multi: Add FindBond to Bonder.

When the server tells us of an unknown v0 bond attempt to find and
recreate it so that it can be refunded later. Useful when restoring
from seed.

client/asset/btc/btc.go

@@ -5026,6 +5026,140 @@ func (btc *baseWallet) RefundBond(ctx context.Context, ver uint16, coinID, scrip
 	return NewOutput(txHash, 0, uint64(msgTx.TxOut[0].Value)), nil
 }
 
+func (btc *baseWallet) decodeV0BondTx(msgTx *wire.MsgTx, txHash *chainhash.Hash, coinID []byte) (*asset.BondDetails, error) {
+	if len(msgTx.TxOut) < 2 {
+		return nil, fmt.Errorf("tx %s is not a v0 bond transaction: too few outputs", txHash)
+	}
+	_, lockTime, pkh, err := dexbtc.ExtractBondCommitDataV0(0, msgTx.TxOut[1].PkScript)
+	if err != nil {
+		return nil, fmt.Errorf("unable to extract bond commitment details from output 1 of %s: %v", txHash, err)
+	}
+	// Sanity check.
+	bondScript, err := dexbtc.MakeBondScript(0, lockTime, pkh[:])
+	if err != nil {
+		return nil, fmt.Errorf("failed to build bond output redeem script: %w", err)
+	}
+	pkScript, err := btc.scriptHashScript(bondScript)
+	if err != nil {
+		return nil, fmt.Errorf("error constructing p2sh script: %v", err)
+	}
+	if !bytes.Equal(pkScript, msgTx.TxOut[0].PkScript) {
+		return nil, fmt.Errorf("bond script does not match commit data for %s: %x != %x",
+			txHash, bondScript, msgTx.TxOut[0].PkScript)
+	}
+	return &asset.BondDetails{
+		Bond: &asset.Bond{
+			Version: 0,
+			AssetID: btc.cloneParams.AssetID,
+			Amount:  uint64(msgTx.TxOut[0].Value),
+			CoinID:  coinID,
+			Data:    bondScript,
+			//
+			// SignedTx and UnsignedTx not populated because this is
+			// an already posted bond and these fields are no longer used.
+			// SignedTx, UnsignedTx []byte
+			//
+			// RedeemTx cannot be populated because we do not have
+			// the private key that only core knows. Core will need
+			// the BondPKH to determine what the private key was.
+			// RedeemTx []byte
+		},
+		LockTime: time.Unix(int64(lockTime), 0),
+		CheckPrivKey: func(bondKey *secp256k1.PrivateKey) bool {
+			pk := bondKey.PubKey().SerializeCompressed()
+			pkhB := btcutil.Hash160(pk)
+			return bytes.Equal(pkh[:], pkhB)
+		},
+	}, nil
+}
+
+// FindBond finds the bond with coinID and returns the values used to create it.
+func (btc *baseWallet) FindBond(_ context.Context, coinID []byte, _ time.Time) (bond *asset.BondDetails, err error) {
+	txHash, vout, err := decodeCoinID(coinID)
+	if err != nil {
+		return nil, err
+	}
+
+	// If the bond was funded by this wallet or had a change output paying
+	// to this wallet, it should be found here.
+	tx, err := btc.node.getWalletTransaction(txHash)
+	if err != nil {
+		return nil, fmt.Errorf("did not find the bond output %v:%d", txHash, vout)
+	}
+	msgTx, err := btc.deserializeTx(tx.Bytes)
+	if err != nil {
+		return nil, fmt.Errorf("invalid hex for tx %s: %v", txHash, err)
+	}
+	return btc.decodeV0BondTx(msgTx, txHash, coinID)
+}
+
+// FindBond finds the bond with coinID and returns the values used to create it.
+// The intermediate wallet is able to brute force finding blocks.
+func (btc *intermediaryWallet) FindBond(
+	_ context.Context,
+	coinID []byte,
+	searchUntil time.Time,
+) (bond *asset.BondDetails, err error) {
+
+	txHash, vout, err := decodeCoinID(coinID)
+	if err != nil {
+		return nil, err
+	}
+
+	// If the bond was funded by this wallet or had a change output paying
+	// to this wallet, it should be found here.
+	tx, err := btc.node.getWalletTransaction(txHash)
+	if err == nil {
+		msgTx, err := btc.deserializeTx(tx.Bytes)
+		if err != nil {
+			return nil, fmt.Errorf("invalid hex for tx %s: %v", txHash, err)
+		}
+		return btc.decodeV0BondTx(msgTx, txHash, coinID)
+	}
+	if !errors.Is(err, asset.CoinNotFoundError) {
+		btc.log.Warnf("Unexpected error looking up bond output %v:%d", txHash, vout)
+	}
+
+	// The bond was not funded by this wallet or had no change output when
+	// restored from seed. This is not a problem. However, we are unable to
+	// use filters because we don't know any output scripts. Brute force
+	// finding the transaction.
+	bestBlockHdr, err := btc.node.getBestBlockHeader()
+	if err != nil {
+		return nil, fmt.Errorf("unable to get best hash: %v", err)
+	}
+	blockHash, err := chainhash.NewHashFromStr(bestBlockHdr.Hash)
+	if err != nil {
+		return nil, fmt.Errorf("invalid best block hash from %s node: %v", btc.symbol, err)
+	}
+	var (
+		blk   *wire.MsgBlock
+		msgTx *wire.MsgTx
+	)
+out:
+	for {
+		blk, err = btc.tipRedeemer.getBlock(*blockHash)
+		if err != nil {
+			return nil, fmt.Errorf("error retrieving block %s: %w", blockHash, err)
+		}
+		if blk.Header.Timestamp.Before(searchUntil) {
+			return nil, fmt.Errorf("searched blocks until %v but did not find the bond tx %s", searchUntil, txHash)
+		}
+		for _, tx := range blk.Transactions {
+			if tx.TxHash() == *txHash {
+				btc.log.Debugf("Found mined tx %s in block %s.", txHash, blk.BlockHash())
+				msgTx = tx
+				break out
+			}
+		}
+		blockHash = &blk.Header.PrevBlock
+		if blockHash == nil {
+			return nil, fmt.Errorf("did not find the bond output %v:%d", txHash, vout)
+		}
+	}
+	return btc.decodeV0BondTx(msgTx, txHash, coinID)
+}
+
 // BondsFeeBuffer suggests how much extra may be required for the transaction
 // fees part of required bond reserves when bond rotation is enabled. The
 // provided fee rate may be zero, in which case the wallet will use it's own