// mosquitto's provisioner — the adapter that makes mosquitto a provider of the mesh `mqtt-topic`
// interface. The reconcile loop, the contributions file, and reading the mesh's minted password are
// the sdk harness's; this writes only the per-service half: how mosquitto creates and removes a
// per-consumer MQTT client (novox/hq ADR 0039/0040/0048).
//
// The `mqtt-topic` interface: a consumer connects as `as` with the password the mesh minted, and
// publishes and subscribes under `<as>/#`, isolated from every other consumer by a Dynamic Security
// role scoped to exactly that subtree — unless it contributed `topics`, the MQTT topic filters its
// work needs (a home-automation hub needs the devices' topics); then the role grants exactly those
// (topics.ts). A list that is not valid topic filters is refused, and the consumer is not created
// or changed until it is fixed.
//
// What a consumer is told (its binding): `at` — the broker's machine — and `port`, the machine port
// of the MQTT listener (the manifest's `serves`); `as` is its login, and its copy of the password is
// the pair credential the mesh delivers to it.
//
// **The login and password are the mesh's, not the provisioner's (ADR 0048).** The mesh derives the
// login and hands it to both ends so they agree, and mints the password and delivers a copy to each.
// mosquitto creates exactly that client with exactly that password — a name or password the
// provisioner invented is one the consumer could never present.

import { runProvisioner, type Provision } from "@novox/mesh-sdk/provisioner";
import { emit } from "@novox/mesh-sdk/events";
import { MosquittoClient } from "../client.js";
import { topicFilters } from "../topics.js";

const mosquitto = MosquittoClient.fromEnv();

/** Emit a lifecycle event without letting a broker hiccup fail the provisioning itself. */
async function announce(type: string, body: Record<string, string>): Promise<void> {
  try {
    await emit(type, body);
  } catch (err) {
    console.error(`[provisioner:mqtt-topic] emit ${type} failed: ${err}`);
  }
}

runProvisioner("mqtt-topic", {
  async create(p: Provision): Promise<void> {
    // By default the consumer's own subtree, so one cannot read another's topics; what it
    // contributed as `topics` otherwise.
    const granted = topicFilters(p.values, p.as);
    if ("problem" in granted) {
      // Thrown, so the harness logs it and retries: the consumer stays as it was (or absent) until
      // its contribution is valid, rather than being given a grant it did not ask for.
      throw new Error(`${p.as}: ${granted.problem}`);
    }
    await mosquitto.createScopedClient(p.as, p.password, granted.filters);
    await announce("topic.provisioned", {
      consumer: p.consumer ?? "",
      username: p.as,
      topicPrefix: granted.own ? p.as : "",
      topics: granted.filters.join(" "),
    });
  },

  async remove(p: { as: string }): Promise<void> {
    await mosquitto.deleteScopedClient(p.as);
    await announce("topic.deprovisioned", { username: p.as });
  },
  // Asked every minute by the harness: whether the backend still holds this consumer exactly as
  // the mesh gave it, so a login lost behind the provisioner's back is made again (novox/hq issue 120).
  async holds(p: Provision): Promise<boolean> {
    const granted = topicFilters(p.values, p.as);
    // An invalid list was never applied; create refuses it again, loudly, on every pass.
    if ("problem" in granted) return false;
    return mosquitto.holdsClient(p.as, p.password, granted.filters);
  },
});