// 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 waddrmgr

import (
	"crypto/rand"
	"crypto/sha512"
	"fmt"
	"sync"
	"time"

	"github.com/lbryio/lbcd/chaincfg"
	btcutil "github.com/lbryio/lbcutil"
	"github.com/lbryio/lbcutil/hdkeychain"
	"github.com/lbryio/lbcwallet/internal/zero"
	"github.com/lbryio/lbcwallet/snacl"
	"github.com/lbryio/lbcwallet/walletdb"
	"github.com/lightninglabs/neutrino/cache/lru"
)

const (
	// MaxAccountNum is the maximum allowed account number.  This value was
	// chosen because accounts are hardened children and therefore must not
	// exceed the hardened child range of extended keys and it provides a
	// reserved account at the top of the range for supporting imported
	// addresses.
	MaxAccountNum = hdkeychain.HardenedKeyStart - 2 // 2^31 - 2

	// MaxAddressesPerAccount is the maximum allowed number of addresses
	// per account number.  This value is based on the limitation of the
	// underlying hierarchical deterministic key derivation.
	MaxAddressesPerAccount = hdkeychain.HardenedKeyStart - 1

	// ImportedAddrAccount is the account number to use for all imported
	// addresses.  This is useful since normal accounts are derived from
	// the root hierarchical deterministic key and imported addresses do
	// not fit into that model.
	ImportedAddrAccount = MaxAccountNum + 1 // 2^31 - 1

	// ImportedAddrAccountName is the name of the imported account.
	ImportedAddrAccountName = "imported"

	// DefaultAccountNum is the number of the default account.
	DefaultAccountNum = 0

	// defaultAccountName is the initial name of the default account.  Note
	// that the default account may be renamed and is not a reserved name,
	// so the default account might not be named "default" and non-default
	// accounts may be named "default".
	//
	// Account numbers never change, so the DefaultAccountNum should be
	// used to refer to (and only to) the default account.
	defaultAccountName = "default"

	// The hierarchy described by BIP0043 is:
	//  m/<purpose>'/*
	// This is further extended by BIP0044 to:
	//  m/44'/<coin type>'/<account>'/<branch>/<address index>
	//
	// The branch is 0 for external addresses and 1 for internal addresses.

	// maxCoinType is the maximum allowed coin type used when structuring
	// the BIP0044 multi-account hierarchy.  This value is based on the
	// limitation of the underlying hierarchical deterministic key
	// derivation.
	maxCoinType = hdkeychain.HardenedKeyStart - 1

	// ExternalBranch is the child number to use when performing BIP0044
	// style hierarchical deterministic key derivation for the external
	// branch.
	ExternalBranch uint32 = 0

	// InternalBranch is the child number to use when performing BIP0044
	// style hierarchical deterministic key derivation for the internal
	// branch.
	InternalBranch uint32 = 1

	// saltSize is the number of bytes of the salt used when hashing
	// private passphrases.
	saltSize = 32
)

// isReservedAccountName returns true if the account name is reserved.
// Reserved accounts may never be renamed, and other accounts may not be
// renamed to a reserved name.
func isReservedAccountName(name string) bool {
	return name == ImportedAddrAccountName
}

// isReservedAccountNum returns true if the account number is reserved.
// Reserved accounts may not be renamed.
func isReservedAccountNum(acct uint32) bool {
	return acct == ImportedAddrAccount
}

// ScryptOptions is used to hold the scrypt parameters needed when deriving new
// passphrase keys.
type ScryptOptions struct {
	N, R, P int
}

// OpenCallbacks houses caller-provided callbacks that may be called when
// opening an existing manager.  The open blocks on the execution of these
// functions.
type OpenCallbacks struct {
	// ObtainSeed is a callback function that is potentially invoked during
	// upgrades.  It is intended to be used to request the wallet seed
	// from the user (or any other mechanism the caller deems fit).
	ObtainSeed ObtainUserInputFunc

	// ObtainPrivatePass is a callback function that is potentially invoked
	// during upgrades.  It is intended to be used to request the wallet
	// private passphrase from the user (or any other mechanism the caller
	// deems fit).
	ObtainPrivatePass ObtainUserInputFunc
}

// DefaultScryptOptions is the default options used with scrypt.
var DefaultScryptOptions = ScryptOptions{
	N: 262144, // 2^18
	R: 8,
	P: 1,
}

// FastScryptOptions are the scrypt options that should be used for testing
// purposes only where speed is more important than security.
var FastScryptOptions = ScryptOptions{
	N: 16,
	R: 8,
	P: 1,
}

// addrKey is used to uniquely identify an address even when those addresses
// would end up being the same bitcoin address (as is the case for
// pay-to-pubkey and pay-to-pubkey-hash style of addresses).
type addrKey string

// accountInfo houses the current state of the internal and external branches
// of an account along with the extended keys needed to derive new keys.  It
// also handles locking by keeping an encrypted version of the serialized
// private extended key so the unencrypted versions can be cleared from memory
// when the address manager is locked.
type accountInfo struct {
	acctName string

	acctType accountType

	// The account key is used to derive the branches which in turn derive
	// the internal and external addresses.  The accountKeyPriv will be nil
	// when the address manager is locked.
	acctKeyEncrypted []byte
	acctKeyPriv      *hdkeychain.ExtendedKey
	acctKeyPub       *hdkeychain.ExtendedKey

	// The external branch is used for all addresses which are intended for
	// external use.
	nextExternalIndex uint32
	lastExternalAddr  ManagedAddress

	// The internal branch is used for all adddresses which are only
	// intended for internal wallet use such as change addresses.
	nextInternalIndex uint32
	lastInternalAddr  ManagedAddress

	// addrSchema serves as a way for an account to override its
	// corresponding address schema with a custom one. For example, this
	// could be used to import accounts that use the traditional BIP-0049
	// derivation scheme into our KeyScopeBIP-0049Plus manager.
	addrSchema *ScopeAddrSchema

	// masterKeyFingerprint represents the fingerprint of the root key
	// corresponding to the master public key (also known as the key with
	// derivation path m/). This may be required by some hardware wallets
	// for proper identification and signing.
	masterKeyFingerprint uint32
}

// AccountProperties contains properties associated with each account, such as
// the account name, number, and the nubmer of derived and imported keys.
type AccountProperties struct {
	// AccountNumber is the internal number used to reference the account.
	AccountNumber uint32

	// AccountName is the user-identifying name of the account.
	AccountName string

	// ExternalKeyCount is the number of internal keys that have been
	// derived for the account.
	ExternalKeyCount uint32

	// InternalKeyCount is the number of internal keys that have been
	// derived for the account.
	InternalKeyCount uint32

	// ImportedKeyCount is the number of imported keys found within the
	// account.
	ImportedKeyCount uint32

	// AccountPubKey is the account's public key that can be used to
	// derive any address relevant to said account.
	//
	// NOTE: This may be nil for imported accounts.
	AccountPubKey *hdkeychain.ExtendedKey

	// MasterKeyFingerprint represents the fingerprint of the root key
	// corresponding to the master public key (also known as the key with
	// derivation path m/). This may be required by some hardware wallets
	// for proper identification and signing.
	MasterKeyFingerprint uint32

	// KeyScope is the key scope the account belongs to.
	KeyScope KeyScope

	// IsWatchOnly indicates whether the is set up as watch-only, i.e., it
	// doesn't contain any private key information.
	IsWatchOnly bool

	// AddrSchema, if non-nil, specifies an address schema override for
	// address generation only applicable to the account.
	AddrSchema *ScopeAddrSchema
}

// unlockDeriveInfo houses the information needed to derive a private key for a
// managed address when the address manager is unlocked.  See the
// deriveOnUnlock field in the Manager struct for more details on how this is
// used.
type unlockDeriveInfo struct {
	managedAddr ManagedAddress
	branch      uint32
	index       uint32
}

// SecretKeyGenerator is the function signature of a method that can generate
// secret keys for the address manager.
type SecretKeyGenerator func(
	passphrase *[]byte, config *ScryptOptions) (*snacl.SecretKey, error)

// defaultNewSecretKey returns a new secret key.  See newSecretKey.
func defaultNewSecretKey(passphrase *[]byte,
	config *ScryptOptions) (*snacl.SecretKey, error) {
	return snacl.NewSecretKey(passphrase, config.N, config.R, config.P)
}

var (
	// secretKeyGen is the inner method that is executed when calling
	// newSecretKey.
	secretKeyGen = defaultNewSecretKey

