Update project structure and build process

libwallet/hdpublickey.go

@@ -0,0 +1,121 @@
+package libwallet
+
+import (
+	"errors"
+	"fmt"
+	"strings"
+
+	"github.com/muun/libwallet/hdpath"
+
+	"github.com/btcsuite/btcutil"
+	"github.com/btcsuite/btcutil/hdkeychain"
+)
+
+// HDPublicKey is an HD capable pub key
+type HDPublicKey struct {
+	key     hdkeychain.ExtendedKey
+	Network *Network
+	Path    string
+}
+
+// NewHDPublicKeyFromString creates an HD pub key from a base58-encoded string
+// If the parsed key is private, it returns an error
+func NewHDPublicKeyFromString(str, path string, network *Network) (*HDPublicKey, error) {
+
+	key, err := hdkeychain.NewKeyFromString(str)
+	if err != nil {
+		return nil, err
+	}
+
+	if key.IsPrivate() {
+		return nil, errors.New("encoded key was not a public key")
+	}
+
+	return &HDPublicKey{key: *key, Network: network, Path: path}, nil
+}
+
+// String return the key base58-encoded
+func (p *HDPublicKey) String() string {
+	return p.key.String()
+}
+
+// DerivedAt derives a new child pub key
+// index should be uint32 but for java compat we use int64
+func (p *HDPublicKey) DerivedAt(index int64) (*HDPublicKey, error) {
+
+	if index&hdkeychain.HardenedKeyStart != 0 {
+		return nil, fmt.Errorf("can't derive a hardened pub key (index %v)", index)
+	}
+
+	child, err := p.key.Child(uint32(index))
+	if err != nil {
+		return nil, err
+	}
+
+	parentPath, err := hdpath.Parse(p.Path)
+	if err != nil {
+		return nil, err
+	}
+	path := parentPath.Child(uint32(index))
+
+	return &HDPublicKey{key: *child, Network: p.Network, Path: path.String()}, nil
+}
+
+func (p *HDPublicKey) DeriveTo(path string) (*HDPublicKey, error) {
+
+	if !strings.HasPrefix(path, p.Path) {
+		return nil, fmt.Errorf("derivation path %v is not prefix of the keys path %v", path, p.Path)
+	}
+
+	firstPath, err := hdpath.Parse(p.Path)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't parse derivation path %v: %w", p.Path, err)
+	}
+
+	secondPath, err := hdpath.Parse(path)
+	if err != nil {
+		return nil, fmt.Errorf("couldn't parse derivation path %v: %w", path, err)
+	}
+
+	indexes := secondPath.IndexesFrom(firstPath)
+	derivedKey := p
+	for depth, index := range indexes {
+		if index.Hardened {
+			return nil, fmt.Errorf("can't derive a hardened pub key (path %v)", path)
+		}
+
+		derivedKey, err = derivedKey.DerivedAt(int64(index.Index))
+		if err != nil {
+			return nil, fmt.Errorf("failed to derive key at path %v on depth %v: %w", path, depth, err)
+		}
+	}
+	// The generated path has no names in it, so replace it
+	derivedKey.Path = path
+
+	return derivedKey, nil
+}
+
+// Raw returns the backing EC compressed raw key
+func (p *HDPublicKey) Raw() []byte {
+
+	key, err := p.key.ECPubKey()
+	if err != nil {
+		panic("failed to extract pub key")
+	}
+
+	return key.SerializeCompressed()
+}
+
+// Fingerprint returns the 4-byte fingerprint for this pubkey
+func (p *HDPublicKey) Fingerprint() []byte {
+
+	key, err := p.key.ECPubKey()
+	if err != nil {
+		panic("failed to extract pub key")
+	}
+
+	bytes := key.SerializeCompressed()
+	hash := btcutil.Hash160(bytes)
+
+	return hash[:4]
+}