feat: file path utility functions

Author: alpha0010

README.md

@@ -169,6 +169,23 @@ type FileStat = {
 - Write content to a file.
   - Default encoding of `data` is assumed utf8.
 
+#### Utility functions.
+
+`Util.basename(path: string, separator?: string): string`
+
+- Get the file/folder name from the end of the path.
+  - Default path `separator` is `/`.
+
+`Util.dirname(path: string, separator?: string): string`
+
+- Get the path containing the file/folder.
+  - Default path `separator` is `/`.
+
+`Util.extname(path: string, separator?: string): string`
+
+- Get the file extension.
+  - Default path `separator` is `/`.
+
 ## Testing
 
 For ease of testing, this library contains a mock implementation:

jest/react-native-file-access.ts

@@ -7,8 +7,12 @@ import type {
   FileStat,
   FsStat,
   HashAlgorithm,
+  Util as UtilFunctions,
 } from 'react-native-file-access';
 
+export const Util: typeof UtilFunctions =
+  require('react-native-file-access/lib/commonjs/util').Util;
+
 export const Dirs = {
   CacheDir: '/mock/CacheDir',
   DatabaseDir: '/mock/DatabaseDir',

src/__tests__/util.test.ts

@@ -0,0 +1,48 @@
+import { Util } from '../util';
+
+it('extracts basename', () => {
+  expect(Util.basename('')).toBe('');
+  expect(Util.basename('/')).toBe('');
+  expect(Util.basename('/abc/def')).toBe('def');
+  expect(Util.basename('abc/')).toBe('abc');
+  expect(Util.basename('abc//def/')).toBe('def');
+  expect(Util.basename('/abc.def/hij.klm')).toBe('hij.klm');
+
+  expect(Util.basename('\\abc\\def', '\\')).toBe('def');
+
+  expect(Util.basename('/abc.def/hij.klm', '$')).toBe('/abc.def/hij.klm');
+  expect(Util.basename('$abc.def$hij.klm', '$')).toBe('hij.klm');
+  expect(Util.basename('abc$$def$', '$')).toBe('def');
+
+  expect(Util.basename('abc::def:', '::')).toBe('def:');
+});
+
+it('extracts dirname', () => {
+  expect(Util.dirname('')).toBe('.');
+  expect(Util.dirname('/')).toBe('/');
+  expect(Util.dirname('/abc/def')).toBe('/abc');
+  expect(Util.dirname('abc/')).toBe('.');
+  expect(Util.dirname('abc//def/')).toBe('abc');
+  expect(Util.dirname('/abc.def/hij.klm')).toBe('/abc.def');
+  expect(Util.dirname('/ab////cd/ef/gh.ij')).toBe('/ab/cd/ef');
+
+  expect(Util.dirname('\\abc\\def', '\\')).toBe('\\abc');
+
+  expect(Util.dirname('/abc.def/hij.klm', '$')).toBe('.');
+  expect(Util.dirname('$abc.def$hij.klm', '$')).toBe('$abc.def');
+  expect(Util.dirname('abc$$def$', '$')).toBe('abc');
+
+  expect(Util.dirname('abc::def:', '::')).toBe('abc');
+});
+
+it('extracts extname', () => {
+  expect(Util.extname('')).toBe('');
+  expect(Util.extname('.hidden')).toBe('');
+  expect(Util.extname('abc/def/.hidden')).toBe('');
+  expect(Util.extname('abc.def')).toBe('def');
+  expect(Util.extname('abc.def/')).toBe('');
+  expect(Util.extname('a.b')).toBe('b');
+  expect(Util.extname('/a.b')).toBe('b');
+  expect(Util.extname('/abc/d.ef/g.hi.jkl')).toBe('jkl');
+  expect(Util.extname('/abc/def.ghi/jkl')).toBe('');
+});

src/index.ts

@@ -24,6 +24,8 @@ export type {
   HashAlgorithm,
 } from './types';
 
+export { Util } from './util';
+
 /**
  * ID tracking next fetch request.
  */

src/util.ts

@@ -0,0 +1,67 @@
+/**
+ * Escape for use as literal string in a regex.
+ */
+function regexEscape(literal: string) {
+  return literal.replace(/[\^$\\.*+?()[\]{}|]/g, '\\$&');
+}
+
+/**
+ * Condense consecutive separators.
+ */
+function normalizeSeparator(path: string, separator: string) {
+  const sepRe = new RegExp(`(${regexEscape(separator)}){2,}`, 'g');
+  return path.replace(sepRe, separator.replaceAll('$', '$$$$'));
+}
+
+/**
+ * Split path on last separator.
+ */
+function splitPath(path: string, separator: string) {
+  let norm = normalizeSeparator(path, separator);
+  if (norm === separator) {
+    return { dir: separator, base: '' };
+  }
+  if (norm.endsWith(separator)) {
+    norm = norm.substring(0, norm.length - separator.length);
+  }
+  const idx = norm.lastIndexOf(separator);
+  if (idx === -1) {
+    return { dir: '.', base: norm };
+  }
+  return {
+    dir: norm.substring(0, idx),
+    base: norm.substring(idx + separator.length),
+  };
+}
+
+export const Util = {
+  /**
+   * Get the file/folder name from the end of the path.
+   */
+  basename(path: string, separator = '/') {
+    return splitPath(path, separator).base;
+  },
+
+  /**
+   * Get the path containing the file/folder.
+   */
+  dirname(path: string, separator = '/') {
+    return splitPath(path, separator).dir;
+  },
+
+  /**
+   * Get the file extension.
+   */
+  extname(path: string, separator = '/') {
+    const extIdx = path.lastIndexOf('.');
+    if (extIdx <= 0) {
+      return '';
+    }
+
+    const sepIdx = path.lastIndexOf(separator);
+    if (sepIdx === -1 || extIdx > sepIdx + separator.length) {
+      return path.substring(extIdx + 1);
+    }
+    return '';
+  },
+};

yarn.lock

@@ -2871,9 +2871,9 @@ camelcase@^6.0.0, camelcase@^6.2.0:
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-  version "1.0.30001228"
-  resolved "https://registry.yarnpkg.com/caniuse-lite/-/caniuse-lite-1.0.30001228.tgz#bfdc5942cd3326fa51ee0b42fbef4da9d492a7fa"
-  integrity sha512-QQmLOGJ3DEgokHbMSA8cj2a+geXqmnpyOFT0lhQV6P3/YOJvGDEwoedcwxEQ30gJIwIIunHIicunJ2rzK5gB2A==
+  version "1.0.30001317"
+  resolved "https://registry.npmjs.org/caniuse-lite/-/caniuse-lite-1.0.30001317.tgz"
+  integrity sha512-xIZLh8gBm4dqNX0gkzrBeyI86J2eCjWzYAs40q88smG844YIrN4tVQl/RhquHvKEKImWWFIVh1Lxe5n1G/N+GQ==
 
 capture-exit@^2.0.0:
   version "2.0.0"