Sources

interface Item {
  id: string; // unique within its source and connection
  text: string; // what Jev judges
  author?: { id: string; name: string; roles?: string[] };
  at: Date; // when it was created at its origin
  // Lean facts shown to Jev, such as { firstMessage: true }
  facts?: Record<string, JsonValue>;
  raw?: unknown; // the original payload; never sent to Jev
}

import { from, monitor, noul, webhook } from "jev-events";

// Any async iterable: log lines, a queue, a database cursor.
const logs = monitor({
  source: from(logLines, { noun: "line" }),
  questions: { outage: noul("Does this log line describe a failure a human should look at?") },
}).on("outage", { min: 0.8 }, (e) => page(e.item.text));

// Or anything that can send a webhook: POST { "text": "…" } to http://127.0.0.1:8787.
const tickets = monitor({
  source: webhook({ port: 8787, secret: process.env.WEBHOOK_SECRET }),
  questions: { angry: noul("Is the customer angry?") },
}).on("angry", { min: 0.7 }, (e) => escalate(e.item.text));

await Promise.all([logs.start(), tickets.start()]);

curl -X POST http://127.0.0.1:8787/ \
  -H "Authorization: Bearer $WEBHOOK_SECRET" \
  -d '{"text": "Your product broke my build again and nobody answers"}'

import { fileStore, monitor, noul, type Item, type Source } from "jev-events";

interface Update {
  id: string;
  text: string;
}

/** A status page that lists its updates as JSON, checked for new ones every 5 minutes. */
function statusPage(url: string): Source<Item, "status-page"> {
  return {
    id: `status-page:${url}`,
    platform: "status-page",
    noun: "update",
    defaults: { every: "5m" },
    async check(ctx) {
      const response = await fetch(url, { signal: ctx.signal });
      // A thrown error becomes an "error" event, and the next check runs as usual.
      if (!response.ok) throw new Error(`${url} answered ${response.status}`);
      const updates = (await response.json()) as Update[];

      // The cursor holds what the last check saw. The first check only notes what's there.
      const seen = await ctx.cursor.get<string[]>();
      for (const update of updates) {
        if (seen && !seen.includes(update.id)) await ctx.emit({ id: update.id, text: update.text, at: new Date() });
      }
      await ctx.cursor.set(updates.map((update) => update.id));
    },
  };
}

const vendors = monitor({
  source: statusPage("https://status.example.com/updates.json"),
  questions: { degraded: noul("Does this update say the service is down or degraded now?") },
}).on("degraded", { min: 0.8 }, (e) => console.warn(`Vendor incident: ${e.item.text}`));

// fileStore() keeps the cursor in .jev-events/, so a restart doesn't judge anything twice.
await vendors.start({ store: fileStore() });