#!/usr/bin/env python3
import asyncio
import datetime
import json
import logging
import os
import shlex
import signal
import sys
import syslog
import urllib.error
import urllib.request
from typing import Any, AsyncIterator


log = logging.getLogger('journal2ntfy')


Json = dict[str, Any]


NTFY_URL = os.environ.get('NTFY_URL', 'https://ntfy.pyrocufflink.blue')
NTFY_TOPIC = os.environ.get('NTFY_TOPIC', 'alerts')


ntfy_lock = asyncio.Lock()


async def follow_journal(*filters: str) -> AsyncIterator[Json]:
    cmd = [
        'journalctl',
        '--since=now',
        '--output=json',
        '--follow',
    ]
    cmd += filters
    if log.isEnabledFor(logging.DEBUG):
        log.debug(
            'Running command: %s', ' '.join(shlex.quote(str(a)) for a in cmd)
        )
    p = await asyncio.create_subprocess_exec(
        *cmd,
        stdin=asyncio.subprocess.DEVNULL,
        stdout=asyncio.subprocess.PIPE,
        stderr=asyncio.subprocess.PIPE,
    )

    assert p.stdout
    try:
        async for line in p.stdout:
            try:
                data = json.loads(line)
            except ValueError as e:
                log.error('Failed to parse journal entry: %s', e)
                continue
            try:
                yield data
            except Exception:
                log.exception('Error handling message:')
                continue
    except asyncio.CancelledError:
        log.debug('Terminating child process')
        p.terminate()
        try:
            await asyncio.wait_for(p.wait(), 10)
        except asyncio.TimeoutError:
            log.warning('Child process did not terminate when asked, killing')
            p.kill()
            await p.wait()
        raise


async def on_message(data: Json) -> None:
    message = data.get('MESSAGE')
    if not message:
        log.debug('Ignoring journal record with empty message')
        return

    try:
        timestamp = datetime.datetime.fromtimestamp(
            int(data['__REALTIME_TIMESTAMP']) / 1e6
        )
    except (KeyError, ValueError) as e:
        log.warning('Could not parse message timestamp: %s', e)
        timestamp = datetime.datetime.now()

    try:
        hostname = data['_HOSTNAME']
    except KeyError:
        hostname = os.uname().nodename

    try:
        ident = data['SYSLOG_IDENTIFIER']
    except KeyError:
        ident = data.get('_TRANSPORT', '')

    message = (
        f'{timestamp.strftime("%b %d %H:%M:%S")} {hostname} {ident}: '
        f'{message}'
    )

    try:
        priority = int(data['PRIORITY'])
    except (KeyError, ValueError):
        priority = 0
    if priority <= syslog.LOG_CRIT:
        tag = 'rotating_light'
    elif priority == syslog.LOG_ERR:
        tag = 'red_circle'
    elif priority == syslog.LOG_WARNING:
        tag = 'warning'
    elif priority == syslog.LOG_NOTICE:
        tag = 'pushpin'
    elif priority == syslog.LOG_INFO:
        tag = 'information_source'
    else:
        tag = 'white_circle'

    req = urllib.request.Request(
        f'{NTFY_URL}/{NTFY_TOPIC}',
        data=message.encode('utf-8'),
        headers={
            'Tags': tag,
            'Content-Type': 'text/plain; charset=utf-8',
        },
    )
    try:
        # The lock ensures that messages are delivered in the order
        # they were read from the journal, while `to_thread` keeps the
        # network request from blocking the event loop.
        async with ntfy_lock:
            res = await asyncio.to_thread(urllib.request.urlopen, req)
    except urllib.error.URLError as e:
        log.error('Could not send ntfy notification: %s', e)
        return
    if res.status == 200:
        log.debug('Successfully sent ntfy notification')
    else:
        log.error('Sending ntfy notification failed: %s', res.reason)


def shutdown(signum: int) -> None:
    log.info('Received %s, shutting down', signal.Signals(signum).name)
    cur_task = asyncio.current_task()
    for task in asyncio.all_tasks():
        if task is not cur_task:
            task.cancel()


async def main():
    logging.basicConfig(level=logging.DEBUG)
    loop = asyncio.get_running_loop()
    loop.add_signal_handler(signal.SIGTERM, shutdown, signal.SIGTERM)
    loop.add_signal_handler(signal.SIGINT, shutdown, signal.SIGINT)

    if len(sys.argv) > 1:
        filters = sys.argv[1:]
    else:
        filters = shlex.split(os.environ.get('JOURNAL2NTFY_FILTERS', ''))

    try:
        async for data in follow_journal(*filters):
            await on_message(data)
    except asyncio.CancelledError:
        return


if __name__ == '__main__':
    asyncio.run(main())