Implement base for nextgen rpc subsystem (#487)

Fixes #494

unittests/rpc/handlers/impl/FakesAndMocks.h

@@ -0,0 +1,168 @@
+//------------------------------------------------------------------------------
+/*
+    This file is part of clio: https://github.com/XRPLF/clio
+    Copyright (c) 2023, 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.
+*/
+//==============================================================================
+
+#pragma once
+
+#include <rpc/RPC.h>
+#include <rpc/common/Specs.h>
+#include <rpc/common/Validators.h>
+
+#include <boost/json/value.hpp>
+#include <boost/json/value_from.hpp>
+#include <boost/json/value_to.hpp>
+#include <gmock/gmock.h>
+
+#include <optional>
+#include <string>
+
+namespace unittests::detail {
+
+// input data for the test handlers below
+struct TestInput
+{
+    std::string hello;
+    std::optional<uint32_t> limit;
+};
+
+// output data produced by the test handlers below
+struct TestOutput
+{
+    std::string computed;
+};
+
+// must be implemented as per rpc/common/Concepts.h
+inline TestInput
+tag_invoke(boost::json::value_to_tag<TestInput>, boost::json::value const& jv)
+{
+    std::optional<uint32_t> optLimit;
+    if (jv.as_object().contains("limit"))
+        optLimit = jv.at("limit").as_int64();
+
+    return {jv.as_object().at("hello").as_string().c_str(), optLimit};
+}
+
+// must be implemented as per rpc/common/Concepts.h
+inline void
+tag_invoke(
+    boost::json::value_from_tag,
+    boost::json::value& jv,
+    TestOutput output)
+{
+    jv = {{"computed", output.computed}};
+}
+
+// example handler
+class HandlerFake
+{
+public:
+    using Input = TestInput;
+    using Output = TestOutput;
+    using Result = RPCng::HandlerReturnType<Output>;
+
+    RPCng::RpcSpecConstRef
+    spec() const
+    {
+        using namespace RPCng::validation;
+
+        // clang-format off
+        static const RPCng::RpcSpec rpcSpec = {
+            {"hello", Required{}, Type<std::string>{}, EqualTo{"world"}},
+            {"limit", Type<uint32_t>{}, Between<uint32_t>{0, 100}} // optional field
+        };
+        // clang-format on
+
+        return rpcSpec;
+    }
+
+    Result
+    process(Input input) const
+    {
+        return Output{
+            input.hello + '_' + std::to_string(input.limit.value_or(0))};
+    }
+};
+
+// example handler that returns custom error
+class FailingHandlerFake
+{
+public:
+    using Input = TestInput;
+    using Output = TestOutput;
+    using Result = RPCng::HandlerReturnType<Output>;
+
+    RPCng::RpcSpecConstRef
+    spec() const
+    {
+        using namespace RPCng::validation;
+
+        // clang-format off
+        static const RPCng::RpcSpec rpcSpec = {
+            {"hello", Required{}, Type<std::string>{}, EqualTo{"world"}},
+            {"limit", Type<uint32_t>{}, Between<uint32_t>{0u, 100u}} // optional field
+        };
+        // clang-format on
+
+        return rpcSpec;
+    }
+
+    Result
+    process([[maybe_unused]] Input input) const
+    {
+        // always fail
+        return RPCng::Error{RPC::Status{"Very custom error"}};
+    }
+};
+
+struct InOutFake
+{
+    std::string something;
+
+    // Note: no spaceship comparison possible for std::string
+    friend bool
+    operator==(InOutFake const& lhs, InOutFake const& rhs) = default;
+};
+
+// must be implemented as per rpc/common/Concepts.h
+inline InOutFake
+tag_invoke(boost::json::value_to_tag<InOutFake>, boost::json::value const& jv)
+{
+    return {jv.as_object().at("something").as_string().c_str()};
+}
+
+// must be implemented as per rpc/common/Concepts.h
+inline void
+tag_invoke(
+    boost::json::value_from_tag,
+    boost::json::value& jv,
+    InOutFake output)
+{
+    jv = {{"something", output.something}};
+}
+
+struct HandlerMock
+{
+    using Input = InOutFake;
+    using Output = InOutFake;
+    using Result = RPCng::HandlerReturnType<Output>;
+
+    MOCK_METHOD(RPCng::RpcSpecConstRef, spec, (), (const));
+    MOCK_METHOD(Result, process, (Input), (const));
+};
+
+}  // namespace unittests::detail