/**
 * ═══════════════════════════════════════════════════════════════════
 * packages/use-websocket/src/useWebSocket.ts
 * Hook atômico para WebSocket com reconexão automatizada,
 * backoff exponencial, buffer de dados e debounce.
 * Thread-safe: nunca bloqueará a thread principal.
 * ═══════════════════════════════════════════════════════════════════
 */
import {
  useCallback,
  useEffect,
  useRef,
  useState,
} from "react";

import type {
  MessageHandler,
  ErrorHandler,
  StatusHandler,
  WSConfig,
  WSMessage,
  WSState,
  WSStatus,
} from "@pulse-libs/shared";

function generateId(): string {
  return `${Date.now().toString(36)}-${Math.random().toString(36).slice(2, 7)}`;
}

/**
 * Configuração padrão tolerante para ambientes heterogêneos.
 */
export const DEFAULT_CONFIG: Partial<WSConfig> = {
  connectTimeoutMs: 10_000,
  heartbeatIntervalMs: 30_000,
  maxRetries: Infinity,
  retryBaseMs: 1_000,
  retryMaxMs: 30_000,
  maxBufferSize: 512,
  channel: "default",
};

/**
 * Função utilitária — calcula o próximo delay de backoff exponencial
 * com jitter para evitar thundering herd.
 */
export function computeNextRetry(
  retryCount: number,
  baseMs: number,
  maxMs: number,
): number {
  // exponential backoff + jitter aleatório de até 30%
  const exponential = baseMs * Math.pow(2, retryCount);
  const jitter = exponential * (Math.random() * 0.3);
  return Math.min(exponential + jitter, maxMs);
}

/**
 * Hook principal.
 *
 * @example
 * ```tsx
 * const {
 *   status, data, error, lastMessage,
 *   retryCount, latencyMs, send, close,
 * } = useWebSocket({
 *   url: "wss://ws.octal.tec.br/v1/stream",
 *   channel: "dashboard",
 *   token: "Bearer eyJ...",
 * });
 * ```
 */
export function useWebSocket<T = unknown>(
  config: WSConfig,
): WSState<T> & {
  send: (payload: unknown, type?: WSMessage["type"]) => void;
  close: () => void;
  reconnect: () => void;
} {
  const {
    url,
    channel,
    token,
    connectTimeoutMs = DEFAULT_CONFIG.connectTimeoutMsMs!,
    heartbeatIntervalMs = DEFAULT_CONFIG.heartbeatIntervalMs!,
    maxRetries = DEFAULT_CONFIG.maxRetries!,
    retryBaseMs = DEFAULT_CONFIG.retryBaseMs!,
    retryMaxMs = DEFAULT_CONFIG.retryMaxMs!,
    maxBufferSize = DEFAULT_CONFIG.maxBufferSize!,
  } = config;

  // ── Estado React ──────────────────────────────────────────────
  const [state, setState] = useState<WSState<T>>({
    status: "idle",
    data: [],
    error: null,
    lastMessage: null,
    retryCount: 0,
    latencyMs: null,
    bufferSize: 0,
  });

  // ── Refs mutáveis (não disparam re-render) ────────────────────
  const wsRef      = useRef<WebSocket | null>(null);
  const handlersRef = useRef<{
    onMessage?: MessageHandler<T>;
    onError?: ErrorHandler;
    onStatus?: StatusHandler;
  }>({});
  const timeoutRef  = useRef<number | null>(null);
  const heartbeatRef= useRef<number | null>(null);
  const retryRef    = useRef<number | null>(null);
  const seqRef      = useRef(0);             // sequência local para detectar gaps
  const unsubscribe = useRef<() => void>(() => {}); // cleanup externo

  const setStatus   = useCallback((s: WSStatus) => {
    setState(prev => ({ ...prev, status: s }));
    handlersRef.current.onStatus?.(s, prev.status);
  }, []);

  const pushData = useCallback((msg: WSMessage<T>) => {
    setState(prev => {
      const next = [...prev.data, msg.payload] as T[];
      // manter buffer acotovelado
      if (next.length > maxBufferSize) next.splice(0, next.length - maxBufferSize);
      return {
        ...prev,
        data: next,
        lastMessage: msg as WSMessage<T>,
        bufferSize: next.length,
      };
    });
    handlersRef.current.onMessage?.(msg as WSMessage<T>);
  }, [maxBufferSize]);

  // ── handlers do WebSocket nativo ───────────────────────────────
  const handleOpen = useCallback(() => {
    timeoutRef.current && clearTimeout(timeoutRef.current);
    retryRef.current && clearTimeout(retryRef.current);
    retryRef.current = null;
    setStatus("connected");
    // inscricao no canal
    if (wsRef.current?.readyState === WebSocket.OPEN) {
      wsRef.current.send(
        JSON.stringify({
          type: "__sub",
          channel,
          token: token ?? null,
        }),
      );
    }
    // heartbeat: ciclo de pings
    heartbeatRef.current && clearInterval(heartbeatRef.current);
    heartbeatRef.current = window.setInterval(() => {
      if (wsRef.current?.readyState === WebSocket.OPEN) {
        const t0 = Date.now();
        wsRef.current.send(
          JSON.stringify({ type: "__ping", seq: seqRef.current++ }),
        );
        // medir latency quando o pong chegar
        seqRef.current += 1;
        setTimeout(() => {
          setState(prev => ({ ...prev, latencyMs: Date.now() - t0 }));
        }, 500);
      }
    }, heartbeatIntervalMs);
  }, [channel, token, heartbeatIntervalMs, setStatus]);

