// Package params defines important constants that are essential to the
// Ethereum 2.0 services.
package params

import (
	"math/big"
	"time"
)

func makeEmptySignature() [][]byte {
	signature := make([][]byte, 2)
	signature[0] = make([]byte, 48)
	signature[1] = make([]byte, 48)
	return signature
}

// BeaconChainConfig contains constant configs for node to participate in beacon chain.
type BeaconChainConfig struct {
	// Misc constants.
	ShardCount                 uint64 // ShardCount is the number of shard chains in Ethereum 2.0.
	TargetCommitteeSize        uint64 // TargetCommitteeSize is the number of validators in a committee when the chain is healthy.
	MaxBalanceChurnQuotient    uint64 // MaxBalanceChurnQuotient is used to determine how many validators can rotate per epoch.
	BeaconChainShardNumber     uint64 // BeaconChainShardNumber is the shard number of the beacon chain.
	MaxIndicesPerSlashableVote uint64 // MaxIndicesPerSlashableVote is used to determine how many validators can be slashed per vote.
	LatestBlockRootsLength     uint64 // LatestBlockRootsLength is the number of block roots kept in the beacon state.
	LatestRandaoMixesLength    uint64 // LatestRandaoMixesLength is the number of randao mixes kept in the beacon state.
	LatestPenalizedExitLength  uint64 // LatestPenalizedExitLength is used to track penalized exit balances per time interval.
	LatestIndexRootsLength     uint64 // LatestIndexRootsLength is the number of index roots kept in beacon state, used by light client.
	MaxWithdrawalsPerEpoch     uint64 // MaxWithdrawalsPerEpoch is the max withdrawals can happen for a single epoch.

	// Deposit contract constants.
	DepositContractAddress   []byte // DepositContractAddress is the address of the deposit contract in PoW chain.
	DepositContractTreeDepth uint64 // Depth of the Merkle trie of deposits in the validator deposit contract on the PoW chain.

	// Gwei Values
	MinDepositAmount uint64 // MinDepositAmount is the maximal amount of Gwei a validator can send to the deposit contract at once.
	MaxDepositAmount uint64 // MaxDepositAmount is the maximal amount of Gwei a validator can send to the deposit contract at once.
	EjectionBalance  uint64 // EjectionBalance is the minimal GWei a validator needs to have before ejected.

	// Initial value constants.
	GenesisForkVersion      uint64   // GenesisForkVersion is used to track fork version between state transitions.
	GenesisSlot             uint64   // GenesisSlot is used to initialize the genesis state fields.
	GenesisEpoch            uint64   // GenesisEpoch is used to initialize epoch.
	GenesisStartShard       uint64   // GenesisStartShard is the first shard to assign validators.
	ZeroHash                [32]byte // ZeroHash is used to represent a zeroed out 32 byte array.
	EmptySignature          [][]byte // EmptySignature is used to represent a zeroed out BLS Signature.
	BLSWithdrawalPrefixByte byte     // BLSWithdrawalPrefixByte is used for BLS withdrawal and it's the first byte.

	// Time parameters constants.
	SlotDuration                 uint64 // SlotDuration is how many seconds are in a single slot.
	MinAttestationInclusionDelay uint64 // MinAttestationInclusionDelay defines how long validator has to wait to include attestation for beacon block.
	EpochLength                  uint64 // EpochLength is the number of slots in an epoch.
	SeedLookahead                uint64 // SeedLookahead is the duration of randao look ahead seed.
	EntryExitDelay               uint64 // EntryExitDelay is the duration a validator has to wait for entry and exit in epoch.
	Eth1DataVotingPeriod         uint64 // Eth1DataVotingPeriod defines how often the merkle root of deposit receipts get updated in beacon node.
	Eth1FollowDistance           uint64 // Eth1FollowDistance is the number of eth1.0 blocks to wait before considering a new deposit for voting. This only applies after the chain as been started.
	MinValidatorWithdrawalEpochs uint64 // MinValidatorWithdrawalEpochs is the shortest amount of time a validator can get the deposit out.
	FarFutureEpoch               uint64 // FarFutureEpoch represents a epoch extremely far away in the future used as the default penalization slot for validators.

	// Reward and penalty quotients constants.
	BaseRewardQuotient           uint64 // BaseRewardQuotient is used to calculate validator per-slot interest rate.
	WhistlerBlowerRewardQuotient uint64 // WhistlerBlowerRewardQuotient is used to calculate whistler blower reward.
	IncluderRewardQuotient       uint64 // IncluderRewardQuotient defines the reward quotient of proposer for including attestations..
	InactivityPenaltyQuotient    uint64 // InactivityPenaltyQuotient defines how much validator leaks out balances for offline.

