feat(wasm-utxo): add PSBT introspection methods to BitGoPsbt

Implement PSBT introspection interface for BitGoPsbt class with methods
to examine inputs and outputs. Add utility interfaces for common PSBT
introspection methods and re-export PSBT data types for consumer use.

Issue: BTC-2650

Co-authored-by: llm-git <llm-git@ttll.de>

Author: OttoAllmendinger

packages/wasm-utxo/js/fixedScriptWallet/BitGoPsbt.ts

@@ -1,4 +1,10 @@
-import { BitGoPsbt as WasmBitGoPsbt } from "../wasm/wasm_utxo.js";
+import {
+  BitGoPsbt as WasmBitGoPsbt,
+  type PsbtInputData,
+  type PsbtOutputData,
+  type PsbtOutputDataWithAddress,
+} from "../wasm/wasm_utxo.js";
+import type { IPsbtIntrospectionWithAddress } from "../psbt.js";
 import { type WalletKeysArg, RootWalletKeys } from "./RootWalletKeys.js";
 import { type ReplayProtectionArg, ReplayProtection } from "./ReplayProtection.js";
 import { type BIP32Arg, BIP32, isBIP32Arg } from "../bip32.js";
@@ -109,7 +115,7 @@ export type AddWalletOutputOptions = {
   value: bigint;
 };
 
-export class BitGoPsbt {
+export class BitGoPsbt implements IPsbtIntrospectionWithAddress {
   protected constructor(protected _wasm: WasmBitGoPsbt) {}
 
   /**
@@ -806,4 +812,65 @@ export class BitGoPsbt {
   getHalfSignedLegacyFormat(): Uint8Array {
     return this._wasm.extract_half_signed_legacy_tx();
   }
+
+  /**
+   * Get the number of inputs in the PSBT
+   * @returns The number of inputs
+   */
+  get inputCount(): number {
+    return this._wasm.input_count();
+  }
+
+  /**
+   * Get the number of outputs in the PSBT
+   * @returns The number of outputs
+   */
+  get outputCount(): number {
+    return this._wasm.output_count();
+  }
+
+  /**
+   * Get all PSBT inputs as an array
+   *
+   * Returns raw PSBT input data including witness_utxo and derivation info.
+   * For parsed transaction data with address identification, use
+   * parseTransactionWithWalletKeys() instead.
+   *
+   * @returns Array of PsbtInputData objects
+   */
+  getInputs(): PsbtInputData[] {
+    return this._wasm.get_inputs() as PsbtInputData[];
+  }
+
+  /**
+   * Get all PSBT outputs as an array
+   *
+   * Returns raw PSBT output data without address resolution.
+   * For output data with addresses, use getOutputsWithAddress().
+   *
+   * @returns Array of PsbtOutputData objects
+   */
+  getOutputs(): PsbtOutputData[] {
+    return this._wasm.get_outputs() as PsbtOutputData[];
+  }
+
+  /**
+   * Get all PSBT outputs with resolved address strings
+   *
+   * Unlike the generic Psbt class which requires a coin parameter,
+   * BitGoPsbt automatically uses the network it was created with to resolve addresses.
+   *
+   * @returns Array of PsbtOutputDataWithAddress objects
+   *
+   * @example
+   * ```typescript
+   * const outputs = psbt.getOutputsWithAddress();
+   * for (const output of outputs) {
+   *   console.log(`${output.address}: ${output.value} satoshis`);
+   * }
+   * ```
+   */
+  getOutputsWithAddress(): PsbtOutputDataWithAddress[] {
+    return this._wasm.get_outputs_with_address() as PsbtOutputDataWithAddress[];
+  }
 }

packages/wasm-utxo/js/fixedScriptWallet/index.ts

@@ -37,6 +37,15 @@ export {
   type CreateEmptyZcashOptions,
 } from "./ZcashBitGoPsbt.js";
 
