import type { PlatformApiClient } from "../api/client";
import type { ServerFileDownloadResponse } from "../api/types";

export async function downloadServerFileResult(client: PlatformApiClient, result: ServerFileDownloadResponse): Promise<string> {
  if (result.status !== "ready") {
    return result.reason ?? "文件读取任务已派发，完成后可再次下载。";
  }
  if (result.content !== undefined) {
    saveBlob(new Blob([result.content], { type: result.contentType ?? "text/plain;charset=utf-8" }), result.filename || "server-file.txt");
    return `下载已开始：${result.filename || result.key}`;
  }
  if (!result.artifact) {
    return "文件内容尚未可用。";
  }
  const chunks: ArrayBuffer[] = [];
  let offset = 0;
  const chunkSize = Math.max(1, result.artifact.chunkSizeBytes || 1024 * 1024);
  while (offset < result.artifact.sizeBytes) {
    const chunk = await client.readArtifactContent(result.artifact.artifactId, offset, Math.min(chunkSize, result.artifact.sizeBytes - offset));
    chunks.push(chunk.payload);
    offset += chunk.contentLength;
    if (chunk.contentLength <= 0) break;
  }
  saveBlob(new Blob(chunks, { type: result.artifact.contentType || "application/octet-stream" }), result.filename || result.artifact.filename);
  return `下载已开始：${result.filename || result.artifact.filename}`;
}

function saveBlob(blob: Blob, filename: string) {
  const url = URL.createObjectURL(blob);
  const anchor = document.createElement("a");
  anchor.href = url;
  anchor.download = safeFilename(filename);
  document.body.appendChild(anchor);
  anchor.click();
  anchor.remove();
  window.setTimeout(() => URL.revokeObjectURL(url), 1000);
}

function safeFilename(filename: string): string {
  const cleaned = filename.replace(/[\\/:*?"<>|]+/g, "-").trim();
  return cleaned || "server-file.txt";
}