feat: include DashTx.utils.rpc(basicAuthUrl, method, arg1, arg2, ...)

Author: coolaj86

README.md

@@ -396,6 +396,9 @@ Tx.appraise({ inputs, outputs });
 
 Tx.parseUnknown(serializedHex);
 
+// RPC, for 'sendrawtransaction' broadcast
+Tx.utils.rpc(basicAuthUrl, method, arg1, arg2, ...);
+
 // Byte-level helpers
 Tx.utils.toVarInt(n);
 Tx.utils.toVarIntSize(n);
@@ -573,6 +576,19 @@ Tx.doubleSha256(txBytes);
 Tx.parseUnknown(serializedHex);
 ```
 
+### RPC Helper
+
+```js
+/**
+ * Make RPC calls to a web service, masternode, or full node
+ *
+ * ex:
+ *   - https://api:[email protected]/
+ *   - http://user:pass@localhost:19998/wallet/foo
+ */
+Tx.utils.rpc(basicAuthUrl, method, arg1, arg2, ...);
+```
+
 ### Utility Functions
 
 ```js

dashtx.js

@@ -1691,6 +1691,40 @@ var DashTx = ("object" === typeof module && exports) || {};
     }
   }
 
+  /**
+   * @param {String} basicAuthUrl - ex: https://api:[email protected]/
+   *                                    http://user:pass@localhost:19998/
+   * @param {String} method - the rpc, such as 'getblockchaininfo',
+   *                          'getaddressdeltas', or 'help'
+   * @param {...any} params - the arguments for the specific rpc
+   *                          ex: rpc(url, 'help', 'getaddressdeltas')
+   */
+  TxUtils.rpc = async function rpc(basicAuthUrl, method, ...params) {
+    let url = new URL(basicAuthUrl);
+    let baseUrl = `${url.protocol}//${url.host}${url.pathname}`;
+    let basicAuth = btoa(`${url.username}:${url.password}`);
+
+    // typically http://localhost:19998/
+    let payload = JSON.stringify({ method, params });
+    let resp = await fetch(baseUrl, {
+      method: "POST",
+      headers: {
+        Authorization: `Basic ${basicAuth}`,
+        "Content-Type": "application/json",
+      },
+      body: payload,
+    });
+
+    let data = await resp.json();
+    if (data.error) {
+      let err = new Error(data.error.message);
+      Object.assign(err, data.error);
+      throw err;
+    }
+
+    return data.result;
+  };
+
   /**
    * @param {String} hex
    */