refactor(types): change TxOutputBare.Target to TxOutTarget interface

Prepares for HF1 output target types (TxOutMultisig, TxOutHTLC).
All call sites updated to type-assert TxOutToKey where needed.

Modified files:
- types/transaction.go: TxOutputBare.Target is now TxOutTarget
- wire/transaction.go: encode/decode use type switch on target
- chain/ring.go: type-assert target to TxOutToKey for key extraction
- wallet/scanner.go: type-assert target before key comparison
- tui/explorer_model.go: type-assert target for display
- wire/transaction_test.go: type-assert in assertions
- wallet/builder_test.go: type-assert in assertions

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

chain/ring.go

@@ -35,7 +35,11 @@ func (c *Chain) GetRingOutputs(amount uint64, offsets []uint64) ([]types.PublicK
 
 		switch out := tx.Vout[outNo].(type) {
 		case types.TxOutputBare:
-			pubs[i] = out.Target.Key
+			toKey, ok := out.Target.(types.TxOutToKey)
+			if !ok {
+				return nil, fmt.Errorf("ring output %d: unsupported target type %T", i, out.Target)
+			}
+			pubs[i] = toKey.Key
 		default:
 			return nil, fmt.Errorf("ring output %d: unsupported output type %T", i, out)
 		}

tui/explorer_model.go

@@ -325,7 +325,11 @@ func (m *ExplorerModel) viewTxDetail() string {
 		for i, out := range tx.Vout {
 			switch v := out.(type) {
 			case types.TxOutputBare:
-				b.WriteString(fmt.Sprintf("  [%d] bare amount=%d key=%x\n", i, v.Amount, v.Target.Key[:4]))
+				if toKey, ok := v.Target.(types.TxOutToKey); ok {
+					b.WriteString(fmt.Sprintf("  [%d] bare amount=%d key=%x\n", i, v.Amount, toKey.Key[:4]))
+				} else {
+					b.WriteString(fmt.Sprintf("  [%d] bare amount=%d target=%T\n", i, v.Amount, v.Target))
+				}
 			case types.TxOutputZarcanum:
 				b.WriteString(fmt.Sprintf("  [%d] zarcanum stealth=%x\n", i, v.StealthAddress[:4]))
 			default:

types/transaction.go

@@ -183,8 +183,9 @@ type TxOutputBare struct {
 	// Amount in atomic units.
 	Amount uint64
 
-	// Target is the one-time output destination (key + mix attribute).
-	Target TxOutToKey
+	// Target is the output destination. Before HF1 this is always TxOutToKey;
+	// after HF1 it may also be TxOutMultisig or TxOutHTLC.
+	Target TxOutTarget
 }
 
 // OutputType returns the wire variant tag for bare outputs.

wallet/builder_test.go

@@ -126,13 +126,21 @@ func TestV1BuilderBasic(t *testing.T) {
 	}
 
 	// Output keys must be non-zero and unique.
-	if out0.Target.Key == (types.PublicKey{}) {
+	toKey0, ok := out0.Target.(types.TxOutToKey)
+	if !ok {
+		t.Fatalf("output 0 target type: got %T, want TxOutToKey", out0.Target)
+	}
+	toKey1, ok := out1.Target.(types.TxOutToKey)
+	if !ok {
+		t.Fatalf("output 1 target type: got %T, want TxOutToKey", out1.Target)
+	}
+	if toKey0.Key == (types.PublicKey{}) {
 		t.Error("output 0 key is zero")
 	}
-	if out1.Target.Key == (types.PublicKey{}) {
+	if toKey1.Key == (types.PublicKey{}) {
 		t.Error("output 1 key is zero")
 	}
-	if out0.Target.Key == out1.Target.Key {
+	if toKey0.Key == toKey1.Key {
 		t.Error("output keys are identical; derivation broken")
 	}
 

wallet/scanner.go

@@ -64,7 +64,11 @@ func (s *V1Scanner) ScanTransaction(tx *types.Transaction, txHash types.Hash,
 			continue
 		}
 
