// Copyright (C) 2019-2025, Lux Industries, Inc. All rights reserved.
// See the file LICENSE for licensing terms.
//
// This file is a derived work, based on the go-ethereum library whose original
// notices appear below.
//
// It is distributed under a license compatible with the licensing terms of the
// original code from which it is derived.
//
// Much love to the original authors for their work.
// **********
// Copyright 2016 The go-ethereum Authors
// This file is part of the go-ethereum library.
//
// The go-ethereum library is free software: you can redistribute it and/or modify
// it under the terms of the GNU Lesser General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// The go-ethereum library 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 Lesser General Public License for more details.
//
// You should have received a copy of the GNU Lesser General Public License
// along with the go-ethereum library. If not, see <http://www.gnu.org/licenses/>.

package core

import (
	"context"
	"math/big"

	"github.com/holiman/uint256"
	"github.com/luxfi/evm/consensus"
	"github.com/luxfi/evm/params"
	"github.com/luxfi/geth/common"
	"github.com/luxfi/geth/consensus/misc/eip4844"
	"github.com/luxfi/geth/core/tracing"
	"github.com/luxfi/geth/core/types"
	"github.com/luxfi/geth/core/vm"
)

type hooks struct{}

var Hooks = &hooks{}

// NewEVMBlockContext creates a new context for use in the EVM.
func NewEVMBlockContext(header *types.Header, chain ChainContext, author *common.Address) vm.BlockContext {
	// Ensure BaseFee is not nil for EIP-1559 transactions
	baseFee := header.BaseFee
	if baseFee == nil && chain != nil && chain.Config() != nil {
		// If BaseFee is nil, check if EIP-1559 is enabled and set a default
		if params.GetExtra(chain.Config()).IsEVM(header.Time) {
			// EVM requires base fee
			baseFee = new(big.Int).Set(params.GetExtra(chain.Config()).FeeConfig.MinBaseFee)
		}
	}

	blockContext := vm.BlockContext{
		CanTransfer: CanTransfer,
		Transfer:    Transfer,
		GetHash:     GetHashFn(header, chain),
		Coinbase:    GetCoinbase(author, header),
		BlockNumber: new(big.Int).Set(header.Number),
		Time:        header.Time,
		Difficulty:  new(big.Int).Set(header.Difficulty),
		BaseFee:     baseFee,
		GasLimit:    header.GasLimit,
		Random:      nil,
		BlobBaseFee: func() *big.Int {
			// Only calculate blob fee if Cancun fork is active AND header has ExcessBlobGas.
			// CalcBlobFee panics with "calculating blob fee on unsupported fork" otherwise.
			if chain != nil && chain.Config() != nil && header.ExcessBlobGas != nil &&
				chain.Config().IsCancun(header.Number, header.Time) {
				return eip4844.CalcBlobFee(chain.Config(), header)
			}
			return nil
		}(),
	}

	// Shangai rules - set Random to Difficulty value
	if chain != nil && chain.Config() != nil {
		rules := chain.Config().Rules(header.Number, params.IsMergeTODO, header.Time)
		if rules.IsShanghai {
			blockContext.Random = new(common.Hash)
			blockContext.Random.SetBytes(header.Difficulty.Bytes())
			blockContext.Difficulty = new(big.Int)
		}
	}

	// Set consensus context for warp precompiles
	if chain != nil {
		if ctx := chain.ConsensusContext(); ctx != nil {
			blockContext.ConsensusContext = ctx
		}
	}

	return blockContext
}

// NewEVMTxContext creates a new transaction context for a single transaction.
func NewEVMTxContext(msg *Message) vm.TxContext {
	ctx := vm.TxContext{
		Origin:     msg.From,
		GasPrice:   new(big.Int).Set(msg.GasPrice),
		BlobHashes: msg.BlobHashes,
		// AccessEvents is not yet part of the Message type in luxfi/geth.
	}
	if msg.BlobGasFeeCap != nil {
		ctx.BlobFeeCap = new(big.Int).Set(msg.BlobGasFeeCap)
	}
	return ctx
}

// GetHashFn returns a GetHashFunc which retrieves header hashes by number
func GetHashFn(ref *types.Header, chain ChainContext) func(n uint64) common.Hash {
	// Cache will initially contain [refHash.parent],
	// Then fill up with [refHash.p, refHash.pp, refHash.ppp, ...]
	var cache []common.Hash

	return func(n uint64) common.Hash {
		if ref.Number.Uint64() <= n {
			// This situation can happen if we're doing tracing and using
			// block overrides.
			return common.Hash{}
		}
		// If there's no hash cache yet, make one
		if len(cache) == 0 {
			cache = append(cache, ref.ParentHash)
		}
		if idx := ref.Number.Uint64() - n - 1; idx < uint64(len(cache)) {
			return cache[idx]
		}
		// No luck in the cache, but we can start iterating from the last element we already know
		lastKnownHash := cache[len(cache)-1]
		lastKnownNumber := ref.Number.Uint64() - uint64(len(cache))

		for {
			header := chain.GetHeader(lastKnownHash, lastKnownNumber)
			if header == nil {
				break
			}
			cache = append(cache, header.ParentHash)
			lastKnownHash = header.ParentHash
			lastKnownNumber = header.Number.Uint64() - 1
			if n == lastKnownNumber {
				return lastKnownHash
			}
		}
		return common.Hash{}
	}
}

// CanTransfer checks whether there are enough funds in the address' account to make a transfer.
// This does not take the necessary gas into account to make the transfer valid.
func CanTransfer(db vm.StateDB, addr common.Address, amount *uint256.Int) bool {
	return db.GetBalance(addr).Cmp(amount) >= 0
}

// Transfer subtracts amount from sender and adds amount to recipient using the given Db
func Transfer(db vm.StateDB, sender, recipient common.Address, amount *uint256.Int) {
	db.SubBalance(sender, amount, tracing.BalanceChangeTransfer)
	db.AddBalance(recipient, amount, tracing.BalanceChangeTransfer)
}

// ChainContext supports retrieving headers and consensus parameters from the
// current blockchain to be used during transaction processing.
type ChainContext interface {
	// Engine retrieves the chain's consensus engine.
	Engine() consensus.Engine

	// GetHeader returns the header corresponding to the hash/number argument pair.
	GetHeader(common.Hash, uint64) *types.Header

	// Config returns the blockchain's chain configuration
	Config() *params.ChainConfig

	// ConsensusContext returns the consensus context for warp messages.
	// May return nil if not set.
	ConsensusContext() context.Context
}

func wrapStateDB(rules params.Rules, db vm.StateDB) vm.StateDB {
	// AP1 was activated at genesis for mainnet; testnet activated at block 3,114,811.
	// No StateDB wrapper is currently required because all active networks
	// are past the AP1 activation point.
	return db
}

// GetCoinbase returns the coinbase for the given header and author.
func GetCoinbase(author *common.Address, header *types.Header) common.Address {
	if author != nil {
		return *author
	}
	return header.Coinbase
}