fix: align MuxedAccount decoding and C-address routing compliance

packages/core-ts/src/muxed/decode.ts

@@ -1,87 +1,20 @@
-import { StrKey } from "@stellar/stellar-sdk";
-
-const BASE32_CHARS = "ABCDEFGHIJKLMNOPQRSTUVWXYZ234567";
-
-/**
- * Decodes a Base32-encoded string into binary data.
- * @internal
- */
-function decodeBase32(input: string): Uint8Array {
-  const s = input.toUpperCase().replace(/=+$/, "");
-  const byteCount = Math.floor((s.length * 5) / 8);
-  const result = new Uint8Array(byteCount);
-  let buffer = 0;
-  let bitsLeft = 0;
-  let byteIndex = 0;
-  for (const ch of s) {
-    const value = BASE32_CHARS.indexOf(ch);
-    if (value === -1) throw new Error(`Invalid base32 character: ${ch}`);
-    buffer = (buffer << 5) | value;
-    bitsLeft += 5;
-    if (bitsLeft >= 8) {
-      if (byteIndex < byteCount) {
-        result[byteIndex++] = (buffer >> (bitsLeft - 8)) & 0xff;
-      }
-      bitsLeft -= 8;
-    }
-  }
-  return result;
-}
-
-/**
- * Computes a 16-bit CRC (CCITT-FALSE).
- * @internal
- */
-function crc16(bytes: Uint8Array): number {
-  let crc = 0;
-  for (const byte of bytes) {
-    crc ^= byte << 8;
-    for (let i = 0; i < 8; i++) {
-      crc = crc & 0x8000 ? (crc << 1) ^ 0x1021 : crc << 1;
-    }
-  }
-  return crc & 0xffff;
-}
-
-/**
- * Validates and decodes a Stellar StrKey string.
- * @internal
- */
-function decodeStrKey(address: string): Uint8Array {
-  const up = address.toUpperCase();
-  const decoded = decodeBase32(up);
-  if (decoded.length < 3) throw new Error("invalid encoded string");
-
-  const data = decoded.slice(0, decoded.length - 2);
-  const checksum =
-    decoded[decoded.length - 2] | (decoded[decoded.length - 1] << 8);
-  const computed = crc16(data);
-  if (computed !== checksum) throw new Error("invalid checksum");
-
-  return data;
-}
+import { MuxedAccount } from "@stellar/stellar-sdk";
 
 /**
  * Decodes a muxed Stellar address (SEP-23) into its base account and ID.
- * The payload is expected to be [Version(1)] [Pubkey(32)] [ID(8)].
+ * Uses the official Stellar SDK MuxedAccount parser to ensure specification compliance.
  * 
  * @param mAddress - The muxed address string starting with 'M'.
  * @returns Metadata containing the base G address and the 64-bit BigInt ID.
+ * @throws {Error} If the address is not a valid muxed address.
  */
 export function decodeMuxed(mAddress: string): { baseG: string; id: bigint } {
-  const data = decodeStrKey(mAddress);
-  if (data.length !== 41) throw new Error("invalid payload length");
-
-  const pubkey = data.slice(1, 33);
-  const idBytes = data.slice(33, 41);
-
-  let id = 0n;
-  for (const byte of idBytes) {
-    id = (id << 8n) + BigInt(byte);
-  }
+  // MuxedAccount.fromAddress requires a sequence number. Since this is an
+  // offline decoding of the address parts, we provide a placeholder.
+  const muxed = MuxedAccount.fromAddress(mAddress, "0");
 
   return {
-    baseG: StrKey.encodeEd25519PublicKey(Buffer.from(pubkey)),
-    id: id,
+    baseG: muxed.baseAccount().accountId(),
+    id: BigInt(muxed.id()),
   };
 }

packages/core-ts/src/routing/extract.ts

@@ -77,10 +77,12 @@ export function extractRouting(input: RoutingInput): RoutingResult {
     const warnings: Warning[] = [...parsed.warnings];
 
     warnings.push({
-      code: "CONTRACT_SENDER_DETECTED",
-      severity: "warn",
-      message:
-        "Contract address detected. Contract addresses cannot be used as transaction senders.",
+      code: "INVALID_DESTINATION",
+      severity: "error",
+      message: "C address is not a valid destination",
+      context: {
+        destinationKind: "C",
+      },
     });
 
     return {