import json
import os
import sys
import urllib.error
import urllib.request
from http.server import BaseHTTPRequestHandler, ThreadingHTTPServer


NTFY_URL = os.environ.get("NTFY_URL", "https://ntfy.kaleschke.info/homelab-alerts")


def priority_for(status, severity):
    if status == "resolved":
        return "2"
    if severity == "critical":
        return "5"
    if severity == "warning":
        return "4"
    return "3"


def tags_for(status, severity):
    if status == "resolved":
        return "white_check_mark"
    if severity == "critical":
        return "rotating_light"
    if severity == "warning":
        return "warning"
    return "information_source"


def alert_message(alert):
    labels = alert.get("labels", {})
    annotations = alert.get("annotations", {})
    status = alert.get("status", "firing")
    severity = labels.get("severity", "info")
    alertname = labels.get("alertname", "Alert")
    target = labels.get("instance") or labels.get("service") or labels.get("mountpoint") or "homelab"
    summary = annotations.get("summary") or alertname
    description = annotations.get("description") or ""

    title = f"{status.upper()} {severity}: {alertname}"
    lines = [
        summary,
        f"Target: {target}",
    ]
    if description and description != summary:
        lines.append(description)
    return title, "\n".join(lines), priority_for(status, severity), tags_for(status, severity)


def send_ntfy(title, message, priority, tags):
    req = urllib.request.Request(
        NTFY_URL,
        data=message.encode("utf-8"),
        headers={
            "Title": title,
            "Priority": priority,
            "Tags": tags,
        },
        method="POST",
    )
    with urllib.request.urlopen(req, timeout=15) as response:
        response.read()


class Handler(BaseHTTPRequestHandler):
    def do_GET(self):
        if self.path == "/healthz":
            self.send_response(200)
            self.end_headers()
            self.wfile.write(b"ok\n")
            return
        self.send_response(404)
        self.end_headers()

    def do_POST(self):
        if self.path != "/alertmanager":
            self.send_response(404)
            self.end_headers()
            return

        length = int(self.headers.get("Content-Length", "0"))
        payload = json.loads(self.rfile.read(length) or b"{}")
        alerts = payload.get("alerts", [])
        sent = 0

        for alert in alerts:
            title, message, priority, tags = alert_message(alert)
            try:
                send_ntfy(title, message, priority, tags)
                sent += 1
            except urllib.error.URLError as exc:
                print(f"ntfy send failed: {exc}", file=sys.stderr, flush=True)
                self.send_response(502)
                self.end_headers()
                self.wfile.write(b"ntfy send failed\n")
                return

        print(f"sent {sent} ntfy notifications", flush=True)
        self.send_response(200)
        self.end_headers()
        self.wfile.write(f"sent {sent}\n".encode("utf-8"))

    def log_message(self, fmt, *args):
        print(fmt % args, flush=True)


if __name__ == "__main__":
    server = ThreadingHTTPServer(("0.0.0.0", 8080), Handler)
    print(f"alertmanager ntfy bridge listening on :8080 -> {NTFY_URL}", flush=True)
    server.serve_forever()