import { useState, useCallback } from "react";

export interface PendingAttachment {
  file: File;
  objectKey: string;
  uploadProgress: number;
  uploadStatus: "pending" | "uploading" | "complete" | "error";
  error?: string;
}

interface UploadResponse {
  id?: number;
  object_key?: string;
}

/**
 * Hook for uploading files via direct multipart POST.
 *
 * Callers provide the target URL; the hook builds a FormData body and uses
 * XMLHttpRequest so that upload progress events are available.
 */
export function useFileUpload() {
  const [uploading, setUploading] = useState(false);

  const upload = useCallback(
    (
      file: File,
      url: string,
      onProgress?: (progress: number) => void,
    ): Promise<PendingAttachment> => {
      setUploading(true);

      return (async () => {
        try {
          const form = new FormData();
          form.append("file", file);

          const result = await new Promise<UploadResponse>(
            (resolve, reject) => {
              const xhr = new XMLHttpRequest();
              xhr.open("POST", url);
              xhr.withCredentials = true;

              xhr.upload.onprogress = (e) => {
                if (e.lengthComputable) {
                  onProgress?.(Math.round((e.loaded / e.total) * 100));
                }
              };

              xhr.onload = () => {
                if (xhr.status >= 200 && xhr.status < 300) {
                  try {
                    resolve(JSON.parse(xhr.responseText) as UploadResponse);
                  } catch {
                    resolve({});
                  }
                } else {
                  reject(new Error(`Upload failed: HTTP ${xhr.status}`));
                }
              };

              xhr.onerror = () => reject(new Error("Upload failed"));
              xhr.send(form);
            },
          );

          return {
            file,
            objectKey: result.object_key ?? "",
            uploadProgress: 100,
            uploadStatus: "complete" as const,
          };
        } catch (e) {
          return {
            file,
            objectKey: "",
            uploadProgress: 0,
            uploadStatus: "error" as const,
            error: e instanceof Error ? e.message : "Upload failed",
          };
        } finally {
          setUploading(false);
        }
      })();
    },
    [],
  );

  return { upload, uploading };
}