import { ref } from "vue";
import { parseJsonEventStream, uiMessageChunkSchema } from "ai";
import { useAuthSession } from "./useAuthSession";

export interface CharacterMessage {
  id: string;
  role: "user" | "assistant";
  content: string;
  createdAt?: string;
}

export interface UseCharacterChatOptions {
  cardSlug: () => string;
  sessionId: () => string | null;
  modelId: () => number | null;
  onStreamComplete?: () => void;
}

function generateId(): string {
  return Date.now().toString(36) + Math.random().toString(36).slice(2);
}

/**
 * 角色对话（纯文本流式），与 useAgentChat 解耦：
 * 不处理工具/思考/审批/图片，只处理 text-delta。
 */
export function useCharacterChat(options: UseCharacterChatOptions) {
  const { cardSlug, sessionId, modelId, onStreamComplete } = options;
  const auth = useAuthSession();

  const messages = ref<CharacterMessage[]>([]);
  const isLoading = ref(false);
  const errorMessage = ref("");
  const isStopped = ref(false);

  let abortController: AbortController | null = null;

  async function loadMessages(sid: string) {
    messages.value = [];
    errorMessage.value = "";
    try {
      const res = await $fetch<{ code: number; data: { messages: CharacterMessage[] } }>(
        `/api/characters/${cardSlug()}/sessions/${sid}/messages`,
      );
      messages.value = res.data?.messages ?? [];
    } catch {
      messages.value = [];
    }
  }

  async function processStream(res: Response, assistantIdx: number) {
    if (!res.body) throw new Error("响应体为空");
    const chunkStream = parseJsonEventStream({
      stream: res.body,
      schema: uiMessageChunkSchema,
    });
    const reader = chunkStream.getReader();
    for (;;) {
      const { done, value: parsed } = await reader.read();
      if (done) break;
      if (!parsed.success) continue;
      const chunk = parsed.value;
      if (chunk.type === "text-delta") {
        const msg = messages.value[assistantIdx];
        if (msg) msg.content += chunk.delta;
      } else if (chunk.type === "error") {
        errorMessage.value = chunk.errorText || "流式响应出错";
      }
    }
  }

  async function send(content: string) {
    const textContent = content.trim();
    const sid = sessionId();
    if (!textContent || sid === null || isLoading.value) return;

    if (!modelId()) {
      errorMessage.value = "请先选择模型后再发送消息";
      const { $toast } = useNuxtApp();
      $toast?.error?.("请先选择模型后再发送消息");
      return;
    }

    errorMessage.value = "";
    isStopped.value = false;

    messages.value.push({ id: generateId(), role: "user", content: textContent });
    const userIdx = messages.value.length - 1;
    messages.value.push({ id: generateId(), role: "assistant", content: "" });
    const assistantIdx = messages.value.length - 1;

    isLoading.value = true;
    abortController = new AbortController();

    try {
      const res = await fetch(`/api/characters/${cardSlug()}/chat`, {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({ sessionId: sid, content: textContent, modelId: modelId() }),
        signal: abortController.signal,
        credentials: "include",
      });

      const dbUserMessageId = res.headers.get("X-User-Message-Id");
      if (dbUserMessageId && userIdx >= 0) {
        messages.value[userIdx]!.id = dbUserMessageId;
      }

      if (!res.ok) {
        const errText = await res.text();
        throw new Error(errText || `请求失败 (${res.status})`);
      }

      await processStream(res, assistantIdx);
      onStreamComplete?.();
    } catch (err: any) {
      if (err.name === "AbortError") {
        isStopped.value = true;
      } else {
        errorMessage.value = err.message || "请求失败";
        const msg = messages.value[assistantIdx];
        if (msg && !msg.content) {
          messages.value.splice(assistantIdx, 1);
        }
      }
    } finally {
      isLoading.value = false;
      abortController = null;
    }
  }

  function stopGeneration() {
    if (abortController) {
      abortController.abort();
      abortController = null;
    }
  }

  async function stopAndSave() {
    const sid = sessionId();
    stopGeneration();
    isStopped.value = true;
    if (sid) {
      try {
        await $fetch(`/api/characters/${cardSlug()}/chat/stop`, {
          method: "POST",
          body: { sessionId: sid },
        });
      } catch {
      }
    }
  }

  function clear() {
    messages.value = [];
    errorMessage.value = "";
    isStopped.value = false;
  }

  return {
    messages,
    isLoading,
    errorMessage,
    isStopped,
    send,
    stopGeneration,
    stopAndSave,
    clear,
    loadMessages,
  };
}