wallet: Replace use of purpose strings with an enum

Instead of storing and passing around fixed strings for the purpose of
an address, use an enum.

This also rationalizes the CAddressBookData struct, documenting all fields and
making them public, and simplifying the representation to avoid bugs like
bitcoin#26761 (comment) and make
it not possible to invalid address data like change addresses with labels.

Co-authored-by: Ryan Ofsky <ryan@ofsky.org>

src/interfaces/wallet.h

@@ -35,6 +35,7 @@ struct bilingual_str;
 namespace wallet {
 class CCoinControl;
 class CWallet;
+enum class AddressPurpose;
 enum isminetype : unsigned int;
 struct CRecipient;
 struct WalletContext;
@@ -103,7 +104,7 @@ class Wallet
     virtual bool haveWatchOnly() = 0;
 
     //! Add or update address.
-    virtual bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::string& purpose) = 0;
+    virtual bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::optional<wallet::AddressPurpose>& purpose) = 0;
 
     // Remove address.
     virtual bool delAddressBook(const CTxDestination& dest) = 0;
@@ -112,7 +113,7 @@ class Wallet
     virtual bool getAddress(const CTxDestination& dest,
         std::string* name,
         wallet::isminetype* is_mine,
-        std::string* purpose) = 0;
+        wallet::AddressPurpose* purpose) = 0;
 
     //! Get wallet address list.
     virtual std::vector<WalletAddress> getAddresses() const = 0;
@@ -293,7 +294,7 @@ class Wallet
     using AddressBookChangedFn = std::function<void(const CTxDestination& address,
         const std::string& label,
         bool is_mine,
-        const std::string& purpose,
+        wallet::AddressPurpose purpose,
         ChangeType status)>;
     virtual std::unique_ptr<Handler> handleAddressBookChanged(AddressBookChangedFn fn) = 0;
 
@@ -352,11 +353,11 @@ struct WalletAddress
 {
     CTxDestination dest;
     wallet::isminetype is_mine;
+    wallet::AddressPurpose purpose;
     std::string name;
-    std::string purpose;
 
-    WalletAddress(CTxDestination dest, wallet::isminetype is_mine, std::string name, std::string purpose)
-        : dest(std::move(dest)), is_mine(is_mine), name(std::move(name)), purpose(std::move(purpose))
+    WalletAddress(CTxDestination dest, wallet::isminetype is_mine, wallet::AddressPurpose purpose, std::string name)
+        : dest(std::move(dest)), is_mine(is_mine), purpose(std::move(purpose)), name(std::move(name))
     {
     }
 };

src/qt/addresstablemodel.cpp

@@ -8,6 +8,7 @@
 #include <qt/walletmodel.h>
 
 #include <key_io.h>
+#include <wallet/types.h>
 #include <wallet/wallet.h>
 
 #include <algorithm>
@@ -52,16 +53,17 @@ struct AddressTableEntryLessThan
 };
 
 /* Determine address type from address purpose */
-static AddressTableEntry::Type translateTransactionType(const QString &strPurpose, bool isMine)
+static AddressTableEntry::Type translateTransactionType(wallet::AddressPurpose purpose, bool isMine)
 {
     AddressTableEntry::Type addressType = AddressTableEntry::Hidden;
     // "refund" addresses aren't shown, and change addresses aren't returned by getAddresses at all.
-    if (strPurpose == "send")
+    if (purpose == wallet::AddressPurpose::SEND) {
         addressType = AddressTableEntry::Sending;
-    else if (strPurpose == "receive")
+    } else if (purpose == wallet::AddressPurpose::RECEIVE) {
         addressType = AddressTableEntry::Receiving;
-    else if (strPurpose == "unknown" || strPurpose == "") // if purpose not set, guess
+    } else {
         addressType = (isMine ? AddressTableEntry::Receiving : AddressTableEntry::Sending);
+    }
     return addressType;
 }
 
@@ -85,7 +87,7 @@ class AddressTablePriv
                     continue;
                 }
                 AddressTableEntry::Type addressType = translateTransactionType(
-                        QString::fromStdString(address.purpose), address.is_mine);
+                        address.purpose, address.is_mine);
                 cachedAddressTable.append(AddressTableEntry(addressType,
                                   QString::fromStdString(address.name),
                                   QString::fromStdString(EncodeDestination(address.dest))));
@@ -97,7 +99,7 @@ class AddressTablePriv
         std::sort(cachedAddressTable.begin(), cachedAddressTable.end(), AddressTableEntryLessThan());
     }
 
