"use client";

import { Bot, MessageCircle, RotateCw, Send, X } from "lucide-react";
import { useCallback, useEffect, useRef, useState } from "react";
import { apiFetch } from "@/lib/api";
import { getToken } from "@/lib/auth";
import { chatAgentApi, type ChatAgentMode } from "@/lib/chat-agent-api";
import { USER_TYPE } from "@/lib/roles";

interface ChatMessage {
  id: number;
  role: "user" | "agent";
  content: string;
}

const GREETING = "您好，我是华夏基金智能助手。您可以咨询基金产品、风险等级和净值信息。";

/**
 * 选择用哪个 Agent：
 * - 已登录客户 → /agent/client/*（能读本人持仓与交易）
 * - 游客 / 员工 → /agent/customer/*（匿名客服，不需要 token）
 * 探测失败一律退回匿名客服，不阻断用户。
 */
async function resolveMode(): Promise<ChatAgentMode> {
  if (!getToken()) return "customer";
  try {
    const result = await apiFetch<{ user?: { user_type?: string | null } }>("/auth/me");
    return result?.user?.user_type === USER_TYPE.CUSTOMER ? "client" : "customer";
  } catch {
    return "customer";
  }
}

export function AgentChat() {
  const [open, setOpen] = useState(false);
  const [input, setInput] = useState("");
  const [sending, setSending] = useState(false);
  const [connecting, setConnecting] = useState(false);
  const [sessionId, setSessionId] = useState<string | null>(null);
  const [mode, setMode] = useState<ChatAgentMode>("customer");
  const [error, setError] = useState<string | null>(null);
  const [messages, setMessages] = useState<ChatMessage[]>([
    { id: 1, role: "agent", content: GREETING },
  ]);

  const abortRef = useRef<AbortController | null>(null);
  const listRef = useRef<HTMLDivElement | null>(null);

  useEffect(() => () => abortRef.current?.abort(), []);
  useEffect(() => {
    listRef.current?.scrollTo({ top: listRef.current.scrollHeight, behavior: "smooth" });
  }, [messages, connecting]);

  /** 建立会话：探测 Agent 类型 → session/create 换取后端签发的 session_id。 */
  const connect = useCallback(async () => {
    setConnecting(true);
    setError(null);
    try {
      const resolved = await resolveMode();
      const session = await chatAgentApi.createSession(resolved);
      setMode(resolved);
      setSessionId(session.session_id);
    } catch (err) {
      setError(err instanceof Error ? err.message : "会话建立失败，请重试");
    } finally {
      setConnecting(false);
    }
  }, []);

  /** 打开面板即建立会话（不是等用户第一次提问才建）。 */
  const openChat = useCallback(() => {
    setOpen(true);
    if (!sessionId && !connecting) void connect();
  }, [connect, connecting, sessionId]);

  /** 关闭面板即结束会话：通知后端清理上下文与限流键，本地一并重置。 */
  const closeChat = useCallback(async () => {
    abortRef.current?.abort();
    setOpen(false);
    setInput("");
    setError(null);
    setMessages([{ id: Date.now(), role: "agent", content: GREETING }]);
    const current = sessionId;
    setSessionId(null);
    if (!current) return;
    try {
      await chatAgentApi.endSession(mode, current);
    } catch {
      /* 会话清理失败不阻断用户 */
    }
  }, [mode, sessionId]);

  const sendMessage = useCallback(async () => {
    const content = input.trim();
    if (!content || sending || connecting) return;
    if (!sessionId) {
      setError("会话尚未建立，请点击重试。");
      return;
    }
    setInput("");
    setError(null);
    setMessages((prev) => [...prev, { id: Date.now(), role: "user", content }]);
    setSending(true);

    const controller = new AbortController();
    abortRef.current = controller;
    try {
      const result = await chatAgentApi.chat(
        mode,
        { session_id: sessionId, query: content },
        controller.signal
      );
      setMessages((prev) => [
        ...prev,
        {
          id: Date.now() + 1,
          role: "agent",
          content: result.error || result.text || "暂时没有找到合适的回答，请稍后再试。",
        },
      ]);
    } catch (err) {
      if ((err as Error)?.name === "AbortError") return;
      setMessages((prev) => [
        ...prev,
        {
          id: Date.now() + 1,
          role: "agent",
          content: err instanceof Error ? err.message : "当前服务暂时不可用，请稍后再试。",
        },
      ]);
    } finally {
      setSending(false);
      abortRef.current = null;
    }
  }, [connecting, input, mode, sending, sessionId]);

