[wallet] Change feebumper from class to functions

Change feebumper from a stateful class into a namespace of stateless
functions.

Having the results of feebumper calls persist in an object makes process
separation between Qt and wallet awkward, because it means the feebumper object
either has to be serialized back and forth between Qt and wallet processes
between fee bump calls, or that the feebumper object needs to stay alive in the
wallet process with an object reference passed back to Qt. It's simpler just to
have fee bumper calls return their results immediately instead of storing them
in an object with an extended lifetime.

In addition to making feebumper stateless, also:

- Move LOCK calls from Qt code to feebumper
- Move TransactionCanBeBumped implementation from Qt code to feebumper

1 files changed, 27 insertions, 34 deletions

diff --git a/src/wallet/feebumper.h b/src/wallet/feebumper.h
index 046bd56001..8eec30440c 100644
--- a/src/wallet/feebumper.h
+++ b/src/wallet/feebumper.h
@@ -25,40 +25,33 @@ enum class Result
     MISC_ERROR,
 };
 
-class FeeBumper
-{
-public:
-    FeeBumper(const CWallet *wallet, const uint256 txid_in, const CCoinControl& coin_control, CAmount total_fee);
-    Result getResult() const { return current_result; }
-    const std::vector<std::string>& getErrors() const { return errors; }
-    CAmount getOldFee() const { return old_fee; }
-    CAmount getNewFee() const { return new_fee; }
-    uint256 getBumpedTxId() const { return bumped_txid; }
-
-    /* signs the new transaction,
-     * returns false if the tx couldn't be found or if it was
-     * impossible to create the signature(s)
-     */
-    bool signTransaction(CWallet *wallet);
-
-    /* commits the fee bump,
-     * returns true, in case of CWallet::CommitTransaction was successful
-     * but, eventually sets errors if the tx could not be added to the mempool (will try later)
-     * or if the old transaction could not be marked as replaced
-     */
-    bool commit(CWallet *wallet);
-
-private:
-    bool preconditionChecks(const CWallet *wallet, const CWalletTx& wtx);
-
-    const uint256 txid;
-    uint256 bumped_txid;
-    CMutableTransaction mtx;
-    std::vector<std::string> errors;
-    Result current_result;
-    CAmount old_fee;
-    CAmount new_fee;
-};
+//! Return whether transaction can be bumped.
+bool TransactionCanBeBumped(CWallet* wallet, const uint256& txid);
+
+//! Create bumpfee transaction.
+Result CreateTransaction(const CWallet* wallet,
+                         const uint256& txid,
+                         const CCoinControl& coin_control,
+                         CAmount total_fee,
+                         std::vector<std::string>& errors,
+                         CAmount& old_fee,
+                         CAmount& new_fee,
+                         CMutableTransaction& mtx);
+
+//! Sign the new transaction,
+//! @return false if the tx couldn't be found or if it was
+//! impossible to create the signature(s)
+bool SignTransaction(CWallet* wallet, CMutableTransaction& mtx);
+
+//! Commit the bumpfee transaction.
+//! @return success in case of CWallet::CommitTransaction was successful,
+//! but sets errors if the tx could not be added to the mempool (will try later)
+//! or if the old transaction could not be marked as replaced.
+Result CommitTransaction(CWallet* wallet,
+                         const uint256& txid,
+                         CMutableTransaction&& mtx,
+                         std::vector<std::string>& errors,
+                         uint256& bumped_txid);
 
 } // namespace feebumper