1 files changed, 31 insertions, 12 deletions

diff --git a/src/interfaces/chain.h b/src/interfaces/chain.h
index 9da5cb9637..4e858d1f89 100644
--- a/src/interfaces/chain.h
+++ b/src/interfaces/chain.h
@@ -41,12 +41,6 @@ namespace interfaces {
 class Handler;
 class Wallet;
 
-//! Hash/height pair to help track and identify blocks.
-struct BlockKey {
-    uint256 hash;
-    int height = -1;
-};
-
 //! Helper for findBlock to selectively return pieces of block data. If block is
 //! found, data will be returned by setting specified output variables. If block
 //! is not found, output variables will keep their previous values.
@@ -96,6 +90,17 @@ struct BlockInfo {
     BlockInfo(const uint256& hash LIFETIMEBOUND) : hash(hash) {}
 };
 
+//! The action to be taken after updating a settings value.
+//! WRITE indicates that the updated value must be written to disk,
+//! while SKIP_WRITE indicates that the change will be kept in memory-only
+//! without persisting it.
+enum class SettingsAction {
+    WRITE,
+    SKIP_WRITE
+};
+
+using SettingsUpdate = std::function<std::optional<interfaces::SettingsAction>(common::SettingsValue&)>;
+
 //! Interface giving clients (wallet processes, maybe other analysis tools in
 //! the future) ability to access to the chain state, receive notifications,
 //! estimate fees, and submit transactions.
@@ -123,7 +128,7 @@ struct BlockInfo {
 class Chain
 {
 public:
-    virtual ~Chain() {}
+    virtual ~Chain() = default;
 
     //! Get current chain height, not including genesis block (returns 0 if
     //! chain only contains genesis block, nullopt if chain does not contain
@@ -309,7 +314,7 @@ public:
     class Notifications
     {
     public:
-        virtual ~Notifications() {}
+        virtual ~Notifications() = default;
         virtual void transactionAddedToMempool(const CTransactionRef& tx) {}
         virtual void transactionRemovedFromMempool(const CTransactionRef& tx, MemPoolRemovalReason reason) {}
         virtual void blockConnected(ChainstateRole role, const BlockInfo& block) {}
@@ -344,9 +349,23 @@ public:
     //! Return <datadir>/settings.json setting value.
     virtual common::SettingsValue getRwSetting(const std::string& name) = 0;
 
-    //! Write a setting to <datadir>/settings.json. Optionally just update the
-    //! setting in memory and do not write the file.
-    virtual bool updateRwSetting(const std::string& name, const common::SettingsValue& value, bool write=true) = 0;
+    //! Updates a setting in <datadir>/settings.json.
+    //! Null can be passed to erase the setting. There is intentionally no
+    //! support for writing null values to settings.json.
+    //! Depending on the action returned by the update function, this will either
+    //! update the setting in memory or write the updated settings to disk.
+    virtual bool updateRwSetting(const std::string& name, const SettingsUpdate& update_function) = 0;
+
+    //! Replace a setting in <datadir>/settings.json with a new value.
+    //! Null can be passed to erase the setting.
+    //! This method provides a simpler alternative to updateRwSetting when
+    //! atomically reading and updating the setting is not required.
+    virtual bool overwriteRwSetting(const std::string& name, common::SettingsValue value, SettingsAction action = SettingsAction::WRITE) = 0;
+
+    //! Delete a given setting in <datadir>/settings.json.
+    //! This method provides a simpler alternative to overwriteRwSetting when
+    //! erasing a setting, for ease of use and readability.
+    virtual bool deleteRwSettings(const std::string& name, SettingsAction action = SettingsAction::WRITE) = 0;
 
     //! Synchronously send transactionAddedToMempool notifications about all
     //! current mempool transactions to the specified handler and return after
@@ -371,7 +390,7 @@ public:
 class ChainClient
 {
 public:
-    virtual ~ChainClient() {}
+    virtual ~ChainClient() = default;
 
     //! Register rpcs.
     virtual void registerRpcs() = 0;