From ef9e86039aee0a43ea4a64eaaaf759b370f6a51e Mon Sep 17 00:00:00 2001
From: Sjors Provoost <sjors@sprovoost.nl>
Date: Wed, 8 Jan 2025 13:03:08 +0100
Subject: [PATCH] rpc: gettarget

---
 src/rpc/blockchain.cpp                       | 21 ++++++++++++++++++++
 src/rpc/util.cpp                             |  8 ++++++++
 src/rpc/util.h                               | 10 ++++++++++
 src/test/fuzz/rpc.cpp                        |  1 +
 test/functional/rpc_blockchain.py            |  9 +++++++++
 test/functional/test_framework/blocktools.py |  6 ++++++
 6 files changed, 55 insertions(+)

diff --git a/src/rpc/blockchain.cpp b/src/rpc/blockchain.cpp
index 3caf4bf4ebe..6756900cb2e 100644
--- a/src/rpc/blockchain.cpp
+++ b/src/rpc/blockchain.cpp
@@ -447,6 +447,26 @@ static RPCHelpMan getdifficulty()
     };
 }
 
+static RPCHelpMan gettarget()
+{
+    return RPCHelpMan{"gettarget",
+                "\nReturns the proof-of-work target.\n",
+                {},
+                RPCResult{
+                    RPCResult::Type::STR_HEX, "", "the proof-of-work target."},
+                RPCExamples{
+                    HelpExampleCli("gettarget", "")
+            + HelpExampleRpc("gettarget", "")
+                },
+        [&](const RPCHelpMan& self, const JSONRPCRequest& request) -> UniValue
+{
+    ChainstateManager& chainman = EnsureAnyChainman(request.context);
+    CBlockIndex& tip{*CHECK_NONFATAL(WITH_LOCK(chainman.GetMutex(), return chainman.ActiveChain().Tip()))};
+    return GetTarget(tip, chainman.GetParams().GetConsensus().powLimit).GetHex();
+},
+    };
+}
+
 static RPCHelpMan getblockfrompeer()
 {
     return RPCHelpMan{
@@ -3382,6 +3402,7 @@ void RegisterBlockchainRPCCommands(CRPCTable& t)
         {"blockchain", &getblockheader},
         {"blockchain", &getchaintips},
         {"blockchain", &getdifficulty},
+        {"blockchain", &gettarget},
         {"blockchain", &getdeploymentinfo},
         {"blockchain", &gettxout},
         {"blockchain", &gettxoutsetinfo},
diff --git a/src/rpc/util.cpp b/src/rpc/util.cpp
index b1fbc256414..2941dda8c0a 100644
--- a/src/rpc/util.cpp
+++ b/src/rpc/util.cpp
@@ -4,6 +4,7 @@
 
 #include <bitcoin-build-config.h> // IWYU pragma: keep
 
+#include <chain.h>
 #include <clientversion.h>
 #include <common/args.h>
 #include <common/messages.h>
@@ -13,6 +14,7 @@
 #include <key_io.h>
 #include <node/types.h>
 #include <outputtype.h>
+#include <pow.h>
 #include <rpc/util.h>
 #include <script/descriptor.h>
 #include <script/interpreter.h>
@@ -1418,3 +1420,9 @@ std::vector<RPCResult> ScriptPubKeyDoc() {
              {RPCResult::Type::STR, "type", "The type (one of: " + GetAllOutputTypes() + ")"},
          };
 }
+
+uint256 GetTarget(const CBlockIndex& blockindex, const uint256 pow_limit)
+{
+    arith_uint256 target{*CHECK_NONFATAL(DeriveTarget(blockindex.nBits, pow_limit))};
+    return ArithToUint256(target);
+}
diff --git a/src/rpc/util.h b/src/rpc/util.h
index 5bb73d32acd..4eafa1eb6e4 100644
--- a/src/rpc/util.h
+++ b/src/rpc/util.h
@@ -516,4 +516,14 @@ void PushWarnings(const std::vector<bilingual_str>& warnings, UniValue& obj);
 
 std::vector<RPCResult> ScriptPubKeyDoc();
 