	// secretKeyGenMtx protects access to secretKeyGen, so that it can be
	// replaced in testing.
	secretKeyGenMtx sync.RWMutex
)

// SetSecretKeyGen replaces the existing secret key generator, and returns the
// previous generator.
func SetSecretKeyGen(keyGen SecretKeyGenerator) SecretKeyGenerator {
	secretKeyGenMtx.Lock()
	oldKeyGen := secretKeyGen
	secretKeyGen = keyGen
	secretKeyGenMtx.Unlock()

	return oldKeyGen
}

// newSecretKey generates a new secret key using the active secretKeyGen.
func newSecretKey(passphrase *[]byte,
	config *ScryptOptions) (*snacl.SecretKey, error) {

	secretKeyGenMtx.RLock()
	defer secretKeyGenMtx.RUnlock()
	return secretKeyGen(passphrase, config)
}

// EncryptorDecryptor provides an abstraction on top of snacl.CryptoKey so that
// our tests can use dependency injection to force the behaviour they need.
type EncryptorDecryptor interface {
	Encrypt(in []byte) ([]byte, error)
	Decrypt(in []byte) ([]byte, error)
	Bytes() []byte
	CopyBytes([]byte)
	Zero()
}

// cryptoKey extends snacl.CryptoKey to implement EncryptorDecryptor.
type cryptoKey struct {
	snacl.CryptoKey
}

// Bytes returns a copy of this crypto key's byte slice.
func (ck *cryptoKey) Bytes() []byte {
	return ck.CryptoKey[:]
}

// CopyBytes copies the bytes from the given slice into this CryptoKey.
func (ck *cryptoKey) CopyBytes(from []byte) {
	copy(ck.CryptoKey[:], from)
}

// defaultNewCryptoKey returns a new CryptoKey.  See newCryptoKey.
func defaultNewCryptoKey() (EncryptorDecryptor, error) {
	key, err := snacl.GenerateCryptoKey()
	if err != nil {
		return nil, err
	}
	return &cryptoKey{*key}, nil
}

// CryptoKeyType is used to differentiate between different kinds of
// crypto keys.
type CryptoKeyType byte

// Crypto key types.
const (
	// CKTPrivate specifies the key that is used for encryption of private
	// key material such as derived extended private keys and imported
	// private keys.
	CKTPrivate CryptoKeyType = iota

	// CKTScript specifies the key that is used for encryption of scripts.
	CKTScript

	// CKTPublic specifies the key that is used for encryption of public
	// key material such as dervied extended public keys and imported public
	// keys.
	CKTPublic
)

// newCryptoKey is used as a way to replace the new crypto key generation
// function used so tests can provide a version that fails for testing error
// paths.
var newCryptoKey = defaultNewCryptoKey

// Manager represents a concurrency safe crypto currency address manager and
// key store.
type Manager struct {
	mtx sync.RWMutex

	// scopedManager is a mapping of scope of scoped manager, the manager
	// itself loaded into memory.
	scopedManagers map[KeyScope]*ScopedKeyManager

	externalAddrSchemas map[AddressType][]KeyScope
	internalAddrSchemas map[AddressType][]KeyScope

	syncState    syncState
	watchingOnly bool
	birthday     time.Time
	locked       bool
	closed       bool
	chainParams  *chaincfg.Params

	// masterKeyPub is the secret key used to secure the cryptoKeyPub key
	// and masterKeyPriv is the secret key used to secure the cryptoKeyPriv
	// key.  This approach is used because it makes changing the passwords
	// much simpler as it then becomes just changing these keys.  It also
	// provides future flexibility.
	//
	// NOTE: This is not the same thing as BIP0032 master node extended
	// key.
	//
	// The underlying master private key will be zeroed when the address
	// manager is locked.
	masterKeyPub  *snacl.SecretKey
	masterKeyPriv *snacl.SecretKey

	// cryptoKeyPub is the key used to encrypt public extended keys and
	// addresses.
	cryptoKeyPub EncryptorDecryptor

	// cryptoKeyPriv is the key used to encrypt private data such as the
	// master hierarchical deterministic extended key.
	//
	// This key will be zeroed when the address manager is locked.
	cryptoKeyPrivEncrypted []byte
	cryptoKeyPriv          EncryptorDecryptor

	// cryptoKeyScript is the key used to encrypt script data.
	//
	// This key will be zeroed when the address manager is locked.
	cryptoKeyScriptEncrypted []byte
	cryptoKeyScript          EncryptorDecryptor

	// privPassphraseSalt and hashedPrivPassphrase allow for the secure
	// detection of a correct passphrase on manager unlock when the
	// manager is already unlocked.  The hash is zeroed each lock.
	privPassphraseSalt   [saltSize]byte
	hashedPrivPassphrase [sha512.Size]byte
}

// WatchOnly returns true if the root manager is in watch only mode, and false
// otherwise.
func (m *Manager) WatchOnly() bool {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	return m.watchOnly()
}

// watchOnly returns true if the root manager is in watch only mode, and false
// otherwise.
//
// NOTE: This method requires the Manager's lock to be held.
func (m *Manager) watchOnly() bool {
	return m.watchingOnly
}

// IsWatchOnlyAccount determines if the account with the given key scope is set
// up as watch-only.
func (m *Manager) IsWatchOnlyAccount(ns walletdb.ReadBucket, keyScope KeyScope,
	account uint32) (bool, error) {

	if m.WatchOnly() {
		return true, nil
	}

	// Assume the default imported account has no private keys.
	//
	// TODO: Actually check whether it does.
	if account == ImportedAddrAccount {
		return true, nil
	}

	scopedMgr, err := m.FetchScopedKeyManager(keyScope)
	if err != nil {
		return false, err
	}
	return scopedMgr.IsWatchOnlyAccount(ns, account)
}

// lock performs a best try effort to remove and zero all secret keys associated
// with the address manager.
//
// This function MUST be called with the manager lock held for writes.
func (m *Manager) lock() {
	for _, manager := range m.scopedManagers {
		// Clear all of the account private keys.
		for _, acctInfo := range manager.acctInfo {
			if acctInfo.acctKeyPriv != nil {
				acctInfo.acctKeyPriv.Zero()
			}
			acctInfo.acctKeyPriv = nil
		}
	}

	// Remove clear text private keys and scripts from all address entries.
	for _, manager := range m.scopedManagers {
		for _, ma := range manager.addrs {
			switch addr := ma.(type) {
			case *managedAddress:
				addr.lock()
			case *scriptAddress:
				addr.lock()
			}
		}
	}

	// Remove clear text private master and crypto keys from memory.
	m.cryptoKeyScript.Zero()
	m.cryptoKeyPriv.Zero()
	m.masterKeyPriv.Zero()

	// Zero the hashed passphrase.
	zero.Bytea64(&m.hashedPrivPassphrase)

	// NOTE: m.cryptoKeyPub is intentionally not cleared here as the address
	// manager needs to be able to continue to read and decrypt public data
	// which uses a separate derived key from the database even when it is
	// locked.

	m.locked = true
}

// Close cleanly shuts down the manager.  It makes a best try effort to remove
// and zero all private key and sensitive public key material associated with
// the address manager from memory.
func (m *Manager) Close() {
	m.mtx.Lock()
	defer m.mtx.Unlock()

	if m.closed {
		return
	}

	for _, manager := range m.scopedManagers {
		// Zero out the account keys (if any) of all sub key managers.
		manager.Close()
	}

	// Attempt to clear private key material from memory.
	if !m.watchingOnly && !m.locked {
		m.lock()
	}

	// Remove clear text public master and crypto keys from memory.
	m.cryptoKeyPub.Zero()
	m.masterKeyPub.Zero()

	m.closed = true
}

// NewScopedKeyManager creates a new scoped key manager from the root manager. A
// scoped key manager is a sub-manager that only has the coin type key of a
// particular coin type and BIP0043 purpose. This is useful as it enables
// callers to create an arbitrary BIP0043 like schema with a stand alone
// manager. Note that a new scoped manager cannot be created if: the wallet is
// watch only, the manager hasn't been unlocked, or the root key has been.
// neutered from the database.
//
// TODO(roasbeef): addrtype of raw key means it'll look in scripts to possibly
// mark as gucci?
func (m *Manager) NewScopedKeyManager(ns walletdb.ReadWriteBucket,
	scope KeyScope, addrSchema ScopeAddrSchema) (*ScopedKeyManager, error) {

	m.mtx.Lock()
	defer m.mtx.Unlock()

	var rootPriv *hdkeychain.ExtendedKey
	if !m.watchingOnly {
		// If the manager is locked, then we can't create a new scoped
		// manager.
		if m.locked {
			return nil, managerError(ErrLocked, errLocked, nil)
		}

