import type { Server as HttpServer } from "node:http";
import { WebSocket, WebSocketServer } from "ws";
import { collectorScheduler } from "@/lib/collectors/scheduler";
import { configStore, type ConfigError } from "@/lib/config/loader";
import { effectiveConfigStore } from "@/lib/config/effective";
import { toPublicConfig } from "@/lib/config/public";
import type { Config } from "@/lib/config/schema";
import type { WidgetResult } from "@/lib/types/widget-result";

type Envelope =
  | { topic: string; type: "result"; ts: number; data: WidgetResult }
  | { topic: "config"; type: "config:update"; ts: number; data: Config }
  | { topic: "config"; type: "config:error"; ts: number; data: { message: string } };

function send(socket: WebSocket, envelope: Envelope): void {
  if (socket.readyState === WebSocket.OPEN) {
    socket.send(JSON.stringify(envelope));
  }
}

export function attachWebSocketServer(httpServer: HttpServer): WebSocketServer {
  const wss = new WebSocketServer({ noServer: true });
  const subscriptions = new Map<string, Set<WebSocket>>();
  const allSockets = new Set<WebSocket>();

  function subscribe(socket: WebSocket, widgetId: string): void {
    let set = subscriptions.get(widgetId);
    if (!set) {
      set = new Set();
      subscriptions.set(widgetId, set);
    }
    set.add(socket);
    const cached = collectorScheduler.getLastResult(widgetId);
    if (cached) {
      send(socket, { topic: `widget:${widgetId}`, type: "result", ts: Date.now(), data: cached });
    }
  }

  function unsubscribe(socket: WebSocket, widgetId: string): void {
    subscriptions.get(widgetId)?.delete(socket);
  }

  function cleanupSocket(socket: WebSocket): void {
    allSockets.delete(socket);
    for (const set of subscriptions.values()) set.delete(socket);
  }

  wss.on("connection", (socket) => {
    allSockets.add(socket);

    try {
      const config = effectiveConfigStore.get();
      send(socket, { topic: "config", type: "config:update", ts: Date.now(), data: toPublicConfig(config) });
    } catch {
      // no valid config loaded yet; client keeps its SSR-seeded config until one arrives
    }

    socket.on("message", (raw) => {
      let message: { action?: string; widgetId?: string };
      try {
        message = JSON.parse(raw.toString());
      } catch {
        return;
      }
      if (message.action === "subscribe" && typeof message.widgetId === "string") {
        subscribe(socket, message.widgetId);
      } else if (message.action === "unsubscribe" && typeof message.widgetId === "string") {
        unsubscribe(socket, message.widgetId);
      }
    });

    socket.on("close", () => cleanupSocket(socket));
    socket.on("error", () => cleanupSocket(socket));
  });

  collectorScheduler.onResult((widgetId, result) => {
    const set = subscriptions.get(widgetId);
    if (!set || set.size === 0) return;
    const envelope: Envelope = { topic: `widget:${widgetId}`, type: "result", ts: Date.now(), data: result };
    for (const socket of set) send(socket, envelope);
  });

  effectiveConfigStore.onUpdate((config) => {
    const envelope: Envelope = {
      topic: "config",
      type: "config:update",
      ts: Date.now(),
      data: toPublicConfig(config),
    };
    for (const socket of allSockets) send(socket, envelope);
  });

  configStore.onError((error: ConfigError) => {
    const envelope: Envelope = {
      topic: "config",
      type: "config:error",
      ts: Date.now(),
      data: { message: error.message },
    };
    for (const socket of allSockets) send(socket, envelope);
  });

  httpServer.on("close", () => wss.close());

  return wss;
}