// Copyright (c) 2014-2016 The btcsuite developers
// Use of this source code is governed by an ISC
// license that can be found in the LICENSE file.

package chaincfg

import (
	"encoding/binary"
	"encoding/hex"
	"errors"
	"math"
	"math/big"
	"strings"
	"time"

	"github.com/btcsuite/btcd/chaincfg/chainhash"
	"github.com/btcsuite/btcd/wire"
)

// These variables are the chain proof-of-work limit parameters for each default
// network.
var (
	// bigOne is 1 represented as a big.Int.  It is defined here to avoid
	// the overhead of creating it multiple times.
	bigOne = big.NewInt(1)

	// mainPowLimit is the highest proof of work value a Bitcoin block can
	// have for the main network.  It is the value 2^240 - 1.
	mainPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 240), bigOne)

	// regressionPowLimit is the highest proof of work value a Bitcoin block
	// can have for the regression test network.  It is the value 2^255 - 1.
	regressionPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), bigOne)

	// testNet3PowLimit is the highest proof of work value a Bitcoin block
	// can have for the test network (version 3).  It is the value
	// 2^240 - 1.
	testNet3PowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 240), bigOne)

	// simNetPowLimit is the highest proof of work value a Bitcoin block
	// can have for the simulation test network.  It is the value 2^255 - 1.
	simNetPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), bigOne)

	// sigNetPowLimit is the highest proof of work value a bitcoin block can
	// have for the signet test network. It is the value 0x0377ae << 216.
	sigNetPowLimit = new(big.Int).Lsh(new(big.Int).SetInt64(0x0377ae), 216)

	// DefaultSignetChallenge is the byte representation of the signet
	// challenge for the default (public, Taproot enabled) signet network.
	// This is the binary equivalent of the bitcoin script
	//  1 03ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d1e086be430
	//  0359ef5021964fe22d6f8e05b2463c9540ce96883fe3b278760f048f5189f2e6c4 2
	//  OP_CHECKMULTISIG
	DefaultSignetChallenge, _ = hex.DecodeString(
		"512103ad5e0edad18cb1f0fc0d28a3d4f1f3e445640337489abb10404f2d" +
			"1e086be430210359ef5021964fe22d6f8e05b2463c9540ce9688" +
			"3fe3b278760f048f5189f2e6c452ae",
	)

	// DefaultSignetDNSSeeds is the list of seed nodes for the default
	// (public, Taproot enabled) signet network.
	DefaultSignetDNSSeeds = []DNSSeed{
		{"178.128.221.177", false},
		{"2a01:7c8:d005:390::5", false},
		{"v7ajjeirttkbnt32wpy3c6w3emwnfr3fkla7hpxcfokr3ysd3kqtzmqd.onion:38333", false},
	}
)

// Checkpoint identifies a known good point in the block chain.  Using
// checkpoints allows a few optimizations for old blocks during initial download
// and also prevents forks from old blocks.
//
// Each checkpoint is selected based upon several factors.  See the
// documentation for blockchain.IsCheckpointCandidate for details on the
// selection criteria.
type Checkpoint struct {
	Height int32
	Hash   *chainhash.Hash
}

// DNSSeed identifies a DNS seed.
type DNSSeed struct {
	// Host defines the hostname of the seed.
	Host string

	// HasFiltering defines whether the seed supports filtering
	// by service flags (wire.ServiceFlag).
	HasFiltering bool
}

// ConsensusDeployment defines details related to a specific consensus rule
// change that is voted in.  This is part of BIP0009.
type ConsensusDeployment struct {
	// BitNumber defines the specific bit number within the block version
	// this particular soft-fork deployment refers to.
	BitNumber uint8

	// StartTime is the median block time after which voting on the
	// deployment starts.
	StartTime uint64

	// ExpireTime is the median block time after which the attempted
	// deployment expires.
	ExpireTime uint64

	// ForceActiveAt is added by LBRY to bypass consensus. Features are activated via hard-fork instead.
	ForceActiveAt int32
}

