StateAccess.h

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#pragma once
 
#include "common/Export.h"
#include "common/Result.h"
#include "common/Value.h"
 
#include <cstddef>
#include <cstdint>
#include <functional>
#include <optional>
#include <span>
#include <string>
#include <string_view>
 
namespace eve::state {
 
using SubjectId = std::string;
 
enum class MutationKind : std::uint8_t {
    Set,
    Remove,
    AddTag,
    RemoveTag,
    AddNumber,
};
 
struct StateMutation {
    SubjectId    subject;
    std::string  key;
    eve::Value   value;
    MutationKind kind       = MutationKind::Set;
    bool         persistent = false;
};
 
struct MutationContext {
    std::string transactionId;
    std::string correlationId;
    std::string causationId;
};
 
struct MutationReceipt {
    std::string transactionId;
    std::size_t changedCount = 0;
};
 
class EVENGINE_API_FOUNDATION_INLINE IStateQuery {
public:
    static constexpr const char* capabilityName = "eve.state.IStateQuery";
    virtual ~IStateQuery()                      = default;
 
    [[nodiscard]] virtual std::optional<eve::Value> value(std::string_view subject, std::string_view key) const = 0;
    [[nodiscard]] virtual std::optional<bool> hasTag(std::string_view subject, std::string_view tag) const = 0;
    [[nodiscard]] virtual std::optional<eve::Value> attribute(std::string_view subject, std::string_view key) const = 0;
    [[nodiscard]] virtual std::optional<eve::Value> resource(std::string_view subject, std::string_view key) const = 0;
    [[nodiscard]] virtual std::optional<eve::Value> state(std::string_view subject, std::string_view key) const = 0;
    [[nodiscard]] virtual std::optional<bool> authority(std::string_view subject, std::string_view scope) const = 0;
};
 
class EVENGINE_API_FOUNDATION_INLINE IStateMutation {
public:
    static constexpr const char* capabilityName = "eve.state.IStateMutation";
    virtual ~IStateMutation()                   = default;
 
    [[nodiscard]] virtual eve::Result<MutationReceipt> apply(std::span<const StateMutation> mutations,
                                                             const MutationContext&         context) = 0;
};
 
}  // namespace eve::state
 
// Root aliases keep the common capability discoverable alongside existing
// interfaces such as eve::ISceneQuery while retaining the state namespace as
// the canonical spelling for new code.
namespace eve {
using IStateQuery     = state::IStateQuery;
using IStateMutation  = state::IStateMutation;
using StateMutation   = state::StateMutation;
using MutationKind    = state::MutationKind;
using MutationContext = state::MutationContext;
using MutationReceipt = state::MutationReceipt;
}  // namespace eve