// 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 dagconfig

import (
	"errors"
	"math"
	"math/big"
	"time"

	"github.com/daglabs/btcd/util"
	"github.com/daglabs/btcd/util/hdkeychain"

	"github.com/daglabs/btcd/util/daghash"
	"github.com/daglabs/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 2^255 - 1.
	mainPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), 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
	// 2^255 - 1.
	testNet3PowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 255), 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)

	// devNetPowLimit is the highest proof of work value a Bitcoin block
	// can have for the development network.  It is the value
	// 2^239 - 1.
	devNetPowLimit = new(big.Int).Sub(new(big.Int).Lsh(bigOne, 239), bigOne)
)

const phantomK = 10

// 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 uint64
	Hash   *daghash.Hash
}

// 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
}

// 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

	// 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 {
	K uint32

	// Name defines a human-readable identifier for the network.
	Name string

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

	// RPCPort defines the rpc server port
	RPCPort string

	// 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 []string

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

	// GenesisHash is the starting block hash.
	GenesisHash *daghash.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

	// BlockRewardMaturity is the number of blocks required before newly mined
	// coins (coinbase or fee transactions) can be spent.
	BlockRewardMaturity uint64

	// SubsidyReductionInterval is the interval of blocks before the subsidy
	// is reduced.
	SubsidyReductionInterval uint64

	// 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 uint64
	MinerConfirmationWindow       uint64
	Deployments                   [DefinedDeployments]ConsensusDeployment

	// Mempool parameters
	RelayNonStdTxs bool

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable bool

	// Human-readable prefix for Bech32 encoded addresses
	Prefix util.Bech32Prefix

	// Address encoding magics
	PrivateKeyID byte // First byte of a WIF private key

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair hdkeychain.HDKeyIDPair

	// 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{
	K:           phantomK,
	Name:        "mainnet",
	Net:         wire.MainNet,
	RPCPort:     "8334",
	DefaultPort: "8333",
	DNSSeeds:    []string{},

	// DAG parameters
	GenesisBlock:             &genesisBlock,
	GenesisHash:              &genesisHash,
	PowLimit:                 mainPowLimit,
	PowLimitBits:             0x207fffff,
	BlockRewardMaturity:      100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 1,   // 1 hour
	TargetTimePerBlock:       time.Second * 1, // 1 second
	RetargetAdjustmentFactor: 4,               // 25% less, 400% more
	ReduceMinDifficulty:      false,
	MinDiffReductionTime:     0,
	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 MinerConfirmationWindow
	MinerConfirmationWindow:       2016, //
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601, // January 1, 2008 UTC
			ExpireTime: 1230767999, // December 31, 2008 UTC
		},
	},

	// Mempool parameters
	RelayNonStdTxs: false,

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable: false,

	// Human-readable part for Bech32 encoded addresses
	Prefix: util.Bech32PrefixDAGCoin,

	// Address encoding magics
	PrivateKeyID: 0x80, // starts with 5 (uncompressed) or K (compressed)

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair: hdkeychain.HDKeyPairMainNet,

	// 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{
	K:           phantomK,
	Name:        "regtest",
	Net:         wire.TestNet,
	RPCPort:     "18334",
	DefaultPort: "18444",
	DNSSeeds:    []string{},

	// Chain parameters
	GenesisBlock:             &regTestGenesisBlock,
	GenesisHash:              &regTestGenesisHash,
	PowLimit:                 regressionPowLimit,
	PowLimitBits:             0x207fffff,
	BlockRewardMaturity:      100,
	SubsidyReductionInterval: 150,
	TargetTimespan:           time.Hour * 1,   // 1 hour
	TargetTimePerBlock:       time.Second * 1, // 1 second
	RetargetAdjustmentFactor: 4,               // 25% less, 400% more
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
	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
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable: false,

	// Human-readable part for Bech32 encoded addresses
	Prefix: util.Bech32PrefixDAGReg,

	// Address encoding magics
	PrivateKeyID: 0xef, // starts with 9 (uncompressed) or c (compressed)

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair: hdkeychain.HDKeyPairRegressionNet,

	// 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{
	K:           phantomK,
	Name:        "testnet3",
	Net:         wire.TestNet3,
	RPCPort:     "18334",
	DefaultPort: "18333",
	DNSSeeds:    []string{},