// Constants that define the deployment offset in the deployments field of the
// parameters for each deployment.  This is useful to be able to get the details
// of a specific deployment by name.
const (
	// DeploymentTestDummy defines the rule change deployment ID for testing
	// purposes.
	DeploymentTestDummy = iota

	// DeploymentCSV defines the rule change deployment ID for the CSV
	// soft-fork package. The CSV package includes the deployment of BIPS
	// 68, 112, and 113.
	DeploymentCSV

	// DeploymentSegwit defines the rule change deployment ID for the
	// Segregated Witness (segwit) soft-fork package. The segwit package
	// includes the deployment of BIPS 141, 142, 144, 145, 147 and 173.
	DeploymentSegwit

	// DeploymentTaproot defines the rule change deployment ID for the
	// Taproot (+Schnorr) soft-fork package. The taproot package includes
	// the deployment of BIPS 340, 341 and 342.
	DeploymentTaproot

	// NOTE: DefinedDeployments must always come last since it is used to
	// determine how many defined deployments there currently are.

	// DefinedDeployments is the number of currently defined deployments.
	DefinedDeployments
)

// Params defines a Bitcoin network by its parameters.  These parameters may be
// used by Bitcoin applications to differentiate networks as well as addresses
// and keys for one network from those intended for use on another network.
type Params struct {
	// Name defines a human-readable identifier for the network.
	Name string

	// Net defines the magic bytes used to identify the network.
	Net wire.BitcoinNet

	// DefaultPort defines the default peer-to-peer port for the network.
	DefaultPort string

	// DNSSeeds defines a list of DNS seeds for the network that are used
	// as one method to discover peers.
	DNSSeeds []DNSSeed

	// GenesisBlock defines the first block of the chain.
	GenesisBlock *wire.MsgBlock

	// GenesisHash is the starting block hash.
	GenesisHash *chainhash.Hash

	// PowLimit defines the highest allowed proof of work value for a block
	// as a uint256.
	PowLimit *big.Int

	// PowLimitBits defines the highest allowed proof of work value for a
	// block in compact form.
	PowLimitBits uint32

	// These fields define the block heights at which the specified softfork
	// BIP became active.
	BIP0034Height int32
	BIP0065Height int32
	BIP0066Height int32

	// CoinbaseMaturity is the number of blocks required before newly mined
	// coins (coinbase transactions) can be spent.
	CoinbaseMaturity uint16

	// SubsidyReductionInterval is the interval of blocks before the subsidy
	// is reduced.
	SubsidyReductionInterval int32

	// TargetTimespan is the desired amount of time that should elapse
	// before the block difficulty requirement is examined to determine how
	// it should be changed in order to maintain the desired block
	// generation rate.
	TargetTimespan time.Duration

	// TargetTimePerBlock is the desired amount of time to generate each
	// block.
	TargetTimePerBlock time.Duration

	// RetargetAdjustmentFactor is the adjustment factor used to limit
	// the minimum and maximum amount of adjustment that can occur between
	// difficulty retargets.
	RetargetAdjustmentFactor int64

	// ReduceMinDifficulty defines whether the network should reduce the
	// minimum required difficulty after a long enough period of time has
	// passed without finding a block.  This is really only useful for test
	// networks and should not be set on a main network.
	ReduceMinDifficulty bool

	// MinDiffReductionTime is the amount of time after which the minimum
	// required difficulty should be reduced when a block hasn't been found.
	//
	// NOTE: This only applies if ReduceMinDifficulty is true.
	MinDiffReductionTime time.Duration

	// GenerateSupported specifies whether or not CPU mining is allowed.
	GenerateSupported bool

	// Checkpoints ordered from oldest to newest.
	Checkpoints []Checkpoint

	// These fields are related to voting on consensus rule changes as
	// defined by BIP0009.
	//
	// RuleChangeActivationThreshold is the number of blocks in a threshold
	// state retarget window for which a positive vote for a rule change
	// must be cast in order to lock in a rule change. It should typically
	// be 95% for the main network and 75% for test networks.
	//
	// MinerConfirmationWindow is the number of blocks in each threshold
	// state retarget window.
	//
	// Deployments define the specific consensus rule changes to be voted
	// on.
	RuleChangeActivationThreshold uint32
	MinerConfirmationWindow       uint32
	Deployments                   [DefinedDeployments]ConsensusDeployment

