add docs

README.md

@@ -1,3 +1,50 @@
 # RClone Crypt
 
-RClone Crypt algorithm implemented in TypeScript/JavaScript.
+RClone Crypt algorithm subset implemented in TypeScript/JavaScript. 
+
+This is basically some line-to-line translations of [`rclone/backend/crypt/cipher.go`](https://github.com/rclone/rclone/blob/master/backend/crypt/cipher.go) and [`rclone/backend/crypt/cipher_test.go`](https://github.com/rclone/rclone/blob/master/backend/crypt/cipher_test.go), with limited features.
+
+# Why
+
+Because I'd like to encrypt files using widely-used rclone format in TypeScript/JavaScript.
+
+# Usage
+
+```bash
+npm install @fyears/rclone-crypt
+```
+
+```typescript
+
+import { Cipher } from './dist/index.js';
+import { deepStrictEqual } from "assert";
+
+(async function(){
+    const password = "custom-password";
+    const salt = "custom-salt";
+    const cipher = new Cipher();
+    await cipher.key(password, salt);
+
+    const fileName = "custom-dir/custom-filename";
+    const encFileName = await cipher.encryptFileName(fileName);
+    console.log(encFileName);
+    const recoveredFileName = await cipher.decryptFileName(encFileName);
+    console.log(recoveredFileName);
+    deepStrictEqual(fileName, recoveredFileName);
+
+    const fileContent = new Uint8Array([1,2,3,4,5]); // user provided
+    const encFileContent = await cipher.encryptData(fileContent);
+    console.log(encFileContent);
+    const recoveredFileContent = await cipher.decryptData(encFileContent);
+    console.log(recoveredFileContent);
+    deepStrictEqual(fileContent, recoveredFileContent);
+})();
+```
+
+# Features
+
+* [x] file name encryption/decryption
+* [x] file content encryption
+* [x] many tests
+* [ ] streaming encryption/decryption
+* [ ] ~~file name obfuscate (not planned)~~