#!/usr/bin/env python3
"""Daily digest of unanswered discourse.eom.dev topics, posted to Matrix.

Lists recent public topics that have no replies yet, skipping pinned, closed
and archived topics, and topics started by staff or EXCLUDE_AUTHORS (by default
Eric and the assistant). Posts one message through grafana-matrix-forwarder (Alertmanager webhook format), and
nothing when every topic has an answer. Standard library only.
"""
import datetime
import hashlib
import json
import os
import sys
import urllib.request

FORUM = os.environ.get("FORUM_URL", "https://discourse.eom.dev").rstrip("/")
FORWARDER = os.environ["FORWARDER_URL"]
MAX_AGE_DAYS = int(os.environ.get("MAX_AGE_DAYS", "30"))
DRY_RUN = os.environ.get("DRY_RUN") == "1"
# Authors whose topics never need a reply from Eric (his own posts and the assistant's).
EXCLUDE = {u.strip() for u in os.environ.get("EXCLUDE_AUTHORS", "eric,claude").split(",") if u.strip()}


def get(path):
    req = urllib.request.Request(FORUM + path, headers={"Accept": "application/json", "User-Agent": "eom-forum-digest"})
    with urllib.request.urlopen(req, timeout=30) as r:
        return json.load(r)


def staff_usernames():
    about = get("/about.json").get("about", {})
    return {u["username"] for key in ("admins", "moderators") for u in about.get(key, [])}


def unanswered():
    staff = staff_usernames()
    data = get("/latest.json?order=created")
    users = {u["id"]: u["username"] for u in data.get("users", [])}
    cutoff = datetime.datetime.now(datetime.timezone.utc) - datetime.timedelta(days=MAX_AGE_DAYS)
    out = []
    for t in data.get("topic_list", {}).get("topics", []):
        if t.get("posts_count", 0) != 1 or t.get("pinned") or t.get("closed") or t.get("archived"):
            continue
        created = datetime.datetime.fromisoformat(t["created_at"].replace("Z", "+00:00"))
        if created < cutoff:
            continue
        op = next((users.get(p["user_id"]) for p in t.get("posters", []) if "Original Poster" in (p.get("description") or "")), None)
        if op in staff or op in EXCLUDE:
            continue
        age = (datetime.datetime.now(datetime.timezone.utc) - created).days
        out.append({"id": t["id"], "title": t["title"], "author": op or "?", "age_days": age,
                    "url": f"{FORUM}/t/{t['slug']}/{t['id']}"})
    return sorted(out, key=lambda x: -x["age_days"])


def post(topics):
    today = datetime.date.today().isoformat()
    lines = [f"- {t['title']} by @{t['author']}, {t['age_days']}d old: {t['url']}" for t in topics]
    summary = f"{len(topics)} forum topic{'s' if len(topics) != 1 else ''} waiting for a reply:\n" + "\n".join(lines)
    alert = {
        "status": "firing",
        "labels": {"alertname": "ForumUnanswered", "severity": "info", "instance": "discourse.eom.dev"},
        "annotations": {"summary": summary, "description": "Daily forum digest (eom-forum-digest CronJob)."},
        "startsAt": datetime.datetime.now(datetime.timezone.utc).isoformat(),
        "endsAt": "0001-01-01T00:00:00Z",
        "generatorURL": FORUM + "/latest",
        # One fingerprint per day: a new message each day rather than a reply thread.
        "fingerprint": hashlib.sha1(f"forum-digest-{today}".encode()).hexdigest()[:16],
    }
    payload = {
        "version": "4", "receiver": "matrix", "status": "firing", "groupKey": f"forum-digest-{today}",
        "externalURL": FORUM, "groupLabels": {"alertname": "ForumUnanswered"},
        "commonLabels": alert["labels"], "commonAnnotations": alert["annotations"], "alerts": [alert],
    }
    if DRY_RUN:
        print(json.dumps(payload, indent=2))
        return
    req = urllib.request.Request(FORWARDER, data=json.dumps(payload).encode(), method="POST",
                                 headers={"Content-Type": "application/json"})
    with urllib.request.urlopen(req, timeout=30) as r:
        print("forwarder:", r.status)


def main():
    topics = unanswered()
    print(f"{len(topics)} unanswered topic(s)")
    for t in topics:
        print(f"  {t['id']} {t['title']} ({t['age_days']}d, @{t['author']})")
    if topics:
        post(topics)
    return 0


if __name__ == "__main__":
    sys.exit(main())