Decouple SigNetChainParams from ArgsManager

SigNet chain params can now be initialized by configuring a
SigNetOptions struct, or with ArgsManager. This offers an interface for
creating SigNetChainParams without a gArgs object.

src/chainparams.cpp

@@ -277,11 +277,12 @@ public:
  */
 class SigNetParams : public CChainParams {
 public:
-    explicit SigNetParams(const ArgsManager& args) {
+    explicit SigNetParams(const SigNetOptions& options)
+    {
         std::vector<uint8_t> bin;
         vSeeds.clear();
 
-        if (!args.IsArgSet("-signetchallenge")) {
+        if (!options.challenge) {
             bin = ParseHex("512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430210359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c452ae");
             vSeeds.emplace_back("seed.signet.bitcoin.sprovoost.nl.");
 
@@ -300,12 +301,7 @@ public:
                 .dTxRate  = 0.02336701143027275,
             };
         } else {
-            const auto signet_challenge = args.GetArgs("-signetchallenge");
+            bin = *options.challenge;
-            if (signet_challenge.size() != 1) {
-                throw std::runtime_error(strprintf("%s: -signetchallenge cannot be multiple values.", __func__));
-            }
-            bin = ParseHex(signet_challenge[0]);
-
             consensus.nMinimumChainWork = uint256{};
             consensus.defaultAssumeValid = uint256{};
             m_assumed_blockchain_size = 0;
@@ -315,11 +311,11 @@ public:
                 0,
                 0,
             };
-            LogPrintf("Signet with challenge %s\n", signet_challenge[0]);
+            LogPrintf("Signet with challenge %s\n", HexStr(bin));
         }
 
-        if (args.IsArgSet("-signetseednode")) {
+        if (options.seeds) {
-            vSeeds = args.GetArgs("-signetseednode");
+            vSeeds = *options.seeds;
         }
 
         strNetworkID = CBaseChainParams::SIGNET;
@@ -382,11 +378,26 @@ public:
     }
 };
 
+void ReadSigNetArgs(const ArgsManager& args, CChainParams::SigNetOptions& options)
+{
+    if (args.IsArgSet("-signetseednode")) {
+        options.seeds.emplace(args.GetArgs("-signetseednode"));
+    }
+    if (args.IsArgSet("-signetchallenge")) {
+        const auto signet_challenge = args.GetArgs("-signetchallenge");
+        if (signet_challenge.size() != 1) {
+            throw std::runtime_error(strprintf("%s: -signetchallenge cannot be multiple values.", __func__));
+        }
+        options.challenge.emplace(ParseHex(signet_challenge[0]));
+    }
+}
+
 /**
  * Regression test: intended for private networks only. Has minimal difficulty to ensure that
  * blocks can be found instantly.
  */
-class CRegTestParams : public CChainParams {
+class CRegTestParams : public CChainParams
+{
 public:
     explicit CRegTestParams(const ArgsManager& args) {
         strNetworkID =  CBaseChainParams::REGTEST;
@@ -570,7 +581,9 @@ std::unique_ptr<const CChainParams> CreateChainParams(const ArgsManager& args, c
     } else if (chain == CBaseChainParams::TESTNET) {
         return std::unique_ptr<CChainParams>(new CTestNetParams());
     } else if (chain == CBaseChainParams::SIGNET) {
-        return std::unique_ptr<CChainParams>(new SigNetParams(args));
+        auto opts = CChainParams::SigNetOptions{};
+        ReadSigNetArgs(args, opts);
+        return std::make_unique<const SigNetParams>(opts);
     } else if (chain == CBaseChainParams::REGTEST) {
         return std::unique_ptr<CChainParams>(new CRegTestParams(args));
     }

src/chainparams.h

@@ -122,6 +122,15 @@ public:
     const MapAssumeutxo& Assumeutxo() const { return m_assumeutxo_data; }
 
     const ChainTxData& TxData() const { return chainTxData; }
+
+    /**
+     * SigNetOptions holds configurations for creating a signet CChainParams.
+     */
+    struct SigNetOptions {
+        std::optional<std::vector<uint8_t>> challenge{};
+        std::optional<std::vector<std::string>> seeds{};
+    };
+
 protected:
     CChainParams() {}