	// Mempool parameters
	RelayNonStdTxs bool

	// Human-readable part for Bech32 encoded segwit addresses, as defined
	// in BIP 173.
	Bech32HRPSegwit string

	// Address encoding magics
	PubKeyHashAddrID byte // First byte of a P2PKH address
	ScriptHashAddrID byte // First byte of a P2SH address
	PrivateKeyID     byte // First byte of a WIF private key

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID [4]byte
	HDPublicKeyID  [4]byte

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType uint32
}

// MainNetParams defines the network parameters for the main Bitcoin network.
var MainNetParams = Params{
	Name:        "mainnet",
	Net:         wire.MainNet,
	DefaultPort: "9246",
	DNSSeeds: []DNSSeed{
		{"dnsseed1.lbry.com", true},
		{"dnsseed2.lbry.com", true},
		{"dnsseed3.lbry.com", true},
		{"seed.lbry.grin.io", true},
		{"seed.allaboutlbc.com", true},
	},

	// Chain parameters
	GenesisBlock:             &genesisBlock,
	GenesisHash:              &genesisHash,
	PowLimit:                 mainPowLimit,
	PowLimitBits:             0x1f00ffff,
	BIP0034Height:            1,
	BIP0065Height:            200000,
	BIP0066Height:            200000,
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 1 << 5,
	TargetTimespan:           time.Second * 150, // retarget every block
	TargetTimePerBlock:       time.Second * 150, // 150 seconds
	RetargetAdjustmentFactor: 4,                 // 25% less, 400% more
	ReduceMinDifficulty:      false,
	MinDiffReductionTime:     0,
	GenerateSupported:        false,

	// Checkpoints ordered from oldest to newest.
	Checkpoints: []Checkpoint{
		{40000, newHashFromStr("4c55584b068108b15c0066a010d11971aa92f46b0a73d479f1b7fa57df8b05f4")},
		{80000, newHashFromStr("6e9facdfb87ba8394a46c61a7c093f7f00b1397a2dabc6a04f2911e0efdcf50a")},
		{120000, newHashFromStr("6a9dba420ec544b927769765dccec8b29e214e6ca9f82b54a52bf20ca517b75a")},
		{160000, newHashFromStr("87b2913a509d857401f7587903c90214db7847af1a1ad63a3b6f245936e3ae9d")},
		{200000, newHashFromStr("0fe8ed6019a83028006435e47be4e37a0d3ed48019cde1dc7ede6562e5829839")},
		{240000, newHashFromStr("cb3c2342afbe7291012f2288403a9d105f46987f78b279d516db2deb4d35b0b7")},
		{280000, newHashFromStr("9835d03eb527ea4ce45c217350c68042926d497c21fb31413b2f7824ff6fc6c3")},
		{320000, newHashFromStr("ad80c7cb91ca1d9c9b7bf68ca1b6d4ba217fe25ca5ded6a7e8acbaba663b143f")},
		{360000, newHashFromStr("f9fd013252439663c1e729a8afb27187a8b9cc63a253336060f867e3cfbe4dcb")},
		{400000, newHashFromStr("f0e56e70782af63ccb49c76e852540688755869ba59ec68cac9c04a6b4d9f5ca")},
		{440000, newHashFromStr("52760e00c369b40781a2ced32836711fab82a720fafb121118c815bb46afd996")},
		{480000, newHashFromStr("cecacaf4d1a8d1ef60da39343540781115abb91f5f0c976bb08afc4d4e3218ac")},
		{520000, newHashFromStr("fa5e9d6dcf9ad57ba60d8ba26fb05585741098d10f42ed9d5e6b5e90ebc278d6")},
		{560000, newHashFromStr("95c6229bd9b40f03a8426b2fec740026b3f06b1628cfb87527b0cbd0da328c0c")},
		{600000, newHashFromStr("532657a97d480feb2d0423bb736cbfd7400b3ac8311e81ac749a2f29103a6c6b")},
		{640000, newHashFromStr("68b69e3e8765e1ddbac63cbfbbf12e1a920da994d242a26fd07624f067743080")},
		{680000, newHashFromStr("7b9f30c959405b5b96d0b0c2ba8fc7c5586cd0ce40df51427de4b8a217859c45")},
		{720000, newHashFromStr("42084d5f88c71c0ae09b8677070969df9c3ef875c5f434133f552d863204f0cb")},
		{760000, newHashFromStr("1887cd8b50375a9ac0dc9686c98fa8ac69bca618eab6254310647057f6fe4fc9")},
		{800000, newHashFromStr("d34bb871b21e6fda4bd9d9e530ebf12e044814004007f088415035c651ecf322")},
		{840000, newHashFromStr("d0e73c5ce3ad5d6fdb4483aa450f0b1cf7e4570987ee3a3806ace4ad2f7cc9af")},
		{880000, newHashFromStr("806a95f26bab603f1d9132b5d4ea72aab9d1198ad55ae18dac1e149f6cb70ce4")},
		{920000, newHashFromStr("83bc84555105436c51728ab200e8da4d9b3a365fd3d1d47a60048ad0f977c55b")},
		{960000, newHashFromStr("60e37b1c2d1f8771290b7f84865cbadf22b5b89d3ce1201d454b09f0775b42c2")},
	},

