package evm

import (
	"math"

	errorsmod "cosmossdk.io/errors"
	sdkmath "cosmossdk.io/math"
	sdk "github.com/cosmos/cosmos-sdk/types"
	errortypes "github.com/cosmos/cosmos-sdk/types/errors"
	authante "github.com/cosmos/cosmos-sdk/x/auth/ante"
	"github.com/ethereum/go-ethereum/params"

	haqqtypes "github.com/haqq-network/haqq/types"
	evmtypes "github.com/haqq-network/haqq/x/evm/types"
)

// NewDynamicFeeChecker returns a `TxFeeChecker` that applies a dynamic fee to
// Cosmos txs using the EIP-1559 fee market logic.
// This can be called in both CheckTx and deliverTx modes.
// a) feeCap = tx.fees / tx.gas
// b) tipFeeCap = tx.MaxPriorityPrice (default) or MaxInt64
// - when `ExtensionOptionDynamicFeeTx` is omitted, `tipFeeCap` defaults to `MaxInt64`.
// - when london hardfork is not enabled, it falls back to SDK default behavior (validator min-gas-prices).
// - Tx priority is set to `effectiveGasPrice / DefaultPriorityReduction`.
func NewDynamicFeeChecker(k DynamicFeeEVMKeeper) authante.TxFeeChecker {
	return func(ctx sdk.Context, tx sdk.Tx) (sdk.Coins, int64, error) {
		feeTx, ok := tx.(sdk.FeeTx)
		if !ok {
			return sdk.Coins{}, 0, errorsmod.Wrap(errortypes.ErrTxDecode, "Tx must be a FeeTx")
		}
		// TODO: in the e2e test, if the fee in the genesis transaction meet the baseFee and minGasPrice in the feemarket, we can remove this code
		if ctx.BlockHeight() == 0 {
			// genesis transactions: fallback to min-gas-price logic
			return checkTxFeeWithValidatorMinGasPrices(ctx, feeTx)
		}

		params := k.GetParams(ctx)
		denom := params.EvmDenom
		ethCfg := params.ChainConfig.EthereumConfig(k.ChainID())

		return FeeChecker(ctx, k, denom, ethCfg, feeTx)
	}
}

// FeeChecker returns the effective fee and priority for a given transaction.
func FeeChecker(
	ctx sdk.Context,
	k DynamicFeeEVMKeeper,
	denom string,
	ethConfig *params.ChainConfig,
	feeTx sdk.FeeTx,
) (sdk.Coins, int64, error) {
	baseFee := k.GetBaseFee(ctx, ethConfig)
	if baseFee == nil {
		// london hardfork is not enabled: fallback to min-gas-prices logic
		return checkTxFeeWithValidatorMinGasPrices(ctx, feeTx)
	}

	// default to `MaxInt64` when there's no extension option.
	maxPriorityPrice := sdkmath.NewInt(math.MaxInt64)

	// get the priority tip cap from the extension option.
	if hasExtOptsTx, ok := feeTx.(authante.HasExtensionOptionsTx); ok {
		for _, opt := range hasExtOptsTx.GetExtensionOptions() {
			if extOpt, ok := opt.GetCachedValue().(*haqqtypes.ExtensionOptionDynamicFeeTx); ok {
				maxPriorityPrice = extOpt.MaxPriorityPrice
				break
			}
		}
	}

	// priority fee cannot be negative
	if maxPriorityPrice.IsNegative() {
		return nil, 0, errorsmod.Wrapf(errortypes.ErrInsufficientFee, "max priority price cannot be negative")
	}

	gas := feeTx.GetGas()
	feeCoins := feeTx.GetFee()
	fee := feeCoins.AmountOfNoDenomValidation(denom)

	feeCap := fee.Quo(sdkmath.NewIntFromUint64(gas))
	baseFeeInt := sdkmath.NewIntFromBigInt(baseFee)

	if feeCap.LT(baseFeeInt) {
		return nil, 0, errorsmod.Wrapf(errortypes.ErrInsufficientFee, "gas prices too low, got: %s%s required: %s%s. Please retry using a higher gas price or a higher fee", feeCap, denom, baseFeeInt, denom)
	}

	// calculate the effective gas price using the EIP-1559 logic.
	effectivePrice := sdkmath.NewIntFromBigInt(evmtypes.EffectiveGasPrice(baseFeeInt.BigInt(), feeCap.BigInt(), maxPriorityPrice.BigInt()))

	// NOTE: create a new coins slice without having to validate the denom
	effectiveFee := sdk.Coins{
		{
			Denom:  denom,
			Amount: effectivePrice.Mul(sdkmath.NewIntFromUint64(gas)),
		},
	}

	bigPriority := effectivePrice.Sub(baseFeeInt).Quo(evmtypes.DefaultPriorityReduction)
	priority := int64(math.MaxInt64)

	if bigPriority.IsInt64() {
		priority = bigPriority.Int64()
	}

	return effectiveFee, priority, nil
}

// checkTxFeeWithValidatorMinGasPrices implements the default fee logic, where the minimum price per
// unit of gas is fixed and set by each validator, and the tx priority is computed from the gas price.
func checkTxFeeWithValidatorMinGasPrices(ctx sdk.Context, tx sdk.FeeTx) (sdk.Coins, int64, error) {
	feeCoins := tx.GetFee()
	minGasPrices := ctx.MinGasPrices()
	gas := int64(tx.GetGas()) //nolint: gosec // G115 -- checked for int overflow on ValidateBasic()

	// Ensure that the provided fees meet a minimum threshold for the validator,
	// if this is a CheckTx. This is only for local mempool purposes, and thus
	// is only ran on check tx.
	if ctx.IsCheckTx() && !minGasPrices.IsZero() {
		requiredFees := make(sdk.Coins, len(minGasPrices))

		// Determine the required fees by multiplying each required minimum gas
		// price by the gas limit, where fee = ceil(minGasPrice * gasLimit).
		glDec := sdkmath.LegacyNewDec(gas)
		for i, gp := range minGasPrices {
			fee := gp.Amount.Mul(glDec)
			requiredFees[i] = sdk.NewCoin(gp.Denom, fee.Ceil().RoundInt())
		}

		if !feeCoins.IsAnyGTE(requiredFees) {
			return nil, 0, errorsmod.Wrapf(errortypes.ErrInsufficientFee, "insufficient fees; got: %s required: %s", feeCoins, requiredFees)
		}
	}

	priority := getTxPriority(feeCoins, gas)
	return feeCoins, priority, nil
}

// getTxPriority returns a naive tx priority based on the amount of the smallest denomination of the gas price
// provided in a transaction.
func getTxPriority(fees sdk.Coins, gas int64) int64 {
	var priority int64

	for _, fee := range fees {
		gasPrice := fee.Amount.QuoRaw(gas)
		amt := gasPrice.Quo(evmtypes.DefaultPriorityReduction)
		p := int64(math.MaxInt64)

		if amt.IsInt64() {
			p = amt.Int64()
		}

		if priority == 0 || p < priority {
			priority = p
		}
	}

	return priority
}