-    void updateEntry(const QString &address, const QString &label, bool isMine, const QString &purpose, int status)
+    void updateEntry(const QString &address, const QString &label, bool isMine, wallet::AddressPurpose purpose, int status)
     {
         // Find address / label in model
         QList<AddressTableEntry>::iterator lower = std::lower_bound(
@@ -239,7 +241,7 @@ bool AddressTableModel::setData(const QModelIndex &index, const QVariant &value,
     if(!index.isValid())
         return false;
     AddressTableEntry *rec = static_cast<AddressTableEntry*>(index.internalPointer());
-    std::string strPurpose = (rec->type == AddressTableEntry::Sending ? "send" : "receive");
+    wallet::AddressPurpose purpose = rec->type == AddressTableEntry::Sending ? wallet::AddressPurpose::SEND : wallet::AddressPurpose::RECEIVE;
     editStatus = OK;
 
     if(role == Qt::EditRole)
@@ -253,7 +255,7 @@ bool AddressTableModel::setData(const QModelIndex &index, const QVariant &value,
                 editStatus = NO_CHANGES;
                 return false;
             }
-            walletModel->wallet().setAddressBook(curAddress, value.toString().toStdString(), strPurpose);
+            walletModel->wallet().setAddressBook(curAddress, value.toString().toStdString(), purpose);
         } else if(index.column() == Address) {
             CTxDestination newAddress = DecodeDestination(value.toString().toStdString());
             // Refuse to set invalid address, set error status and return false
@@ -282,7 +284,7 @@ bool AddressTableModel::setData(const QModelIndex &index, const QVariant &value,
                 // Remove old entry
                 walletModel->wallet().delAddressBook(curAddress);
                 // Add new entry with new address
-                walletModel->wallet().setAddressBook(newAddress, value.toString().toStdString(), strPurpose);
+                walletModel->wallet().setAddressBook(newAddress, value.toString().toStdString(), purpose);
             }
         }
         return true;
@@ -334,7 +336,7 @@ QModelIndex AddressTableModel::index(int row, int column, const QModelIndex &par
 }
 
 void AddressTableModel::updateEntry(const QString &address,
-        const QString &label, bool isMine, const QString &purpose, int status)
+        const QString &label, bool isMine, wallet::AddressPurpose purpose, int status)
 {
     // Update address book model from Bitcoin core
     priv->updateEntry(address, label, isMine, purpose, status);
@@ -365,7 +367,7 @@ QString AddressTableModel::addRow(const QString &type, const QString &label, con
         }
 
         // Add entry
-        walletModel->wallet().setAddressBook(DecodeDestination(strAddress), strLabel, "send");
+        walletModel->wallet().setAddressBook(DecodeDestination(strAddress), strLabel, wallet::AddressPurpose::SEND);
     }
     else if(type == Receive)
     {
@@ -416,18 +418,18 @@ QString AddressTableModel::labelForAddress(const QString &address) const
     return QString();
 }
 
-QString AddressTableModel::purposeForAddress(const QString &address) const
+std::optional<wallet::AddressPurpose> AddressTableModel::purposeForAddress(const QString &address) const
 {
-    std::string purpose;
+    wallet::AddressPurpose purpose;
     if (getAddressData(address, /* name= */ nullptr, &purpose)) {
-        return QString::fromStdString(purpose);
+        return purpose;
     }
-    return QString();
+    return std::nullopt;
 }
 
 bool AddressTableModel::getAddressData(const QString &address,
         std::string* name,
-        std::string* purpose) const {
+        wallet::AddressPurpose* purpose) const {
     CTxDestination destination = DecodeDestination(address.toStdString());
     return walletModel->wallet().getAddress(destination, name, /* is_mine= */ nullptr, purpose);
 }

src/qt/addresstablemodel.h

@@ -5,6 +5,8 @@
 #ifndef BITCOIN_QT_ADDRESSTABLEMODEL_H
 #define BITCOIN_QT_ADDRESSTABLEMODEL_H
 
+#include <optional>
+
 #include <QAbstractTableModel>
 #include <QStringList>
 
@@ -16,6 +18,9 @@ class WalletModel;
 namespace interfaces {
 class Wallet;
 }
+namespace wallet {
+enum class AddressPurpose;
+} // namespace wallet
 
 /**
    Qt model of the address book in the core. This allows views to access and modify the address book.
@@ -71,7 +76,7 @@ class AddressTableModel : public QAbstractTableModel
     QString labelForAddress(const QString &address) const;
 
     /** Look up purpose for address in address book, if not found return empty string. */
-    QString purposeForAddress(const QString &address) const;
+    std::optional<wallet::AddressPurpose> purposeForAddress(const QString &address) const;
 
     /* Look up row index of an address in the model.
        Return -1 if not found.
@@ -89,15 +94,15 @@ class AddressTableModel : public QAbstractTableModel
     EditStatus editStatus = OK;
 
