plane/packages/services/src/file/helper.ts

// external imports
import { fileTypeFromBuffer } from "file-type";
// plane imports
import { TFileMetaDataLite, TFileSignedURLResponse } from "@plane/types";

/**
 * @description from the provided signed URL response, generate a payload to be used to upload the file
 * @param {TFileSignedURLResponse} signedURLResponse
 * @param {File} file
 * @returns {FormData} file upload request payload
 */
export const generateFileUploadPayload = (signedURLResponse: TFileSignedURLResponse, file: File): FormData => {
  const formData = new FormData();
  Object.entries(signedURLResponse.upload_data.fields).forEach(([key, value]) => formData.append(key, value));
  formData.append("file", file);
  return formData;
};

/**
 * @description Detect MIME type from file signature using file-type library
 * @param {File} file
 * @returns {Promise<string>} detected MIME type or empty string if unknown
 */
const detectMimeTypeFromSignature = async (file: File): Promise<string> => {
  try {
    // Read first 4KB which is usually sufficient for most file type detection
    const chunk = file.slice(0, 4096);
    const buffer = await chunk.arrayBuffer();
    const uint8Array = new Uint8Array(buffer);

    const fileType = await fileTypeFromBuffer(uint8Array);
    return fileType?.mime || "";
  } catch (_error) {
    return "";
  }
};

/**
 * @description Determine the MIME type of a file using multiple detection methods
 * @param {File} file
 * @returns {Promise<string>} detected MIME type
 */
const detectFileType = async (file: File): Promise<string> => {
  // check if the file has a MIME type
  if (file.type && file.type.trim() !== "") {
    return file.type;
  }

  // detect from file signature using file-type library
  try {
    const signatureType = await detectMimeTypeFromSignature(file);
    if (signatureType) {
      return signatureType;
    }
  } catch (_error) {
    console.error("Error detecting file type from signature:", _error);
  }

  // fallback for unknown files
  return "application/octet-stream";
};

/**
 * @description returns the necessary file meta data to upload a file
 * @param {File} file
 * @returns {Promise<TFileMetaDataLite>} payload with file info
 */
export const getFileMetaDataForUpload = async (file: File): Promise<TFileMetaDataLite> => {
  const fileType = await detectFileType(file);
  return {
    name: file.name,
    size: file.size,
    type: fileType,
  };
};

/**
 * @description this function returns the assetId from the asset source
 * @param {string} src
 * @returns {string} assetId
 */
export const getAssetIdFromUrl = (src: string): string => {
  const sourcePaths = src.split("/");
  const assetUrl = sourcePaths[sourcePaths.length - 1];
  return assetUrl ?? "";
};