import { useCallback, useState } from "react";
import { chatStream } from "./api";
import { connectWs, isWsOpen } from "./ws";
import { useAppStore } from "../store/useAppStore";
import { useModeStore } from "../store/useModeStore";
import { now } from "./util";

/** Drives one user turn: push the user bubble, blanket a streaming assistant
 *  bubble, trigger the backend loop over REST (`stream:true`), and let the WS
 *  stream render into that bubble. Falls back to the WS `chat` channel when the
 *  REST trigger fails so the demo still works without a wired loop.
 *
 *  The behavior mode is NOT chosen by the user at send time — the agent / backend
 *  hot-switches it (design/01 §3), and each message carries its own mode, so the
 *  bubble renders per that message's mode. Until the backend advertises a
 *  per-message mode, a new assistant bubble defaults to the current UI mode. */
export function useSendChat(): {
  send: (text: string, image?: string) => Promise<void>;
  sending: boolean;
} {
  const [sending, setSending] = useState(false);
  const sessionId = useAppStore((s) => s.sessionId);
  const addUserMessage = useAppStore((s) => s.addUserMessage);
  const beginAssistant = useAppStore((s) => s.beginAssistant);
  const endStream = useAppStore((s) => s.endStream);
  const appendChunk = useAppStore((s) => s.appendChunk);
  const addTool = useAppStore((s) => s.addTool);
  const appendTaskLog = useAppStore((s) => s.appendTaskLog);
  const mode = useModeStore((s) => s.mode);

  const send = useCallback(
    async (text: string, image?: string) => {
      const trimmed = text.trim();
      if ((!trimmed && !image) || sending) return;
      setSending(true);
      if (!isWsOpen()) connectWs();

      // The gateway's chat body still requires a non-empty text, so a pure image
      // turn (vision) falls back to a default prompt to keep the trigger valid.
      const prompt = trimmed || (image ? "分析这张图片" : "");
      addUserMessage(trimmed, undefined, image);
      beginAssistant(mode);

      try {
        await chatStream(sessionId, prompt, image);
      } catch (err: unknown) {
        // Backend loop not wired or gateway unreachable: show the failure inline
        // rather than leaving a permanently-streaming bubble.
        endStream();
        const msg = err instanceof Error ? err.message : "触发失败";
        appendChunk(`[stream 触发失败] ${msg}`);
        appendTaskLog("main", `[error] ${msg}\n`);
        addTool({ name: "stream_trigger", summary: "失败", ok: false, detail: msg, at: now() });
      } finally {
        setSending(false);
      }
    },
    [sending, sessionId, mode, addUserMessage, beginAssistant, endStream, appendChunk, addTool, appendTaskLog]
  );

  return { send, sending };
}