feat: Choose writer by cluster communication (#2830)

Fixes #1974

src/etl/WriterState.cpp

@@ -0,0 +1,88 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2025, the clio developers.
+
+    Permission to use, copy, modify, and distribute this software for any
+    purpose with or without fee is hereby granted, provided that the above
+    copyright notice and this permission notice appear in all copies.
+
+    THE  SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+    WITH  REGARD  TO  THIS  SOFTWARE  INCLUDING  ALL  IMPLIED  WARRANTIES  OF
+    MERCHANTABILITY  AND  FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+    ANY  SPECIAL,  DIRECT,  INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+    WHATSOEVER  RESULTING  FROM  LOSS  OF USE, DATA OR PROFITS, WHETHER IN AN
+    ACTION  OF  CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+    OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+*/
+//==============================================================================
+
+#include "etl/WriterState.hpp"
+
+#include "etl/SystemState.hpp"
+
+#include <memory>
+#include <utility>
+
+namespace etl {
+
+WriterState::WriterState(std::shared_ptr<SystemState> state) : systemState_(std::move(state))
+{
+}
+
+bool
+WriterState::isReadOnly() const
+{
+    return systemState_->isStrictReadonly;
+}
+
+bool
+WriterState::isWriting() const
+{
+    return systemState_->isWriting;
+}
+
+void
+WriterState::startWriting()
+{
+    if (isWriting())
+        return;
+
+    systemState_->writeCommandSignal(SystemState::WriteCommand::StartWriting);
+}
+
+void
+WriterState::giveUpWriting()
+{
+    if (not isWriting())
+        return;
+
+    systemState_->writeCommandSignal(SystemState::WriteCommand::StopWriting);
+}
+
+void
+WriterState::setWriterDecidingFallback()
+{
+    systemState_->isWriterDecidingFallback = true;
+}
+
+bool
+WriterState::isFallback() const
+{
+    return systemState_->isWriterDecidingFallback;
+}
+
+bool
+WriterState::isLoadingCache() const
+{
+    return systemState_->isLoadingCache;
+}
+
+std::unique_ptr<WriterStateInterface>
+WriterState::clone() const
+{
+    auto c = WriterState(*this);
+    return std::make_unique<WriterState>(std::move(c));
+}
+
+}  // namespace etl