NpcAiECS.h

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#pragma once
#include "common/Export.h"
 
 
#include "common/ECS.h"
#include "npc_ai/NpcAi.h"
 
#include <cstddef>
#include <span>
#include <string>
#include <string_view>
#include <vector>
 
namespace eve::npc_ai {
 
struct EVENGINE_API_PLATFORM NpcAgentState {
    AgentHandle agent;
 
    [[nodiscard]] static Result<NpcAgentState> create(NpcAiWorld& world, std::string_view behaviorId);
    [[nodiscard]] Result<void> releaseAgent(NpcAiWorld& world);
};
 
struct NpcAiProjection {
    std::string              activeState;
    std::vector<std::string> activePath;
    std::uint64_t            lastTick = 0;
 
    void replace(const AgentSnapshot& snapshot) {
        activeState = snapshot.activeState;
        activePath  = snapshot.activePath;
        lastTick    = snapshot.lastTick;
    }
};
 
struct NpcAiEcsStepReport {
    std::size_t linkedEntities = 0;
    TickReport  runtime;
};
 
struct NpcAiSystemContract {
    std::string_view name;
    std::string_view entityScope;
    std::string_view view;
    std::string_view readSet;
    std::string_view writeSet;
    std::string_view structuralChanges;
    std::string_view events;
    std::string_view services;
    std::string_view phase;
    std::string_view determinism;
};
 
[[nodiscard]] std::span<const NpcAiSystemContract> npcAiSystemContracts() noexcept;
 
class NpcAiEcsSystem {
public:
    template <class EntityRoot>
    [[nodiscard]] static Result<NpcAiEcsStepReport> step(NpcAiWorld& world, const TickContext& context) {
        std::size_t linked = 0;
        {
            auto view = ecs::View<EntityRoot, NpcAgentState, NpcAiProjection>();
            for (auto it = view.begin(); it != view.end(); ++it) {
                auto [state, projection] = *it;
                (void)projection;
                auto current = world.snapshot(state->agent);
                if (!current.ok()) return Result<NpcAiEcsStepReport>::failure(current.status());
                ++linked;
            }
        }
 
        auto advanced = world.tick(context);
        if (!advanced.ok()) return Result<NpcAiEcsStepReport>::failure(advanced.status());
 
        {
            auto view = ecs::View<EntityRoot, NpcAgentState, NpcAiProjection>();
            for (auto it = view.begin(); it != view.end(); ++it) {
                auto [state, projection] = *it;
                auto current             = world.snapshot(state->agent);
                if (!current.ok()) return Result<NpcAiEcsStepReport>::failure(current.status());
                projection->replace(current.value());
            }
        }
        return Result<NpcAiEcsStepReport>::success({linked, advanced.value()});
    }
};
 
}  // namespace eve::npc_ai