chore: import upstream snapshot with attribution

open-sse/shared/qoder/encoding.js

@@ -0,0 +1,55 @@
+/**
+ * Qoder body encoding ported from qoder2api's QoderEncoding.java (via the
+ * CLIProxyAPIPlus qoder-provider branch).
+ *
+ * Algorithm:
+ *   1. base64-encode the plaintext bytes (standard alphabet).
+ *   2. Rearrange: split into thirds, reorder as [tail][mid][head].
+ *   3. Substitute each character via a custom alphabet mapping.
+ *
+ * The encoded body must be sent with `&Encode=1` appended to the URL so the
+ * server decodes in reverse. The obfuscation prevents Alibaba Cloud WAF from
+ * pattern-matching the plaintext request body.
+ */
+
+const QODER_STD_ALPHABET = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
+const QODER_CUSTOM_ALPHABET = "_doRTgHZBKcGVjlvpC,@aFSx#DPuNJme&i*MzLOEn)sUrthbf%Y^w.(kIQyXqWA!";
+
+const QODER_S2C = (() => {
+  const table = new Int16Array(128).fill(-1);
+  for (let i = 0; i < 64; i++) {
+    table[QODER_STD_ALPHABET.charCodeAt(i)] = QODER_CUSTOM_ALPHABET.charCodeAt(i);
+  }
+  table["=".charCodeAt(0)] = "$".charCodeAt(0);
+  return table;
+})();
+
+/**
+ * Encode plaintext bytes/string using Qoder's WAF-bypass scheme.
+ * @param {Buffer|Uint8Array|string} plaintext
+ * @returns {string} encoded string
+ */
+export function qoderEncodeBody(plaintext) {
+  const buf = Buffer.isBuffer(plaintext)
+    ? plaintext
+    : typeof plaintext === "string"
+      ? Buffer.from(plaintext, "utf8")
+      : Buffer.from(plaintext);
+
+  const std = buf.toString("base64");
+  const n = std.length;
+  const a = Math.floor(n / 3);
+  // [tail][mid][head]
+  const rearranged = std.slice(n - a) + std.slice(a, n - a) + std.slice(0, a);
+
+  const out = Buffer.alloc(n);
+  for (let i = 0; i < n; i++) {
+    const c = rearranged.charCodeAt(i);
+    if (c < 128 && QODER_S2C[c] >= 0) {
+      out[i] = QODER_S2C[c];
+    } else {
+      out[i] = c;
+    }
+  }
+  return out.toString("latin1");
+}