     /** Look up address book data given an address string. */
-    bool getAddressData(const QString &address, std::string* name, std::string* purpose) const;
+    bool getAddressData(const QString &address, std::string* name, wallet::AddressPurpose* purpose) const;
 
     /** Notify listeners that data changed. */
     void emitDataChanged(int index);
 
 public Q_SLOTS:
     /* Update address list from core.
      */
-    void updateEntry(const QString &address, const QString &label, bool isMine, const QString &purpose, int status);
+    void updateEntry(const QString &address, const QString &label, bool isMine, wallet::AddressPurpose purpose, int status);
 
     friend class AddressTablePriv;
 };

src/qt/editaddressdialog.cpp

@@ -8,6 +8,8 @@
 #include <qt/addresstablemodel.h>
 #include <qt/guiutil.h>
 
+#include <wallet/types.h>
+
 #include <QDataWidgetMapper>
 #include <QMessageBox>
 
@@ -137,9 +139,9 @@ QString EditAddressDialog::getDuplicateAddressWarning() const
 {
     QString dup_address = ui->addressEdit->text();
     QString existing_label = model->labelForAddress(dup_address);
-    QString existing_purpose = model->purposeForAddress(dup_address);
+    auto existing_purpose = model->purposeForAddress(dup_address);
 
-    if (existing_purpose == "receive" &&
+    if (existing_purpose == wallet::AddressPurpose::RECEIVE &&
             (mode == NewSendingAddress || mode == EditSendingAddress)) {
         return tr(
             "Address \"%1\" already exists as a receiving address with label "

src/qt/test/addressbooktests.cpp

@@ -113,8 +113,8 @@ void TestAddAddressesToSendBook(interfaces::Node& node)
 
     {
         LOCK(wallet->cs_wallet);
-        wallet->SetAddressBook(r_key_dest, r_label.toStdString(), "receive");
-        wallet->SetAddressBook(s_key_dest, s_label.toStdString(), "send");
+        wallet->SetAddressBook(r_key_dest, r_label.toStdString(), wallet::AddressPurpose::RECEIVE);
+        wallet->SetAddressBook(s_key_dest, s_label.toStdString(), wallet::AddressPurpose::SEND);
     }
 
     auto check_addbook_size = [&wallet](int expected_size) {

src/qt/test/wallettests.cpp

@@ -174,7 +174,7 @@ void TestGUI(interfaces::Node& node)
         WalletDescriptor w_desc(std::move(desc), 0, 0, 1, 1);
         if (!wallet->AddWalletDescriptor(w_desc, provider, "", false)) assert(false);
         CTxDestination dest = GetDestinationForKey(test.coinbaseKey.GetPubKey(), wallet->m_default_address_type);
-        wallet->SetAddressBook(dest, "", "receive");
+        wallet->SetAddressBook(dest, "", wallet::AddressPurpose::RECEIVE);
         wallet->SetLastBlockProcessed(105, WITH_LOCK(node.context()->chainman->GetMutex(), return node.context()->chainman->ActiveChain().Tip()->GetBlockHash()));
     }
     {

src/qt/walletmodel.cpp

@@ -138,7 +138,7 @@ void WalletModel::updateTransaction()
 }
 
 void WalletModel::updateAddressBook(const QString &address, const QString &label,
-        bool isMine, const QString &purpose, int status)
+        bool isMine, wallet::AddressPurpose purpose, int status)
 {
     if(addressTableModel)
         addressTableModel->updateEntry(address, label, isMine, purpose, status);
@@ -280,11 +280,11 @@ void WalletModel::sendCoins(WalletModelTransaction& transaction)
                 if (!m_wallet->getAddress(
                      dest, &name, /* is_mine= */ nullptr, /* purpose= */ nullptr))
                 {
-                    m_wallet->setAddressBook(dest, strLabel, "send");
+                    m_wallet->setAddressBook(dest, strLabel, wallet::AddressPurpose::SEND);
                 }
                 else if (name != strLabel)
                 {
-                    m_wallet->setAddressBook(dest, strLabel, ""); // "" means don't change purpose
+                    m_wallet->setAddressBook(dest, strLabel, {}); // {} means don't change purpose
                 }
             }
         }
@@ -377,18 +377,17 @@ static void NotifyKeyStoreStatusChanged(WalletModel *walletmodel)
 
 static void NotifyAddressBookChanged(WalletModel *walletmodel,
         const CTxDestination &address, const std::string &label, bool isMine,
-        const std::string &purpose, ChangeType status)
+        wallet::AddressPurpose purpose, ChangeType status)
 {
     QString strAddress = QString::fromStdString(EncodeDestination(address));
     QString strLabel = QString::fromStdString(label);
-    QString strPurpose = QString::fromStdString(purpose);
 
