package network

import (
	"errors"
	"math/big"

	"github.com/ethereum/go-ethereum/common"
	"github.com/harmony-one/harmony/common/denominations"
	"github.com/harmony-one/harmony/consensus/engine"
	"github.com/harmony-one/harmony/consensus/reward"
	"github.com/harmony-one/harmony/internal/utils"
	"github.com/harmony-one/harmony/numeric"
	"github.com/harmony-one/harmony/shard"
)

var (
	// BlockReward is the block reward, to be split evenly among block signers.
	BlockReward = new(big.Int).Mul(big.NewInt(24), big.NewInt(denominations.One))
	// BaseStakedReward is the flat-rate block reward for epos staking launch.
	BaseStakedReward = numeric.NewDecFromBigInt(new(big.Int).Mul(
		big.NewInt(28), big.NewInt(denominations.One),
	))
	// BlockRewardStakedCase is the baseline block reward in staked case -
	totalTokens = numeric.NewDecFromBigInt(
		new(big.Int).Mul(big.NewInt(12600000000), big.NewInt(denominations.One)),
	)
	targetStakedPercentage = numeric.MustNewDecFromStr("0.35")
	dynamicAdjust          = numeric.MustNewDecFromStr("0.4")
	// ErrPayoutNotEqualBlockReward ..
	ErrPayoutNotEqualBlockReward = errors.New(
		"total payout not equal to blockreward",
	)
	// NoReward ..
	NoReward = common.Big0
	// EmptyPayout ..
	EmptyPayout = noReward{}
)

type ignoreMissing struct{}

func (ignoreMissing) MissingSigners() shard.SlotList {
	return shard.SlotList{}
}

type noReward struct{ ignoreMissing }

func (noReward) ReadRoundResult() *reward.CompletedRound {
	return &reward.CompletedRound{
		Total:            common.Big0,
		BeaconchainAward: []reward.Payout{},
		ShardChainAward:  []reward.Payout{},
	}
}

type preStakingEra struct {
	ignoreMissing
	payout *big.Int
}

// NewPreStakingEraRewarded ..
func NewPreStakingEraRewarded(totalAmount *big.Int) reward.Reader {
	return &preStakingEra{ignoreMissing{}, totalAmount}
}

func (p *preStakingEra) ReadRoundResult() *reward.CompletedRound {
	return &reward.CompletedRound{
		Total:            p.payout,
		BeaconchainAward: []reward.Payout{},
		ShardChainAward:  []reward.Payout{},
	}
}

type stakingEra struct {
	reward.CompletedRound
	missingSigners shard.SlotList
}

// NewStakingEraRewardForRound ..
func NewStakingEraRewardForRound(
	totalPayout *big.Int,
	mia shard.SlotList,
) reward.Reader {

	return &stakingEra{
		CompletedRound: reward.CompletedRound{
			Total:            totalPayout,
			BeaconchainAward: []reward.Payout{},
			ShardChainAward:  []reward.Payout{},
		},
		missingSigners: mia,
	}
}

func (r *stakingEra) MissingSigners() shard.SlotList {
	return r.missingSigners
}

// ReadRoundResult ..
func (r *stakingEra) ReadRoundResult() *reward.CompletedRound {
	return &r.CompletedRound
}

func adjust(amount numeric.Dec) numeric.Dec {
	return amount.MulTruncate(
		numeric.NewDecFromBigInt(big.NewInt(denominations.One)),
	)
}

// Adjustment ..
func Adjustment(percentageStaked numeric.Dec) (numeric.Dec, numeric.Dec) {
	howMuchOff := targetStakedPercentage.Sub(percentageStaked)
	adjustBy := adjust(
		howMuchOff.MulTruncate(numeric.NewDec(100)).Mul(dynamicAdjust),
	)
	return howMuchOff, adjustBy
}

// WhatPercentStakedNow ..
func WhatPercentStakedNow(
	beaconchain engine.ChainReader,
	timestamp int64,
) (*big.Int, *numeric.Dec, error) {
	stakedNow := numeric.ZeroDec()
	// Only elected validators' stake is counted in stake ratio because only their stake is under slashing risk
	active, err := beaconchain.ReadElectedValidatorList()
	if err != nil {
		return nil, nil, err
	}

	soFarDoledOut, err := beaconchain.ReadBlockRewardAccumulator(
		beaconchain.CurrentHeader().Number().Uint64(),
	)

	if err != nil {
		return nil, nil, err
	}

	dole := numeric.NewDecFromBigInt(soFarDoledOut)

	for i := range active {
		wrapper, err := beaconchain.ReadValidatorInformation(active[i])
		if err != nil {
			return nil, nil, err
		}
		stakedNow = stakedNow.Add(
			numeric.NewDecFromBigInt(wrapper.TotalDelegation()),
		)
	}
	percentage := stakedNow.Quo(totalTokens.Mul(
		reward.PercentageForTimeStamp(timestamp),
	).Add(dole))
	utils.Logger().Info().
		Str("so-far-doled-out", dole.String()).
		Str("staked-percentage", percentage.String()).
		Str("currently-staked", stakedNow.String()).
		Msg("Computed how much staked right now")
	return soFarDoledOut, &percentage, nil
}