Add findFork and findBlock to the Chain interface

And use them to remove uses of chainActive and mapBlockIndex in wallet code

This commit does not change behavior.

Co-authored-by: Ben Woosley <ben.woosley@gmail.com>

src/interfaces/chain.cpp

@@ -5,6 +5,8 @@
 #include <interfaces/chain.h>
 
 #include <chain.h>
+#include <chainparams.h>
+#include <primitives/block.h>
 #include <sync.h>
 #include <uint256.h>
 #include <util/system.h>
@@ -58,6 +60,22 @@ class LockImpl : public Chain::Lock
         assert(block != nullptr);
         return block->GetMedianTimePast();
     }
+    Optional<int> findFork(const uint256& hash, Optional<int>* height) override
+    {
+        const CBlockIndex* block = LookupBlockIndex(hash);
+        const CBlockIndex* fork = block ? ::chainActive.FindFork(block) : nullptr;
+        if (height) {
+            if (block) {
+                *height = block->nHeight;
+            } else {
+                height->reset();
+            }
+        }
+        if (fork) {
+            return fork->nHeight;
+        }
+        return nullopt;
+    }
 };
 
 class LockingStateImpl : public LockImpl, public UniqueLock<CCriticalSection>
@@ -77,6 +95,27 @@ public:
         return std::move(result);
     }
     std::unique_ptr<Chain::Lock> assumeLocked() override { return MakeUnique<LockImpl>(); }
+    bool findBlock(const uint256& hash, CBlock* block, int64_t* time, int64_t* time_max) override
+    {
+        CBlockIndex* index;
+        {
+            LOCK(cs_main);
+            index = LookupBlockIndex(hash);
+            if (!index) {
+                return false;
+            }
+            if (time) {
+                *time = index->GetBlockTime();
+            }
+            if (time_max) {
+                *time_max = index->GetBlockTimeMax();
+            }
+        }
+        if (block && !ReadBlockFromDisk(*block, index, Params().GetConsensus())) {
+            block->SetNull();
+        }
+        return true;
+    }
 };
 
 } // namespace

src/interfaces/chain.h

@@ -12,6 +12,7 @@
 #include <string>
 #include <vector>
 
+class CBlock;
 class CScheduler;
 class uint256;
 
@@ -56,6 +57,13 @@ public:
         //! Get block median time past. Height must be valid or this function
         //! will abort.
         virtual int64_t getBlockMedianTimePast(int height) = 0;
+
+        //! Return height of the highest block on the chain that is an ancestor
+        //! of the specified block, or nullopt if no common ancestor is found.
+        //! Also return the height of the specified block as an optional output
+        //! parameter (to avoid the cost of a second hash lookup in case this
+        //! information is desired).
+        virtual Optional<int> findFork(const uint256& hash, Optional<int>* height) = 0;
     };
 
     //! Return Lock interface. Chain is locked when this is called, and
@@ -66,6 +74,17 @@ public:
     //! method is temporary and is only used in a few places to avoid changing
     //! behavior while code is transitioned to use the Chain::Lock interface.
     virtual std::unique_ptr<Lock> assumeLocked() = 0;
+
+    //! Return whether node has the block and optionally return block metadata
+    //! or contents.
+    //!
+    //! If a block pointer is provided to retrieve the block contents, and the
+    //! block exists but doesn't have data (for example due to pruning), the
+    //! block will be empty and all fields set to null.
+    virtual bool findBlock(const uint256& hash,
+        CBlock* block = nullptr,
+        int64_t* time = nullptr,
+        int64_t* max_time = nullptr) = 0;
 };
 
 //! Interface to let node manage chain clients (wallets, or maybe tools for