import { CallbackTool } from "@ai-zen/agents-core";
import * as fsp from "fs/promises";
import * as path from "path";

/**
 * 下载文件（图片、PDF、视频等二进制文件）并保存到本地。
 * 可用于保存 AI 生成的图片、下载网络资源等。
 */
export const downloadFileTool = new CallbackTool({
  function: {
    name: "downloadFile",
    description:
      "从 URL 下载文件（图片、PDF 等二进制文件）并保存到本地磁盘。自动从 URL 推断文件名，也可指定保存路径。",
    parameters: {
      type: "object",
      properties: {
        url: {
          type: "string",
          description: "文件下载链接",
        },
        outputPath: {
          type: "string",
          description:
            "保存路径（可选）。可以是目录或完整文件路径。不指定则下载到当前工作目录，自动从 URL 推断文件名。",
        },
      },
      required: ["url"],
      additionalProperties: false,
    },
  },
  async callback(input): Promise<string> {
    try {
      const url = input.url as string;
      if (!url) throw new Error("url 不能为空");

      let savePath: string;
      if (input.outputPath) {
        savePath = input.outputPath as string;
        const stat = await fsp.stat(savePath).catch(() => null);
        if (stat?.isDirectory()) {
          const urlPath = new URL(url).pathname;
          const fileName = path.basename(urlPath) || `download_${Date.now()}`;
          savePath = path.join(savePath, fileName);
        }
      } else {
        const urlPath = new URL(url).pathname;
        const fileName = path.basename(urlPath) || `download_${Date.now()}`;
        savePath = path.join(process.cwd(), fileName);
      }

      await fsp.mkdir(path.dirname(savePath), { recursive: true });

      const response = await fetch(url);
      if (!response.ok) {
        throw new Error(`下载失败: HTTP ${response.status} ${response.statusText}`);
      }

      const contentType = response.headers.get("content-type") || "";
      const arrayBuffer = await response.arrayBuffer();
      const buffer = Buffer.from(arrayBuffer);
      await fsp.writeFile(savePath, buffer);

      const stats = await fsp.stat(savePath);
      const fileSizeKB = (stats.size / 1024).toFixed(1);

      return JSON.stringify({
        success: true,
        filePath: path.resolve(savePath),
        fileSize: `${fileSizeKB} KB`,
        contentType,
        note: "文件已保存到本地",
      });
    } catch (error: any) {
      return JSON.stringify({
        success: false,
        error: error?.message || "下载失败",
      });
    }
  },
});