Truncate file names to safe length during Android file downloads

src/libs/fileDownload/FileUtils.ts

@@ -161,15 +161,41 @@ function cleanFileName(fileName: string): string {
 
 function appendTimeToFileName(fileName: string): string {
     const file = splitExtensionFromFileName(fileName);
-    let newFileName = `${file.fileName}-${DateUtils.getDBTime()}`;
+
+    const fileNameWithoutExtension = file.fileName;
+    const fileExtension = file.fileExtension;
+
+    const time = DateUtils.getDBTime();
+    const timeSuffix = `-${time}`;
+
+    const lengthSafeFileNameWithoutExtension =
+        Platform.OS === 'android' ? truncateFileNameToSafeLengthOnAndroid({fileNameWithoutExtension, fileSuffixLength: timeSuffix.length}) : fileNameWithoutExtension;
+
+    let newFileName = `${lengthSafeFileNameWithoutExtension}${timeSuffix}`;
+
     // Replace illegal characters before trying to download the attachment.
     newFileName = newFileName.replace(CONST.REGEX.ILLEGAL_FILENAME_CHARACTERS, '_');
-    if (file.fileExtension) {
-        newFileName += `.${file.fileExtension}`;
+    if (fileExtension) {
+        newFileName += `.${fileExtension}`;
     }
     return newFileName;
 }
 
+const ANDROID_SAFE_FILE_NAME_LENGTH = 70;
+
+/**
+ * Truncates the file name to a safe length on Android
+ * @param params - An object containing:
+ *   @param params.fileNameWithoutExtension - The file name without the extension
+ *   @param params.fileSuffixLength - The length of the file suffix
+ * @returns The truncated file name
+ */
+function truncateFileNameToSafeLengthOnAndroid({fileNameWithoutExtension, fileSuffixLength}: {fileNameWithoutExtension: string; fileSuffixLength: number}): string {
+    const safeFileNameLengthWithoutSuffix = ANDROID_SAFE_FILE_NAME_LENGTH - fileSuffixLength;
+
+    return fileNameWithoutExtension.substring(0, safeFileNameLengthWithoutSuffix);
+}
+
 /**
  * Reads a locally uploaded file
  * @param path - the blob url of the locally uploaded file
@@ -754,6 +780,8 @@ export {
     getFileType,
     cleanFileName,
     appendTimeToFileName,
+    ANDROID_SAFE_FILE_NAME_LENGTH,
+    truncateFileNameToSafeLengthOnAndroid,
     readFileAsync,
     base64ToFile,
     isLocalFile,

tests/unit/FileUtilsTest.ts

@@ -1,3 +1,4 @@
+import {Platform} from 'react-native';
 import CONST from '../../src/CONST';
 import DateUtils from '../../src/libs/DateUtils';
 import * as FileUtils from '../../src/libs/fileDownload/FileUtils';
@@ -9,6 +10,8 @@ const createMockFile = (name: string, size: number) => ({
     size,
 });
 
+const createFileNameFromLength = ({length, extension}: {length: number; extension?: string | undefined}): string => `${'a'.repeat(length)}${extension ? `.${extension}` : ''}`;
+
 describe('FileUtils', () => {
     describe('splitExtensionFromFileName', () => {
         it('should return correct file name and extension', () => {
@@ -42,6 +45,52 @@ describe('FileUtils', () => {
             const expectedFileName = `image-${DateUtils.getDBTime()}`;
             expect(actualFileName).toEqual(expectedFileName.replace(CONST.REGEX.ILLEGAL_FILENAME_CHARACTERS, '_'));
         });
+
+        describe('on Android', () => {
+            let platformReplaceProperty: jest.ReplaceProperty<string>;
+
+            beforeEach(() => {
+                platformReplaceProperty = jest.replaceProperty(Platform, 'OS', 'android');
+            });
+
+            afterEach(() => {
+                platformReplaceProperty.restore();
+            });
+
+            it('should truncate the file name to safe length when length exceeds the safe length', () => {
+                const fileNameExceedingSafeLength = createFileNameFromLength({length: FileUtils.ANDROID_SAFE_FILE_NAME_LENGTH + 1, extension: 'doc'});
+
+                const actualFileName = FileUtils.appendTimeToFileName(fileNameExceedingSafeLength);
+                const expectedTruncatedFileName = `${createFileNameFromLength({length: FileUtils.ANDROID_SAFE_FILE_NAME_LENGTH - 24})}-${DateUtils.getDBTime()}.doc`;
+
+                expect(actualFileName).toEqual(expectedTruncatedFileName.replace(CONST.REGEX.ILLEGAL_FILENAME_CHARACTERS, '_'));
+            });
+        });
+
+        describe('on Non-Android', () => {
+            const nonAndroidPlatforms = ['ios', 'macos', 'windows', 'web'] as const;
+
+            describe.each(nonAndroidPlatforms)('%s', (platform) => {
+                let platformReplaceProperty: jest.ReplaceProperty<string>;
+
+                beforeEach(() => {
+                    platformReplaceProperty = jest.replaceProperty(Platform, 'OS', platform);
+                });
+
+                afterEach(() => {
+                    platformReplaceProperty.restore();
+                });
+
+                it('should not truncate the file name even when length exceeds the Android safe length', () => {
+                    const fileNameExceedingAndroidSafeLength = createFileNameFromLength({length: FileUtils.ANDROID_SAFE_FILE_NAME_LENGTH + 1, extension: 'doc'});
+
+                    const actualFileName = FileUtils.appendTimeToFileName(fileNameExceedingAndroidSafeLength);
+                    const expectedFileName = `${createFileNameFromLength({length: FileUtils.ANDROID_SAFE_FILE_NAME_LENGTH + 1})}-${DateUtils.getDBTime()}.doc`;
+
+                    expect(actualFileName).toEqual(expectedFileName.replace(CONST.REGEX.ILLEGAL_FILENAME_CHARACTERS, '_'));
+                });
+            });
+        });
     });
 
     describe('validateAttachment', () => {