	// Consensus rule change deployments.
	//
	// The miner confirmation window is defined as:
	//   target proof of work timespan / target proof of work spacing
	RuleChangeActivationThreshold: 1916, // 95% of MinerConfirmationWindow
	MinerConfirmationWindow:       2016, //
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601, // January 1, 2008 UTC
			ExpireTime: 1230767999, // December 31, 2008 UTC
		},
		DeploymentCSV: {
			BitNumber:     0,
			StartTime:     1462060800, // May 1st, 2016
			ExpireTime:    1493596800, // May 1st, 2017
			ForceActiveAt: 200000,
		},
		DeploymentSegwit: {
			BitNumber:     1,
			StartTime:     1547942400, // Jan 20, 2019
			ExpireTime:    1548288000, // Jan 24, 2019
			ForceActiveAt: 680770,
		},
	},

	// Mempool parameters
	RelayNonStdTxs: false,

	// Human-readable part for Bech32 encoded segwit addresses, as defined in
	// BIP 173.
	Bech32HRPSegwit: "lbc",

	// Address encoding magics
	PubKeyHashAddrID: 0x55,
	ScriptHashAddrID: 0x7a,
	PrivateKeyID:     0x1c,

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID: [4]byte{0x04, 0x88, 0xad, 0xe4},
	HDPublicKeyID:  [4]byte{0x04, 0x88, 0xb2, 0x1e},

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType: 0,
}

// RegressionNetParams defines the network parameters for the regression test
// Bitcoin network.  Not to be confused with the test Bitcoin network (version
// 3), this network is sometimes simply called "testnet".
var RegressionNetParams = Params{
	Name:        "regtest",
	Net:         wire.TestNet,
	DefaultPort: "29246",
	DNSSeeds:    []DNSSeed{},

	// Chain parameters
	GenesisBlock:             &regTestGenesisBlock,
	GenesisHash:              &regTestGenesisHash,
	PowLimit:                 regressionPowLimit,
	PowLimitBits:             0x207fffff,
	CoinbaseMaturity:         100,
	BIP0034Height:            1000,
	BIP0065Height:            1351, // Used by regression tests
	BIP0066Height:            1251, // Used by regression tests
	SubsidyReductionInterval: 1 << 5,
	TargetTimespan:           time.Second,
	TargetTimePerBlock:       time.Second,
	RetargetAdjustmentFactor: 4, // 25% less, 400% more
	ReduceMinDifficulty:      false,
	MinDiffReductionTime:     0,
	GenerateSupported:        true,