		// Now that we know the manager is unlocked, we'll need to
		// fetch the root master HD private key. This is required as
		// we'll be attempting the following derivation:
		// m/purpose'/cointype'
		//
		// Note that the path to the coin type is requires hardened
		// derivation, therefore this can only be done if the wallet's
		// root key hasn't been neutered.
		masterRootPrivEnc, _ := fetchMasterHDKeys(ns)

		// If the master root private key isn't found within the
		// database, but we need to bail here as we can't create the
		// cointype key without the master root private key.
		if masterRootPrivEnc == nil {
			return nil, managerError(ErrWatchingOnly, "", nil)
		}

		// Before we can derive any new scoped managers using this
		// key, we'll need to fully decrypt it.
		serializedMasterRootPriv, err :=
			m.cryptoKeyPriv.Decrypt(masterRootPrivEnc)
		if err != nil {
			str := fmt.Sprintf("failed to decrypt master root " +
				"serialized private key")
			return nil, managerError(ErrLocked, str, err)
		}

		// Now that we know the root priv is within the database,
		// we'll decode it into a usable object.
		rootPriv, err = hdkeychain.NewKeyFromString(
			string(serializedMasterRootPriv),
		)
		zero.Bytes(serializedMasterRootPriv)
		if err != nil {
			str := fmt.Sprintf("failed to create master extended " +
				"private key")
			return nil, managerError(ErrKeyChain, str, err)
		}
	}

	// Now that we have the root private key, we'll fetch the scope bucket
	// so we can create the proper internal name spaces.
	scopeBucket := ns.NestedReadWriteBucket(scopeBucketName)

	// Now that we know it's possible to actually create a new scoped
	// manager, we'll carve out its bucket space within the database.
	if err := createScopedManagerNS(scopeBucket, &scope); err != nil {
		return nil, err
	}

	// With the database state created, we'll now write down the address
	// schema of this particular scope type.
	scopeSchemas := ns.NestedReadWriteBucket(scopeSchemaBucketName)
	if scopeSchemas == nil {
		str := "scope schema bucket not found"
		return nil, managerError(ErrDatabase, str, nil)
	}
	scopeKey := scopeToBytes(&scope)
	schemaBytes := scopeSchemaToBytes(&addrSchema)
	err := scopeSchemas.Put(scopeKey[:], schemaBytes)
	if err != nil {
		return nil, err
	}

	if !m.watchingOnly {
		// With the database state created, we'll now derive the
		// cointype key using the master HD private key, then encrypt
		// it along with the first account using our crypto keys.
		err = createManagerKeyScope(
			ns, scope, rootPriv, m.cryptoKeyPub, m.cryptoKeyPriv,
		)
		if err != nil {
			return nil, err
		}
	}

	// Finally, we'll register this new scoped manager with the root
	// manager.
	m.scopedManagers[scope] = &ScopedKeyManager{
		scope:        scope,
		addrSchema:   addrSchema,
		rootManager:  m,
		addrs:        make(map[addrKey]ManagedAddress),
		acctInfo:     make(map[uint32]*accountInfo),
		privKeyCache: lru.NewCache(defaultPrivKeyCacheSize),
	}
	m.externalAddrSchemas[addrSchema.ExternalAddrType] = append(
		m.externalAddrSchemas[addrSchema.ExternalAddrType], scope,
	)
	m.internalAddrSchemas[addrSchema.InternalAddrType] = append(
		m.internalAddrSchemas[addrSchema.InternalAddrType], scope,
	)

	return m.scopedManagers[scope], nil
}

// FetchScopedKeyManager attempts to fetch an active scoped manager according to
// its registered scope. If the manger is found, then a nil error is returned
// along with the active scoped manager. Otherwise, a nil manager and a non-nil
// error will be returned.
func (m *Manager) FetchScopedKeyManager(scope KeyScope) (*ScopedKeyManager, error) {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	sm, ok := m.scopedManagers[scope]
	if !ok {
		str := fmt.Sprintf("scope %v not found", scope)
		return nil, managerError(ErrScopeNotFound, str, nil)
	}

	return sm, nil
}

// ActiveScopedKeyManagers returns a slice of all the active scoped key
// managers currently known by the root key manager.
func (m *Manager) ActiveScopedKeyManagers() []*ScopedKeyManager {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	var scopedManagers []*ScopedKeyManager
	for _, smgr := range m.scopedManagers {
		scopedManagers = append(scopedManagers, smgr)
	}

	return scopedManagers
}

// ScopesForExternalAddrType returns the set of key scopes that are able to
// produce the target address type as external addresses.
func (m *Manager) ScopesForExternalAddrType(addrType AddressType) []KeyScope {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	return m.externalAddrSchemas[addrType]
}

// ScopesForInternalAddrTypes returns the set of key scopes that are able to
// produce the target address type as internal addresses.
func (m *Manager) ScopesForInternalAddrTypes(addrType AddressType) []KeyScope {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	return m.internalAddrSchemas[addrType]
}

// NeuterRootKey is a special method that should be used once a caller is
// *certain* that no further scoped managers are to be created. This method
// will *delete* the encrypted master HD root private key from the database.
func (m *Manager) NeuterRootKey(ns walletdb.ReadWriteBucket) error {
	m.mtx.Lock()
	defer m.mtx.Unlock()

	// First, we'll fetch the current master HD keys from the database.
	masterRootPrivEnc, _ := fetchMasterHDKeys(ns)

	// If the root master private key is already nil, then we'll return a
	// nil error here as the root key has already been permanently
	// neutered.
	if masterRootPrivEnc == nil {
		return nil
	}
	zero.Bytes(masterRootPrivEnc)

	// Otherwise, we'll neuter the root key permanently by deleting the
	// encrypted master HD key from the database.
	return ns.NestedReadWriteBucket(mainBucketName).Delete(masterHDPrivName)
}

// Address returns a managed address given the passed address if it is known to
// the address manager. A managed address differs from the passed address in
// that it also potentially contains extra information needed to sign
// transactions such as the associated private key for pay-to-pubkey and
// pay-to-pubkey-hash addresses and the script associated with
// pay-to-script-hash addresses.
func (m *Manager) Address(ns walletdb.ReadBucket,
	address btcutil.Address) (ManagedAddress, error) {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	// We'll iterate through each of the known scoped managers, and see if
	// any of them now of the target address.
	for _, scopedMgr := range m.scopedManagers {
		addr, err := scopedMgr.Address(ns, address)
		if err != nil {
			continue
		}

		return addr, nil
	}

	// If the address wasn't known to any of the scoped managers, then
	// we'll return an error.
	str := fmt.Sprintf("unable to find key for addr %v", address)
	return nil, managerError(ErrAddressNotFound, str, nil)
}

// MarkUsed updates the used flag for the provided address.
func (m *Manager) MarkUsed(ns walletdb.ReadWriteBucket, address btcutil.Address) error {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	// Run through all the known scoped managers, and attempt to mark the
	// address as used for each one.

