#!/usr/bin/python3

"""Query the status of the lxd snap."""

# Python implementation of:
# $ curl -s --unix /run/snapd.socket 'http://unix.socket/v2/changes?select=in-progress&for=lxd'  | jq -r '.result[0].kind'
# auto-refresh

# The full JSON output when querying the in-progress changes for the lxd snap:
# $ curl -s --unix /run/snapd.socket 'http://snapd/v2/changes?select=in-progress&for=lxd' | jq -r .
# {
#   "type": "sync",
#   "status-code": 200,
#   "status": "OK",
#   "result": [
#     {
#       "id": "1907",
#       "kind": "auto-refresh",
#       "summary": "Auto-refresh snap \"lxd\"",
#       "status": "Hold",
#       "ready": true,
#       "spawn-time": "2024-02-19T10:21:34.429396408-05:00",
#       "data": {
#         "snap-names": [
#           "lxd"
#         ]
#       }
#     }
#   ]
# }

# Heavily inspired from snapd's api-client.py:
# https://github.com/snapcore/snapd/blob/master/tests/main/theme-install/api-client/bin/api-client.py

import http.client
import json
import socket
import sys


# This class is a subclass of http.client.HTTPConnection that connects to a Unix socket instead of a TCP socket.
class UnixSocketHTTPConnection(http.client.HTTPConnection):
    def __init__(self, socket_path):
        super().__init__("snapd")
        self._socket_path = socket_path

    def connect(self):
        s = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
        s.connect(self._socket_path)
        self.sock = s


# This function connects to the Unix socket and requests the in-progress changes for the lxd snap.
# Returns the kind of the first result, or an empty string if an error occurs.
def main():
    # Try to connect to the Unix socket and request the in-progress changes for the lxd snap.
    # If an exception occurs, print an error message and return an empty string.
    try:
        conn = UnixSocketHTTPConnection("/run/snapd.socket")
        conn.request("GET", "/v2/changes?select=in-progress&for=lxd")
        response = conn.getresponse()
        body = response.read().decode()
    except FileNotFoundError:
        print("missing socket", file=sys.stderr)
        return ""
    except http.client.HTTPException as e:
        print("HTTP exception:", e, file=sys.stderr)
        return ""
    finally:
        conn.close()

    # If the response status is not 200, print an error message and return an empty string.
    if response.status != 200:
        print("HTTP error:", response.status, file=sys.stderr)
        return ""

    # If the response body is missing or empty, print an error message and return an empty string.
    if not body:
        print("Missing/empty body", file=sys.stderr)
        return ""

    # Try to parse the response body as JSON, and extract the "kind" field from the first result.
    try:
        data = json.loads(body)
    except json.JSONDecodeError as e:
        print("JSON decode exception:", e, file=sys.stderr)
        return ""

    if "result" in data and isinstance(data["result"], list) and len(data["result"]):
        return data["result"][0].get("kind", "")

    return ""


if __name__ == "__main__":
    print(main())