feat(docs): add guide for detecting if address is a smart account (#1259)

Author: fassko

docs/smart-accounts/guides/typescript-viem/01-state-lookup.mdx

@@ -23,6 +23,7 @@ import YouTubeEmbed from "@site/src/components/YouTubeEmbed";
 In this guide, you will learn how to get the following using the Viem TypeScript library:
 
 - the Flare address that corresponds to an XRPL account
+- whether a Flare address is a smart account
 - the total value of FXRP that belongs to a personal account tied to an XRPL address
 - a list of all the registered vaults
 - the total value of FXRP of a personal account, in each of the registered vaults
@@ -131,6 +132,33 @@ export async function getContractAddressByName(name: string) {
 }
 ```
 
+## Checking if a Flare address is a smart account
+
+A Flare address is a smart account (PersonalAccount) if calling the `xrplOwner()` function on it returns an XRPL account using the [`IPersonalAccount`](/smart-accounts/reference/IPersonalAccount) interface.
+The `PersonalAccount` contract exposes the `xrplOwner()` function — the XRPL address that controls it.
+If the call succeeds and returns a non-empty and valid XRPL address, the address is a smart account.
+
+```typescript
+export async function getXrplAccountForAddress(
+  evmAddress: Address,
+): Promise<`0x${string}`> {
+  const xrplOwner = await publicClient.readContract({
+    address: evmAddress,
+    abi: coston2.iPersonalAccountAbi,
+    functionName: "xrplOwner",
+    args: [],
+  });
+  return xrplOwner && xrplOwner.length > 0
+    ? evmAddress
+    : "0x0000000000000000000000000000000000000000";
+}
+
+export async function isSmartAccount(evmAddress: Address): Promise<boolean> {
+  const smartAccountAddress = await getXrplAccountForAddress(evmAddress);
+  return smartAccountAddress !== "0x0000000000000000000000000000000000000000";
+}
+```
+
 ## Personal account of an XRPL address
 
 There are many situations when it is important or even necessary to know the address of the `PersonalAccount` of an XRPL address;

docs/smart-accounts/reference/IPersonalAccount.mdx

@@ -21,6 +21,11 @@ Returns the XRPL owner address associated with this personal account.
 function xrplOwner() external view returns (string memory);
 ```
 
+:::tip Smart account detection
+If a contract at a given Flare address returns an XRPL account when the `xrplOwner()` function is called, then it is a smart account.
+Use this to [detect whether an arbitrary Flare address is a smart account](/smart-accounts/guides/typescript-viem/state-lookup-ts#checking-if-a-flare-address-is-a-smart-account).
+:::
+
 ### `controllerAddress`
 
 Returns the `MasterAccountController` address that manages this personal account.