	// First, we'll figure out which scoped manager this address belong to.
	for _, scopedMgr := range m.scopedManagers {
		if _, err := scopedMgr.Address(ns, address); err != nil {
			continue
		}

		// We've found the manager that this address belongs to, so we
		// can mark the address as used and return.
		return scopedMgr.MarkUsed(ns, address)
	}

	// If we get to this point, then we weren't able to find the address in
	// any of the managers, so we'll exit with an error.
	str := fmt.Sprintf("unable to find key for addr %v", address)
	return managerError(ErrAddressNotFound, str, nil)
}

// AddrAccount returns the account to which the given address belongs. We also
// return the scoped manager that owns the addr+account combo.
func (m *Manager) AddrAccount(ns walletdb.ReadBucket,
	address btcutil.Address) (*ScopedKeyManager, uint32, error) {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for _, scopedMgr := range m.scopedManagers {
		if _, err := scopedMgr.Address(ns, address); err != nil {
			continue
		}

		// We've found the manager that this address belongs to, so we
		// can retrieve the address' account along with the manager
		// that the addr belongs to.
		accNo, err := scopedMgr.AddrAccount(ns, address)
		if err != nil {
			return nil, 0, err
		}

		return scopedMgr, accNo, err
	}

	// If we get to this point, then we weren't able to find the address in
	// any of the managers, so we'll exit with an error.
	str := fmt.Sprintf("unable to find key for addr %v", address)
	return nil, 0, managerError(ErrAddressNotFound, str, nil)
}

// ForEachActiveAccountAddress calls the given function with each active
// address of the given account stored in the manager, across all active
// scopes, breaking early on error.
//
// TODO(tuxcanfly): actually return only active addresses
func (m *Manager) ForEachActiveAccountAddress(ns walletdb.ReadBucket,
	account uint32, fn func(maddr ManagedAddress) error) error {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for _, scopedMgr := range m.scopedManagers {
		err := scopedMgr.ForEachActiveAccountAddress(ns, account, fn)
		if err != nil {
			return err
		}
	}

	return nil
}

// ForEachActiveAddress calls the given function with each active address
// stored in the manager, breaking early on error.
func (m *Manager) ForEachActiveAddress(ns walletdb.ReadBucket, fn func(addr btcutil.Address) error) error {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for _, scopedMgr := range m.scopedManagers {
		err := scopedMgr.ForEachActiveAddress(ns, fn)
		if err != nil {
			return err
		}
	}

	return nil
}

// ForEachRelevantActiveAddress invokes the given closure on each active
// address relevant to the wallet. Ideally, only addresses within the default
// key scopes would be relevant, but due to a bug (now fixed) in which change
// addresses could be created outside of the default key scopes, we now need to
// check for those as well.
func (m *Manager) ForEachRelevantActiveAddress(ns walletdb.ReadBucket,
	fn func(addr btcutil.Address) error) error {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for _, scopedMgr := range m.scopedManagers {
		// If the manager is for a default key scope, we'll return all
		// addresses, otherwise we'll only return internal addresses, as
		// that's the branch used for change addresses.
		isDefaultKeyScope := false
		for _, defaultKeyScope := range DefaultKeyScopes {
			if scopedMgr.Scope() == defaultKeyScope {
				isDefaultKeyScope = true
				break
			}
		}

		var err error
		if isDefaultKeyScope {
			err = scopedMgr.ForEachActiveAddress(ns, fn)
		} else {
			err = scopedMgr.ForEachInternalActiveAddress(ns, fn)
		}
		if err != nil {
			return err
		}
	}

	return nil
}

// ForEachAccountAddress calls the given function with each address of
// the given account stored in the manager, breaking early on error.
func (m *Manager) ForEachAccountAddress(ns walletdb.ReadBucket, account uint32,
	fn func(maddr ManagedAddress) error) error {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for _, scopedMgr := range m.scopedManagers {
		err := scopedMgr.ForEachAccountAddress(ns, account, fn)
		if err != nil {
			return err
		}
	}

	return nil
}

// ChainParams returns the chain parameters for this address manager.
func (m *Manager) ChainParams() *chaincfg.Params {
	// NOTE: No need for mutex here since the net field does not change
	// after the manager instance is created.

	return m.chainParams
}

// ChangePassphrase changes either the public or private passphrase to the
// provided value depending on the private flag.  In order to change the
// private password, the address manager must not be watching-only.  The new
// passphrase keys are derived using the scrypt parameters in the options, so
// changing the passphrase may be used to bump the computational difficulty
// needed to brute force the passphrase.
func (m *Manager) ChangePassphrase(ns walletdb.ReadWriteBucket, oldPassphrase,
	newPassphrase []byte, private bool, config *ScryptOptions) error {

	// No private passphrase to change for a watching-only address manager.
	if private && m.watchingOnly {
		return managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	m.mtx.Lock()
	defer m.mtx.Unlock()

	// Ensure the provided old passphrase is correct.  This check is done
	// using a copy of the appropriate master key depending on the private
	// flag to ensure the current state is not altered.  The temp key is
	// cleared when done to avoid leaving a copy in memory.
	var keyName string
	secretKey := snacl.SecretKey{Key: &snacl.CryptoKey{}}
	if private {
		keyName = "private"
		secretKey.Parameters = m.masterKeyPriv.Parameters
	} else {
		keyName = "public"
		secretKey.Parameters = m.masterKeyPub.Parameters
	}
	if err := secretKey.DeriveKey(&oldPassphrase); err != nil {
		if err == snacl.ErrInvalidPassword {
			str := fmt.Sprintf("invalid passphrase for %s master "+
				"key", keyName)
			return managerError(ErrWrongPassphrase, str, nil)
		}

		str := fmt.Sprintf("failed to derive %s master key", keyName)
		return managerError(ErrCrypto, str, err)
	}
	defer secretKey.Zero()

	// Generate a new master key from the passphrase which is used to secure
	// the actual secret keys.
	newMasterKey, err := newSecretKey(&newPassphrase, config)
	if err != nil {
		str := "failed to create new master private key"
		return managerError(ErrCrypto, str, err)
	}
	newKeyParams := newMasterKey.Marshal()

	if private {
		// Technically, the locked state could be checked here to only
		// do the decrypts when the address manager is locked as the
		// clear text keys are already available in memory when it is
		// unlocked, but this is not a hot path, decryption is quite
		// fast, and it's less cyclomatic complexity to simply decrypt
		// in either case.

		// Create a new salt that will be used for hashing the new
		// passphrase each unlock.
		var passphraseSalt [saltSize]byte
		_, err := rand.Read(passphraseSalt[:])
		if err != nil {
			str := "failed to read random source for passhprase salt"
			return managerError(ErrCrypto, str, err)
		}

		// Re-encrypt the crypto private key using the new master
		// private key.
		decPriv, err := secretKey.Decrypt(m.cryptoKeyPrivEncrypted)
		if err != nil {
			str := "failed to decrypt crypto private key"
			return managerError(ErrCrypto, str, err)
		}
		encPriv, err := newMasterKey.Encrypt(decPriv)
		zero.Bytes(decPriv)
		if err != nil {
			str := "failed to encrypt crypto private key"
			return managerError(ErrCrypto, str, err)
		}

		// Re-encrypt the crypto script key using the new master
		// private key.
		decScript, err := secretKey.Decrypt(m.cryptoKeyScriptEncrypted)
		if err != nil {
			str := "failed to decrypt crypto script key"
			return managerError(ErrCrypto, str, err)
		}
		encScript, err := newMasterKey.Encrypt(decScript)
		zero.Bytes(decScript)
		if err != nil {
			str := "failed to encrypt crypto script key"
			return managerError(ErrCrypto, str, err)
		}

		// When the manager is locked, ensure the new clear text master
		// key is cleared from memory now that it is no longer needed.
		// If unlocked, create the new passphrase hash with the new
		// passphrase and salt.
		var hashedPassphrase [sha512.Size]byte
		if m.locked {
			newMasterKey.Zero()
		} else {
			saltedPassphrase := append(passphraseSalt[:],
				newPassphrase...)
			hashedPassphrase = sha512.Sum512(saltedPassphrase)
			zero.Bytes(saltedPassphrase)
		}

		// Save the new keys and params to the db in a single
		// transaction.
		err = putCryptoKeys(ns, nil, encPriv, encScript)
		if err != nil {
			return maybeConvertDbError(err)
		}

		err = putMasterKeyParams(ns, nil, newKeyParams)
		if err != nil {
			return maybeConvertDbError(err)
		}

		// Now that the db has been successfully updated, clear the old
		// key and set the new one.
		copy(m.cryptoKeyPrivEncrypted, encPriv)
		copy(m.cryptoKeyScriptEncrypted, encScript)
		m.masterKeyPriv.Zero() // Clear the old key.
		m.masterKeyPriv = newMasterKey
		m.privPassphraseSalt = passphraseSalt
		m.hashedPrivPassphrase = hashedPassphrase
	} else {
		// Re-encrypt the crypto public key using the new master public
		// key.
		encryptedPub, err := newMasterKey.Encrypt(m.cryptoKeyPub.Bytes())
		if err != nil {
			str := "failed to encrypt crypto public key"
			return managerError(ErrCrypto, str, err)
		}

