// Copyright (c) 2026 The Limenka developers
// Distributed under the MIT software license, see the accompanying
// file COPYING or http://www.opensource.org/licenses/mit-license.php.

#ifndef LIMENKA_POW_FORK_H
#define LIMENKA_POW_FORK_H

#include <arith_uint256.h>
#include <consensus/params.h>

#include <cstdint>

class CBlockIndex;
struct CBlockHeader;

/** Per-block fork DAA state (memory-only on CBlockIndex, not persisted). */
struct ForkDAAState {
    arith_uint256 nForkTarget{};
    int64_t nForkAvgError{};       // EMA accumulator (integral action)
    int64_t nForkLastBlockTime{};  // nTime of the previous fork block
};

/** Compute the next required difficulty target for a fork block.
 *  Pure: does not mutate any state.  `out` (if non-null) receives the
 *  DAA state to store on the new block when it is connected.
 *
 *  Measurement basis: e = pblock->nTime - prev nTime (direct stamp
 *  delta).  Controller: PI asymmetric with corrected naming -
 *  P (proportional, kp) acts on the instantaneous error, I (integral,
 *  ki_up/ki_down) acts on the EMA accumulator.  Raise slow / lower
 *  fast.  The setpoint nForkIntervalTarget is calibrated above 600s to
 *  cancel the asymmetric-integral rectification bias.
 */
uint32_t CalculateForkTarget(const CBlockIndex* pindexPrev,
                               const CBlockHeader* pblock,
                               const Consensus::Params& params,
                               ForkDAAState* out = nullptr);

/** Initialize fork DAA state at activation, seeding from the block's own
 *  difficulty so the fork continues the parent chain's cadence. */
void InitForkDAAState(CBlockIndex* pindex);

/** Get the current DAA target. */
arith_uint256 GetForkTarget(const CBlockIndex* pindex);

#endif // LIMENKA_POW_FORK_H