+// PSBT introspection types (re-exported for consumer convenience)
+export type {
+  PsbtBip32Derivation,
+  PsbtInputData,
+  PsbtOutputData,
+  PsbtOutputDataWithAddress,
+  PsbtWitnessUtxo,
+} from "../wasm/wasm_utxo.js";
+
 import type { ScriptType } from "./scriptType.js";
 
 /**

packages/wasm-utxo/js/index.ts

@@ -130,4 +130,8 @@ export { WrapDescriptor as Descriptor } from "./wasm/wasm_utxo.js";
 export { WrapMiniscript as Miniscript } from "./wasm/wasm_utxo.js";
 export { WrapPsbt as Psbt } from "./wasm/wasm_utxo.js";
 export { DashTransaction, Transaction, ZcashTransaction } from "./transaction.js";
-export { hasPsbtMagic } from "./psbt.js";
+export {
+  hasPsbtMagic,
+  type IPsbtIntrospection,
+  type IPsbtIntrospectionWithAddress,
+} from "./psbt.js";

packages/wasm-utxo/js/psbt.ts

@@ -1,3 +1,18 @@
+import type { PsbtInputData, PsbtOutputData, PsbtOutputDataWithAddress } from "./wasm/wasm_utxo.js";
+
+/** Common interface for PSBT introspection methods */
+export interface IPsbtIntrospection {
+  readonly inputCount: number;
+  readonly outputCount: number;
+  getInputs(): PsbtInputData[];
+  getOutputs(): PsbtOutputData[];
+}
+
+/** Extended introspection with address resolution (no coin parameter needed) */
+export interface IPsbtIntrospectionWithAddress extends IPsbtIntrospection {
+  getOutputsWithAddress(): PsbtOutputDataWithAddress[];
+}
+
 /** PSBT magic bytes: "psbt" (0x70 0x73 0x62 0x74) followed by separator 0xff */
 const PSBT_MAGIC = new Uint8Array([0x70, 0x73, 0x62, 0x74, 0xff]);
 

packages/wasm-utxo/src/wasm/fixed_script_wallet/mod.rs

@@ -628,6 +628,40 @@ impl BitGoPsbt {
         }
     }
 
+    /// Get the number of inputs in the PSBT
+    pub fn input_count(&self) -> usize {
+        self.psbt.psbt().inputs.len()
+    }
+
+    /// Get the number of outputs in the PSBT
+    pub fn output_count(&self) -> usize {
+        self.psbt.psbt().outputs.len()
+    }
+
+    /// Get all PSBT inputs as an array of PsbtInputData
+    ///
+    /// Returns an array with witness_utxo, bip32_derivation, and tap_bip32_derivation
+    /// for each input.
+    pub fn get_inputs(&self) -> Result<JsValue, WasmUtxoError> {
+        crate::wasm::psbt::get_inputs_from_psbt(self.psbt.psbt())
+    }
+
+    /// Get all PSBT outputs as an array of PsbtOutputData
+    ///
+    /// Returns an array with script, value, bip32_derivation, and tap_bip32_derivation
+    /// for each output.
+    pub fn get_outputs(&self) -> Result<JsValue, WasmUtxoError> {
+        crate::wasm::psbt::get_outputs_from_psbt(self.psbt.psbt())
+    }
+
+    /// Get all PSBT outputs with resolved address strings.
+    ///
+    /// Unlike the generic WrapPsbt which requires a coin parameter, BitGoPsbt
+    /// uses the network it was created/deserialized with to resolve addresses.
+    pub fn get_outputs_with_address(&self) -> Result<JsValue, WasmUtxoError> {
+        crate::wasm::psbt::get_outputs_with_address_from_psbt(self.psbt.psbt(), self.psbt.network())
+    }
+
     /// Parse transaction with wallet keys to identify wallet inputs/outputs
     pub fn parse_transaction_with_wallet_keys(
         &self,

