first commit

packages/pubsub/src/resp.ts

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+/**
+ * Minimal RESP (REdis Serialization Protocol) codec — just enough to drive
+ * Redis pub/sub over a raw TCP socket, with no external client dependency.
+ *
+ * Encodes commands as arrays of bulk strings, and streaming-parses the replies
+ * we care about: simple strings (+), errors (-), integers (:), bulk strings ($),
+ * and arrays (*) — which is what SUBSCRIBE/PSUBSCRIBE confirmations and
+ * message/pmessage pushes are made of.
+ */
+
+export type RespValue = string | number | null | RespValue[];
+
+const encoder = new TextEncoder();
+const decoder = new TextDecoder();
+
+/** Encode a command (`["PUBLISH", topic, payload]`) as a RESP array of bulk strings. */
+export function encodeCommand(args: string[]): Uint8Array {
+  let head = `*${args.length}\r\n`;
+  const parts: Uint8Array[] = [];
+  for (const arg of args) {
+    const bytes = encoder.encode(arg);
+    head += `$${bytes.length}\r\n`;
+    parts.push(encoder.encode(head), bytes, encoder.encode("\r\n"));
+    head = "";
+  }
+  return concat(parts);
+}
+
+/** Concatenate byte arrays. */
+export function concat(parts: Uint8Array[]): Uint8Array {
+  let len = 0;
+  for (const p of parts) len += p.length;
+  const out = new Uint8Array(len);
+  let off = 0;
+  for (const p of parts) {
+    out.set(p, off);
+    off += p.length;
+  }
+  return out;
+}
+
+function indexOfCRLF(buf: Uint8Array, from: number): number {
+  for (let i = from; i + 1 < buf.length; i++) {
+    if (buf[i] === 13 && buf[i + 1] === 10) return i;
+  }
+  return -1;
+}
+
+/**
+ * Parse one RESP reply from `buf` at `off`. Returns the value and the offset just
+ * past it, or `null` if the buffer doesn't yet hold a complete reply (caller
+ * should wait for more bytes).
+ */
+export function parseReply(buf: Uint8Array, off = 0): { value: RespValue; next: number } | null {
+  if (off >= buf.length) return null;
+  const type = buf[off];
+  const lineEnd = indexOfCRLF(buf, off + 1);
+  if (lineEnd === -1) return null;
+  const line = decoder.decode(buf.subarray(off + 1, lineEnd));
+  const after = lineEnd + 2;
+
+  switch (type) {
+    case 43: // '+' simple string
+    case 45: // '-' error
+      return { value: line, next: after };
+    case 58: // ':' integer
+      return { value: Number(line), next: after };
+    case 36: {
+      // '$' bulk string
+      const len = Number(line);
+      if (len === -1) return { value: null, next: after };
+      if (after + len + 2 > buf.length) return null;
+      return { value: decoder.decode(buf.subarray(after, after + len)), next: after + len + 2 };
+    }
+    case 42: {
+      // '*' array
+      const count = Number(line);
+      if (count === -1) return { value: null, next: after };
+      const arr: RespValue[] = [];
+      let cur = after;
+      for (let i = 0; i < count; i++) {
+        const r = parseReply(buf, cur);
+        if (!r) return null;
+        arr.push(r.value);
+        cur = r.next;
+      }
+      return { value: arr, next: cur };
+    }
+    default:
+      return null;
+  }
+}