import type { Attachment, AttachmentAdapter, CompleteAttachment, PendingAttachment } from "@assistant-ui/react";

type AttachmentApi = {
  uploadAttachment(file: File): Promise<{ attachment: { attachmentId: string } }>;
  deleteAttachment(attachmentId: string): Promise<unknown>;
};

export class HarnessAttachmentAdapter implements AttachmentAdapter {
  public readonly accept = "image/jpeg,image/png,image/webp";
  readonly #previews = new Map<string, string>();

  public constructor(private readonly api: AttachmentApi) {}

  public async add({ file }: { file: File }): Promise<PendingAttachment> {
    if (!this.accept.split(",").includes(file.type)) throw new Error("仅支持 JPEG、PNG 和 WebP 图片");
    const preview = URL.createObjectURL(file);
    try {
      const response = await this.api.uploadAttachment(file);
      this.#previews.set(response.attachment.attachmentId, preview);
      return {
        id: response.attachment.attachmentId,
        type: "image",
        name: file.name,
        contentType: file.type,
        file,
        status: { type: "requires-action", reason: "composer-send" },
      };
    } catch (error) {
      URL.revokeObjectURL(preview);
      throw error;
    }
  }

  public async remove(attachment: Attachment): Promise<void> {
    if (attachment.id.startsWith("att_")) await this.api.deleteAttachment(attachment.id);
    this.#revoke(attachment.id);
  }

  public send(attachment: PendingAttachment): Promise<CompleteAttachment> {
    this.#revoke(attachment.id);
    return Promise.resolve({
      id: attachment.id,
      type: "image",
      name: attachment.name,
      contentType: attachment.contentType,
      status: { type: "complete" },
      content: [],
    });
  }

  public previewUrl(attachmentId: string): string | undefined {
    return this.#previews.get(attachmentId);
  }

  public dispose(): void {
    for (const url of this.#previews.values()) URL.revokeObjectURL(url);
    this.#previews.clear();
  }

  #revoke(attachmentId: string): void {
    const preview = this.#previews.get(attachmentId);
    if (preview !== undefined) URL.revokeObjectURL(preview);
    this.#previews.delete(attachmentId);
  }
}