feat(json-pack): 🎸 implement command decoding

Author: streamich

src/json-pack/resp/RespDecoder.ts

@@ -81,6 +81,25 @@ export class RespDecoder<R extends IReader & IReaderResettable = IReader & IRead
     }
   }
 
+  public readCmd(): [cmd: string, ...args: Uint8Array[]] {
+    const reader = this.reader;
+    const type = reader.u8();
+    if (type !== RESP.ARR) throw new Error('INVALID_COMMAND');
+    const c = reader.peak();
+    if (c === RESP.MINUS) throw new Error('INVALID_COMMAND');
+    const length = this.readLength();
+    if (length === 0) throw new Error('INVALID_COMMAND');
+    const cmd = this.readAsciiAsStrBulk().toUpperCase();
+    const args: [cmd: string, ...args: Uint8Array[]] = [cmd];
+    this.tryUtf8 = false;
+    for (let i = 1; i < length; i++) {
+      const type = reader.u8();
+      if (type !== RESP.STR_BULK) throw new Error('INVALID_COMMAND');
+      args.push(this.readStrBulk() as Uint8Array);
+    }
+    return args;
+  }
+
   // ---------------------------------------------------------- Boolean reading
 
   public readBool(): boolean {

src/json-pack/resp/__tests__/RespDecoder.spec.ts

@@ -3,7 +3,7 @@ import {RespDecoder} from '../RespDecoder';
 import {bufferToUint8Array} from '../../../util/buffers/bufferToUint8Array';
 import {RespAttributes, RespPush} from '../extensions';
 import {Writer} from '../../../util/buffers/Writer';
-import {Uint} from '@automerge/automerge';
+import {utf8} from '../../../util/buffers/strings';
 
 const decode = (encoded: string | Uint8Array): unknown => {
   const decoder = new RespDecoder();
@@ -215,3 +215,21 @@ describe('nulls', () => {
     expect(decoded).toBe(null);
   });
 });
+
+describe('commands', () => {
+  test('can decode a PING command', () => {
+    const encoded = encoder.encodeCmd(['PING']);
+    const decoder = new RespDecoder();
+    decoder.reader.reset(encoded);
+    const decoded = decoder.readCmd();
+    expect(decoded).toEqual(['PING']);
+  });
+
+  test('can decode a SET command', () => {
+    const encoded = encoder.encodeCmd(['SET', 'foo', 'bar']);
+    const decoder = new RespDecoder();
+    decoder.reader.reset(encoded);
+    const decoded = decoder.readCmd();
+    expect(decoded).toEqual(['SET', utf8`foo`, utf8`bar`]);
+  });
+});

src/util/buffers/strings.ts

@@ -0,0 +1,16 @@
+import {bufferToUint8Array} from "./bufferToUint8Array";
+
+export const ascii = (txt: TemplateStringsArray | string | [string]): Uint8Array => {
+  if (typeof txt === 'string') return ascii([txt]);
+  [txt] = txt;
+  const len = txt.length;
+  const res = new Uint8Array(len);
+  for (let i = 0; i < len; i++) res[i] = txt.charCodeAt(i);
+  return res;
+};
+
+export const utf8 = (txt: TemplateStringsArray | [string] | string): Uint8Array => {
+  if (typeof txt === 'string') return utf8([txt]);
+  [txt] = txt;
+  return bufferToUint8Array(Buffer.from(txt, 'utf8'));
+};