Refactor transaction creation and transaction funding logic

In preparation for more create transaction and fund transcation RPCs,
refactor the transaction creation and funding logic into separate
functions.

2 files changed, 73 insertions, 64 deletions

diff --git a/src/rpc/rawtransaction.cpp b/src/rpc/rawtransaction.cpp
index 63548bff05..c27601e47f 100644
--- a/src/rpc/rawtransaction.cpp
+++ b/src/rpc/rawtransaction.cpp
@@ -332,80 +332,25 @@ static UniValue verifytxoutproof(const JSONRPCRequest& request)
     return res;
 }
 
-static UniValue createrawtransaction(const JSONRPCRequest& request)
+CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniValue& outputs_in, const UniValue& locktime, const UniValue& rbf)
 {
-    if (request.fHelp || request.params.size() < 2 || request.params.size() > 4) {
-        throw std::runtime_error(
-            // clang-format off
-            "createrawtransaction [{\"txid\":\"id\",\"vout\":n},...] [{\"address\":amount},{\"data\":\"hex\"},...] ( locktime ) ( replaceable )\n"
-            "\nCreate a transaction spending the given inputs and creating new outputs.\n"
-            "Outputs can be addresses or data.\n"
-            "Returns hex-encoded raw transaction.\n"
-            "Note that the transaction's inputs are not signed, and\n"
-            "it is not stored in the wallet or transmitted to the network.\n"
-
-            "\nArguments:\n"
-            "1. \"inputs\"                (array, required) A json array of json objects\n"
-            "     [\n"
-            "       {\n"
-            "         \"txid\":\"id\",      (string, required) The transaction id\n"
-            "         \"vout\":n,         (numeric, required) The output number\n"
-            "         \"sequence\":n      (numeric, optional) The sequence number\n"
-            "       } \n"
-            "       ,...\n"
-            "     ]\n"
-            "2. \"outputs\"               (array, required) a json array with outputs (key-value pairs)\n"
-            "   [\n"
-            "    {\n"
-            "      \"address\": x.xxx,    (obj, optional) A key-value pair. The key (string) is the bitcoin address, the value (float or string) is the amount in " + CURRENCY_UNIT + "\n"
-            "    },\n"
-            "    {\n"
-            "      \"data\": \"hex\"        (obj, optional) A key-value pair. The key must be \"data\", the value is hex encoded data\n"
-            "    }\n"
-            "    ,...                     More key-value pairs of the above form. For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
-            "                             accepted as second parameter.\n"
-            "   ]\n"
-            "3. locktime                  (numeric, optional, default=0) Raw locktime. Non-0 value also locktime-activates inputs\n"
-            "4. replaceable               (boolean, optional, default=false) Marks this transaction as BIP125 replaceable.\n"
-            "                             Allows this transaction to be replaced by a transaction with higher fees. If provided, it is an error if explicit sequence numbers are incompatible.\n"
-            "\nResult:\n"
-            "\"transaction\"              (string) hex string of the transaction\n"
-
-            "\nExamples:\n"
-            + HelpExampleCli("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"address\\\":0.01}]\"")
-            + HelpExampleCli("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
-            + HelpExampleRpc("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\", \"[{\\\"address\\\":0.01}]\"")
-            + HelpExampleRpc("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\", \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
-            // clang-format on
-        );
-    }
-
-    RPCTypeCheck(request.params, {
-        UniValue::VARR,
-        UniValueType(), // ARR or OBJ, checked later
-        UniValue::VNUM,
-        UniValue::VBOOL
-        }, true
-    );
-    if (request.params[0].isNull() || request.params[1].isNull())
+    if (inputs_in.isNull() || outputs_in.isNull())
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, arguments 1 and 2 must be non-null");
 
-    UniValue inputs = request.params[0].get_array();
-    const bool outputs_is_obj = request.params[1].isObject();
-    UniValue outputs = outputs_is_obj ?
-                           request.params[1].get_obj() :
-                           request.params[1].get_array();
+    UniValue inputs = inputs_in.get_array();
+    const bool outputs_is_obj = outputs_in.isObject();
+    UniValue outputs = outputs_is_obj ? outputs_in.get_obj() : outputs_in.get_array();
 
     CMutableTransaction rawTx;
 
-    if (!request.params[2].isNull()) {
-        int64_t nLockTime = request.params[2].get_int64();
+    if (!locktime.isNull()) {
+        int64_t nLockTime = locktime.get_int64();
         if (nLockTime < 0 || nLockTime > std::numeric_limits<uint32_t>::max())
             throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter, locktime out of range");
         rawTx.nLockTime = nLockTime;
     }
 