	// Chain parameters
	GenesisBlock:             &testNet3GenesisBlock,
	GenesisHash:              &testNet3GenesisHash,
	PowLimit:                 testNet3PowLimit,
	PowLimitBits:             0x207fffff,
	BlockRewardMaturity:      100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 1,   // 1 hour
	TargetTimePerBlock:       time.Second * 1, // 1 second
	RetargetAdjustmentFactor: 4,               // 25% less, 400% more
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
	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: 1512, // 75% of MinerConfirmationWindow
	MinerConfirmationWindow:       2016,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601, // January 1, 2008 UTC
			ExpireTime: 1230767999, // December 31, 2008 UTC
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable: false,

	// Human-readable part for Bech32 encoded addresses
	Prefix: util.Bech32PrefixDAGTest,

	// Address encoding magics
	PrivateKeyID: 0xef, // starts with 9 (uncompressed) or c (compressed)

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair: hdkeychain.HDKeyPairTestNet,

	// 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{
	K:           phantomK,
	Name:        "simnet",
	Net:         wire.SimNet,
	RPCPort:     "18556",
	DefaultPort: "18555",
	DNSSeeds:    []string{}, // NOTE: There must NOT be any seeds.

	// Chain parameters
	GenesisBlock:             &simNetGenesisBlock,
	GenesisHash:              &simNetGenesisHash,
	PowLimit:                 simNetPowLimit,
	PowLimitBits:             0x207fffff,
	BlockRewardMaturity:      100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 1,   // 1 hour
	TargetTimePerBlock:       time.Second * 1, // 1 second
	RetargetAdjustmentFactor: 4,               // 25% less, 400% more
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
	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
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable: false,

	PrivateKeyID: 0x64, // starts with 4 (uncompressed) or F (compressed)
	// Human-readable part for Bech32 encoded addresses
	Prefix: util.Bech32PrefixDAGSim,

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair: hdkeychain.HDKeyPairSimNet,

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

// DevNetParams defines the network parameters for the development Bitcoin network.
var DevNetParams = Params{
	K:           phantomK,
	Name:        "devnet",
	Net:         wire.DevNet,
	RPCPort:     "18334",
	DefaultPort: "18333",
	DNSSeeds:    []string{"devnet-dnsseed.daglabs.com"},

	// Chain parameters
	GenesisBlock:             &devNetGenesisBlock,
	GenesisHash:              &devNetGenesisHash,
	PowLimit:                 devNetPowLimit,
	PowLimitBits:             util.BigToCompact(devNetPowLimit), // 0x1e7fffff
	BlockRewardMaturity:      100,
	SubsidyReductionInterval: 210000,
	TargetTimespan:           time.Hour * 1,   // 1 hour
	TargetTimePerBlock:       time.Second * 1, // 1 second
	RetargetAdjustmentFactor: 4,               // 25% less, 400% more
	ReduceMinDifficulty:      true,
	MinDiffReductionTime:     time.Minute * 20, // TargetTimePerBlock * 2
	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: 1512, // 75% of MinerConfirmationWindow
	MinerConfirmationWindow:       2016,
	Deployments: [DefinedDeployments]ConsensusDeployment{
		DeploymentTestDummy: {
			BitNumber:  28,
			StartTime:  1199145601, // January 1, 2008 UTC
			ExpireTime: 1230767999, // December 31, 2008 UTC
		},
	},

	// Mempool parameters
	RelayNonStdTxs: true,

	// AcceptUnroutable specifies whether this network accepts unroutable
	// IP addresses, such as 10.0.0.0/8
	AcceptUnroutable: true,

	// Human-readable part for Bech32 encoded addresses
	Prefix: util.Bech32PrefixDAGTest,

	// Address encoding magics
	PrivateKeyID: 0xef, // starts with 9 (uncompressed) or c (compressed)

	// BIP32 hierarchical deterministic extended key magics
	HDKeyIDPair: hdkeychain.HDKeyPairDevNet,

	// 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")
)

var (
	registeredNets = make(map[wire.BitcoinNet]struct{})
)

// 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{}{}

	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())
	}
}

// newHashFromStr converts the passed big-endian hex string into a
// daghash.Hash.  It only differs from the one available in daghash 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) *daghash.Hash {
	hash, err := daghash.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)
}