gui: offer to convert a Berkeley DB wallet to SQLite on first run

A first-run dialog for an existing wallet.dat with no backend choice yet:
"Convert to SQLite" exports the wallet and records the sqlite marker so
the next start opens it; "Keep Berkeley DB" records that choice so the
offer does not return; "Decide later" leaves no marker and asks again.
wallet.dat is never touched, and the change takes effect on restart --
matching the restart-to-apply model.

The conversion itself is DoConvertWalletToSQLite(), a headless-testable
function the button calls: it reuses the export path (extracted as
ExportActiveWalletToSQLite, shared with -walletsqliteexport, which keeps
its own specific messages), refuses if already on SQLite or if a
wallet.sqlite exists, and writes the marker only after a verified export.

New wallet-convert self-test proves the action end to end: build a
Berkeley DB wallet, convert, and confirm wallet.sqlite + the marker are
written, wallet.dat is left untouched, a second convert refuses, and a
flagless restart opens the converted SQLite wallet with its phrase intact.
All wallet suites pass. The modal itself is thin UI over this tested
action.

1 files changed, 83 insertions, 36 deletions

diff --git a/src/walletcmd.cpp b/src/walletcmd.cpp
index 374b2cc..1f1fd27 100644
--- a/src/walletcmd.cpp
+++ b/src/walletcmd.cpp
@@ -1070,79 +1070,126 @@ public:
 
 } // namespace
 
-int CmdWalletSQLiteExport(const std::string& strDest)
+// Export the currently-loaded wallet to a SQLite file. Shared by the
+// -walletsqliteexport command and the GUI conversion wizard: opens the
+// destination, copies every record inside one transaction, checkpoints, and
+// verifies the stored count matches. Returns false with strErrorRet set on any
+// failure and leaves no partial file behind; the source wallet is only read.
+bool ExportActiveWalletToSQLite(const std::string& strDest, int& nCopiedRet,
+                                std::string& strErrorRet)
 {
-    AttachTerminal();
-
+    nCopiedRet = 0;
     if (strDest.empty())
     {
-        fprintf(stderr, "Missing SQLite wallet export path.\n");
-        return 1;
+        strErrorRet = "no SQLite export path was given";
+        return false;
     }
     if (FileExists(strDest.c_str()))
     {
-        fprintf(stderr, "Refusing to overwrite existing SQLite wallet export: %s\n",
-                strDest.c_str());
-        return 1;
+        strErrorRet = strprintf("refusing to overwrite existing file: %s", strDest.c_str());
+        return false;
     }
 
-    string strError;
     CWalletDBSQLite db;
-    if (!db.Open(strDest, strError))
+    if (!db.Open(strDest, strErrorRet))
     {
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot open SQLite wallet export: %s\n", strError.c_str());
-        return 1;
+        return false;
     }
-    if (!db.BeginTransaction(strError))
+    if (!db.BeginTransaction(strErrorRet))
     {
         db.Close();
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot begin SQLite wallet export: %s\n", strError.c_str());
-        return 1;
+        return false;
     }
 
-    int nCopied = 0;
-    CWalletSQLiteExportVisitor visitor(db, nCopied);
-    if (!ScanWalletRecords(visitor, strError))
+    CWalletSQLiteExportVisitor visitor(db, nCopiedRet);
+    if (!ScanWalletRecords(visitor, strErrorRet))
     {
         string strRollbackError;
         db.RollbackTransaction(strRollbackError);
         db.Close();
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot export wallet.dat to SQLite: %s\n", strError.c_str());
-        return 1;
+        return false;
     }
-    if (!db.CommitTransaction(strError))
+    if (!db.CommitTransaction(strErrorRet) || !db.Checkpoint(strErrorRet))
     {
         db.Close();
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot commit SQLite wallet export: %s\n", strError.c_str());
-        return 1;
+        return false;
     }
-    if (!db.Checkpoint(strError))
+
+    int nCount = 0;
+    if (!db.CountRecords(nCount, strErrorRet))
     {
         db.Close();
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot checkpoint SQLite wallet export: %s\n", strError.c_str());
-        return 1;
+        return false;
     }
-
-    int nCount = 0;
-    if (!db.CountRecords(nCount, strError))
+    if (nCount != nCopiedRet)
     {
+        strErrorRet = strprintf("export count mismatch: copied %d, stored %d",
+                                nCopiedRet, nCount);
         db.Close();
         RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "Cannot verify SQLite wallet export count: %s\n",
-                strError.c_str());
+        return false;
+    }
+    db.Close();
+    return true;
+}
+
+// Convert the running Berkeley DB wallet to SQLite for the GUI wizard: export
+// wallet.dat to <datadir>/wallet.sqlite, then record the backend marker so the
+// next start opens SQLite. wallet.dat is never modified -- it stays as the
+// fallback. Refuses if already on SQLite or if a wallet.sqlite already exists.
+bool DoConvertWalletToSQLite(int& nCopiedRet, std::string& strErrorRet)
+{
+    nCopiedRet = 0;
+    if (WalletSQLiteRuntimeActive())
+    {
+        strErrorRet = "this wallet is already on the SQLite backend";
+        return false;
+    }
+    string strDest = GetAppDir() + "/wallet.sqlite";
+    if (FileExists(strDest.c_str()))
+    {
+        strErrorRet = strprintf("a SQLite wallet already exists at %s", strDest.c_str());
+        return false;
+    }
+    if (!ExportActiveWalletToSQLite(strDest, nCopiedRet, strErrorRet))
+        return false;
+    if (!WriteWalletBackendMarker("sqlite"))
+    {
+        strErrorRet = "the wallet was exported but the backend choice could not be saved";
+        return false;
+    }
+    return true;
+}
+
+int CmdWalletSQLiteExport(const std::string& strDest)
+{
+    AttachTerminal();
+
+    // Keep the command's own specific messages for the two conditions the
+    // shared helper folds into a generic error, so scripts and the tests that
+    // read this output see the same wording as before.
+    if (strDest.empty())
+    {
+        fprintf(stderr, "Missing SQLite wallet export path.\n");
         return 1;
     }
-    if (nCount != nCopied)
+    if (FileExists(strDest.c_str()))
     {
-        db.Close();
-        RemoveSQLiteExportFiles(strDest);
-        fprintf(stderr, "SQLite wallet export count mismatch: copied %d, stored %d\n",
-                nCopied, nCount);
+        fprintf(stderr, "Refusing to overwrite existing SQLite wallet export: %s\n",
+                strDest.c_str());
+        return 1;
+    }
+
+    int nCopied = 0;
+    string strError;
+    if (!ExportActiveWalletToSQLite(strDest, nCopied, strError))
+    {
+        fprintf(stderr, "Cannot export wallet to SQLite: %s\n", strError.c_str());
         return 1;
     }