import { useCallback, useState } from "react";
import { ApiError, chatStream } from "./api";
import { connectWs, isWsOpen } from "./ws";
import { useAppStore } from "../store/useAppStore";
import { useModeStore } from "../store/useModeStore";
import { getClientId } from "./client";
import { now, uid } 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. If the REST trigger fails, the failure is
 *  surfaced inline on the bubble rather than left streaming forever.
 *
 *  The behavior mode is chosen by the agent / backend hot-switch (design/01 §3);
 *  each message carries the mode in effect when the turn is sent, and the bubble
 *  renders per that message's mode. We read the current UI mode here and pass it
 *  on the turn so the backend persists it alongside the message (A3). */
export function useSendChat(): {
  send: (text: string, image?: string, opts?: { parallel?: boolean }) => Promise<void>;
  sending: boolean;
} {
  const [sending, setSending] = useState(false);
  const sessionId = useAppStore((s) => s.activeSessionId);
  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 markLocalDelivery = useAppStore((s) => s.markLocalDelivery);
  const alignDuplicateMessage = useAppStore((s) => s.alignDuplicateMessage);
  const mode = useModeStore((s) => s.mode);

  const send = useCallback(
    async (text: string, image?: string, opts: { parallel?: boolean } = {}) => {
      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" : "");
      // Tag this browser's persistent client id onto the optimistic bubbles so the
      // source label shows immediately and matches the persisted turn (design/16 §4.5).
      const clientId = getClientId();
      // 幂等键（契约 §4.3）：随上行一起发，服务端判重命中会回 `chat_duplicate` 帧或
      // `{duplicate:true,messageId}`（REST 面），本端据此把本地气泡对齐到既有 id ——
      // 重发/双发不会多出一条气泡。
      const clientMsgId = uid();
      addUserMessage(trimmed, undefined, image, clientId, clientMsgId);
      beginAssistant(mode, clientId);

      try {
        const res = await chatStream(
          sessionId,
          prompt,
          image,
          mode,
          clientMsgId,
          opts.parallel
        );
        // 响应面得如实消费（契约 §4.6）：202 排队不是错误。
        // `pending_ack` 帧是队列深度的真源，这里只做「万一那条帧没到」的兜底标注；
        // `duplicate` 同理（同一条事实的 REST 面）。
        if (res.duplicate && res.messageId) {
          alignDuplicateMessage(clientMsgId, res.messageId, sessionId);
        } else if (res.queued) {
          markLocalDelivery("queued");
        }
      } catch (err: unknown) {
        endStream();
        // ⑥ 被拒：`409 chat_busy`（队列满）—— 这不是「触发失败」，气泡要明确说
        // 「未送达」，让人知道这句话没进去（而不是只看到一行错误日志）。
        if (err instanceof ApiError && err.code === "chat_busy") {
          markLocalDelivery("rejected", { rejectReason: "会话正忙：排队已满，这条未送达" });
          appendTaskLog("main", "[chat_busy] 排队已满，本条未送达\n");
          return;
        }
        // Backend loop not wired or gateway unreachable: show the failure inline
        // rather than leaving a permanently-streaming bubble.
        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, markLocalDelivery, alignDuplicateMessage]
  );

  return { send, sending };
}