  const ready = !!sessionId;

  return (
    <div className="fixed bottom-3 right-7 z-50">
      {open && (
        <div
          role="dialog"
          aria-label="华夏基金智能助手"
          className="mb-4 flex h-[520px] w-[380px] flex-col overflow-hidden rounded-2xl border border-slate-200 bg-white shadow-2xl"
        >
          <div className="flex items-center justify-between bg-[var(--brand-navy)] px-5 py-4 text-white">
            <div className="flex items-center gap-3">
              <div className="flex h-9 w-9 items-center justify-center rounded-xl bg-[var(--brand-primary)]">
                <Bot className="h-5 w-5" />
              </div>
              <div>
                <p className="text-sm font-semibold">华夏基金智能助手</p>
                <p className="mt-0.5 text-xs text-blue-100">
                  {mode === "client" ? "已接入您的账户数据" : "在线为您提供基金信息服务"}
                </p>
              </div>
            </div>
            <button
              aria-label="关闭聊天框"
              onClick={() => void closeChat()}
              className="rounded-lg p-2 text-blue-100 transition hover:bg-white/10 hover:text-white"
            >
              <X className="h-4 w-4" />
            </button>
          </div>

          <div ref={listRef} className="flex-1 space-y-4 overflow-y-auto bg-slate-50 p-4">
            {messages.map((message) => (
              <div
                key={message.id}
                className={`flex ${message.role === "user" ? "justify-end" : "justify-start"}`}
              >
                <div
                  className={`max-w-[82%] rounded-2xl px-4 py-3 text-sm leading-6 ${
                    message.role === "user"
                      ? "rounded-br-md bg-[var(--brand-primary)] text-white"
                      : "rounded-bl-md border border-slate-200 bg-white text-slate-700"
                  }`}
                >
                  {message.content}
                </div>
              </div>
            ))}

            {connecting && (
              <div className="flex items-center gap-2 text-xs text-slate-400">
                <RotateCw className="h-3 w-3 animate-spin" />
                正在建立会话...
              </div>
            )}
            {sending && !connecting && <div className="text-xs text-slate-400">正在整理信息...</div>}
          </div>

          {error && (
            <div className="flex items-center justify-between gap-3 border-t border-rose-100 bg-rose-50 px-4 py-2.5">
              <span className="text-xs text-rose-600">{error}</span>
              {!ready && (
                <button
                  onClick={() => void connect()}
                  disabled={connecting}
                  className="shrink-0 rounded-lg border border-rose-200 bg-white px-2.5 py-1 text-xs text-rose-600 transition hover:bg-rose-100 disabled:opacity-50"
                >
                  重试
                </button>
              )}
            </div>
          )}

          <form
            onSubmit={(event) => {
              event.preventDefault();
              void sendMessage();
            }}
            className="flex gap-2 border-t border-slate-200 bg-white p-3"
          >
            <input
              value={input}
              onChange={(event) => setInput(event.target.value)}
              placeholder={ready ? "输入您的问题" : "正在准备会话..."}
              disabled={connecting}
              className="min-w-0 flex-1 rounded-xl border border-slate-200 px-3 py-2.5 text-sm outline-none transition focus:border-[var(--brand-primary)] disabled:bg-slate-50"
            />
            <button
              type="submit"
              aria-label="发送消息"
              className="flex h-10 w-10 shrink-0 items-center justify-center rounded-xl bg-[var(--brand-primary)] text-white transition hover:bg-[var(--brand-primary-dark)] disabled:cursor-not-allowed disabled:opacity-50"
              disabled={sending || connecting || !input.trim()}
            >
              <Send className="h-4 w-4" />
            </button>
          </form>
        </div>
      )}

      <button
        aria-label={open ? "收起智能助手" : "打开智能助手"}
        onClick={() => (open ? void closeChat() : openChat())}
        className="flex h-14 w-14 items-center justify-center rounded-full bg-[var(--brand-primary)] text-white shadow-lg shadow-indigo-900/25 transition hover:-translate-y-0.5 hover:bg-[var(--brand-primary-dark)]"
      >
        {open ? <X className="h-5 w-5" /> : <MessageCircle className="h-5 w-5" />}
      </button>
    </div>
  );
}