/**
 * @factory/observability — service resource attributes (TASK-0135).
 *
 * Every span/metric/log emitted by the four apps carries the SAME resource
 * so the collector can demux by `service.name`. The names are fixed by the
 * phase-15 spec (NOT the bare "api"/"worker" the NFR doc sketched — the spec
 * wins; recorded conflict, AGENTS rule 29): `factory-web`, `factory-api`,
 * `factory-worker`, `factory-realtime`.
 *
 * NOTE: OTel JS 2.x line (T-190b) — SDK core 2.12.0 + exporters 0.223.0 +
 * semantic-conventions 1.43.0 + `@prisma/instrumentation` 6.19.3 (Prisma 6.x
 * pairs with the 2.x train; the 1.x pairing predates it). In 2.x the
 * `Resource` class is GONE — resources are built with the
 * `resourceFromAttributes(...)` factory, and `Resource` is the TYPE (the old
 * `IResource` was renamed to `Resource`).
 */
import { resourceFromAttributes, type Resource } from "@opentelemetry/resources";

/** The four app service names (phase-15 spec, verbatim). */
export const SERVICE_NAMES = {
  web: "factory-web",
  api: "factory-api",
  worker: "factory-worker",
  realtime: "factory-realtime"
} as const;

export type ServiceName = (typeof SERVICE_NAMES)[keyof typeof SERVICE_NAMES];

export function isServiceName(name: string): name is ServiceName {
  return Object.values(SERVICE_NAMES).includes(name as ServiceName);
}

export interface BuildResourceOptions {
  /** `deployment.environment` attribute value (NODE_ENV). */
  environment?: string;
  /** Service version — defaults to the package version (0.1.0). */
  version?: string;
  /** Host name — defaults to the HOSTNAME/HOST env or "local". */
  hostName?: string;
}

/**
 * Build the OTel `Resource` for one app. Stable attributes only (host name,
 * not IP — a pod IP churns on every reschedule and would fragment the
 * series).
 */
export function buildResource(serviceName: ServiceName, opts: BuildResourceOptions = {}): Resource {
  const { environment, version, hostName } = opts;
  const versionValue = version ?? "0.1.0";
  return resourceFromAttributes({
    "service.name": serviceName,
    "service.version": versionValue,
    "deployment.environment": environment ?? process.env.NODE_ENV ?? "development",
    "host.name": hostName ?? safeHostname()
  });
}

function safeHostname(): string {
  return process.env.HOSTNAME || process.env.HOST || "local";
}