DownloadUtils.ts

import * as ApiUtils from '@libs/ApiUtils';
import tryResolveUrlFromApiRoot from '@libs/tryResolveUrlFromApiRoot';
import * as Link from '@userActions/Link';
import CONST from '@src/CONST';
import * as FileUtils from './FileUtils';
import type {FileDownload} from './types';

const createDownloadLink = (href: string, fileName: string) => {
    // creating anchor tag to initiate download
    const link = document.createElement('a');
    // adding href to anchor
    link.href = href;
    link.style.display = 'none';

    // eslint-disable-next-line @typescript-eslint/prefer-nullish-coalescing -- Disabling this line for safeness as nullish coalescing works only if the value is undefined or null, and since fileName can be an empty string we want to default to `FileUtils.getFileName(url)`
    link.download = fileName;

    // Append to html link element page
    document.body.appendChild(link);

    // Start download
    link.click();

    // Clean up and remove the link
    URL.revokeObjectURL(link.href);
    link.parentNode?.removeChild(link);
};

/**
 * The function downloads an attachment on web/desktop platforms.
 */
// eslint-disable-next-line @typescript-eslint/no-unused-vars
const fetchFileDownload: FileDownload = (url, fileName, successMessage = '', shouldOpenExternalLink = false, formData = undefined, requestType = 'get', onDownloadFailed?: () => void) => {
    const resolvedUrl = tryResolveUrlFromApiRoot(url);

    const isApiUrl = resolvedUrl.startsWith(ApiUtils.getApiRoot());
    const isAttachmentUrl = CONST.ATTACHMENT_LOCAL_URL_PREFIX.some((prefix) => resolvedUrl.startsWith(prefix));
    const isSageUrl = url === CONST.EXPENSIFY_PACKAGE_FOR_SAGE_INTACCT;
    if (
        // We have two file download cases that we should allow: 1. downloading attachments 2. downloading Expensify package for Sage Intacct
        shouldOpenExternalLink ||
        (!isApiUrl && !isAttachmentUrl && !isSageUrl)
    ) {
        // Different origin URLs might pose a CORS issue during direct downloads.
        // Opening in a new tab avoids this limitation, letting the browser handle the download.
        Link.openExternalLink(url);
        return Promise.resolve();
    }

    const fetchOptions: RequestInit = {
        method: requestType,
        body: formData,
    };

    return fetch(url, fetchOptions)
        .then((response) => response.blob())
        .then((blob) => {
            // Create blob link to download
            const href = URL.createObjectURL(new Blob([blob]));
            const completeFileName = FileUtils.appendTimeToFileName(fileName ?? FileUtils.getFileName(url));
            createDownloadLink(href, completeFileName);
        })
        .catch(() => {
            if (onDownloadFailed) {
                onDownloadFailed();
            } else {
                // file could not be downloaded, open sourceURL in new tab
                Link.openExternalLink(url);
            }
        });
};

export default fetchFileDownload;