	// Checkpoints ordered from oldest to newest.
	Checkpoints: nil,

	// Consensus rule change deployments.
	//
	// The miner confirmation window is defined as:
	//   target proof of work timespan / target proof of work spacing
	RuleChangeActivationThreshold: 108, // 75%  of MinerConfirmationWindow
	MinerConfirmationWindow:       144,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  0,             // Always available for vote
			ExpireTime: math.MaxInt64, // Never expires
		},
		DeploymentCSV: {
			BitNumber:     0,
			StartTime:     0,             // Always available for vote
			ExpireTime:    math.MaxInt64, // Never expires
			ForceActiveAt: 1,
		},
		DeploymentSegwit: {
			BitNumber:     1,
			StartTime:     0,
			ExpireTime:    math.MaxInt64,
			ForceActiveAt: 150,
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// Human-readable part for Bech32 encoded segwit addresses, as defined in
	// BIP 173.
	Bech32HRPSegwit: "rlbc",

	// Address encoding magics
	PubKeyHashAddrID: 111, // starts with m or n
	ScriptHashAddrID: 196, // starts with 2
	PrivateKeyID:     239, // starts with 9 (uncompressed) or c (compressed)

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94}, // starts with tprv
	HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf}, // starts with tpub

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType: 1,
}

// TestNet3Params defines the network parameters for the test Bitcoin network
// (version 3).  Not to be confused with the regression test network, this
// network is sometimes simply called "testnet".
var TestNet3Params = Params{
	Name:        "testnet3",
	Net:         wire.TestNet3,
	DefaultPort: "19246",
	DNSSeeds: []DNSSeed{
		{"testdnsseed1.lbry.com", true},
		{"testdnsseed2.lbry.com", true},
	},

	// Chain parameters
	GenesisBlock:             &testNet3GenesisBlock,
	GenesisHash:              &testNet3GenesisHash,
	PowLimit:                 testNet3PowLimit,
	PowLimitBits:             0x1f00ffff,
	BIP0034Height:            21111, // 0x0000000023b3a96d3484e5abb3755c413e7d41500f8e2a5c3f0dd01299cd8ef8
	BIP0065Height:            1200000,
	BIP0066Height:            1200000,
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 1 << 5,
	TargetTimespan:           time.Second * 150, // retarget every block
	TargetTimePerBlock:       time.Second * 150, // 150 seconds
	RetargetAdjustmentFactor: 4,                 // 25% less, 400% more
	ReduceMinDifficulty:      false,
	MinDiffReductionTime:     0,
	GenerateSupported:        true,

	// Checkpoints ordered from oldest to newest.
	Checkpoints: []Checkpoint{},

	// Consensus rule change deployments.
	//
	// The miner confirmation window is defined as:
	//   target proof of work timespan / target proof of work spacing
	RuleChangeActivationThreshold: 1512, // 75% of MinerConfirmationWindow
	MinerConfirmationWindow:       2016,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601, // January 1, 2008 UTC
			ExpireTime: 1230767999, // December 31, 2008 UTC
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  1456790400, // March 1st, 2016
			ExpireTime: 1493596800, // May 1st, 2017
		},
		DeploymentSegwit: {
			BitNumber:     1,
			StartTime:     1462060800, // May 1st 2016
			ExpireTime:    1493596800, // May 1st 2017
			ForceActiveAt: 1198600,
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// Human-readable part for Bech32 encoded segwit addresses, as defined in
	// BIP 173.
	Bech32HRPSegwit: "tlbc",

	// Address encoding magics
	PubKeyHashAddrID: 111,
	ScriptHashAddrID: 196,
	PrivateKeyID:     239,

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94}, // starts with tprv
	HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf}, // starts with tpub

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType: 1,
}

// SimNetParams defines the network parameters for the simulation test Bitcoin
// network.  This network is similar to the normal test network except it is
// intended for private use within a group of individuals doing simulation
// testing.  The functionality is intended to differ in that the only nodes
// which are specifically specified are used to create the network rather than
// following normal discovery rules.  This is important as otherwise it would
// just turn into another public testnet.
var SimNetParams = Params{
	Name:        "simnet",
	Net:         wire.SimNet,
	DefaultPort: "18555",
	DNSSeeds:    []DNSSeed{}, // NOTE: There must NOT be any seeds.

