added multipath function

Author: AmosOO7

src/descriptor_handler.rs

@@ -1,6 +1,7 @@
 use crate::commands::GenerateDescriptorArgs;
 use anyhow::{anyhow, Result};
-use bdk_wallet::bitcoin::bip32::Xpriv;
+#[allow(deprecated)]
+use bdk_wallet::bitcoin::bip32::{ExtendedPubKey, Xpriv};
 use bdk_wallet::bitcoin::secp256k1::Secp256k1;
 use bdk_wallet::bitcoin::Network;
 use bdk_wallet::descriptor::Segwitv0;
@@ -76,13 +77,47 @@ pub fn generate_new_bip84_descriptor_with_mnemonic(network: Network) -> Result<s
     }))
 }
 
-fn generate_multipath_descriptor(
-    _network: &Network,
+pub fn generate_multipath_descriptor(
+    network: &Network,
     script_type: u8,
     key: &str,
-) -> Result<Value, anyhow::Error> {
-    // TODO: Implement multipath logic
-    Ok(json!({ "multipath": true, "key": key, "type": script_type }))
+) -> Result<Value> {
+    // Only BIP84 supported in this example
+    if script_type != 84 {
+        return Err(anyhow!("Only BIP84 is supported for multipath at the moment."));
+    }
+
+    #[allow(deprecated)]
+    let xpub: ExtendedPubKey = key.parse().map_err(|e| anyhow!("Invalid xpub: {e}"))?;
+
+    let derivation_path = DerivationPath::from_str("m/84h/1h/0h")?;
+    let fingerprint = xpub.fingerprint();
+
+    let make_desc = |change: u32| -> Result<(String, DescriptorPublicKey)> {
+        let branch_path = DerivationPath::from_str(&change.to_string())?;
+
+        let desc_xpub = DescriptorXKey {
+            origin: Some((fingerprint, derivation_path.clone())),
+            xkey: xpub,
+            derivation_path: branch_path,
+            wildcard: Wildcard::Unhardened,
+        };
+
+        let desc_key = DescriptorPublicKey::XPub(desc_xpub);
+        let descriptor = Descriptor::new_wpkh(desc_key.clone())?;
+        Ok((descriptor.to_string(), desc_key))
+    };
+
+    let (external_desc, _) = make_desc(0)?;
+    let (internal_desc, _) = make_desc(1)?;
+
+    Ok(json!({
+        "type": "bip84-multipath",
+        "external": external_desc,
+        "internal": internal_desc,
+        "fingerprint": fingerprint.to_string(),
+        "network": network.to_string(),
+    }))
 }
 
 fn generate_standard_descriptor(