kernel: Expose consensus parameters (btck_ConsensusParams)

Library users currently need to maintain a full context object to perform
context-free block validation. Exposing an opaque `btck_ConsensusParams`
struct allows callers to supply only the required consensus parameters,
resulting in a lighter-weight API and a clearer expression of the actual
validation behavior.

Co-authored-by: yuvicc <yuvichh01@gmail.com>

src/kernel/bitcoinkernel.cpp

@@ -50,6 +50,10 @@
 #include <utility>
 #include <vector>
 
+namespace Consensus {
+struct Params;
+} // namespace Consensus
+
 using kernel::ChainstateRole;
 using util::ImmediateTaskRunner;
 
@@ -496,6 +500,7 @@ struct btck_TransactionOutPoint: Handle<btck_TransactionOutPoint, COutPoint> {};
 struct btck_Txid: Handle<btck_Txid, Txid> {};
 struct btck_PrecomputedTransactionData : Handle<btck_PrecomputedTransactionData, PrecomputedTransactionData> {};
 struct btck_BlockHeader: Handle<btck_BlockHeader, CBlockHeader> {};
+struct btck_ConsensusParams: Handle<btck_ConsensusParams, Consensus::Params> {};
 
 btck_Transaction* btck_transaction_create(const void* raw_transaction, size_t raw_transaction_len)
 {
@@ -823,6 +828,11 @@ btck_ChainParameters* btck_chain_parameters_copy(const btck_ChainParameters* cha
     return btck_ChainParameters::copy(chain_parameters);
 }
 
+const btck_ConsensusParams* btck_chain_parameters_get_consensus_params(const btck_ChainParameters* chain_parameters)
+{
+    return btck_ConsensusParams::ref(&btck_ChainParameters::get(chain_parameters).GetConsensus());
+}
+
 void btck_chain_parameters_destroy(btck_ChainParameters* chain_parameters)
 {
     delete chain_parameters;

src/kernel/bitcoinkernel.h

@@ -225,6 +225,11 @@ typedef struct btck_Block btck_Block;
  */
 typedef struct btck_BlockValidationState btck_BlockValidationState;
 
+/**
+ * Opaque data structure for holding the Consensus Params.
+ */
+typedef struct btck_ConsensusParams btck_ConsensusParams;
+
 /**
  * Opaque data structure for holding the currently known best-chain associated
  * with a chainstate.
@@ -864,6 +869,17 @@ BITCOINKERNEL_API btck_ChainParameters* BITCOINKERNEL_WARN_UNUSED_RESULT btck_ch
 BITCOINKERNEL_API btck_ChainParameters* BITCOINKERNEL_WARN_UNUSED_RESULT btck_chain_parameters_copy(
     const btck_ChainParameters* chain_parameters) BITCOINKERNEL_ARG_NONNULL(1);
 
+/**
+ * @brief Get btck_ConsensusParams from btck_ChainParameters. The returned
+ * btck_ConsensusParams pointer is valid only for the lifetime of the
+ * btck_ChainParameters object and must not be destroyed by the caller.
+ *
+ * @param[in] chain_parameters  Non-null.
+ * @return                      The btck_ConsensusParams.
+ */
+BITCOINKERNEL_API const btck_ConsensusParams* BITCOINKERNEL_WARN_UNUSED_RESULT btck_chain_parameters_get_consensus_params(
+    const btck_ChainParameters* chain_parameters) BITCOINKERNEL_ARG_NONNULL(1);
+
 /**
  * Destroy the chain parameters.
  */

src/kernel/bitcoinkernel_wrapper.h

@@ -777,6 +777,12 @@ public:
         : Handle{header} {}
 };
 
+class ConsensusParamsView : public View<btck_ConsensusParams>
+{
+public:
+    explicit ConsensusParamsView(const btck_ConsensusParams* ptr) : View{ptr} {}
+};
+
 class Block : public Handle<btck_Block, btck_block_copy, btck_block_destroy>
 {
 public:
@@ -971,6 +977,11 @@ class ChainParams : public Handle<btck_ChainParameters, btck_chain_parameters_co
 public:
     ChainParams(ChainType chain_type)
         : Handle{btck_chain_parameters_create(static_cast<btck_ChainType>(chain_type))} {}
+
+    ConsensusParamsView GetConsensusParams() const
+    {
+        return ConsensusParamsView{btck_chain_parameters_get_consensus_params(get())};
+    }
 };
 
 class ContextOptions : public UniqueHandle<btck_ContextOptions, btck_context_options_destroy>