	// Chain parameters
	GenesisBlock:             &simNetGenesisBlock,
	GenesisHash:              &simNetGenesisHash,
	PowLimit:                 simNetPowLimit,
	PowLimitBits:             0x207fffff,
	BIP0034Height:            0, // Always active on simnet
	BIP0065Height:            0, // Always active on simnet
	BIP0066Height:            0, // Always active on simnet
	CoinbaseMaturity:         100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Second * 150,
	TargetTimePerBlock:       time.Second * 150,
	RetargetAdjustmentFactor: 4, // 25% less, 400% more
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     0,
	GenerateSupported:        true,

	// Checkpoints ordered from oldest to newest.
	Checkpoints: nil,

	// Consensus rule change deployments.
	//
	// The miner confirmation window is defined as:
	//   target proof of work timespan / target proof of work spacing
	RuleChangeActivationThreshold: 75, // 75% of MinerConfirmationWindow
	MinerConfirmationWindow:       100,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  0,             // Always available for vote
			ExpireTime: math.MaxInt64, // Never expires
		},
		DeploymentCSV: {
			BitNumber:  0,
			StartTime:  0,             // Always available for vote
			ExpireTime: math.MaxInt64, // Never expires
		},
		DeploymentSegwit: {
			BitNumber:  1,
			StartTime:  0,
			ExpireTime: math.MaxInt64,
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// Human-readable part for Bech32 encoded segwit addresses, as defined in
	// BIP 173.
	Bech32HRPSegwit: "slbc",

	// Address encoding magics
	PubKeyHashAddrID: 111,
	ScriptHashAddrID: 196,
	PrivateKeyID:     239,

	// BIP32 hierarchical deterministic extended key magics
	HDPrivateKeyID: [4]byte{0x04, 0x20, 0xb9, 0x00}, // starts with sprv
	HDPublicKeyID:  [4]byte{0x04, 0x20, 0xbd, 0x3a}, // starts with spub

	// BIP44 coin type used in the hierarchical deterministic path for
	// address generation.
	HDCoinType: 115, // ASCII for s
}

// SigNetParams defines the network parameters for the default public signet
// Bitcoin network. Not to be confused with the regression test network, this
// network is sometimes simply called "signet" or "taproot signet".
var SigNetParams = CustomSignetParams(
	DefaultSignetChallenge, DefaultSignetDNSSeeds,
)

// CustomSignetParams creates network parameters for a custom signet network
// from a challenge. The challenge is the binary compiled version of the block
// challenge script.
func CustomSignetParams(challenge []byte, dnsSeeds []DNSSeed) Params {
	// The message start is defined as the first four bytes of the sha256d
	// of the challenge script, as a single push (i.e. prefixed with the
	// challenge script length).
	challengeLength := byte(len(challenge))
	hashDouble := chainhash.DoubleHashB(
		append([]byte{challengeLength}, challenge...),
	)

	// We use little endian encoding of the hash prefix to be in line with
	// the other wire network identities.
	net := binary.LittleEndian.Uint32(hashDouble[0:4])
	return Params{
		Name:        "signet",
		Net:         wire.BitcoinNet(net),
		DefaultPort: "38333",
		DNSSeeds:    dnsSeeds,

		// Chain parameters
		GenesisBlock:             &sigNetGenesisBlock,
		GenesisHash:              &sigNetGenesisHash,
		PowLimit:                 sigNetPowLimit,
		PowLimitBits:             0x1e0377ae,
		BIP0034Height:            1,
		BIP0065Height:            1,
		BIP0066Height:            1,
		CoinbaseMaturity:         100,
		SubsidyReductionInterval: 210000,
		TargetTimespan:           time.Hour * 24 * 14, // 14 days
		TargetTimePerBlock:       time.Minute * 10,    // 10 minutes
		RetargetAdjustmentFactor: 4,                   // 25% less, 400% more
		ReduceMinDifficulty:      false,
		MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
		GenerateSupported:        false,

