// route-adapter's one pass — the module's own code (novox/hq ADR 0039), run as a step (ADR 0052)
// and run *again* whenever what it reads changes.
//
// **A step, not a loop.** Everything this module does is a function of two files the mesh writes:
// the contributions at `receives.route`, and its settings. The manifest's container is `run-once`
// and names both under `restart-on`, so the host runs it once and runs it again the moment either
// changes — which is the mechanism already in the catalogue for "a fact arrived, do it again"
// (novox/hq ADR 0099). A watcher of its own would be a second way to notice the same event, and it
// would keep running after the module was unassigned.
//
// It connects to no broker: this is an offline file operation on the machine it runs on, and
// `mesh-tools run` gives it exactly that.

import { readFile } from "node:fs/promises";

import { reconcile, routesFrom, settingsFrom } from "./adapter.js";

const receives = process.env.MESH_RECEIVES ?? "/var/lib/route-adapter/routes/mesh.json";
const configFile = process.env.MESH_ROUTE_ADAPTER_CONFIG ?? "/run/config/config.json";

// The settings the node laid over the module's defaults. Absent is not an error — the mesh always
// writes the file, and a node that overrode nothing leaves it holding the defaults.
const settings = settingsFrom(await readJSON(configFile));

// The contributions. Absent is also not an error here: the host writes this file before it starts
// the container, and the empty case — nothing contributed — means every route this module wrote is
// to be taken away, which is a real instruction and not a reason to stop.
const { routes, skipped } = routesFrom(await readJSON(receives), settings.machine);
for (const why of skipped) {
  console.warn(`[route-adapter] ${why}`);
}

const pass = await reconcile(routes, settings);
for (const why of pass.skipped) {
  console.warn(`[route-adapter] ${why}`);
}
console.log(
  `[route-adapter] ${routes.length} route(s) contributed; ` +
    `wrote ${pass.written.length} and removed ${pass.removed.length} in ${settings.dynamic}` +
    (pass.written.length > 0 ? `: ${pass.written.join(", ")}` : "") +
    (pass.removed.length > 0 ? `; gone: ${pass.removed.join(", ")}` : ""),
);

async function readJSON(path: string): Promise<unknown> {
  const raw = await readFile(path, "utf8").catch(() => undefined);
  if (raw === undefined) {
    return undefined;
  }
  return JSON.parse(raw) as unknown;
}