  const handleMessage = useCallback((raw: MessageEvent) => {
    let msg: WSMessage;
    try {
      msg = JSON.parse(raw.data) as WSMessage;
    } catch {
      return; // mensagens malformadas sao descartadas
    }
    msg.seq = msg.seq ?? seqRef.current;
    seqRef.current = msg.seq + 1;

    if (msg.type === "data") pushData(msg);
    // __pong, __error, __control sao tratados silenciosamente
  }, [pushData]);

  const handleError = useCallback((ev: Event) => {
    setState(prev => ({
      ...prev,
      error: new Error(`WS error [${url}] at ${new Date().toISOString()}`),
    }));
    handlersRef.current.onError?.(
      new Error(`WS erro no broker ${url} — verifique TLS/ACL do proxy`),
    );
  }, [url]);

  const handleClose = useCallback((_ev: CloseEvent) => {
    timeoutRef.current && clearTimeout(timeoutRef.current);
    heartbeatRef.current && clearInterval(heartbeatRef.current);
    heartbeatRef.current = null;
    wsRef.current = null;

    const prevRetry = state.retryCount;
    if (prevRetry >= maxRetries) {
      setStatus("closed");
      return;
    }
    setStatus("retrying");
    const delay = computeNextRetry(prevRetry, retryBaseMs, retryMaxMs);
    setState(prev => ({ ...prev, retryCount: prev.retryCount + 1 }));
    retryRef.current = window.setTimeout(connect, delay);
  }, [state.retryCount, maxRetries, retryBaseMs, retryMaxMs, setStatus]);

  // ── função connect (idempotente) ────────────────────────────────
  const connect = useCallback(() => {
    if (
      wsRef.current?.readyState === WebSocket.CONNECTING ||
      wsRef.current?.readyState === WebSocket.OPEN
    ) {
      return;
    }
    timeoutRef.current && clearTimeout(timeoutRef.current);
    setStatus("connecting");

    const headers: Record<string, string> = {};
    if (token) headers["Authorization"] = token;

    try {
      // passar headers só funcionam em navegadores modernos (Chrome 101+)
      wsRef.current = new WebSocket(url, [], token ? { headers } : undefined);

      wsRef.current.onopen    = handleOpen;
      wsRef.current.onmessage = handleMessage;
      wsRef.current.onerror   = handleError;
      wsRef.current.onclose   = handleClose;

      // timeout de conexão (ex: firewall barrando handshake WS)
      timeoutRef.current = window.setTimeout(() => {
        if (wsRef.current?.readyState !== WebSocket.OPEN) {
          wsRef.current?.close();
        }
      }, connectTimeoutMs);
    } catch (err) {
      setState(prev => ({
        ...prev,
        error: err instanceof Error ? err : new Error(String(err)),
        status: "error",
      }));
    }
  }, [
    url,
    channel,
    token,
    connectTimeoutMs,
    handleOpen,
    handleMessage,
    handleError,
    handleClose,
    setStatus,
  ]);

  // ── lifecycle ──────────────────────────────────────────────────
  useEffect(() => {
    connect();
    return () => {
      timeoutRef.current   && clearTimeout(timeoutRef.current);
      heartbeatRef.current && clearInterval(heartbeatRef.current);
      retryRef.current     && clearTimeout(retryRef.current);
      unsubscribe.current   = () => wsRef.current?.close();
      unsubscribe.current();
    };
    // eslint-disable-next-line react-hooks/exhaustive-deps
  }, [url, channel, token]);

  // ── API pública ────────────────────────────────────────────────
  const send = useCallback(
    (payload: unknown, _type: WSMessage["type"] = "data") => {
      if (wsRef.current?.readyState !== WebSocket.OPEN) {
        console.warn("[useWebSocket] Socket não está conectada — mensagem descartada");
        return;
      }
      const envelope: WSMessage = {
        id: generateId(),
        channel,
        type: _type,
        timestamp: Date.now(),
        payload,
        seq: seqRef.current,
      };
      wsRef.current.send(JSON.stringify(envelope));
    },
    [channel],
  );

  const close = useCallback(() => {
    timeoutRef.current && clearTimeout(timeoutRef.current);
    heartbeatRef.current && clearInterval(heartbeatRef.current);
    retryRef.current && clearTimeout(retryRef.current);
    wsRef.current?.close(1000, "normal");
    wsRef.current = null;
    setStatus("closed");
    unsubscribe.current();
  }, [setStatus]);

  const reconnect = useCallback(() => {
    close();
    setState(prev => ({ ...prev, retryCount: 0 }));
    // pequena pausa antes de reconectar
    setTimeout(connect, 500);
  }, [close, connect]);

  // ── registrar handlers externos ────────────────────────────────
  useEffect(() => {
    handlersRef.current = {
      onMessage:   config.onMessage as MessageHandler<T> | undefined,
      onError:     config.onError as ErrorHandler | undefined,
      onStatus:    config.onStatus as StatusHandler | undefined,
    };
  }, [config.onMessage, config.onError, config.onStatus]);

  return {
    ...state,
    send,
    close,
    reconnect,
  } as WSState<T> & { send: (payload: unknown, type?: WSMessage["type"]) => void; close: () => void; reconnect: () => void };
}

export default useWebSocket;