		// Checkpoints ordered from oldest to newest.
		Checkpoints: nil,

		// Consensus rule change deployments.
		//
		// The miner confirmation window is defined as:
		//   target proof of work timespan / target proof of work spacing
		RuleChangeActivationThreshold: 1916, // 95% of 2016
		MinerConfirmationWindow:       2016,
		Deployments: [DefinedDeployments]ConsensusDeployment{
			DeploymentTestDummy: {
				BitNumber:  28,
				StartTime:  1199145601, // January 1, 2008 UTC
				ExpireTime: 1230767999, // December 31, 2008 UTC
			},
			DeploymentCSV: {
				BitNumber:  29,
				StartTime:  0,             // Always available for vote
				ExpireTime: math.MaxInt64, // Never expires
			},
			DeploymentSegwit: {
				BitNumber:  29,
				StartTime:  0,             // Always available for vote
				ExpireTime: math.MaxInt64, // Never expires.
			},
			DeploymentTaproot: {
				BitNumber:  29,
				StartTime:  0,             // Always available for vote
				ExpireTime: math.MaxInt64, // Never expires.
			},
		},

		// Mempool parameters
		RelayNonStdTxs: false,

		// Human-readable part for Bech32 encoded segwit addresses, as defined in
		// BIP 173.
		Bech32HRPSegwit: "slbc",

		// Address encoding magics
		PubKeyHashAddrID: 0x6f, // starts with m or n
		ScriptHashAddrID: 0xc4, // starts with 2
		PrivateKeyID:     0xef, // starts with 9 (uncompressed) or c (compressed)

		// BIP32 hierarchical deterministic extended key magics
		HDPrivateKeyID: [4]byte{0x04, 0x35, 0x83, 0x94}, // starts with tprv
		HDPublicKeyID:  [4]byte{0x04, 0x35, 0x87, 0xcf}, // starts with tpub

		// BIP44 coin type used in the hierarchical deterministic path for
		// address generation.
		HDCoinType: 1,
	}
}

var (
	// ErrDuplicateNet describes an error where the parameters for a Bitcoin
	// network could not be set due to the network already being a standard
	// network or previously-registered into this package.
	ErrDuplicateNet = errors.New("duplicate Bitcoin network")

	// ErrUnknownHDKeyID describes an error where the provided id which
	// is intended to identify the network for a hierarchical deterministic
	// private extended key is not registered.
	ErrUnknownHDKeyID = errors.New("unknown hd private extended key bytes")

	// ErrInvalidHDKeyID describes an error where the provided hierarchical
	// deterministic version bytes, or hd key id, is malformed.
	ErrInvalidHDKeyID = errors.New("invalid hd extended key version bytes")
)

var (
	registeredNets       = make(map[wire.BitcoinNet]struct{})
	pubKeyHashAddrIDs    = make(map[byte]struct{})
	scriptHashAddrIDs    = make(map[byte]struct{})
	bech32SegwitPrefixes = make(map[string]struct{})
	hdPrivToPubKeyIDs    = make(map[[4]byte][]byte)
)

// String returns the hostname of the DNS seed in human-readable form.
func (d DNSSeed) String() string {
	return d.Host
}

// Register registers the network parameters for a Bitcoin network.  This may
// error with ErrDuplicateNet if the network is already registered (either
// due to a previous Register call, or the network being one of the default
// networks).
//
// Network parameters should be registered into this package by a main package
// as early as possible.  Then, library packages may lookup networks or network
// parameters based on inputs and work regardless of the network being standard
// or not.
func Register(params *Params) error {
	if _, ok := registeredNets[params.Net]; ok {
		return ErrDuplicateNet
	}
	registeredNets[params.Net] = struct{}{}
	pubKeyHashAddrIDs[params.PubKeyHashAddrID] = struct{}{}
	scriptHashAddrIDs[params.ScriptHashAddrID] = struct{}{}

	err := RegisterHDKeyID(params.HDPublicKeyID[:], params.HDPrivateKeyID[:])
	if err != nil {
		return err
	}

	// A valid Bech32 encoded segwit address always has as prefix the
	// human-readable part for the given net followed by '1'.
	bech32SegwitPrefixes[params.Bech32HRPSegwit+"1"] = struct{}{}
	return nil
}

