import type { AiRequestBody } from "@/lib/ai/types";

export async function streamAiCompletion(
  body: AiRequestBody,
  onUpdate: (text: string) => void,
): Promise<void> {
  const res = await fetch("/api/ai", {
    method: "POST",
    headers: { "Content-Type": "application/json" },
    body: JSON.stringify(body),
  });

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

  if (!res.body) {
    throw new Error("AI 响应为空");
  }

  const reader = res.body.getReader();
  const decoder = new TextDecoder();
  let text = "";

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