refactor: Implement restorewallet() logic in the wallet section

Currently restorewallet() logic is written in the RPC layer
and it can´t be reused by GUI. So it reimplements this in the
wallet and interface sections and then, GUI can access it.

src/interfaces/wallet.h

@@ -322,6 +322,9 @@ public:
    //! Return default wallet directory.
    virtual std::string getWalletDir() = 0;
 
+   //! Restore backup wallet
+   virtual std::unique_ptr<Wallet> restoreWallet(const std::string& backup_file, const std::string& wallet_name, bilingual_str& error, std::vector<bilingual_str>& warnings) = 0;
+
    //! Return available wallets in wallet directory.
    virtual std::vector<std::string> listWalletDir() = 0;
 

src/wallet/interfaces.cpp

@@ -552,6 +552,12 @@ public:
         options.require_existing = true;
         return MakeWallet(m_context, LoadWallet(m_context, name, true /* load_on_start */, options, status, error, warnings));
     }
+    std::unique_ptr<Wallet> restoreWallet(const std::string& backup_file, const std::string& wallet_name, bilingual_str& error, std::vector<bilingual_str>& warnings) override
+    {
+        DatabaseStatus status;
+
+        return MakeWallet(m_context, RestoreWallet(m_context, backup_file, wallet_name, /*load_on_start=*/true, status, error, warnings));
+    }
     std::string getWalletDir() override
     {
         return fs::PathToString(GetWalletDir());

src/wallet/wallet.cpp

@@ -357,6 +357,31 @@ std::shared_ptr<CWallet> CreateWallet(WalletContext& context, const std::string&
     return wallet;
 }
 
+std::shared_ptr<CWallet> RestoreWallet(WalletContext& context, const std::string& backup_file, const std::string& wallet_name, std::optional<bool> load_on_start, DatabaseStatus& status, bilingual_str& error, std::vector<bilingual_str>& warnings)
+{
+    DatabaseOptions options;
+    options.require_existing = true;
+
+    if (!fs::exists(fs::u8path(backup_file))) {
+        error = Untranslated("Backup file does not exist");
+        status = DatabaseStatus::FAILED_BAD_PATH;
+        return nullptr;
+    }
+
+    const fs::path wallet_path = fsbridge::AbsPathJoin(GetWalletDir(), fs::u8path(wallet_name));
+
+    if (fs::exists(wallet_path) || !TryCreateDirectories(wallet_path)) {
+        error = Untranslated(strprintf("Failed to create database path '%s'. Database already exists.", fs::PathToString(wallet_path)));
+        status = DatabaseStatus::FAILED_ALREADY_EXISTS;
+        return nullptr;
+    }
+
+    auto wallet_file = wallet_path / "wallet.dat";
+    fs::copy_file(backup_file, wallet_file, fs::copy_option::fail_if_exists);
+
+    return LoadWallet(context, wallet_name, load_on_start, options, status, error, warnings);
+}
+
 /** @defgroup mapWallet
  *
  * @{

src/wallet/wallet.h

@@ -60,6 +60,7 @@ std::vector<std::shared_ptr<CWallet>> GetWallets(WalletContext& context);
 std::shared_ptr<CWallet> GetWallet(WalletContext& context, const std::string& name);
 std::shared_ptr<CWallet> LoadWallet(WalletContext& context, const std::string& name, std::optional<bool> load_on_start, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error, std::vector<bilingual_str>& warnings);
 std::shared_ptr<CWallet> CreateWallet(WalletContext& context, const std::string& name, std::optional<bool> load_on_start, DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error, std::vector<bilingual_str>& warnings);
+std::shared_ptr<CWallet> RestoreWallet(WalletContext& context, const std::string& backup_file, const std::string& wallet_name, std::optional<bool> load_on_start, DatabaseStatus& status, bilingual_str& error, std::vector<bilingual_str>& warnings);
 std::unique_ptr<interfaces::Handler> HandleLoadWallet(WalletContext& context, LoadWalletFn load_wallet);
 std::unique_ptr<WalletDatabase> MakeWalletDatabase(const std::string& name, const DatabaseOptions& options, DatabaseStatus& status, bilingual_str& error);