		// Save the new keys and params to the the db in a single
		// transaction.
		err = putCryptoKeys(ns, encryptedPub, nil, nil)
		if err != nil {
			return maybeConvertDbError(err)
		}

		err = putMasterKeyParams(ns, newKeyParams, nil)
		if err != nil {
			return maybeConvertDbError(err)
		}

		// Now that the db has been successfully updated, clear the old
		// key and set the new one.
		m.masterKeyPub.Zero()
		m.masterKeyPub = newMasterKey
	}

	return nil
}

// ConvertToWatchingOnly converts the current address manager to a locked
// watching-only address manager.
//
// WARNING: This function removes private keys from the existing address manager
// which means they will no longer be available.  Typically the caller will make
// a copy of the existing wallet database and modify the copy since otherwise it
// would mean permanent loss of any imported private keys and scripts.
//
// Executing this function on a manager that is already watching-only will have
// no effect.
func (m *Manager) ConvertToWatchingOnly(ns walletdb.ReadWriteBucket) error {
	m.mtx.Lock()
	defer m.mtx.Unlock()

	// Exit now if the manager is already watching-only.
	if m.watchingOnly {
		return nil
	}

	var err error

	// Remove all private key material and mark the new database as
	// watching only.
	if err := deletePrivateKeys(ns); err != nil {
		return maybeConvertDbError(err)
	}

	err = putWatchingOnly(ns, true)
	if err != nil {
		return maybeConvertDbError(err)
	}

	// Lock the manager to remove all clear text private key material from
	// memory if needed.
	if !m.locked {
		m.lock()
	}

	// This section clears and removes the encrypted private key material
	// that is ordinarily used to unlock the manager.  Since the the manager
	// is being converted to watching-only, the encrypted private key
	// material is no longer needed.

	// Clear and remove all of the encrypted acount private keys.
	for _, manager := range m.scopedManagers {
		for _, acctInfo := range manager.acctInfo {
			zero.Bytes(acctInfo.acctKeyEncrypted)
			acctInfo.acctKeyEncrypted = nil
		}
	}

	// Clear and remove encrypted private keys and encrypted scripts from
	// all address entries.
	for _, manager := range m.scopedManagers {
		for _, ma := range manager.addrs {
			switch addr := ma.(type) {
			case *managedAddress:
				zero.Bytes(addr.privKeyEncrypted)
				addr.privKeyEncrypted = nil
			case *scriptAddress:
				zero.Bytes(addr.scriptEncrypted)
				addr.scriptEncrypted = nil
			}
		}
	}

	// Clear and remove encrypted private and script crypto keys.
	zero.Bytes(m.cryptoKeyScriptEncrypted)
	m.cryptoKeyScriptEncrypted = nil
	m.cryptoKeyScript = nil
	zero.Bytes(m.cryptoKeyPrivEncrypted)
	m.cryptoKeyPrivEncrypted = nil
	m.cryptoKeyPriv = nil

	// The master private key is derived from a passphrase when the manager
	// is unlocked, so there is no encrypted version to zero.  However,
	// it is no longer needed, so nil it.
	m.masterKeyPriv = nil

	// Mark the manager watching-only.
	m.watchingOnly = true
	return nil

}

// IsLocked returns whether or not the address managed is locked.  When it is
// unlocked, the decryption key needed to decrypt private keys used for signing
// is in memory.
func (m *Manager) IsLocked() bool {
	m.mtx.RLock()
	defer m.mtx.RUnlock()

	return m.isLocked()
}

// isLocked is an internal method returning whether or not the address manager
// is locked via an unprotected read.
//
// NOTE: The caller *MUST* acquire the Manager's mutex before invocation to
// avoid data races.
func (m *Manager) isLocked() bool {
	return m.locked
}

// Lock performs a best try effort to remove and zero all secret keys associated
// with the address manager.
//
// This function will return an error if invoked on a watching-only address
// manager.
func (m *Manager) Lock() error {
	// A watching-only address manager can't be locked.
	if m.watchingOnly {
		return managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	m.mtx.Lock()
	defer m.mtx.Unlock()

	// Error on attempt to lock an already locked manager.
	if m.locked {
		return managerError(ErrLocked, errLocked, nil)
	}

	m.lock()
	return nil
}

// Unlock derives the master private key from the specified passphrase.  An
// invalid passphrase will return an error.  Otherwise, the derived secret key
// is stored in memory until the address manager is locked.  Any failures that
// occur during this function will result in the address manager being locked,
// even if it was already unlocked prior to calling this function.
//
// This function will return an error if invoked on a watching-only address
// manager.
func (m *Manager) Unlock(ns walletdb.ReadBucket, passphrase []byte) error {
	// A watching-only address manager can't be unlocked.
	if m.watchingOnly {
		return managerError(ErrWatchingOnly, errWatchingOnly, nil)
	}

	m.mtx.Lock()
	defer m.mtx.Unlock()

	// Avoid actually unlocking if the manager is already unlocked
	// and the passphrases match.
	if !m.locked {
		saltedPassphrase := append(m.privPassphraseSalt[:],
			passphrase...)
		hashedPassphrase := sha512.Sum512(saltedPassphrase)
		zero.Bytes(saltedPassphrase)
		if hashedPassphrase != m.hashedPrivPassphrase {
			m.lock()
			str := "invalid passphrase for master private key"
			return managerError(ErrWrongPassphrase, str, nil)
		}
		return nil
	}

	// Derive the master private key using the provided passphrase.
	if err := m.masterKeyPriv.DeriveKey(&passphrase); err != nil {
		m.lock()
		if err == snacl.ErrInvalidPassword {
			str := "invalid passphrase for master private key"
			return managerError(ErrWrongPassphrase, str, nil)
		}

		str := "failed to derive master private key"
		return managerError(ErrCrypto, str, err)
	}

	// Use the master private key to decrypt the crypto private key.
	decryptedKey, err := m.masterKeyPriv.Decrypt(m.cryptoKeyPrivEncrypted)
	if err != nil {
		m.lock()
		str := "failed to decrypt crypto private key"
		return managerError(ErrCrypto, str, err)
	}
	m.cryptoKeyPriv.CopyBytes(decryptedKey)
	zero.Bytes(decryptedKey)

	// Use the crypto private key to decrypt all of the account private
	// extended keys.
	for _, manager := range m.scopedManagers {
		for account, acctInfo := range manager.acctInfo {
			decrypted, err := m.cryptoKeyPriv.Decrypt(acctInfo.acctKeyEncrypted)
			if err != nil {
				m.lock()
				str := fmt.Sprintf("failed to decrypt account %d "+
					"private key", account)
				return managerError(ErrCrypto, str, err)
			}

			acctKeyPriv, err := hdkeychain.NewKeyFromString(string(decrypted))
			zero.Bytes(decrypted)
			if err != nil {
				m.lock()
				str := fmt.Sprintf("failed to regenerate account %d "+
					"extended key", account)
				return managerError(ErrKeyChain, str, err)
			}
			acctInfo.acctKeyPriv = acctKeyPriv
		}

		// We'll also derive any private keys that are pending due to
		// them being created while the address manager was locked.
		for _, info := range manager.deriveOnUnlock {
			addressKey, _, _, err := manager.deriveKeyFromPath(
				ns, info.managedAddr.InternalAccount(),
				info.branch, info.index, true,
			)
			if err != nil {
				m.lock()
				return err
			}

			// It's ok to ignore the error here since it can only
			// fail if the extended key is not private, however it
			// was just derived as a private key.
			privKey, _ := addressKey.ECPrivKey()
			addressKey.Zero()

			privKeyBytes := privKey.Serialize()
			privKeyEncrypted, err := m.cryptoKeyPriv.Encrypt(privKeyBytes)
			zero.BigInt(privKey.D)
			if err != nil {
				m.lock()
				str := fmt.Sprintf("failed to encrypt private key for "+
					"address %s", info.managedAddr.Address())
				return managerError(ErrCrypto, str, err)
			}

			switch a := info.managedAddr.(type) {
			case *managedAddress:
				a.privKeyEncrypted = privKeyEncrypted
				a.privKeyCT = privKeyBytes
			case *scriptAddress:
			}