-    qDebug() << "NotifyAddressBookChanged: " + strAddress + " " + strLabel + " isMine=" + QString::number(isMine) + " purpose=" + strPurpose + " status=" + QString::number(status);
+    qDebug() << "NotifyAddressBookChanged: " + strAddress + " " + strLabel + " isMine=" + QString::number(isMine) + " purpose=" + QString::number(static_cast<uint8_t>(purpose)) + " status=" + QString::number(status);
     bool invoked = QMetaObject::invokeMethod(walletmodel, "updateAddressBook",
                               Q_ARG(QString, strAddress),
                               Q_ARG(QString, strLabel),
                               Q_ARG(bool, isMine),
-                              Q_ARG(QString, strPurpose),
+                              Q_ARG(wallet::AddressPurpose, purpose),
                               Q_ARG(int, status));
     assert(invoked);
 }

src/qt/walletmodel.h

@@ -236,7 +236,7 @@ public Q_SLOTS:
     /* New transaction, or transaction changed status */
     void updateTransaction();
     /* New, updated or removed address book entry */
-    void updateAddressBook(const QString &address, const QString &label, bool isMine, const QString &purpose, int status);
+    void updateAddressBook(const QString &address, const QString &label, bool isMine, wallet::AddressPurpose purpose, int status);
     /* Watch-only added */
     void updateWatchOnlyFlag(bool fHaveWatchonly);
     /* Current, immature or unconfirmed balance might have changed - emit 'balanceChanged' if so */

src/wallet/interfaces.cpp

@@ -178,7 +178,7 @@ class WalletImpl : public Wallet
         }
         return false;
     };
-    bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::string& purpose) override
+    bool setAddressBook(const CTxDestination& dest, const std::string& name, const std::optional<AddressPurpose>& purpose) override
     {
         return m_wallet->SetAddressBook(dest, name, purpose);
     }
@@ -189,29 +189,34 @@ class WalletImpl : public Wallet
     bool getAddress(const CTxDestination& dest,
         std::string* name,
         isminetype* is_mine,
-        std::string* purpose) override
+        AddressPurpose* purpose) override
     {
         LOCK(m_wallet->cs_wallet);
         const auto& entry = m_wallet->FindAddressBookEntry(dest, /*allow_change=*/false);
         if (!entry) return false; // addr not found
         if (name) {
             *name = entry->GetLabel();
         }
+        std::optional<isminetype> dest_is_mine;
+        if (is_mine || purpose) {
+            dest_is_mine = m_wallet->IsMine(dest);
+        }
         if (is_mine) {
-            *is_mine = m_wallet->IsMine(dest);
+            *is_mine = *dest_is_mine;
         }
         if (purpose) {
-            *purpose = entry->purpose;
+            *purpose = entry->purpose ? *entry->purpose : *dest_is_mine ? AddressPurpose::RECEIVE : AddressPurpose::SEND;
         }
         return true;
     }
     std::vector<WalletAddress> getAddresses() const override
     {
         LOCK(m_wallet->cs_wallet);
         std::vector<WalletAddress> result;
-        m_wallet->ForEachAddrBookEntry([&](const CTxDestination& dest, const std::string& label, const std::string& purpose, bool is_change) EXCLUSIVE_LOCKS_REQUIRED(m_wallet->cs_wallet) {
+        m_wallet->ForEachAddrBookEntry([&](const CTxDestination& dest, const std::string& label, bool is_change, const std::optional<AddressPurpose>& purpose) EXCLUSIVE_LOCKS_REQUIRED(m_wallet->cs_wallet) {
             if (is_change) return;
-            result.emplace_back(dest, m_wallet->IsMine(dest), label, purpose);
+            isminetype is_mine = m_wallet->IsMine(dest);
+            result.emplace_back(dest, is_mine, purpose ? *purpose : is_mine ? AddressPurpose::RECEIVE : AddressPurpose::SEND, label);
         });
         return result;
     }
@@ -501,7 +506,7 @@ class WalletImpl : public Wallet
     {
         return MakeSignalHandler(m_wallet->NotifyAddressBookChanged.connect(
             [fn](const CTxDestination& address, const std::string& label, bool is_mine,
-                 const std::string& purpose, ChangeType status) { fn(address, label, is_mine, purpose, status); }));
+                 AddressPurpose purpose, ChangeType status) { fn(address, label, is_mine, purpose, status); }));
     }
     std::unique_ptr<Handler> handleTransactionChanged(TransactionChangedFn fn) override
     {