destiny-2-Sunrise/Sunrise/src/middleware/bap/activity_message/squad_auth_body.h

#pragma once

#include <array>
#include <cstddef>
#include <cstdint>
#include <optional>
#include <span>

namespace sunrise::middleware::bap::activity_message::squad_auth {

/** ClientRef slot type for the activity-local squad sensor body. */
inline constexpr std::uint8_t kSlotType = 1;
/** Runtime schema handle for the slot-type-1 auth body. */
inline constexpr std::uint32_t kSchema = 0x80807EC9;
/**
 * The count lane is four bits wide, but the array it indexes holds eight elements.
 * The client walker does not clamp, so a count of 9 to 15 runs past the array.
 * The bound is the array, never the lane.
 */
inline constexpr std::size_t kMinimumRequestedCountLength = 1;
inline constexpr std::size_t kMaximumRequestedCountLength = 8;
/** Fixed fields and presence bits outside the requested-count values. */
inline constexpr std::size_t kBaseBitCount = 59;
/** Each requested member count is one signed 32-bit field. */
inline constexpr std::size_t kRequestedCountBitCount = 32;
/** The name hash is always sent: an absent field reads as zero, which is a real name. */
inline constexpr std::size_t kNameHashBitCount = 32;
/**
 * Spawn references `.11` and `.12`, each one nested 0x80809C42 ClientRef.
 * Both always carry the unset form, which is the sentinel that keeps the package's own
 * authored spawn rule. 32-bit key, 7-bit type, 16-bit index, after one presence bit.
 */
inline constexpr std::size_t kSpawnReferenceBitCount = 55;
inline constexpr std::size_t kSpawnReferenceCount = 2;
/** Exact nested field-5 payload: lane selector plus four actor-definition profile values. */
inline constexpr std::size_t kAuthoredProfileBitCount = 13;
/**
 * Exact meaningful bit count for one body carrying this many requested counts.
 * It lives here so the sum has one home. A second copy in the roster encoder drifted from this
 * one and refused every squad body Sunrise sent; that copy is gone.
 */
[[nodiscard]] constexpr std::size_t exact_body_bit_count(std::size_t counts) noexcept {
    return kBaseBitCount + kAuthoredProfileBitCount + kSpawnReferenceBitCount * kSpawnReferenceCount
           + kRequestedCountBitCount * counts + kNameHashBitCount;
}

/** Buffer one squad body needs at the full requested-count length. */
inline constexpr std::size_t kMaximumBitCount = exact_body_bit_count(kMaximumRequestedCountLength);
inline constexpr std::size_t kMaximumByteCount = (kMaximumBitCount + 7) / 8;
/** A retained body may carry the objective fields too, up to 1,313 bits. */
inline constexpr std::size_t kMaximumRetainedBitCount = 1'313;
inline constexpr std::size_t kMaximumRetainedByteCount = (kMaximumRetainedBitCount + 7U) / 8U;
/** Spawn generation is an unsigned logical value stored in a 31-bit field. */
inline constexpr std::uint32_t kMaximumGeneration = 0x7FFFFFFF;

/** Mode 3 skips ordinary placement and keeps the requests for a passenger delivery. */
enum class Mode : std::uint8_t {
    mode0 = 0,
    mode2 = 2,
    reserve = 3,
};
[[nodiscard]] constexpr bool valid_mode(Mode mode) noexcept {
    return mode == Mode::mode0 || mode == Mode::mode2 || mode == Mode::reserve;
}

/** Last accepted positive spawn generation for one ClientRef. */
struct GenerationGuard final {
    std::uint32_t last{};
    bool hasLast{};
};

/** One canonical activity-local squad request. Zero counts select native actor destruction. */
struct Preset final {
    std::span<const std::int32_t> requestedCounts{};
    std::uint32_t generation{};
    Mode mode{Mode::mode0};
    std::optional<std::uint32_t> nameHash{};
    /** Actor-definition bytes +56..+59; field 5.0 remains the exact candidate lane zero. */
    std::array<std::int8_t, 4> authoredProfile{};
};

/** Finds the next positive 31-bit spawn generation without wrapping. */
[[nodiscard]] bool next_generation(const GenerationGuard& guard, std::uint32_t& next) noexcept;

/**
 * Encodes one canonical slot-type-1 body without changing a refused output buffer.
 * Counts must be nonnegative and the generation must be newer than the guard.
 */
[[nodiscard]] bool encode(const Preset& preset,
                          const GenerationGuard& guard,
                          std::span<std::byte> output,
                          std::size_t& writtenBytes,
                          std::size_t& writtenBits) noexcept;

} // namespace sunrise::middleware::bap::activity_message::squad_auth