// mustRegister performs the same function as Register except it panics if there
// is an error.  This should only be called from package init functions.
func mustRegister(params *Params) {
	if err := Register(params); err != nil {
		panic("failed to register network: " + err.Error())
	}
}

// IsPubKeyHashAddrID returns whether the id is an identifier known to prefix a
// pay-to-pubkey-hash address on any default or registered network.  This is
// used when decoding an address string into a specific address type.  It is up
// to the caller to check both this and IsScriptHashAddrID and decide whether an
// address is a pubkey hash address, script hash address, neither, or
// undeterminable (if both return true).
func IsPubKeyHashAddrID(id byte) bool {
	_, ok := pubKeyHashAddrIDs[id]
	return ok
}

// IsScriptHashAddrID returns whether the id is an identifier known to prefix a
// pay-to-script-hash address on any default or registered network.  This is
// used when decoding an address string into a specific address type.  It is up
// to the caller to check both this and IsPubKeyHashAddrID and decide whether an
// address is a pubkey hash address, script hash address, neither, or
// undeterminable (if both return true).
func IsScriptHashAddrID(id byte) bool {
	_, ok := scriptHashAddrIDs[id]
	return ok
}

// IsBech32SegwitPrefix returns whether the prefix is a known prefix for segwit
// addresses on any default or registered network.  This is used when decoding
// an address string into a specific address type.
func IsBech32SegwitPrefix(prefix string) bool {
	prefix = strings.ToLower(prefix)
	_, ok := bech32SegwitPrefixes[prefix]
	return ok
}

// RegisterHDKeyID registers a public and private hierarchical deterministic
// extended key ID pair.
//
// Non-standard HD version bytes, such as the ones documented in SLIP-0132,
// should be registered using this method for library packages to lookup key
// IDs (aka HD version bytes). When the provided key IDs are invalid, the
// ErrInvalidHDKeyID error will be returned.
//
// Reference:
//   SLIP-0132 : Registered HD version bytes for BIP-0032
//   https://github.com/satoshilabs/slips/blob/master/slip-0132.md
func RegisterHDKeyID(hdPublicKeyID []byte, hdPrivateKeyID []byte) error {
	if len(hdPublicKeyID) != 4 || len(hdPrivateKeyID) != 4 {
		return ErrInvalidHDKeyID
	}

	var keyID [4]byte
	copy(keyID[:], hdPrivateKeyID)
	hdPrivToPubKeyIDs[keyID] = hdPublicKeyID

	return nil
}

// HDPrivateKeyToPublicKeyID accepts a private hierarchical deterministic
// extended key id and returns the associated public key id.  When the provided
// id is not registered, the ErrUnknownHDKeyID error will be returned.
func HDPrivateKeyToPublicKeyID(id []byte) ([]byte, error) {
	if len(id) != 4 {
		return nil, ErrUnknownHDKeyID
	}

	var key [4]byte
	copy(key[:], id)
	pubBytes, ok := hdPrivToPubKeyIDs[key]
	if !ok {
		return nil, ErrUnknownHDKeyID
	}

	return pubBytes, nil
}

// newHashFromStr converts the passed big-endian hex string into a
// chainhash.Hash.  It only differs from the one available in chainhash in that
// it panics on an error since it will only (and must only) be called with
// hard-coded, and therefore known good, hashes.
func newHashFromStr(hexStr string) *chainhash.Hash {
	hash, err := chainhash.NewHashFromStr(hexStr)
	if err != nil {
		// Ordinarily I don't like panics in library code since it
		// can take applications down without them having a chance to
		// recover which is extremely annoying, however an exception is
		// being made in this case because the only way this can panic
		// is if there is an error in the hard-coded hashes.  Thus it
		// will only ever potentially panic on init and therefore is
		// 100% predictable.
		panic(err)
	}
	return hash
}

func init() {
	// Register all default networks when the package is initialized.
	mustRegister(&MainNetParams)
	mustRegister(&TestNet3Params)
	mustRegister(&RegressionNetParams)
	mustRegister(&SimNetParams)
}