/*
 * This file is part of the Flowee project
 * Copyright (C) 2009-2010 Satoshi Nakamoto
 * Copyright (C) 2009-2015 The Bitcoin Core developers
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation, either version 3 of the License, or
 * (at your option) any later version.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

#ifndef FLOWEE_SCRIPT_INTERPRETER_H
#define FLOWEE_SCRIPT_INTERPRETER_H

#include "script_error.h"
#include "../primitives/Tx.h"
#include <cstdint>
#include <vector>

class PublicKey;
class CScript;
class CScriptNum;
class CTransaction;
class uint256;

/** Signature hash types/flags */
enum
{
    SIGHASH_ALL = 1,
    SIGHASH_NONE = 2,
    SIGHASH_SINGLE = 3,
    SIGHASH_UTXOS = 0x20,
    SIGHASH_FORKID = 0x40,
    SIGHASH_ANYONECANPAY = 0x80,
};

/** Script verification flags */
enum
{
    SCRIPT_VERIFY_NONE      = 0,

    // Evaluate P2SH subscripts (softfork safe, BIP16).
    SCRIPT_VERIFY_P2SH      = (1U << 0),

    // Passing a non-strict-DER signature or one with undefined hashtype to a checksig operation causes script failure.
    // Evaluating a pubkey that is not (0x04 + 64 bytes) or (0x02 or 0x03 + 32 bytes) by checksig causes script failure.
    // (softfork safe, but not used or intended as a consensus rule).
    SCRIPT_VERIFY_STRICTENC = (1U << 1),

    // Passing a non-strict-DER signature to a checksig operation causes script failure (softfork safe, BIP62 rule 1)
    SCRIPT_VERIFY_DERSIG    = (1U << 2),

    // Passing a non-strict-DER signature or one with S > order/2 to a checksig operation causes script failure
    // (softfork safe, BIP62 rule 5).
    SCRIPT_VERIFY_LOW_S     = (1U << 3),

    // verify dummy stack item consumed by CHECKMULTISIG is of zero-length (softfork safe, BIP62 rule 7).
    SCRIPT_VERIFY_NULLDUMMY = (1U << 4),

    // Using a non-push operator in the scriptSig causes script failure (softfork safe, BIP62 rule 2).
    SCRIPT_VERIFY_SIGPUSHONLY = (1U << 5),

    // Require minimal encodings for all push operations (OP_0... OP_16, OP_1NEGATE where possible, direct
    // pushes up to 75 bytes, OP_PUSHDATA up to 255 bytes, OP_PUSHDATA2 for anything larger). Evaluating
    // any other push causes the script to fail (BIP62 rule 3).
    // In addition, whenever a stack element is interpreted as a number, it must be of minimal length (BIP62 rule 4).
    // (softfork safe)
    SCRIPT_VERIFY_MINIMALDATA = (1U << 6),

    // Discourage use of NOPs reserved for upgrades (NOP1-10)
    //
    // Provided so that nodes can avoid accepting or mining transactions
    // containing executed NOP's whose meaning may change after a soft-fork,
    // thus rendering the script invalid; with this flag set executing
    // discouraged NOPs fails the script. This verification flag will never be
    // a mandatory flag applied to scripts in a block. NOPs that are not
    // executed, e.g.  within an unexecuted IF ENDIF block, are *not* rejected.
    SCRIPT_VERIFY_DISCOURAGE_UPGRADABLE_NOPS  = (1U << 7),

    // Require that only a single stack element remains after evaluation. This changes the success criterion from
    // "At least one stack element must remain, and when interpreted as a boolean, it must be true" to
    // "Exactly one stack element must remain, and when interpreted as a boolean, it must be true".
    // (softfork safe, BIP62 rule 6)
    // Note: CLEANSTACK should never be used without P2SH.
    SCRIPT_VERIFY_CLEANSTACK = (1U << 8),

    // Verify CHECKLOCKTIMEVERIFY
    //
    // See BIP65 for details.
    SCRIPT_VERIFY_CHECKLOCKTIMEVERIFY = (1U << 9),

    // support CHECKSEQUENCEVERIFY opcode
    //
    // See BIP112 for details
    SCRIPT_VERIFY_CHECKSEQUENCEVERIFY = (1U << 10),

    // Signature(s) must be empty vector if an CHECK(MULTI)SIG operation failed
    //
    SCRIPT_VERIFY_NULLFAIL = (1U << 14),

    // Do we accept signature using SIGHASH_FORKID
    //
    SCRIPT_ENABLE_SIGHASH_FORKID = (1U << 16),

    // If OP_CHECKDATASIG* are allowed.
    SCRIPT_ENABLE_CHECKDATASIG = (1U << 17),

    SCRIPT_ENABLE_SCHNORR = (1U << 18),

    SCRIPT_ENABLE_SCHNORR_MULTISIG = (1U << 19),

    // Allows the miner to appropriate coins sent to p2sh segwit addresses
    SCRIPT_ALLOW_SEGWIT_RECOVERY = (1U << 20),

