wtxmgr: add method OutputsToWatch

This commit adds a new method `OutputsToWatch`, which returns a list of
outpoints the rescan process should be watching for during the startup.

Author: yyforyongyu

wtxmgr/tx.go

@@ -805,6 +805,95 @@ func (s *Store) rollback(ns walletdb.ReadWriteBucket, height int32) error {
 	return putMinedBalance(ns, minedBalance)
 }
 
+// OutputsToWatch returns a list of outputs to monitor during the wallet's
+// startup. The returned items are similar to UnspentOutputs, exccept the
+// locked outputs and unmined credits are also returned here. In addition, we
+// only set the field `OutPoint` and `PkScript` for the `Credit`, as these are
+// the only fields used during the rescan.
+func (s *Store) OutputsToWatch(ns walletdb.ReadBucket) ([]Credit, error) {
+	var (
+		unspent []Credit
+		op      wire.OutPoint
+		block   Block
+	)
+
+	err := ns.NestedReadBucket(bucketUnspent).ForEach(func(k,
+		v []byte) error {
+
+		err := readCanonicalOutPoint(k, &op)
+		if err != nil {
+			return err
+		}
+
+		err = readUnspentBlock(v, &block)
+		if err != nil {
+			return err
+		}
+
+		// TODO(jrick): reading the entire transaction should be
+		// avoidable. Creating the credit only requires the output
+		// amount and pkScript.
+		rec, err := fetchTxRecord(ns, &op.Hash, &block)
+		if err != nil {
+			return fmt.Errorf("unable to retrieve tx %v: %w",
+				op.Hash, err)
+		}
+
+		txOut := rec.MsgTx.TxOut[op.Index]
+		cred := Credit{
+			OutPoint: op,
+			PkScript: txOut.PkScript,
+		}
+		unspent = append(unspent, cred)
+
+		return nil
+	})
+	if err != nil {
+		if _, ok := err.(Error); ok {
+			return nil, err
+		}
+		str := "failed iterating unspent bucket"
+		return nil, storeError(ErrDatabase, str, err)
+	}
+
+	err = ns.NestedReadBucket(bucketUnminedCredits).ForEach(func(k,
+		v []byte) error {
+
+		if err := readCanonicalOutPoint(k, &op); err != nil {
+			return err
+		}
+
+		// TODO(jrick): Reading/parsing the entire transaction record
+		// just for the output amount and script can be avoided.
+		recVal := existsRawUnmined(ns, op.Hash[:])
+
+		var rec TxRecord
+		err = readRawTxRecord(&op.Hash, recVal, &rec)
+		if err != nil {
+			return fmt.Errorf("unable to retrieve raw tx%v: %w",
+				op.Hash, err)
+		}
+
+		txOut := rec.MsgTx.TxOut[op.Index]
+		cred := Credit{
+			OutPoint: op,
+			PkScript: txOut.PkScript,
+		}
+		unspent = append(unspent, cred)
+
+		return nil
+	})
+	if err != nil {
+		if _, ok := err.(Error); ok {
+			return nil, err
+		}
+		str := "failed iterating unmined credits bucket"
+		return nil, storeError(ErrDatabase, str, err)
+	}
+
+	return unspent, nil
+}
+
 // UnspentOutputs returns all unspent received transaction outputs.
 // The order is undefined.
 func (s *Store) UnspentOutputs(ns walletdb.ReadBucket) ([]Credit, error) {