(device)

    # only one partition containing the root filesystem supported for now
    assert len(report["partitions"]) == 1

    with mount(device + "p1") as tree:
        report["packages"] = sorted(subprocess_check_output(["rpm", "--root", tree, "-qa"], str.split))
        report["os_release"] = read_os_release(tree)

        with open(f"{tree}/etc/fstab") as f:
            report["fstab"] = sorted([line.split() for line in f.read().split("\n") if line and not line.startswith("#")])

        with open(f"{tree}/etc/passwd") as f:
            report["passwd"] = sorted(f.read().strip().split("\n"))

        with open(f"{tree}/etc/group") as f:
            report["groups"] = sorted(f.read().strip().split("\n"))

        report["bootmenu"] = [read_bls_conf(f) for f in glob.glob(f"{tree}/boot/loader/entries/*.conf")]


json.dump(report, sys.stdout, sort_keys=True, indent=2)