packages/wasm-utxo/src/wasm/psbt.rs

@@ -203,6 +203,46 @@ impl PsbtOutputDataWithAddress {
     }
 }
 
+// ============================================================================
+// Helper functions for PSBT introspection - shared by WrapPsbt and BitGoPsbt
+// ============================================================================
+
+/// Get all PSBT inputs as an array of PsbtInputData
+pub fn get_inputs_from_psbt(psbt: &Psbt) -> Result<JsValue, WasmUtxoError> {
+    let inputs: Vec<PsbtInputData> = psbt.inputs.iter().map(PsbtInputData::from).collect();
+    inputs.try_to_js_value()
+}
+
+/// Get all PSBT outputs as an array of PsbtOutputData
+pub fn get_outputs_from_psbt(psbt: &Psbt) -> Result<JsValue, WasmUtxoError> {
+    let outputs: Vec<PsbtOutputData> = psbt
+        .unsigned_tx
+        .output
+        .iter()
+        .zip(psbt.outputs.iter())
+        .map(|(tx_out, psbt_out)| PsbtOutputData::from(tx_out, psbt_out))
+        .collect();
+    outputs.try_to_js_value()
+}
+
+/// Get all PSBT outputs with resolved address strings
+pub fn get_outputs_with_address_from_psbt(
+    psbt: &Psbt,
+    network: crate::Network,
+) -> Result<JsValue, WasmUtxoError> {
+    let outputs: Vec<PsbtOutputDataWithAddress> = psbt
+        .unsigned_tx
+        .output
+        .iter()
+        .zip(psbt.outputs.iter())
+        .map(|(tx_out, psbt_out)| {
+            let base = PsbtOutputData::from(tx_out, psbt_out);
+            PsbtOutputDataWithAddress::from(base, network)
+        })
+        .collect::<Result<Vec<_>, _>>()?;
+    outputs.try_to_js_value()
+}
+
 #[wasm_bindgen]
 pub struct WrapPsbt(Psbt);
 
@@ -585,8 +625,7 @@ impl WrapPsbt {
     /// for each input. This is useful for introspecting the PSBT structure.
     #[wasm_bindgen(js_name = getInputs)]
     pub fn get_inputs(&self) -> Result<JsValue, WasmUtxoError> {
-        let inputs: Vec<PsbtInputData> = self.0.inputs.iter().map(PsbtInputData::from).collect();
-        inputs.try_to_js_value()
+        get_inputs_from_psbt(&self.0)
     }
 
     /// Get all PSBT outputs as an array of PsbtOutputData
@@ -595,15 +634,7 @@ impl WrapPsbt {
     /// for each output. This is useful for introspecting the PSBT structure.
     #[wasm_bindgen(js_name = getOutputs)]
     pub fn get_outputs(&self) -> Result<JsValue, WasmUtxoError> {
-        let outputs: Vec<PsbtOutputData> = self
-            .0
-            .unsigned_tx
-            .output
-            .iter()
-            .zip(self.0.outputs.iter())
-            .map(|(tx_out, psbt_out)| PsbtOutputData::from(tx_out, psbt_out))
-            .collect();
-        outputs.try_to_js_value()
+        get_outputs_from_psbt(&self.0)
     }
 
     /// Get all PSBT outputs with resolved address strings.
@@ -614,18 +645,7 @@ impl WrapPsbt {
     pub fn get_outputs_with_address(&self, coin: &str) -> Result<JsValue, WasmUtxoError> {
         let network = crate::Network::from_coin_name(coin)
             .ok_or_else(|| WasmUtxoError::new(&format!("Unknown coin: {}", coin)))?;
-        let outputs: Vec<PsbtOutputDataWithAddress> = self
-            .0
-            .unsigned_tx
-            .output
-            .iter()
-            .zip(self.0.outputs.iter())
-            .map(|(tx_out, psbt_out)| {
-                let base = PsbtOutputData::from(tx_out, psbt_out);
-                PsbtOutputDataWithAddress::from(base, network)
-            })
-            .collect::<Result<Vec<_>, _>>()?;
-        outputs.try_to_js_value()
+        get_outputs_with_address_from_psbt(&self.0, network)
     }
 
     /// Get partial signatures for an input