-    bool rbfOptIn = request.params[3].isTrue();
+    bool rbfOptIn = rbf.isTrue();
 
     for (unsigned int idx = 0; idx < inputs.size(); idx++) {
         const UniValue& input = inputs[idx];
@@ -485,10 +430,71 @@ static UniValue createrawtransaction(const JSONRPCRequest& request)
         }
     }
 
-    if (!request.params[3].isNull() && rbfOptIn != SignalsOptInRBF(rawTx)) {
+    if (!rbf.isNull() && rbfOptIn != SignalsOptInRBF(rawTx)) {
         throw JSONRPCError(RPC_INVALID_PARAMETER, "Invalid parameter combination: Sequence number(s) contradict replaceable option");
     }
 
+    return rawTx;
+}
+
+static UniValue createrawtransaction(const JSONRPCRequest& request)
+{
+    if (request.fHelp || request.params.size() < 2 || request.params.size() > 4) {
+        throw std::runtime_error(
+            // clang-format off
+            "createrawtransaction [{\"txid\":\"id\",\"vout\":n},...] [{\"address\":amount},{\"data\":\"hex\"},...] ( locktime ) ( replaceable )\n"
+            "\nCreate a transaction spending the given inputs and creating new outputs.\n"
+            "Outputs can be addresses or data.\n"
+            "Returns hex-encoded raw transaction.\n"
+            "Note that the transaction's inputs are not signed, and\n"
+            "it is not stored in the wallet or transmitted to the network.\n"
+
+            "\nArguments:\n"
+            "1. \"inputs\"                (array, required) A json array of json objects\n"
+            "     [\n"
+            "       {\n"
+            "         \"txid\":\"id\",      (string, required) The transaction id\n"
+            "         \"vout\":n,         (numeric, required) The output number\n"
+            "         \"sequence\":n      (numeric, optional) The sequence number\n"
+            "       } \n"
+            "       ,...\n"
+            "     ]\n"
+            "2. \"outputs\"               (array, required) a json array with outputs (key-value pairs)\n"
+            "   [\n"
+            "    {\n"
+            "      \"address\": x.xxx,    (obj, optional) A key-value pair. The key (string) is the bitcoin address, the value (float or string) is the amount in " + CURRENCY_UNIT + "\n"
+            "    },\n"
+            "    {\n"
+            "      \"data\": \"hex\"        (obj, optional) A key-value pair. The key must be \"data\", the value is hex encoded data\n"
+            "    }\n"
+            "    ,...                     More key-value pairs of the above form. For compatibility reasons, a dictionary, which holds the key-value pairs directly, is also\n"
+            "                             accepted as second parameter.\n"
+            "   ]\n"
+            "3. locktime                  (numeric, optional, default=0) Raw locktime. Non-0 value also locktime-activates inputs\n"
+            "4. replaceable               (boolean, optional, default=false) Marks this transaction as BIP125 replaceable.\n"
+            "                             Allows this transaction to be replaced by a transaction with higher fees. If provided, it is an error if explicit sequence numbers are incompatible.\n"
+            "\nResult:\n"
+            "\"transaction\"              (string) hex string of the transaction\n"
+
+            "\nExamples:\n"
+            + HelpExampleCli("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"address\\\":0.01}]\"")
+            + HelpExampleCli("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\" \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+            + HelpExampleRpc("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\", \"[{\\\"address\\\":0.01}]\"")
+            + HelpExampleRpc("createrawtransaction", "\"[{\\\"txid\\\":\\\"myid\\\",\\\"vout\\\":0}]\", \"[{\\\"data\\\":\\\"00010203\\\"}]\"")
+            // clang-format on
+        );
+    }
+
+    RPCTypeCheck(request.params, {
+        UniValue::VARR,
+        UniValueType(), // ARR or OBJ, checked later
+        UniValue::VNUM,
+        UniValue::VBOOL
+        }, true
+    );
+
+    CMutableTransaction rawTx = ConstructTransaction(request.params[0], request.params[1], request.params[2], request.params[3]);
+
     return EncodeHexTx(rawTx);
 }
 
diff --git a/src/rpc/rawtransaction.h b/src/rpc/rawtransaction.h
index ec9d1f2cf0..52dccc90e8 100644
--- a/src/rpc/rawtransaction.h
+++ b/src/rpc/rawtransaction.h
@@ -12,4 +12,7 @@ class UniValue;
 /** Sign a transaction with the given keystore and previous transactions */
 UniValue SignTransaction(CMutableTransaction& mtx, const UniValue& prevTxs, CBasicKeyStore *keystore, bool tempKeystore, const UniValue& hashType);
 
+/** Create a transaction from univalue parameters */
+CMutableTransaction ConstructTransaction(const UniValue& inputs_in, const UniValue& outputs_in, const UniValue& locktime, const UniValue& rbf);
+
 #endif // BITCOIN_RPC_RAWTRANSACTION_H