+/***
+ * Get the target for a given block index.
+ *
+ * @param[in] blockindex    the block
+ * @param[in] pow_limit     PoW limit (consensus parameter)
+ *
+ * @return  the target
+ */
+uint256 GetTarget(const CBlockIndex& blockindex, const uint256 pow_limit);
+
 #endif // BITCOIN_RPC_UTIL_H
diff --git a/src/test/fuzz/rpc.cpp b/src/test/fuzz/rpc.cpp
index 7bf90b9b775..57aa2f35f4e 100644
--- a/src/test/fuzz/rpc.cpp
+++ b/src/test/fuzz/rpc.cpp
@@ -147,6 +147,7 @@ const std::vector<std::string> RPC_COMMANDS_SAFE_FOR_FUZZING{
     "getorphantxs",
     "getpeerinfo",
     "getprioritisedtransactions",
+    "gettarget",
     "getrawaddrman",
     "getrawmempool",
     "getrawtransaction",
diff --git a/test/functional/rpc_blockchain.py b/test/functional/rpc_blockchain.py
index ae95beae2c1..6dbd25cb1b9 100755
--- a/test/functional/rpc_blockchain.py
+++ b/test/functional/rpc_blockchain.py
@@ -11,6 +11,7 @@ Test the following RPCs:
     - gettxoutsetinfo
     - getblockheader
     - getdifficulty
+    - gettarget
     - getnetworkhashps
     - waitforblockheight
     - getblock
@@ -31,10 +32,12 @@ from test_framework.blocktools import (
     MAX_FUTURE_BLOCK_TIME,
     TIME_GENESIS_BLOCK,
     REGTEST_N_BITS,
+    REGTEST_TARGET,
     create_block,
     create_coinbase,
     create_tx_with_script,
     nbits_str,
+    target_str,
 )
 from test_framework.messages import (
     CBlockHeader,
@@ -90,6 +93,7 @@ class BlockchainTest(BitcoinTestFramework):
         self._test_gettxoutsetinfo()
         self._test_getblockheader()
         self._test_getdifficulty()
+        self._test_gettarget()
         self._test_getnetworkhashps()
         self._test_stopatheight()
         self._test_waitforblock() # also tests waitfornewblock
@@ -440,6 +444,11 @@ class BlockchainTest(BitcoinTestFramework):
         # binary => decimal => binary math is why we do this check
         assert abs(difficulty * 2**31 - 1) < 0.0001
 
+    def _test_gettarget(self):
+        self.log.info("Test gettarget")
+        target = self.nodes[0].gettarget()
+        assert_equal(target, target_str(REGTEST_TARGET))
+
     def _test_getnetworkhashps(self):
         self.log.info("Test getnetworkhashps")
         assert_raises_rpc_error(
diff --git a/test/functional/test_framework/blocktools.py b/test/functional/test_framework/blocktools.py
index c92b1398c39..7c455ea52f2 100644
--- a/test/functional/test_framework/blocktools.py
+++ b/test/functional/test_framework/blocktools.py
@@ -27,6 +27,7 @@ from .messages import (
     hash256,
     ser_uint256,
     tx_from_hex,
+    uint256_from_compact,
     uint256_from_str,
     WITNESS_SCALE_FACTOR,
 )
@@ -66,10 +67,15 @@ VERSIONBITS_LAST_OLD_BLOCK_VERSION = 4
 MIN_BLOCKS_TO_KEEP = 288
 
 REGTEST_N_BITS = 0x207fffff  # difficulty retargeting is disabled in REGTEST chainparams"
+REGTEST_TARGET = 0x7fffff0000000000000000000000000000000000000000000000000000000000
+assert_equal(uint256_from_compact(REGTEST_N_BITS), REGTEST_TARGET)
 
 def nbits_str(nbits):
     return f"{nbits:08x}"
 
+def target_str(target):
+    return f"{target:064x}"
+
 def create_block(hashprev=None, coinbase=None, ntime=None, *, version=None, tmpl=None, txlist=None):
     """Create a block (with regtest difficulty)."""
     block = CBlock()