Feat/public fee estimation

package.json

@@ -1,6 +1,6 @@
 {
   "name": "@nockbox/iris-sdk",
-  "version": "0.2.0",
+  "version": "0.3.0",
   "description": "TypeScript SDK for interacting with Iris wallet extension",
   "type": "module",
   "main": "./dist/index.js",

src/constants.ts

@@ -22,6 +22,9 @@ export const PROVIDER_METHODS = {
 
   /** Sign a nockchain transaction */
   SIGN_TX: 'nock_signTx',
+
+  /** Estimate the network fee for a simple send (read-only, no approval popup) */
+  ESTIMATE_TRANSACTION_FEE: 'nock_estimateTransactionFee',
 } as const;
 
 export type ProviderMethod = (typeof PROVIDER_METHODS)[keyof typeof PROVIDER_METHODS];

src/provider.ts

@@ -15,6 +15,8 @@ import type {
   SignMessageResponse,
   ConnectRequest,
   SendTransactionRequest,
+  EstimateTransactionFeeRequest,
+  EstimateTransactionFeeResponse,
 } from './types.js';
 import { WalletNotInstalledError, UserRejectedError, RpcError, NoAccountError } from './errors.js';
 import { PROVIDER_METHODS, RPC_API_VERSION } from './constants.js';
@@ -134,6 +136,37 @@ export class NockchainProvider {
     });
   }
 
+  /**
+   * Estimate the network fee for a simple send without sending it.
+   * Read-only: requires an approved origin and unlocked wallet, but shows no approval popup.
+   * Requires API 1 (`nock_estimateTransactionFee` is not available on legacy API 0 wallets).
+   *
+   * The estimate is advisory: it depends on the wallet's current UTXO set and may
+   * drift slightly between estimation and an actual send.
+   *
+   * @param request - Recipient and amount in nicks
+   * @returns Promise resolving to the estimated fee in nicks
+   * @throws {NoAccountError} If no account is connected
+   * @throws {RpcError} If the RPC call fails (e.g. wallet locked, no UTXOs)
+   *
+   * @example
+   * ```typescript
+   * const { fee } = await provider.estimateTransactionFee({ to: recipient, amount });
+   * ```
+   */
+  async estimateTransactionFee(
+    request: EstimateTransactionFeeRequest
+  ): Promise<EstimateTransactionFeeResponse> {
+    if (!this.isConnected) {
+      throw new NoAccountError();
+    }
+
+    return this.request<EstimateTransactionFeeRequest, EstimateTransactionFeeResponse>({
+      method: PROVIDER_METHODS.ESTIMATE_TRANSACTION_FEE,
+      params: request,
+    });
+  }
+
   /**
    * Sign an arbitrary message with the current account
    * @param message - The message to sign

src/types.ts

@@ -83,10 +83,27 @@ export interface SendTransactionRequest {
   to: Address;
   /** Amount to send in nicks (legacy number + canonical string/bigint accepted) */
   amount: Nicks;
-  /** Transaction fee in nicks (legacy number + canonical string/bigint accepted) */
+  /**
+   * Transaction fee in nicks (legacy number + canonical string/bigint accepted).
+   * Optional: when omitted, the wallet estimates the fee, shows it in the approval
+   * popup, and auto-calculates the exact fee at build time. The send response
+   * reports the actual fee used.
+   */
   fee?: Nicks;
 }
 
+export interface EstimateTransactionFeeRequest {
+  /** Recipient address (base58-encoded public key hash / PKH) */
+  to: Address;
+  /** Amount to send in nicks (legacy number + canonical string/bigint accepted) */
+  amount: Nicks;
+}
+
+export interface EstimateTransactionFeeResponse {
+  /** Estimated fee in nicks (canonical string) */
+  fee: Nicks;
+}
+
 export interface SignTxRequest {
   tx: NockchainTx;
   /**