"use client";

import { useEffect, useRef, useState, useCallback, useMemo } from "react";
import {
  WebSocketConnection,
  getWebSocketUrl,
} from "@/lib/websocket/connection";
import { CEO_AGENT_ID, STREAM_MAX_MESSAGES } from "@/lib/constants";

// Re-export ConnectionState type
export type { ConnectionState } from "@/lib/websocket/connection";
import type { ConnectionState } from "@/lib/websocket/connection";

// =============================================================================
// Types
// =============================================================================

export interface AgentStreamMessage {
  type: "connected" | "agent.stream";
  agent_id: string;
  chunk?: string;
  watcher_count?: number;
  timestamp?: string;
}

export interface ChannelMessage {
  type: "connected" | "message.new" | "session.closed";
  channel_id?: string;
  message_id?: string;
  agent_id?: string;
  content?: string;
  message_type?: string;
  subscriber_count?: number;
  timestamp?: string;
}

export interface NotificationMessage {
  type: "connected" | "notification";
  agent_id?: string;
  notification_id?: string;
  notification_type?: string;
  subject?: string;
  priority?: string;
  timestamp?: string;
}

// =============================================================================
// Generic WebSocket Hook
// =============================================================================

export function useWebSocket<T>(
  endpoint: string,
  queryParams?: Record<string, string>,
  enabled: boolean = true,
) {
  const [state, setState] = useState<ConnectionState>("disconnected");
  const [lastMessage, setLastMessage] = useState<T | null>(null);
  const [messages, setMessages] = useState<T[]>([]);
  const connectionRef = useRef<WebSocketConnection | null>(null);

  // Memoize queryParams string to prevent unnecessary reconnects
  const queryString = queryParams
    ? new URLSearchParams(queryParams).toString()
    : "";

  useEffect(() => {
    // Don't connect if disabled or no endpoint
    if (!enabled || !endpoint) {
      return;
    }

    // Build URL
    const baseUrl = getWebSocketUrl();
    const url = baseUrl + endpoint + (queryString ? "?" + queryString : "");

    // Create connection
    const connection = new WebSocketConnection({
      url,
      onMessage: (data) => {
        const message = data as T;
        setLastMessage(message);
        setMessages((prev) => [
          ...prev.slice(-(STREAM_MAX_MESSAGES - 1)),
          message,
        ]);
      },
      onStateChange: setState,
    });

    connectionRef.current = connection;
    connection.connect();

    // Cleanup on unmount or when dependencies change. Disconnect AND clear the
    // snapshot — otherwise a dep change (navigating to another stream) leaves
    // the prior subscription's messages/lastMessage/state visible until a fresh
    // frame arrives, surfacing another stream's stale buffer as live (#79).
    return () => {
      connection.disconnect();
      connectionRef.current = null;
      setMessages([]);
      setLastMessage(null);
      setState("disconnected");
    };
  }, [enabled, endpoint, queryString]); // Stable dependencies

  const disconnect = useCallback(() => {
    connectionRef.current?.disconnect();
    connectionRef.current = null;
    setState("disconnected");
  }, []);

  const clearMessages = useCallback(() => {
    setMessages([]);
    setLastMessage(null);
  }, []);

  return {
    state,
    lastMessage,
    messages,
    disconnect,
    clearMessages,
    isConnected: state === "connected",
    isConnecting: state === "connecting" || state === "reconnecting",
  };
}

// =============================================================================
// Specialized Hooks
// =============================================================================

/**
 * Subscribe to an agent's output stream
 */
export function useAgentStream(agentId: string | null) {
  const {
    state,
    lastMessage,
    messages,
    clearMessages,
    isConnected,
    isConnecting,
  } = useWebSocket<AgentStreamMessage>(
    agentId ? "/agents/" + agentId : "",
    { viewer_id: CEO_AGENT_ID },
    !!agentId,
  );

  // Extract stream chunks
  const streamChunks = messages
    .filter((m) => m.type === "agent.stream" && m.chunk)
    .map((m) => m.chunk as string);

  // Combine chunks into full output
  const streamOutput = streamChunks.join("");

  return {
    state,
    lastMessage,
    messages,
    streamChunks,
    streamOutput,
    clearMessages,
    isConnected,
    isConnecting,
  };
}

/**
 * Subscribe to a channel's message stream
 */
export function useChannelStream(channelId: string | null) {
  const {
    state,
    lastMessage,
    messages,
    clearMessages,
    isConnected,
    isConnecting,
  } = useWebSocket<ChannelMessage>(
    channelId ? "/channels/" + channelId : "",
    { agent_id: CEO_AGENT_ID },
    !!channelId,
  );

  // Filter to only actual messages
  const channelMessages = messages.filter((m) => m.type === "message.new");

  return {
    state,
    lastMessage,
    channelMessages,
    allMessages: messages,
    clearMessages,
    isConnected,
    isConnecting,
  };
}

/**
 * Subscribe to notifications for the CEO
 */
export function useNotificationStream() {
  const {
    state,
    lastMessage,
    messages,
    clearMessages,
    isConnected,
    isConnecting,
  } = useWebSocket<NotificationMessage>(
    "/notifications/" + CEO_AGENT_ID,
    undefined,
    true,
  );

  // Filter to notification events, de-duplicated by notification_id so a
  // stream replay (e.g. after a websocket reconnect) does not surface — or
  // count — the same notification twice. Walk newest→oldest keeping the most
  // recent copy of each id, then restore arrival order. Events without an id
  // (older payloads) are always kept.
  const notifications = useMemo(() => {
    const seen = new Set<string>();
    const deduped: NotificationMessage[] = [];
    for (let i = messages.length - 1; i >= 0; i--) {
      const m = messages[i];
      if (m.type !== "notification") continue;
      const id = m.notification_id;
      if (id) {
        if (seen.has(id)) continue;
        seen.add(id);
      }
      deduped.push(m);
    }
    deduped.reverse();
    return deduped;
  }, [messages]);

  return {
    state,
    lastMessage,
    notifications,
    allMessages: messages,
    clearMessages,
    isConnected,
    isConnecting,
  };
}

// =============================================================================
// Connection Status Hook (for UI indicators)
// =============================================================================

export function useConnectionStatus() {
  const [connections, setConnections] = useState<
    Record<string, ConnectionState>
  >({});

  const updateConnection = useCallback((id: string, state: ConnectionState) => {
    setConnections((prev) => ({ ...prev, [id]: state }));
  }, []);

  const removeConnection = useCallback((id: string) => {
    setConnections((prev) => {
      const next = { ...prev };
      delete next[id];
      return next;
    });
  }, []);

  const hasActiveConnections = Object.values(connections).some(
    (s) => s === "connected" || s === "connecting" || s === "reconnecting",
  );

  const allConnected = Object.values(connections).every(
    (s) => s === "connected",
  );

  return {
    connections,
    updateConnection,
    removeConnection,
    hasActiveConnections,
    allConnected,
  };
}