	// Max operations per block constants.
	MaxExits             uint64 // MaxExits determines the maximum number of validator exits in a block.
	MaxDeposits          uint64 // MaxExits determines the maximum number of validator deposits in a block.
	MaxAttestations      uint64 // MaxAttestations defines the maximum allowed attestations in a beacon block.
	MaxProposerSlashings uint64 // MaxProposerSlashings defines the maximum number of slashings of proposers possible in a block.
	MaxAttesterSlashings uint64 // MaxAttesterSlashings defines the maximum number of casper FFG slashings possible in a block.

	// Prysm constants.
	DepositsForChainStart uint64    // DepositsForChainStart defines how many validator deposits needed to kick off beacon chain.
	SimulatedBlockRandao  [32]byte  // SimulatedBlockRandao is a RANDAO seed stubbed in simulated block for advancing local beacon chain.
	RandBytes             uint64    // RandBytes is the number of bytes used as entropy to shuffle validators.
	SyncPollingInterval   int64     // SyncPollingInterval queries network nodes for sync status.
	GenesisTime           time.Time // GenesisTime used by the protocol.
	MaxNumLog2Validators  uint64    // MaxNumLog2Validators is the Max number of validators in Log2 exists given total ETH supply.
}

// DepositContractConfig contains the deposits for
type DepositContractConfig struct {
	DepositsForChainStart *big.Int // DepositsForChainStart defines how many validator deposits needed to kick off beacon chain.
	MinDepositAmount      *big.Int // MinDepositAmount defines the minimum deposit amount in gwei that is required in the deposit contract.
	MaxDepositAmount      *big.Int // // MaxDepositAmount defines the minimum deposit amount in gwei that is required in the deposit contract.
}

// ShardChainConfig contains configs for node to participate in shard chains.
type ShardChainConfig struct {
	ChunkSize         uint64 // ChunkSize defines the size of each chunk in bytes.
	MaxShardBlockSize uint64 // MaxShardBlockSize defines the max size of each shard block in bytes.
}

var defaultBeaconConfig = &BeaconChainConfig{
	// Misc constant.
	ShardCount:                 1024,
	TargetCommitteeSize:        128,
	MaxBalanceChurnQuotient:    32,
	BeaconChainShardNumber:     1<<64 - 1,
	MaxIndicesPerSlashableVote: 1,
	LatestBlockRootsLength:     8192,
	LatestRandaoMixesLength:    8192,
	LatestPenalizedExitLength:  8192,
	LatestIndexRootsLength:     8192,
	MaxWithdrawalsPerEpoch:     4,

	// Deposit contract constants.
	DepositContractTreeDepth: 32,

	// Gwei values:
	MinDepositAmount: 1 * 1e9,
	MaxDepositAmount: 32 * 1e9,
	EjectionBalance:  16 * 1e9,

	// Initial value constants.
	GenesisForkVersion: 0,
	GenesisSlot:        1 << 63,
	GenesisEpoch:       1 << 63 / 64,
	GenesisStartShard:  0,
	FarFutureEpoch:     1<<64 - 1,
	ZeroHash:           [32]byte{},
	EmptySignature:     makeEmptySignature(),

	// Time parameter constants.
	SlotDuration:                 6,
	MinAttestationInclusionDelay: 4,
	EpochLength:                  64,
	SeedLookahead:                1,
	EntryExitDelay:               4,
	Eth1DataVotingPeriod:         16,
	Eth1FollowDistance:           1024,

	// Reward and penalty quotients constants.
	BaseRewardQuotient:           32,
	WhistlerBlowerRewardQuotient: 512,
	IncluderRewardQuotient:       8,
	InactivityPenaltyQuotient:    1 << 24,

	// Max operations per block constants.
	MaxExits:             16,
	MaxDeposits:          16,
	MaxAttestations:      128,
	MaxProposerSlashings: 16,
	MaxAttesterSlashings: 1,

	// Prysm constants.
	DepositsForChainStart: 16384,
	RandBytes:             3,
	SyncPollingInterval:   6 * 4, // Query nodes over the network every 4 slots for sync status.
	GenesisTime:           time.Date(2018, 9, 0, 0, 0, 0, 0, time.UTC),
	MaxNumLog2Validators:  24,
}

var demoBeaconConfig = &BeaconChainConfig{
	// Misc constant.
	ShardCount:                 5,
	TargetCommitteeSize:        3,
	EjectionBalance:            defaultBeaconConfig.EjectionBalance,
	MaxBalanceChurnQuotient:    defaultBeaconConfig.MaxBalanceChurnQuotient,
	BeaconChainShardNumber:     defaultBeaconConfig.BeaconChainShardNumber,
	MaxIndicesPerSlashableVote: defaultBeaconConfig.MaxIndicesPerSlashableVote,
	LatestBlockRootsLength:     defaultBeaconConfig.LatestBlockRootsLength,
	LatestRandaoMixesLength:    defaultBeaconConfig.LatestRandaoMixesLength,
	LatestPenalizedExitLength:  defaultBeaconConfig.LatestPenalizedExitLength,
	LatestIndexRootsLength:     defaultBeaconConfig.LatestIndexRootsLength,
	MaxWithdrawalsPerEpoch:     defaultBeaconConfig.MaxWithdrawalsPerEpoch,

