kernel: Add headerTip method to notifications

This commit is part of the libbitcoinkernel project and seeks to remove
the ChainstateManager's and, more generally, the kernel library's
dependency on interface_ui with options methods in this and the following
few commits. By removing interface_ui from the kernel library, its
dependency on boost is reduced to just boost::multi_index.

src/bitcoin-chainstate.cpp

@@ -32,6 +32,7 @@
 #include <validationinterface.h>
 
 #include <cassert>
+#include <cstdint>
 #include <filesystem>
 #include <functional>
 #include <iosfwd>
@@ -89,6 +90,10 @@ int main(int argc, char* argv[])
         {
             std::cout << "Block tip changed" << std::endl;
         }
+        void headerTip(SynchronizationState, int64_t height, int64_t timestamp, bool presync) override
+        {
+            std::cout << "Header tip changed: " << height << ", " << timestamp << ", " << presync << std::endl;
+        }
     };
     auto notifications = std::make_unique<KernelNotifications>();
 

src/kernel/notifications_interface.h

@@ -5,6 +5,8 @@
 #ifndef BITCOIN_KERNEL_NOTIFICATIONS_INTERFACE_H
 #define BITCOIN_KERNEL_NOTIFICATIONS_INTERFACE_H
 
+#include <cstdint>
+
 class CBlockIndex;
 enum class SynchronizationState;
 
@@ -20,6 +22,7 @@ public:
     virtual ~Notifications(){};
 
     virtual void blockTip(SynchronizationState state, CBlockIndex& index) {}
+    virtual void headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync) {}
 };
 } // namespace kernel
 

src/node/kernel_notifications.cpp

@@ -13,4 +13,9 @@ void KernelNotifications::blockTip(SynchronizationState state, CBlockIndex& inde
     uiInterface.NotifyBlockTip(state, &index);
 }
 
+void KernelNotifications::headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync)
+{
+    uiInterface.NotifyHeaderTip(state, height, timestamp, presync);
+}
+
 } // namespace node

src/node/kernel_notifications.h

@@ -7,6 +7,8 @@
 
 #include <kernel/notifications_interface.h>
 
+#include <cstdint>
+
 class CBlockIndex;
 enum class SynchronizationState;
 
@@ -15,6 +17,8 @@ class KernelNotifications : public kernel::Notifications
 {
 public:
     void blockTip(SynchronizationState state, CBlockIndex& index) override;
+
+    void headerTip(SynchronizationState state, int64_t height, int64_t timestamp, bool presync) override;
 };
 } // namespace node
 

src/validation.cpp

@@ -3097,7 +3097,7 @@ static bool NotifyHeaderTip(Chainstate& chainstate) LOCKS_EXCLUDED(cs_main) {
     }
     // Send block tip changed notifications without cs_main
     if (fNotify) {
-        uiInterface.NotifyHeaderTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader->nHeight, pindexHeader->nTime, false);
+        chainstate.m_chainman.GetNotifications().headerTip(GetSynchronizationState(fInitialBlockDownload), pindexHeader->nHeight, pindexHeader->nTime, false);
     }
     return fNotify;
 }
@@ -3920,7 +3920,7 @@ void ChainstateManager::ReportHeadersPresync(const arith_uint256& work, int64_t
         m_last_presync_update = now;
     }
     bool initial_download = chainstate.IsInitialBlockDownload();
-    uiInterface.NotifyHeaderTip(GetSynchronizationState(initial_download), height, timestamp, /*presync=*/true);
+    GetNotifications().headerTip(GetSynchronizationState(initial_download), height, timestamp, /*presync=*/true);
     if (initial_download) {
         const int64_t blocks_left{(GetTime() - timestamp) / GetConsensus().nPowTargetSpacing};
         const double progress{100.0 * height / (height + blocks_left)};