import { useEffect, useMemo, useRef, useState } from "react";
import { useAppStore } from "../store/useAppStore";
import { useCurrentPersona } from "../store/personaSelectors";
import { useModeStore } from "../store/useModeStore";
import { useSendChat } from "../lib/useChat";
import { sendUp } from "../lib/ws";
import { HistoryList } from "../components/messages/HistoryList";
import { ChatInput } from "../components/ChatInput";
import { EmptyState } from "../components/primitives";
import { Icon } from "../components/Icon";
import { SessionStatusHint, ApprovalNoticeHint } from "../components/status";
import { personaChatBackground, type Orientation } from "../lib/persona";

/**
 * The single shared page (design/07 §1). All behavior modes live in ONE message
 * stream; each message carries its own `mode` (assigned by the agent at runtime,
 * design/01 §3 hot-switch), so its bubble renders per that mode. There is no
 * manual mode selector — the agent / backend drives the mode.
 */
export function ChatShell(): React.ReactNode {
  const messages = useAppStore((s) => s.messages);
  // The chat wallpaper follows the *active session's* role (design/22 §4.6).
  const currentPersona = useCurrentPersona();
  const { send, sending } = useSendChat();
  const bottomRef = useRef<HTMLDivElement>(null);

  // Chat wallpaper follows the current orientation (landscape when wide, else
  // portrait) and re-evaluates on window resize.
  const [orientation, setOrientation] = useState<Orientation>(() =>
    window.innerWidth > window.innerHeight ? "landscape" : "portrait"
  );

  useEffect(() => {
    const onResize = () =>
      setOrientation(window.innerWidth > window.innerHeight ? "landscape" : "portrait");
    window.addEventListener("resize", onResize);
    return () => window.removeEventListener("resize", onResize);
  }, []);

  // The persona's own wallpaper for the current orientation; undefined keeps the
  // plain Miuix surface (never another role's image).
  const chatBackground = personaChatBackground(currentPersona, orientation);

  // The latest assistant message is the one being streamed right now; only it
  // carries the live 唤醒路径 node sequence (WakePath), so the capacity state
  // reflects the current turn rather than a collapsed historical message.
  const lastAssistantId = useMemo(() => {
    for (let i = messages.length - 1; i >= 0; i--) {
      if (messages[i].role === "assistant") return messages[i].id;
    }
    return undefined;
  }, [messages]);

  // Scroll to the newest message only when a *new* message reaches the tail
  // (append/session-switch), not when the user hot-pages older history into the
  // list — otherwise "load earlier" would yank the viewport to the bottom.
  const lastMessageId = messages[messages.length - 1]?.id;
  useEffect(() => {
    bottomRef.current?.scrollIntoView({ behavior: "smooth", block: "end" });
  }, [lastMessageId]);

  return (
    <div className="flex h-full flex-col">
      <div className="relative min-h-0 flex-1">
        {chatBackground ? (
          <div className="absolute inset-0 overflow-hidden" aria-hidden>
            <img
              src={chatBackground}
              alt=""
              draggable={false}
              className="h-full w-full object-cover"
            />
            <div className="absolute inset-0 bg-[var(--mu-surface-2)]/40" />
          </div>
        ) : null}
        <div className="relative h-full overflow-y-auto">
          <div className="mx-auto flex max-w-2xl flex-col gap-4 p-4">
            <SessionStatusHint />
            <ApprovalNoticeHint />
            {messages.length === 0 ? (
              <EmptyState
                icon={<Icon name="chat" size={24} />}
                title="开始与昔涟对话"
                hint="模式只改变消息框的呈现方式，会话上下文与记忆保持不变"
              />
            ) : (
              <HistoryList lastAssistantId={lastAssistantId} />
            )}
            <div ref={bottomRef} />
          </div>
        </div>
      </div>
      <ChatInput
        onSend={(t, image) => void send(t, image)}
        sending={sending}
        onVoice={() => {
          // Voice is not wired to a live pipeline yet (real call deferred). Activate
          // the voice_input uplink and switch the shell to voice mode so the agent
          // (or the demo) reflects a voice session.
          useModeStore.getState().setMode("voice");
          sendUp({ type: "voice_input", data: { mode: "voice" } });
        }}
      />
    </div>
  );
}