Adds support for History data, allowing us to store specific interesting occurrences in the data flow, and recall them later.

Signed-off-by: Deukhoofd <Deukhoofd@gmail.com>

src/Battling/History/HistoryHolder.hpp

@@ -0,0 +1,68 @@
+#ifndef CREATURELIB_HISTORYHOLDER_HPP
+#define CREATURELIB_HISTORYHOLDER_HPP
+
+#include <cstddef>
+#include <cstdint>
+#include "../../Library/Exceptions/CreatureException.hpp"
+#include "HistoryElements/HistoryElement.hpp"
+
+template <class T> concept HistoryElementType = std::is_base_of<CreatureLib::Battling::HistoryElement, T>::value;
+
+namespace CreatureLib::Battling {
+    class HistoryHolder {
+        size_t _offset;
+        size_t _capacity;
+        uint8_t* _memory = nullptr;
+        HistoryElement* _top = nullptr;
+
+        static constexpr size_t initialSize = 2048;
+        static constexpr size_t stepSize = 1024;
+
+    public:
+        HistoryHolder() : _offset(0), _capacity(2048) {
+            auto ptr = malloc(_capacity);
+            if (ptr == nullptr) {
+                THROW_CREATURE("Out of memory.");
+            }
+            _memory = static_cast<uint8_t*>(ptr);
+        }
+        HistoryHolder(const HistoryHolder&) = delete;
+        HistoryHolder& operator=(const HistoryHolder&) = delete;
+
+        ~HistoryHolder() {
+            if (_top != nullptr)
+                _top->Clear();
+            free(_memory);
+        }
+
+        template <HistoryElementType T, class... parameters> void Register(parameters... args) {
+            if (_offset + sizeof(T) >= _capacity) {
+                _capacity += stepSize;
+                auto newPtr = realloc(_memory, _capacity);
+                if (newPtr == nullptr) {
+                    THROW_CREATURE("Out of memory.");
+                }
+                _memory = static_cast<uint8_t*>(newPtr);
+            }
+            uint8_t* ptr = _memory + _offset;
+            T* element = new (ptr) T(args...);
+            _offset += sizeof(T);
+            element->_previous = _top;
+            _top = element;
+        }
+
+        ArbUt::BorrowedPtr<const HistoryElement> GetTopElement() const noexcept { return _top; }
+
+        ArbUt::BorrowedPtr<const HistoryElement> GetLastUsedAttack() const noexcept {
+            const auto* c = _top;
+            while (c != nullptr) {
+                if (c->GetKind() == HistoryElementKind::AttackUse)
+                    return c;
+                c = c->_previous;
+            }
+            return nullptr;
+        }
+    };
+}
+
+#endif // CREATURELIB_HISTORYHOLDER_HPP