1 files changed, 95 insertions, 0 deletions
diff --git a/src/buildtool/build_engine/expression/expression_ptr.hpp b/src/buildtool/build_engine/expression/expression_ptr.hpp
new file mode 100644
index 00000000..8cc26c50
--- /dev/null
+++ b/src/buildtool/build_engine/expression/expression_ptr.hpp
@@ -0,0 +1,95 @@
+#ifndef INCLUDED_SRC_BUILDTOOL_BUILD_ENGINE_EXPRESSION_EXPRESSION_PTR_HPP
+#define INCLUDED_SRC_BUILDTOOL_BUILD_ENGINE_EXPRESSION_EXPRESSION_PTR_HPP
+
+#include <functional>
+#include <memory>
+#include <string>
+#include <type_traits>
+
+#include "nlohmann/json.hpp"
+#include "src/buildtool/build_engine/expression/function_map.hpp"
+#include "src/buildtool/build_engine/expression/linked_map.hpp"
+#include "src/buildtool/logging/logger.hpp"
+
+class Configuration;
+class Expression;
+
+class ExpressionPtr {
+  public:
+    // Initialize to nullptr
+    explicit ExpressionPtr(std::nullptr_t /*ptr*/) noexcept : ptr_{nullptr} {}
+
+    // Initialize from Expression's variant type or Expression
+    template <class T>
+    requires(not std::is_same_v<std::remove_cvref_t<T>, ExpressionPtr>)
+        // NOLINTNEXTLINE(bugprone-forwarding-reference-overload)
+        explicit ExpressionPtr(T&& data) noexcept
+        : ptr_{std::make_shared<Expression>(std::forward<T>(data))} {}
+
+    ExpressionPtr() noexcept;
+    ExpressionPtr(ExpressionPtr const&) noexcept = default;
+    ExpressionPtr(ExpressionPtr&&) noexcept = default;
+    ~ExpressionPtr() noexcept = default;
+    auto operator=(ExpressionPtr const&) noexcept -> ExpressionPtr& = default;
+    auto operator=(ExpressionPtr&&) noexcept -> ExpressionPtr& = default;
+
+    explicit operator bool() const { return static_cast<bool>(ptr_); }
+    [[nodiscard]] auto operator*() const& -> Expression const& { return *ptr_; }
+    [[nodiscard]] auto operator*() && -> Expression;
+    [[nodiscard]] auto operator->() const& -> Expression const* {
+        return ptr_.get();
+    }
+    [[nodiscard]] auto operator->() && -> Expression const* = delete;
+    [[nodiscard]] auto operator[](
+        std::string const& key) const& -> ExpressionPtr const&;
+    [[nodiscard]] auto operator[](std::string const& key) && -> ExpressionPtr;
+    [[nodiscard]] auto operator[](
+        ExpressionPtr const& key) const& -> ExpressionPtr const&;
+    [[nodiscard]] auto operator[](ExpressionPtr const& key) && -> ExpressionPtr;
+    [[nodiscard]] auto operator[](size_t pos) const& -> ExpressionPtr const&;
+    [[nodiscard]] auto operator[](size_t pos) && -> ExpressionPtr;
+    [[nodiscard]] auto operator<(ExpressionPtr const& other) const -> bool;
+    [[nodiscard]] auto operator==(ExpressionPtr const& other) const -> bool;
+    template <class T>
+    [[nodiscard]] auto operator==(T const& other) const -> bool {
+        return ptr_ and *ptr_ == other;
+    }
+    template <class T>
+    [[nodiscard]] auto operator!=(T const& other) const -> bool {
+        return not(*this == other);
+    }
+    [[nodiscard]] auto Evaluate(
+        Configuration const& env,
+        FunctionMapPtr const& functions,
+        std::function<void(std::string const&)> const& logger =
+            [](std::string const& error) noexcept -> void {
+            Logger::Log(LogLevel::Error, error);
+        },
+        std::function<void(void)> const& note_user_context =
+            []() noexcept -> void {}) const noexcept -> ExpressionPtr;
+
+    [[nodiscard]] auto IsCacheable() const noexcept -> bool;
+    [[nodiscard]] auto ToIdentifier() const noexcept -> std::string;
+    [[nodiscard]] auto ToJson() const noexcept -> nlohmann::json;
+
+    using linked_map_t = LinkedMap<std::string, ExpressionPtr, ExpressionPtr>;
+    [[nodiscard]] auto IsNotNull() const noexcept -> bool;
+    [[nodiscard]] auto LinkedMap() const& -> linked_map_t const&;
+    [[nodiscard]] static auto Make(linked_map_t&& map) -> ExpressionPtr;
+
+  private:
+    std::shared_ptr<Expression> ptr_;
+};
+
+[[nodiscard]] auto operator+(ExpressionPtr const& lhs, ExpressionPtr const& rhs)
+    -> ExpressionPtr;
+
+namespace std {
+template <>
+struct hash<ExpressionPtr> {
+    [[nodiscard]] auto operator()(ExpressionPtr const& p) const noexcept
+        -> std::size_t;
+};
+}  // namespace std
+
+#endif  // INCLUDED_SRC_BUILDTOOL_BUILD_ENGINE_EXPRESSION_EXPRESSION_PTR_HPP