// R-P8b (RA-C2) — real live board pub/sub. Uses the repo's existing in-process
// EventEmitter (`~/utils/stream/emitter.server`, the same one that already backs
// the workflow-execution SSE stream) so board mutations (stage move, bulk move,
// create, update, undo, archive) push real change-events to the connected
// pipeline-board SSE clients instead of only a snapshot + heartbeat. No new infra
// dependency is introduced.
//
// Scope caveat: this emitter is per web process. With a single web instance (the
// current deployment) every board client shares the process, so events reach all
// of them. Horizontal scaling of `hivegrid-web` would need a cross-process
// transport (e.g. Redis pub/sub) behind the same publish/subscribe API — tracked
// as a follow-up, out of this ticket's scope. This is server-only (.server) and
// is never imported by projectService.server (kept out of the pure-service test
// import graph) — publishing happens in the route-level orchestration helpers.

import { publishDashboardChange } from "~/services/dashboard/dashboardEvents.server";
import { emitter } from "~/utils/stream/emitter.server";
import type { ProjectBoardChange, ProjectBoardChangeType } from "./projectBoardEvents.shared";

/**
 * In-process channel name for one pipeline board. Includes the tenantId as
 * defence-in-depth even though pipeline ids are already globally unique — a
 * subscriber only ever binds to its own tenant+pipeline channel.
 */
export function projectBoardChannel(tenantId: string, pipelineId: string): string {
  return `projectBoard:${tenantId}:${pipelineId}`;
}

let listenerCapRaised = false;

/** Subscribe an SSE stream to a pipeline board channel. Returns an unsubscribe fn. */
export function subscribeToProjectBoard(tenantId: string, pipelineId: string, onChange: (payload: string) => void): () => void {
  // Many concurrent board viewers can subscribe to the same channel; lift the
  // default 10-listener cap so Node does not log a MaxListenersExceededWarning.
  if (!listenerCapRaised) {
    emitter.setMaxListeners(0);
    listenerCapRaised = true;
  }
  const channel = projectBoardChannel(tenantId, pipelineId);
  emitter.on(channel, onChange);
  return () => {
    emitter.off(channel, onChange);
  };
}

/** Publish a board change so connected clients of this pipeline board revalidate. */
export function publishProjectBoardChange(input: {
  tenantId: string;
  pipelineId: string;
  projectId?: string;
  type: ProjectBoardChangeType;
}): void {
  const payload: ProjectBoardChange = {
    type: input.type,
    pipelineId: input.pipelineId,
    projectId: input.projectId,
    at: new Date().toISOString(),
  };
  emitter.emit(projectBoardChannel(input.tenantId, input.pipelineId), JSON.stringify(payload));
  // Project mutations also feed the tenant-wide dashboard stream (R-P11b):
  // sales/project KPI widgets recompute their snapshot on these changes.
  publishDashboardChange({ tenantId: input.tenantId, source: "projects" });
}