// posts_on_publish — docs TRIGGER on the `posts` collection (create|update).
// When a post transitions INTO "published", enqueue batched reader-notification
// jobs onto the `post-notifications` queue (decoupling the burst from delivery,
// and staying well under the per-execution emission ceiling via chunking).
let ev = ctx.event.docs;
if ev == () { return; }
let data = ev.data;
if data == () { return; }

let was = if ev.prev_data == () { () } else { ev.prev_data.status };
let became_published = data.status == "published" && was != "published";
if !became_published { return; }

// collect reader emails in chunks of 50
let res = users::list(#{ "$limit": 500 });
let batch = [];
let total = 0;
for u in res.users {
    if users::has_role(u.id, "reader") {
        batch.push(u.email);
        total += 1;
        if batch.len() >= 50 {
            queue::enqueue("post-notifications",
                #{ post_id: ev.id, title: data.title, slug: data.slug, emails: batch });
            batch = [];
        }
    }
}
if batch.len() > 0 {
    queue::enqueue("post-notifications",
        #{ post_id: ev.id, title: data.title, slug: data.slug, emails: batch });
}
log::info("queued post notifications", #{ post: ev.id, title: data.title, readers: total });