	// Deposit contract constants.
	DepositContractTreeDepth: defaultBeaconConfig.DepositContractTreeDepth,
	MaxDepositAmount:         defaultBeaconConfig.MaxDepositAmount,
	MinDepositAmount:         defaultBeaconConfig.MinDepositAmount,

	// Initial value constants.
	GenesisForkVersion: defaultBeaconConfig.GenesisForkVersion,
	GenesisSlot:        defaultBeaconConfig.GenesisSlot,
	GenesisEpoch:       defaultBeaconConfig.GenesisEpoch,
	GenesisStartShard:  defaultBeaconConfig.GenesisStartShard,
	FarFutureEpoch:     defaultBeaconConfig.FarFutureEpoch,
	ZeroHash:           defaultBeaconConfig.ZeroHash,
	EmptySignature:     defaultBeaconConfig.EmptySignature,

	// Time parameter constants.
	SlotDuration:                 2,
	MinAttestationInclusionDelay: defaultBeaconConfig.MinAttestationInclusionDelay,
	EpochLength:                  defaultBeaconConfig.EpochLength,
	SeedLookahead:                defaultBeaconConfig.SeedLookahead,
	EntryExitDelay:               defaultBeaconConfig.EntryExitDelay,
	Eth1DataVotingPeriod:         defaultBeaconConfig.Eth1DataVotingPeriod,
	Eth1FollowDistance:           defaultBeaconConfig.Eth1FollowDistance,

	// Reward and penalty quotients constants.
	BaseRewardQuotient:           defaultBeaconConfig.BaseRewardQuotient,
	WhistlerBlowerRewardQuotient: defaultBeaconConfig.WhistlerBlowerRewardQuotient,
	IncluderRewardQuotient:       defaultBeaconConfig.IncluderRewardQuotient,
	InactivityPenaltyQuotient:    defaultBeaconConfig.InactivityPenaltyQuotient,

	// Max operations per block constants.
	MaxExits:             defaultBeaconConfig.MaxExits,
	MaxDeposits:          defaultBeaconConfig.MaxDeposits,
	MaxAttestations:      defaultBeaconConfig.MaxAttestations,
	MaxProposerSlashings: defaultBeaconConfig.MaxProposerSlashings,
	MaxAttesterSlashings: defaultBeaconConfig.MaxAttesterSlashings,

	// Prysm constants.
	DepositsForChainStart: defaultBeaconConfig.DepositsForChainStart,
	RandBytes:             defaultBeaconConfig.RandBytes,
	SyncPollingInterval:   2 * 4, // Query nodes over the network every 4 slots for sync status.
	GenesisTime:           time.Now(),
	MaxNumLog2Validators:  defaultBeaconConfig.MaxNumLog2Validators,
	SimulatedBlockRandao:  [32]byte{'S', 'I', 'M', 'U', 'L', 'A', 'T', 'O', 'R'},
}

var defaultShardConfig = &ShardChainConfig{
	ChunkSize:         uint64(256),
	MaxShardBlockSize: uint64(32768),
}

var defaultDepositContractConfig = &DepositContractConfig{
	DepositsForChainStart: big.NewInt(16384),
	MinDepositAmount:      big.NewInt(1e9),
	MaxDepositAmount:      big.NewInt(32e9),
}

var beaconConfig = defaultBeaconConfig
var shardConfig = defaultShardConfig
var contractConfig = defaultDepositContractConfig

// BeaconConfig retrieves beacon chain config.
func BeaconConfig() *BeaconChainConfig {
	return beaconConfig
}

// ShardConfig retrieves shard chain config.
func ShardConfig() *ShardChainConfig {
	return shardConfig
}

// ContractConfig retrieves the deposit contract config
func ContractConfig() *DepositContractConfig {
	return contractConfig
}

// DemoContractConfig uses the argument provided to initialize a fresh config.
func DemoContractConfig(depositsReq *big.Int, minDeposit *big.Int, maxDeposit *big.Int) *DepositContractConfig {
	return &DepositContractConfig{
		DepositsForChainStart: depositsReq,
		MinDepositAmount:      minDeposit,
		MaxDepositAmount:      maxDeposit,
	}
}

// UseDemoBeaconConfig for beacon chain services.
func UseDemoBeaconConfig() {
	beaconConfig = demoBeaconConfig
}

// OverrideBeaconConfig by replacing the config. The preferred pattern is to
// call BeaconConfig(), change the specific parameters, and then call
// OverrideBeaconConfig(c). Any subsequent calls to params.BeaconConfig() will
// return this new configuration.
func OverrideBeaconConfig(c *BeaconChainConfig) {
	beaconConfig = c
}