			// Avoid re-deriving this key on subsequent unlocks.
			manager.deriveOnUnlock[0] = nil
			manager.deriveOnUnlock = manager.deriveOnUnlock[1:]
		}
	}

	m.locked = false
	saltedPassphrase := append(m.privPassphraseSalt[:], passphrase...)
	m.hashedPrivPassphrase = sha512.Sum512(saltedPassphrase)
	zero.Bytes(saltedPassphrase)
	return nil
}

// ValidateAccountName validates the given account name and returns an error, if any.
func ValidateAccountName(name string) error {
	if name == "" {
		str := "accounts may not be named the empty string"
		return managerError(ErrInvalidAccount, str, nil)
	}
	if isReservedAccountName(name) {
		str := "reserved account name"
		return managerError(ErrInvalidAccount, str, nil)
	}
	return nil
}

// LookupAccount returns the corresponding key scope and account number for the
// account with the given name.
func (m *Manager) LookupAccount(ns walletdb.ReadBucket, name string) (KeyScope,
	uint32, error) {

	m.mtx.RLock()
	defer m.mtx.RUnlock()

	for keyScope, scopedMgr := range m.scopedManagers {
		acct, err := scopedMgr.LookupAccount(ns, name)
		if err == nil {
			return keyScope, acct, nil
		}
	}

	str := fmt.Sprintf("account name '%s' not found", name)
	return KeyScope{}, 0, managerError(ErrAccountNotFound, str, nil)
}

// selectCryptoKey selects the appropriate crypto key based on the key type. An
// error is returned when an invalid key type is specified or the requested key
// requires the manager to be unlocked when it isn't.
//
// This function MUST be called with the manager lock held for reads.
func (m *Manager) selectCryptoKey(keyType CryptoKeyType) (EncryptorDecryptor, error) {
	if keyType == CKTPrivate || keyType == CKTScript {
		// The manager must be unlocked to work with the private keys.
		if m.locked || m.watchingOnly {
			return nil, managerError(ErrLocked, errLocked, nil)
		}
	}

	var cryptoKey EncryptorDecryptor
	switch keyType {
	case CKTPrivate:
		cryptoKey = m.cryptoKeyPriv
	case CKTScript:
		cryptoKey = m.cryptoKeyScript
	case CKTPublic:
		cryptoKey = m.cryptoKeyPub
	default:
		return nil, managerError(ErrInvalidKeyType, "invalid key type",
			nil)
	}

	return cryptoKey, nil
}

// Encrypt in using the crypto key type specified by keyType.
func (m *Manager) Encrypt(keyType CryptoKeyType, in []byte) ([]byte, error) {
	// Encryption must be performed under the manager mutex since the
	// keys are cleared when the manager is locked.
	m.mtx.Lock()
	defer m.mtx.Unlock()

	cryptoKey, err := m.selectCryptoKey(keyType)
	if err != nil {
		return nil, err
	}

	encrypted, err := cryptoKey.Encrypt(in)
	if err != nil {
		return nil, managerError(ErrCrypto, "failed to encrypt", err)
	}
	return encrypted, nil
}

// Decrypt in using the crypto key type specified by keyType.
func (m *Manager) Decrypt(keyType CryptoKeyType, in []byte) ([]byte, error) {
	// Decryption must be performed under the manager mutex since the keys
	// are cleared when the manager is locked.
	m.mtx.Lock()
	defer m.mtx.Unlock()

	cryptoKey, err := m.selectCryptoKey(keyType)
	if err != nil {
		return nil, err
	}

	decrypted, err := cryptoKey.Decrypt(in)
	if err != nil {
		return nil, managerError(ErrCrypto, "failed to decrypt", err)
	}
	return decrypted, nil
}

// newManager returns a new locked address manager with the given parameters.
func newManager(chainParams *chaincfg.Params, masterKeyPub *snacl.SecretKey,
	masterKeyPriv *snacl.SecretKey, cryptoKeyPub EncryptorDecryptor,
	cryptoKeyPrivEncrypted, cryptoKeyScriptEncrypted []byte, syncInfo *syncState,
	birthday time.Time, privPassphraseSalt [saltSize]byte,
	scopedManagers map[KeyScope]*ScopedKeyManager, watchingOnly bool) *Manager {

	m := &Manager{
		chainParams:              chainParams,
		syncState:                *syncInfo,
		locked:                   true,
		birthday:                 birthday,
		masterKeyPub:             masterKeyPub,
		masterKeyPriv:            masterKeyPriv,
		cryptoKeyPub:             cryptoKeyPub,
		cryptoKeyPrivEncrypted:   cryptoKeyPrivEncrypted,
		cryptoKeyPriv:            &cryptoKey{},
		cryptoKeyScriptEncrypted: cryptoKeyScriptEncrypted,
		cryptoKeyScript:          &cryptoKey{},
		privPassphraseSalt:       privPassphraseSalt,
		scopedManagers:           scopedManagers,
		externalAddrSchemas:      make(map[AddressType][]KeyScope),
		internalAddrSchemas:      make(map[AddressType][]KeyScope),
		watchingOnly:             watchingOnly,
	}

	for _, sMgr := range m.scopedManagers {
		externalType := sMgr.AddrSchema().ExternalAddrType
		internalType := sMgr.AddrSchema().InternalAddrType
		scope := sMgr.Scope()

		m.externalAddrSchemas[externalType] = append(
			m.externalAddrSchemas[externalType], scope,
		)
		m.internalAddrSchemas[internalType] = append(
			m.internalAddrSchemas[internalType], scope,
		)
	}

	return m
}

// deriveCoinTypeKey derives the cointype key which can be used to derive the
// extended key for an account according to the hierarchy described by BIP0044
// given the coin type key.
//
// In particular this is the hierarchical deterministic extended key path:
// m/purpose'/<coin type>'
func deriveCoinTypeKey(masterNode *hdkeychain.ExtendedKey,
	scope KeyScope) (*hdkeychain.ExtendedKey, error) {

	// Enforce maximum coin type.
	if scope.Coin > maxCoinType {
		err := managerError(ErrCoinTypeTooHigh, errCoinTypeTooHigh, nil)
		return nil, err
	}

	// The hierarchy described by BIP0043 is:
	//  m/<purpose>'/*
	//
	// This is further extended by BIP0044 to:
	//  m/44'/<coin type>'/<account>'/<branch>/<address index>
	//
	// However, as this is a generic key store for any family for BIP0044
	// standards, we'll use the custom scope to govern our key derivation.
	//
	// The branch is 0 for external addresses and 1 for internal addresses.

	// Derive the purpose key as a child of the master node.
	purpose, err := masterNode.DeriveNonStandard( // nolint:staticcheck
		scope.Purpose + hdkeychain.HardenedKeyStart,
	)
	if err != nil {
		return nil, err
	}

	// Derive the coin type key as a child of the purpose key.
	coinTypeKey, err := purpose.DeriveNonStandard( // nolint:staticcheck
		scope.Coin + hdkeychain.HardenedKeyStart,
	)
	if err != nil {
		return nil, err
	}

	return coinTypeKey, nil
}

// deriveAccountKey derives the extended key for an account according to the
// hierarchy described by BIP0044 given the master node.
//
// In particular this is the hierarchical deterministic extended key path:
//   m/purpose'/<coin type>'/<account>'
func deriveAccountKey(coinTypeKey *hdkeychain.ExtendedKey,
	account uint32) (*hdkeychain.ExtendedKey, error) {

	// Enforce maximum account number.
	if account > MaxAccountNum {
		err := managerError(ErrAccountNumTooHigh, errAcctTooHigh, nil)
		return nil, err
	}

	// Derive the account key as a child of the coin type key.
	return coinTypeKey.DeriveNonStandard( // nolint:staticcheck
		account + hdkeychain.HardenedKeyStart,
	)
}

// checkBranchKeys ensures deriving the extended keys for the internal and
// external branches given an account key does not result in an invalid child
// error which means the chosen seed is not usable.  This conforms to the
// hierarchy described by the BIP0044 family so long as the account key is
// already derived accordingly.
//
// In particular this is the hierarchical deterministic extended key path:
//   m/purpose'/<coin type>'/<account>'/<branch>
//
// The branch is 0 for external addresses and 1 for internal addresses.
func checkBranchKeys(acctKey *hdkeychain.ExtendedKey) error {
	// Derive the external branch as the first child of the account key.
	if _, err := acctKey.DeriveNonStandard(ExternalBranch); err != nil { // nolint:staticcheck
		return err
	}

