Add explore top query.

Author: evoskuil

include/bitcoin/node/protocols/protocol_explore.hpp

@@ -60,6 +60,9 @@ class BCN_API protocol_explore
 
     /// REST interface handlers.
 
+    bool handle_get_top(const code& ec, interface::top,
+        uint8_t version, uint8_t media) NOEXCEPT;
+
     bool handle_get_block(const code& ec, interface::block,
         uint8_t version, uint8_t media, std::optional<system::hash_cptr> hash,
         std::optional<uint32_t> height, bool witness) NOEXCEPT;

src/parse/target.cpp

@@ -91,7 +91,11 @@ code parse_target(request_t& out, const std::string_view& path) NOEXCEPT
     // transaction, address, inputs, and outputs are identical excluding names;
     // input and output are identical excluding names; block is unique.
     const auto target = segments[segment++];
-    if (target == "address")
+    if (target == "top")
+    {
+        method = "top";
+    }
+    else if (target == "address")
     {
         if (segment == segments.size())
             return error::missing_hash;

src/protocols/protocol_explore.cpp

@@ -207,6 +207,30 @@ std::string to_hex_ptr_array(const Collection& collection, size_t size,
     return out;
 }
 
+bool protocol_explore::handle_get_top(const code& ec, interface::top,
+    uint8_t, uint8_t media) NOEXCEPT
+{
+    if (stopped(ec))
+        return false;
+
+    const auto height = archive().get_top_confirmed();
+    switch (media)
+    {
+        case data:
+            send_chunk(to_little_endian_size(height));
+            return true;
+        case text:
+            send_text(encode_base16(to_little_endian_size(height)));
+            return true;
+        case json:
+            send_json(height, two * sizeof(height));
+            return true;
+    }
+
+    send_not_found();
+    return true;
+}
+
 bool protocol_explore::handle_get_block(const code& ec, interface::block,
     uint8_t, uint8_t media, std::optional<hash_cptr> hash,
     std::optional<uint32_t> height, bool witness) NOEXCEPT