    // Whether the new OP_REVERSEBYTES opcode can be used.
    SCRIPT_ENABLE_OP_REVERSEBYTES = (1U << 21),

    // Enable pay-to-script-hash using OP_HASH256 with a 32-byte script hash.
    SCRIPT_ENABLE_P2SH_32 = (1U << 22),

    // Enable CHIP-2024-07-BigInt high-precision script integer arithmetic.
    SCRIPT_ENABLE_MAY2025 = (1U << 23),

    // Enable May 2022 native transaction introspection opcodes.
    SCRIPT_ENABLE_NATIVE_INTROSPECTION = (1U << 24),

    // Enable May 2023 SIGHASH_UTXOS signing serialization.
    SCRIPT_ENABLE_SIGHASH_UTXOS = (1U << 25),

    // Enable May 2023 CashTokens script introspection.
    SCRIPT_ENABLE_CASHTOKENS = (1U << 26),

    // Use May 2025 VM-limit relay costing rules.
    SCRIPT_VM_LIMITS_STANDARD = (1U << 27),

    // Enable May 2026 script upgrades.
    SCRIPT_ENABLE_MAY2026 = (1U << 28),

    // Enable May 2022 64-bit script integer arithmetic.
    SCRIPT_ENABLE_64_BIT_INTEGERS = (1U << 29),
};

uint256 SignatureHash(const CScript &scriptCode, const CTransaction& txTo, unsigned int nIn, int64_t amount, int nHashType,
        uint32_t flags = SCRIPT_ENABLE_SIGHASH_FORKID, const std::vector<Tx::Output> *spentOutputs = nullptr,
        size_t *bytesHashed = nullptr);

class BaseSignatureChecker
{
public:
    virtual bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey,
                          const CScript& scriptCode, uint32_t flags, size_t *bytesHashed = nullptr) const
    {
        if (bytesHashed)
            *bytesHashed = 0;
        return false;
    }

    virtual bool CheckLockTime(const CScriptNum& nLockTime) const
    {
         return false;
    }

    virtual bool CheckSequence(const CScriptNum& nSequence) const
    {
         return false;
    }

    virtual bool hasTransactionContext() const
    {
        return false;
    }

    virtual const CTransaction* transaction() const
    {
        return nullptr;
    }

    virtual Tx tx() const
    {
        return Tx();
    }

    virtual unsigned int inputIndex() const
    {
        return 0;
    }

    virtual bool isLimitedContext() const
    {
        return true;
    }

    virtual bool spentOutput(unsigned int, Tx::Output&) const
    {
        return false;
    }

    virtual ~BaseSignatureChecker() {}
};

class TransactionSignatureChecker : public BaseSignatureChecker
{
private:
    const CTransaction* oldTxTo;
    const Tx &txTo;
    unsigned int nIn;
    int64_t amount;
    const std::vector<Tx::Output> *spentOutputs;

protected:
    virtual bool VerifySignature(const std::vector<unsigned char>& vchSig, const PublicKey& vchPubKey, const uint256& sighash, uint32_t flags) const;

public:
    TransactionSignatureChecker(const CTransaction* oldTxToIn, const Tx &txToIn, unsigned int nInIn, int64_t amountIn,
                                const std::vector<Tx::Output> *spentOutputsIn = nullptr)
        : oldTxTo(oldTxToIn), txTo(txToIn), nIn(nInIn), amount(amountIn), spentOutputs(spentOutputsIn) {}
    bool CheckSig(const std::vector<unsigned char>& scriptSig, const std::vector<unsigned char>& vchPubKey,
                  const CScript& scriptCode, uint32_t flags, size_t *bytesHashed = nullptr) const override;
    bool CheckLockTime(const CScriptNum& nLockTime) const override;
    bool CheckSequence(const CScriptNum& nSequence) const override;
    bool hasTransactionContext() const override;
    const CTransaction* transaction() const override;
    Tx tx() const override;
    unsigned int inputIndex() const override;
    bool isLimitedContext() const override;
    bool spentOutput(unsigned int index, Tx::Output &output) const override;
};


namespace Script {
struct State {
    State() = default;
    State(uint32_t flags) : flags(flags) {}
    uint32_t flags = SCRIPT_VERIFY_NONE; // validation flags
    uint32_t sigCheckCount = 0;
    uint64_t vmLimitScriptSigSize = 0;
    int64_t opCost = 0;
    int64_t hashDigestIterations = 0;
    ScriptError error = SCRIPT_ERR_OK;

    const char* errorString() const;
};

bool eval(std::vector<std::vector<unsigned char> > &stack, const CScript &script, const BaseSignatureChecker &checker, Script::State &state);
bool verify(const CScript& scriptSig, const CScript& scriptPubKey, const BaseSignatureChecker& checker, Script::State &state);

bool checkTransactionSignatureEncoding(const std::vector<unsigned char> &vchSig, State &state);
}


#endif