const { canReceiveEvent, toClientEvent } = require("../services/events");

const HEARTBEAT_INTERVAL_MS = 25_000;

function writeSseEvent(raw, event) {
  const clientEvent = toClientEvent(event);
  if (!clientEvent) {
    return;
  }

  raw.write(`id: ${clientEvent.id}\n`);
  raw.write(`event: ${clientEvent.type}\n`);
  raw.write(`data: ${JSON.stringify(clientEvent)}\n\n`);
}

async function eventsRoutes(fastify) {
  fastify.get(
    "/events",
    {
      preHandler: fastify.authenticate,
    },
    async (request, reply) => {
      const canManageInvoice = fastify.hasPermission(request.employee, "invoice.manage");
      reply.hijack();
      reply.raw.writeHead(200, {
        "content-type": "text/event-stream; charset=utf-8",
        "cache-control": "no-cache, no-transform",
        "connection": "keep-alive",
        "x-accel-buffering": "no",
      });
      reply.raw.write(": connected\n\n");

      const unsubscribe = fastify.appEvents.subscribe((event) => {
        if (!canReceiveEvent(request.employee, event, { canManageInvoice })) {
          return;
        }
        writeSseEvent(reply.raw, event);
      });

      const heartbeat = setInterval(() => {
        reply.raw.write(": heartbeat\n\n");
      }, HEARTBEAT_INTERVAL_MS);

      request.raw.on("close", () => {
        clearInterval(heartbeat);
        unsubscribe();
      });
    },
  );
}

module.exports = eventsRoutes;