	// Derive the internal branch as the second child of the account key.
	_, err := acctKey.DeriveNonStandard(InternalBranch) // nolint:staticcheck
	return err
}

// loadManager returns a new address manager that results from loading it from
// the passed opened database.  The public passphrase is required to decrypt
// the public keys.
func loadManager(ns walletdb.ReadBucket, pubPassphrase []byte,
	chainParams *chaincfg.Params) (*Manager, error) {

	// Verify the version is neither too old or too new.
	version, err := fetchManagerVersion(ns)
	if err != nil {
		str := "failed to fetch version for update"
		return nil, managerError(ErrDatabase, str, err)
	}
	if version < latestMgrVersion {
		str := "database upgrade required"
		return nil, managerError(ErrUpgrade, str, nil)
	} else if version > latestMgrVersion {
		str := "database version is greater than latest understood version"
		return nil, managerError(ErrUpgrade, str, nil)
	}

	// Load whether or not the manager is watching-only from the db.
	watchingOnly, err := fetchWatchingOnly(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}

	// Load the master key params from the db.
	masterKeyPubParams, masterKeyPrivParams, err := fetchMasterKeyParams(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}

	// Load the crypto keys from the db.
	cryptoKeyPubEnc, cryptoKeyPrivEnc, cryptoKeyScriptEnc, err :=
		fetchCryptoKeys(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}

	// Load the sync state from the db.
	syncedTo, err := fetchSyncedTo(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}
	startBlock, err := FetchStartBlock(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}
	birthday, err := fetchBirthday(ns)
	if err != nil {
		return nil, maybeConvertDbError(err)
	}

	// When not a watching-only manager, set the master private key params,
	// but don't derive it now since the manager starts off locked.
	var masterKeyPriv snacl.SecretKey
	if !watchingOnly {
		err := masterKeyPriv.Unmarshal(masterKeyPrivParams)
		if err != nil {
			str := "failed to unmarshal master private key"
			return nil, managerError(ErrCrypto, str, err)
		}
	}

	// Derive the master public key using the serialized params and provided
	// passphrase.
	var masterKeyPub snacl.SecretKey
	if err := masterKeyPub.Unmarshal(masterKeyPubParams); err != nil {
		str := "failed to unmarshal master public key"
		return nil, managerError(ErrCrypto, str, err)
	}
	if err := masterKeyPub.DeriveKey(&pubPassphrase); err != nil {
		str := "invalid passphrase for master public key"
		return nil, managerError(ErrWrongPassphrase, str, nil)
	}

	// Use the master public key to decrypt the crypto public key.
	cryptoKeyPub := &cryptoKey{snacl.CryptoKey{}}
	cryptoKeyPubCT, err := masterKeyPub.Decrypt(cryptoKeyPubEnc)
	if err != nil {
		str := "failed to decrypt crypto public key"
		return nil, managerError(ErrCrypto, str, err)
	}
	cryptoKeyPub.CopyBytes(cryptoKeyPubCT)
	zero.Bytes(cryptoKeyPubCT)

	// Create the sync state struct.
	syncInfo := newSyncState(startBlock, syncedTo)

	// Generate private passphrase salt.
	var privPassphraseSalt [saltSize]byte
	_, err = rand.Read(privPassphraseSalt[:])
	if err != nil {
		str := "failed to read random source for passphrase salt"
		return nil, managerError(ErrCrypto, str, err)
	}

	// Next, we'll need to load all known manager scopes from disk. Each
	// scope is on a distinct top-level path within our HD key chain.
	scopedManagers := make(map[KeyScope]*ScopedKeyManager)
	err = forEachKeyScope(ns, func(scope KeyScope) error {
		scopeSchema, err := fetchScopeAddrSchema(ns, &scope)
		if err != nil {
			return err
		}

		scopedManagers[scope] = &ScopedKeyManager{
			scope:        scope,
			addrSchema:   *scopeSchema,
			addrs:        make(map[addrKey]ManagedAddress),
			acctInfo:     make(map[uint32]*accountInfo),
			privKeyCache: lru.NewCache(defaultPrivKeyCacheSize),
		}

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

	// Create new address manager with the given parameters.  Also,
	// override the defaults for the additional fields which are not
	// specified in the call to new with the values loaded from the
	// database.
	mgr := newManager(
		chainParams, &masterKeyPub, &masterKeyPriv,
		cryptoKeyPub, cryptoKeyPrivEnc, cryptoKeyScriptEnc, syncInfo,
		birthday, privPassphraseSalt, scopedManagers, watchingOnly,
	)

	for _, scopedManager := range scopedManagers {
		scopedManager.rootManager = mgr
	}

	return mgr, nil
}

// Open loads an existing address manager from the given namespace.  The public
// passphrase is required to decrypt the public keys used to protect the public
// information such as addresses.  This is important since access to BIP0032
// extended keys means it is possible to generate all future addresses.
//
// If a config structure is passed to the function, that configuration will
// override the defaults.
//
// A ManagerError with an error code of ErrNoExist will be returned if the
// passed manager does not exist in the specified namespace.
func Open(ns walletdb.ReadBucket, pubPassphrase []byte,
	chainParams *chaincfg.Params) (*Manager, error) {

	// Return an error if the manager has NOT already been created in the
	// given database namespace.
	exists := managerExists(ns)
	if !exists {
		str := "the specified address manager does not exist"
		return nil, managerError(ErrNoExist, str, nil)
	}

	return loadManager(ns, pubPassphrase, chainParams)
}

// createManagerKeyScope creates a new key scoped for a target manager's scope.
// This partitions key derivation for a particular purpose+coin tuple, allowing
// multiple address derivation schems to be maintained concurrently.
func createManagerKeyScope(ns walletdb.ReadWriteBucket,
	scope KeyScope, root *hdkeychain.ExtendedKey,
	cryptoKeyPub, cryptoKeyPriv EncryptorDecryptor) error {

	// Derive the cointype key according to the passed scope.
	coinTypeKeyPriv, err := deriveCoinTypeKey(root, scope)
	if err != nil {
		str := "failed to derive cointype extended key"
		return managerError(ErrKeyChain, str, err)
	}
	defer coinTypeKeyPriv.Zero()

	// Derive the account key for the first account according our
	// BIP0044-like derivation.
	acctKeyPriv, err := deriveAccountKey(coinTypeKeyPriv, 0)
	if err != nil {
		// The seed is unusable if the any of the children in the
		// required hierarchy can't be derived due to invalid child.
		if err == hdkeychain.ErrInvalidChild {
			str := "the provided seed is unusable"
			return managerError(ErrKeyChain, str,
				hdkeychain.ErrUnusableSeed)
		}

		return err
	}

	// Ensure the branch keys can be derived for the provided seed according
	// to our BIP0044-like derivation.
	if err := checkBranchKeys(acctKeyPriv); err != nil {
		// The seed is unusable if the any of the children in the
		// required hierarchy can't be derived due to invalid child.
		if err == hdkeychain.ErrInvalidChild {
			str := "the provided seed is unusable"
			return managerError(ErrKeyChain, str,
				hdkeychain.ErrUnusableSeed)
		}

		return err
	}

	// The address manager needs the public extended key for the account.
	acctKeyPub, err := acctKeyPriv.Neuter()
	if err != nil {
		str := "failed to convert private key for account 0"
		return managerError(ErrKeyChain, str, err)
	}

	// Encrypt the cointype keys with the associated crypto keys.
	coinTypeKeyPub, err := coinTypeKeyPriv.Neuter()
	if err != nil {
		str := "failed to convert cointype private key"
		return managerError(ErrKeyChain, str, err)
	}
	coinTypePubEnc, err := cryptoKeyPub.Encrypt([]byte(coinTypeKeyPub.String()))
	if err != nil {
		str := "failed to encrypt cointype public key"
		return managerError(ErrCrypto, str, err)
	}
	coinTypePrivEnc, err := cryptoKeyPriv.Encrypt([]byte(coinTypeKeyPriv.String()))
	if err != nil {
		str := "failed to encrypt cointype private key"
		return managerError(ErrCrypto, str, err)
	}

	// Encrypt the default account keys with the associated crypto keys.
	acctPubEnc, err := cryptoKeyPub.Encrypt([]byte(acctKeyPub.String()))
	if err != nil {
		str := "failed to  encrypt public key for account 0"
		return managerError(ErrCrypto, str, err)
	}
	acctPrivEnc, err := cryptoKeyPriv.Encrypt([]byte(acctKeyPriv.String()))
	if err != nil {
		str := "failed to encrypt private key for account 0"
		return managerError(ErrCrypto, str, err)
	}

