// AI 免费对话 - 前端逻辑
(function () {
  const chatEl = document.getElementById("chat");
  const inputEl = document.getElementById("input");
  const sendBtn = document.getElementById("send");

  // 保存对话历史（用于多轮上下文）
  const history = [];
  let sending = false;

  /** 获取当前选择的 provider */
  function getProvider() {
    const el = document.querySelector('input[name="provider"]:checked');
    return el ? el.value : "deepseek";
  }

  /** 追加一条消息到界面 */
  function appendMessage(role, content) {
    const wrapper = document.createElement("div");
    wrapper.className = `message ${role}`;
    const bubble = document.createElement("div");
    bubble.className = "bubble";
    bubble.textContent = content;
    wrapper.appendChild(bubble);
    chatEl.appendChild(wrapper);
    chatEl.scrollTop = chatEl.scrollHeight;
    return bubble;
  }

  /** 发送消息并接收 SSE 流 */
  async function send() {
    if (sending) return;
    const text = inputEl.value.trim();
    if (!text) return;

    sending = true;
    sendBtn.disabled = true;
    inputEl.value = "";

    // 展示用户消息
    appendMessage("user", text);
    history.push({ role: "user", content: text });

    // 展示助手占位
    const bubble = appendMessage("assistant", "");
    bubble.classList.add("cursor");

    let assistantText = "";

    try {
      const resp = await fetch("api/chat", {
        method: "POST",
        headers: { "Content-Type": "application/json" },
        body: JSON.stringify({
          provider: getProvider(),
          messages: history,
        }),
      });

      if (!resp.ok || !resp.body) {
        throw new Error("网络请求失败");
      }

      const reader = resp.body.getReader();
      const decoder = new TextDecoder("utf-8");
      let buffer = "";

      while (true) {
        const { done, value } = await reader.read();
        if (done) break;
        buffer += decoder.decode(value, { stream: true });

        // 按 SSE 事件分隔（\n\n）
        const parts = buffer.split("\n\n");
        buffer = parts.pop(); // 保留最后不完整片段

        for (const part of parts) {
          const line = part.trim();
          if (!line.startsWith("data:")) continue;
          const data = line.slice(5).trim();
          if (data === "[DONE]") continue;
          try {
            const obj = JSON.parse(data);
            if (obj.error) {
              assistantText += `\n[错误] ${obj.error}`;
              bubble.textContent = assistantText;
            } else if (obj.content) {
              assistantText += obj.content;
              bubble.textContent = assistantText;
              chatEl.scrollTop = chatEl.scrollHeight;
            }
          } catch (e) {
            // 忽略解析错误
          }
        }
      }
    } catch (err) {
      assistantText += `\n[错误] ${err.message}`;
      bubble.textContent = assistantText;
    } finally {
      bubble.classList.remove("cursor");
      if (assistantText) {
        history.push({ role: "assistant", content: assistantText });
      }
      sending = false;
      sendBtn.disabled = false;
      inputEl.focus();
    }
  }

  // 事件绑定
  sendBtn.addEventListener("click", send);
  inputEl.addEventListener("keydown", function (e) {
    if (e.key === "Enter" && !e.shiftKey) {
      e.preventDefault();
      send();
    }
  });
})();