#!/usr/bin/env python3
"""Receive Beszel's Shoutrrr JSON and deliver through the supported postbox CLI."""
import json
import os
import subprocess
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer


def deliver(payload):
    title = payload.get('title', 'Beszel fleet alert')
    message = payload.get('message')
    if not isinstance(title, str) or not isinstance(message, str) or not message.strip():
        raise ValueError('Expected a nonempty message and string title')
    result = subprocess.run(
        [os.environ['POSTBOX'], '--json', 'send', '--to', os.environ['BESZEL_ALERT_RECIPIENT'],
         '--subject', '[Beszel] ' + title],
        input=message + '\n\nHub: http://10.250.50.70:8090\n',
        text=True, capture_output=True, timeout=25,
    )
    if result.returncode:
        raise RuntimeError('postbox delivery failed: ' + result.stderr.strip())
    receipt = json.loads(result.stdout)
    print(json.dumps({'event': 'delivered', 'title': title, 'receipt': receipt}), flush=True)
    return receipt


class Handler(BaseHTTPRequestHandler):
    def respond(self, status, body):
        data = json.dumps(body).encode()
        self.send_response(status)
        self.send_header('Content-Type', 'application/json')
        self.send_header('Content-Length', str(len(data)))
        self.end_headers()
        self.wfile.write(data)

    def do_GET(self):
        self.respond(200 if self.path == '/healthz' else 404,
                     {'service': 'beszel-althing', 'delivery': 'verified per POST'})

    def do_POST(self):
        if self.path != '/beszel':
            return self.respond(404, {'error': 'Unknown route'})
        if self.client_address[0] not in os.environ['BESZEL_ALLOWED_SOURCES'].split(','):
            return self.respond(403, {'error': 'Source not allowed'})
        try:
            length = int(self.headers.get('Content-Length', '0'))
            if not 0 < length <= 65536:
                raise ValueError('Invalid body size')
            self.connection.settimeout(10)
            payload = json.loads(self.rfile.read(length))
            if not isinstance(payload, dict):
                raise ValueError('Expected JSON object')
            receipt = deliver(payload)
        except (ValueError, TypeError) as exc:
            return self.respond(400, {'error': str(exc)})
        except (OSError, RuntimeError, subprocess.TimeoutExpired) as exc:
            print(json.dumps({'event': 'delivery_failed', 'error': str(exc)}), flush=True)
            return self.respond(502, {'error': 'Althing delivery failed; inspect service journal'})
        self.respond(200, {'delivered': True, 'receipt': receipt})


if __name__ == '__main__':
    ThreadingHTTPServer((os.environ['BESZEL_BIND_HOST'], int(os.environ.get('BESZEL_BIND_PORT', '8096'))), Handler).serve_forever()