	// Save the encrypted cointype keys to the database.
	err = putCoinTypeKeys(ns, &scope, coinTypePubEnc, coinTypePrivEnc)
	if err != nil {
		return err
	}

	// Save the information for the default account to the database.
	err = putDefaultAccountInfo(
		ns, &scope, DefaultAccountNum, acctPubEnc, acctPrivEnc, 0, 0,
		defaultAccountName,
	)
	if err != nil {
		return err
	}

	return putDefaultAccountInfo(
		ns, &scope, ImportedAddrAccount, nil, nil, 0, 0,
		ImportedAddrAccountName,
	)
}

// Create creates a new address manager in the given namespace.
//
// The seed must conform to the standards described in
// hdkeychain.NewMaster and will be used to create the master root
// node from which all hierarchical deterministic addresses are
// derived.  This allows all chained addresses in the address manager
// to be recovered by using the same seed.
//
// If the provided seed value is nil the address manager will be
// created in watchingOnly mode in which case no default accounts or
// scoped managers are created - it is up to the caller to create a
// new one with NewAccountWatchingOnly and NewScopedKeyManager.
//
// All private and public keys and information are protected by secret
// keys derived from the provided private and public passphrases.  The
// public passphrase is required on subsequent opens of the address
// manager, and the private passphrase is required to unlock the
// address manager in order to gain access to any private keys and
// information.
//
// If a config structure is passed to the function, that configuration
// will override the defaults.
//
// A ManagerError with an error code of ErrAlreadyExists will be
// returned the address manager already exists in the specified
// namespace.
func Create(ns walletdb.ReadWriteBucket, rootKey *hdkeychain.ExtendedKey,
	pubPassphrase, privPassphrase []byte,
	chainParams *chaincfg.Params, config *ScryptOptions,
	birthday time.Time) error {

	// If the seed argument is nil we create in watchingOnly mode.
	isWatchingOnly := rootKey == nil

	// Return an error if the manager has already been created in
	// the given database namespace.
	exists := managerExists(ns)
	if exists {
		return managerError(ErrAlreadyExists, errAlreadyExists, nil)
	}

	// Ensure the private passphrase is not empty.
	if !isWatchingOnly && len(privPassphrase) == 0 {
		str := "private passphrase may not be empty"
		return managerError(ErrEmptyPassphrase, str, nil)
	}

	// Perform the initial bucket creation and database namespace setup.
	defaultScopes := map[KeyScope]ScopeAddrSchema{}
	if !isWatchingOnly {
		defaultScopes = ScopeAddrMap
	}
	if err := createManagerNS(ns, defaultScopes); err != nil {
		return maybeConvertDbError(err)
	}

	if config == nil {
		config = &DefaultScryptOptions
	}

	// Generate new master keys.  These master keys are used to protect the
	// crypto keys that will be generated next.
	masterKeyPub, err := newSecretKey(&pubPassphrase, config)
	if err != nil {
		str := "failed to master public key"
		return managerError(ErrCrypto, str, err)
	}

	// Generate new crypto public, private, and script keys.  These keys are
	// used to protect the actual public and private data such as addresses,
	// extended keys, and scripts.
	cryptoKeyPub, err := newCryptoKey()
	if err != nil {
		str := "failed to generate crypto public key"
		return managerError(ErrCrypto, str, err)
	}

	// Encrypt the crypto keys with the associated master keys.
	cryptoKeyPubEnc, err := masterKeyPub.Encrypt(cryptoKeyPub.Bytes())
	if err != nil {
		str := "failed to encrypt crypto public key"
		return managerError(ErrCrypto, str, err)
	}

	// Use the genesis block for the passed chain as the created at block
	// for the default.
	createdAt := &BlockStamp{
		Hash:      *chainParams.GenesisHash,
		Height:    0,
		Timestamp: chainParams.GenesisBlock.Header.Timestamp,
	}

	// Create the initial sync state.
	syncInfo := newSyncState(createdAt, createdAt)

	pubParams := masterKeyPub.Marshal()

	var privParams []byte
	var masterKeyPriv *snacl.SecretKey
	var cryptoKeyPrivEnc []byte
	var cryptoKeyScriptEnc []byte
	if !isWatchingOnly {
		masterKeyPriv, err = newSecretKey(&privPassphrase, config)
		if err != nil {
			str := "failed to master private key"
			return managerError(ErrCrypto, str, err)
		}
		defer masterKeyPriv.Zero()

		// Generate the private passphrase salt.  This is used when
		// hashing passwords to detect whether an unlock can be
		// avoided when the manager is already unlocked.
		var privPassphraseSalt [saltSize]byte
		_, err = rand.Read(privPassphraseSalt[:])
		if err != nil {
			str := "failed to read random source for passphrase salt"
			return managerError(ErrCrypto, str, err)
		}

		cryptoKeyPriv, err := newCryptoKey()
		if err != nil {
			str := "failed to generate crypto private key"
			return managerError(ErrCrypto, str, err)
		}
		defer cryptoKeyPriv.Zero()
		cryptoKeyScript, err := newCryptoKey()
		if err != nil {
			str := "failed to generate crypto script key"
			return managerError(ErrCrypto, str, err)
		}
		defer cryptoKeyScript.Zero()

		cryptoKeyPrivEnc, err =
			masterKeyPriv.Encrypt(cryptoKeyPriv.Bytes())
		if err != nil {
			str := "failed to encrypt crypto private key"
			return managerError(ErrCrypto, str, err)
		}
		cryptoKeyScriptEnc, err =
			masterKeyPriv.Encrypt(cryptoKeyScript.Bytes())
		if err != nil {
			str := "failed to encrypt crypto script key"
			return managerError(ErrCrypto, str, err)
		}

		// Generate the BIP0044 HD key structure to ensure the
		// provided seed can generate the required structure with no
		// issues.
		rootPubKey, err := rootKey.Neuter()
		if err != nil {
			str := "failed to neuter master extended key"
			return managerError(ErrKeyChain, str, err)
		}

		// Next, for each registers default manager scope, we'll
		// create the hardened cointype key for it, as well as the
		// first default account.
		for _, defaultScope := range DefaultKeyScopes {
			err := createManagerKeyScope(
				ns, defaultScope, rootKey, cryptoKeyPub, cryptoKeyPriv,
			)
			if err != nil {
				return maybeConvertDbError(err)
			}
		}

		// Before we proceed, we'll also store the root master private
		// key within the database in an encrypted format. This is
		// required as in the future, we may need to create additional
		// scoped key managers.
		masterHDPrivKeyEnc, err :=
			cryptoKeyPriv.Encrypt([]byte(rootKey.String()))
		if err != nil {
			return maybeConvertDbError(err)
		}
		masterHDPubKeyEnc, err :=
			cryptoKeyPub.Encrypt([]byte(rootPubKey.String()))
		if err != nil {
			return maybeConvertDbError(err)
		}
		err = putMasterHDKeys(ns, masterHDPrivKeyEnc, masterHDPubKeyEnc)
		if err != nil {
			return maybeConvertDbError(err)
		}

		privParams = masterKeyPriv.Marshal()
	}

	// Save the master key params to the database.
	err = putMasterKeyParams(ns, pubParams, privParams)
	if err != nil {
		return maybeConvertDbError(err)
	}

	// Save the encrypted crypto keys to the database.
	err = putCryptoKeys(ns, cryptoKeyPubEnc, cryptoKeyPrivEnc,
		cryptoKeyScriptEnc)
	if err != nil {
		return maybeConvertDbError(err)
	}

	// Save the watching-only mode of the address manager to the
	// database.
	err = putWatchingOnly(ns, isWatchingOnly)
	if err != nil {
		return maybeConvertDbError(err)
	}

	// Save the initial synced to state.
	err = PutSyncedTo(ns, &syncInfo.syncedTo)
	if err != nil {
		return maybeConvertDbError(err)
	}
	err = putStartBlock(ns, &syncInfo.startBlock)
	if err != nil {
		return maybeConvertDbError(err)
	}

	// Use 48 hours as margin of safety for wallet birthday.
	return putBirthday(ns, birthday.Add(-48*time.Hour))
}