const { EventEmitter } = require("node:events");

function uniqueStrings(values) {
  return Array.from(
    new Set(
      (Array.isArray(values) ? values : [])
        .map((value) => (typeof value === "string" ? value.trim() : ""))
        .filter(Boolean),
    ),
  );
}

function createAppEventBus() {
  const emitter = new EventEmitter();
  emitter.setMaxListeners(500);
  let sequence = 0;

  return {
    publish(event) {
      const payload = {
        id: `${Date.now()}-${++sequence}`,
        createdAt: new Date().toISOString(),
        ...event,
        audienceEmployeeIds: uniqueStrings(event?.audienceEmployeeIds),
      };
      emitter.emit("event", payload);
      return payload;
    },
    subscribe(handler) {
      emitter.on("event", handler);
      return () => emitter.off("event", handler);
    },
  };
}

function buildInvoiceUpdatedEvent({
  invoiceId,
  status,
  updatedAt = null,
  audienceEmployeeIds = [],
}) {
  return {
    type: "invoice.updated",
    invoiceId,
    status,
    updatedAt: updatedAt ?? new Date().toISOString(),
    audienceEmployeeIds: uniqueStrings(audienceEmployeeIds),
  };
}

function publishInvoiceUpdated(fastify, event) {
  if (!fastify?.appEvents || typeof fastify.appEvents.publish !== "function") {
    return null;
  }
  return fastify.appEvents.publish(buildInvoiceUpdatedEvent(event));
}

function canReceiveEvent(employee, event, options = {}) {
  if (!employee) {
    return false;
  }

  if (event?.type === "invoice.updated" && options.canManageInvoice) {
    return true;
  }

  const audience = uniqueStrings(event?.audienceEmployeeIds);
  if (!audience.length) {
    return false;
  }

  return audience.includes(employee.id);
}

function toClientEvent(event) {
  if (!event) {
    return null;
  }

  if (event.type === "invoice.updated") {
    return {
      id: event.id,
      type: event.type,
      invoiceId: event.invoiceId,
      status: event.status ?? null,
      updatedAt: event.updatedAt ?? event.createdAt ?? null,
      createdAt: event.createdAt ?? null,
    };
  }

  return {
    id: event.id,
    type: event.type,
    createdAt: event.createdAt ?? null,
  };
}

module.exports = {
  buildInvoiceUpdatedEvent,
  canReceiveEvent,
  createAppEventBus,
  publishInvoiceUpdated,
  toClientEvent,
};