-		if types.PublicKey(expectedPub) != bare.Target.Key {
+		toKey, ok := bare.Target.(types.TxOutToKey)
+		if !ok {
+			continue
+		}
+		if types.PublicKey(expectedPub) != toKey.Key {
 			continue
 		}
 

wire/transaction.go

@@ -250,9 +250,12 @@ func encodeOutputsV1(enc *Encoder, vout []types.TxOutput) {
 		case types.TxOutputBare:
 			enc.WriteVarint(v.Amount)
 			// Target is a variant (txout_target_v)
-			enc.WriteVariantTag(types.TargetTypeToKey)
-			enc.WriteBlob32((*[32]byte)(&v.Target.Key))
-			enc.WriteUint8(v.Target.MixAttr)
+			switch tgt := v.Target.(type) {
+			case types.TxOutToKey:
+				enc.WriteVariantTag(types.TargetTypeToKey)
+				enc.WriteBlob32((*[32]byte)(&tgt.Key))
+				enc.WriteUint8(tgt.MixAttr)
+			}
 		}
 	}
 }
@@ -272,8 +275,10 @@ func decodeOutputsV1(dec *Decoder) []types.TxOutput {
 		}
 		switch tag {
 		case types.TargetTypeToKey:
-			dec.ReadBlob32((*[32]byte)(&out.Target.Key))
-			out.Target.MixAttr = dec.ReadUint8()
+			var tgt types.TxOutToKey
+			dec.ReadBlob32((*[32]byte)(&tgt.Key))
+			tgt.MixAttr = dec.ReadUint8()
+			out.Target = tgt
 		default:
 			dec.err = fmt.Errorf("wire: unsupported target tag 0x%02x", tag)
 			return vout
@@ -291,9 +296,12 @@ func encodeOutputsV2(enc *Encoder, vout []types.TxOutput) {
 		switch v := out.(type) {
 		case types.TxOutputBare:
 			enc.WriteVarint(v.Amount)
-			enc.WriteVariantTag(types.TargetTypeToKey)
-			enc.WriteBlob32((*[32]byte)(&v.Target.Key))
-			enc.WriteUint8(v.Target.MixAttr)
+			switch tgt := v.Target.(type) {
+			case types.TxOutToKey:
+				enc.WriteVariantTag(types.TargetTypeToKey)
+				enc.WriteBlob32((*[32]byte)(&tgt.Key))
+				enc.WriteUint8(tgt.MixAttr)
+			}
 		case types.TxOutputZarcanum:
 			enc.WriteBlob32((*[32]byte)(&v.StealthAddress))
 			enc.WriteBlob32((*[32]byte)(&v.ConcealingPoint))
@@ -322,8 +330,10 @@ func decodeOutputsV2(dec *Decoder) []types.TxOutput {
 			out.Amount = dec.ReadVarint()
 			targetTag := dec.ReadVariantTag()
 			if targetTag == types.TargetTypeToKey {
-				dec.ReadBlob32((*[32]byte)(&out.Target.Key))
-				out.Target.MixAttr = dec.ReadUint8()
+				var tgt types.TxOutToKey
+				dec.ReadBlob32((*[32]byte)(&tgt.Key))
+				tgt.MixAttr = dec.ReadUint8()
+				out.Target = tgt
 			} else {
 				dec.err = fmt.Errorf("wire: unsupported target tag 0x%02x", targetTag)
 				return vout

wire/transaction_test.go

@@ -65,8 +65,12 @@ func TestCoinbaseTxEncodeDecode_Good(t *testing.T) {
 	if bare.Amount != 1000000 {
 		t.Errorf("amount: got %d, want 1000000", bare.Amount)
 	}
-	if bare.Target.Key[0] != 0xDE || bare.Target.Key[1] != 0xAD {
-		t.Errorf("target key: got %x, want DE AD...", bare.Target.Key[:2])
+	toKey, ok := bare.Target.(types.TxOutToKey)
+	if !ok {
+		t.Fatalf("target type: got %T, want TxOutToKey", bare.Target)
+	}
+	if toKey.Key[0] != 0xDE || toKey.Key[1] != 0xAD {
+		t.Errorf("target key: got %x, want DE AD...", toKey.Key[:2])
 	}
 }