feat(types): add TxOutMultisig and TxOutHTLC target types

Output target types for HF1 HTLC and multisig transactions.

Co-Authored-By: Charon <charon@lethean.io>

types/transaction.go

@@ -131,6 +131,30 @@ type TxOutToKey struct {
 // TargetType returns the wire variant tag for to_key targets.
 func (t TxOutToKey) TargetType() uint8 { return TargetTypeToKey }
 
+// TxOutMultisig is the txout_multisig target variant (HF1+).
+// Spendable when minimum_sigs of the listed keys sign.
+type TxOutMultisig struct {
+	MinimumSigs uint64
+	Keys        []PublicKey
+}
+
+// TargetType returns the wire variant tag for multisig targets.
+func (t TxOutMultisig) TargetType() uint8 { return TargetTypeMultisig }
+
+// TxOutHTLC is the txout_htlc target variant (HF1+).
+// Hash Time-Locked Contract: redeemable with hash preimage before
+// expiration, refundable after expiration.
+type TxOutHTLC struct {
+	HTLCHash   Hash      // 32-byte hash lock
+	Flags      uint8     // bit 0: 0=SHA256, 1=RIPEMD160
+	Expiration uint64    // block height deadline
+	PKRedeem   PublicKey // recipient key (can redeem before expiration)
+	PKRefund   PublicKey // sender key (can refund after expiration)
+}
+
+// TargetType returns the wire variant tag for HTLC targets.
+func (t TxOutHTLC) TargetType() uint8 { return TargetTypeHTLC }
+
 // TxOutRef is one element of a txin_to_key key_offsets vector.
 // Each element is a variant: either a uint64 global index or a ref_by_id.
 type TxOutRef struct {

types/transaction_test.go

@@ -13,3 +13,20 @@ func TestTxOutToKey_TargetType_Good(t *testing.T) {
 		t.Errorf("TargetType: got %d, want %d", target.TargetType(), TargetTypeToKey)
 	}
 }
+
+func TestTxOutMultisig_TargetType_Good(t *testing.T) {
+	var target TxOutTarget = TxOutMultisig{MinimumSigs: 2, Keys: []PublicKey{{1}, {2}}}
+	if target.TargetType() != TargetTypeMultisig {
+		t.Errorf("TargetType: got %d, want %d", target.TargetType(), TargetTypeMultisig)
+	}
+}
+
+func TestTxOutHTLC_TargetType_Good(t *testing.T) {
+	var target TxOutTarget = TxOutHTLC{
+		Flags:      0,
+		Expiration: 10080,
+	}
+	if target.TargetType() != TargetTypeHTLC {
+		t.Errorf("TargetType: got %d, want %d", target.TargetType(), TargetTypeHTLC)
+	}
+}