import { NextRequest, NextResponse } from "next/server";
import { auth } from "@/app/(auth)/auth";
import { callQwen3Vl } from "@/lib/ai/qwen3-vl";
import { createLogger } from "@/lib/observability/logger";

const logger = createLogger("canvas-auto-title");

export async function POST(request: NextRequest) {
  logger.debug("request_received");
  
  try {
    const session = await auth();
    if (!session?.user?.id) {
      logger.warn("unauthorized");
      return NextResponse.json({ error: "Unauthorized" }, { status: 401 });
    }

    const { imageUrl } = await request.json();

    if (!imageUrl) {
      return NextResponse.json({ error: "Image URL is required" }, { status: 400 });
    }

    logger.debug("model_selected", { model: "qwen3-vl" });

    // 构造 Prompt
    const prompt = "请用2-4个字概括这张图片的主体内容，作为文件标题。直接返回标题，不要包含任何标点符号或其他文字。";

    const { text, model } = await callQwen3Vl({
      imageUrl,
      prompt,
      temperature: 0.2,
      maxTokens: 50,
    });

    let title = (text || "").trim();
    title = title.replace(/[\s\p{P}\p{S}]+/gu, "");
    if (title.length > 4) title = title.slice(0, 4);
    if (title.length < 2) title = "新画布";
    logger.info("title_generated", { model, titleLength: title.length });
    return NextResponse.json({ title });

  } catch (error) {
    logger.error("auto_title_failed", error);
    // 失败时返回默认标题，不报错中断流程
    return NextResponse.json({ title: "新画布" });
  }
}