import { Document } from "../../document.js";
import { BufferLoader } from "./buffer.js";

/**
 * A class that extends the `BufferLoader` class. It represents a document
 * loader that loads documents from DOCX files.
 */
export class DocxLoader extends BufferLoader {
  constructor(filePathOrBlob: string | Blob) {
    super(filePathOrBlob);
  }

  /**
   * A method that takes a `raw` buffer and `metadata` as parameters and
   * returns a promise that resolves to an array of `Document` instances. It
   * uses the `extractRawText` function from the `mammoth` module to extract
   * the raw text content from the buffer. If the extracted text content is
   * empty, it returns an empty array. Otherwise, it creates a new
   * `Document` instance with the extracted text content and the provided
   * metadata, and returns it as an array.
   * @param raw The raw buffer from which to extract text content.
   * @param metadata The metadata to be associated with the created `Document` instance.
   * @returns A promise that resolves to an array of `Document` instances.
   */
  public async parse(
    raw: Buffer,
    metadata: Document["metadata"]
  ): Promise<Document[]> {
    const { extractRawText } = await DocxLoaderImports();
    const docx = await extractRawText({
      buffer: raw,
    });

    if (!docx.value) return [];

    return [
      new Document({
        pageContent: docx.value,
        metadata,
      }),
    ];
  }
}

async function DocxLoaderImports() {
  try {
    const { default: mod } = await import("mammoth");
    const { extractRawText } = mod;
    return { extractRawText };
  } catch (e) {
    console.error(e);
    throw new Error(
      "Failed to load mammoth. Please install it with eg. `npm install mammoth`."
    );
  }
}