handle db initialization

src/core/database.cpp

@@ -1,11 +1,13 @@
 #include "database.h"
 
+#include <filesystem>
 #include <iostream>
 #include <stdexcept>
 
 Database::Database(const std::string& dbname) : db_(nullptr)
 {
-    const int errCode = sqlite3_open(dbname.c_str(), &db_);
+    dbname_ = dbname;
+    const int errCode = sqlite3_open(dbname_.c_str(), &db_);
     if (errCode) {
         throw std::runtime_error("Could not open database file.");
     }
@@ -26,8 +28,11 @@ void Database::exec(const std::string& sql)
     }
 }
 
-void Database::init()
+void Database::createNew()
 {
+    std::string sqlCreateKima2{"CREATE TABLE IF NOT EXISTS kima2 ("
+                               "version INTEGER NOT NULL);"
+                               "INSERT INTO kima2 (version) VALUES (1);"};
     std::string sqlCreateSellers{"CREATE TABLE IF NOT EXISTS sellers ("
                                  "id TEXT PRIMARY KEY NOT NULL, "
                                  "seller_no INTEGER, "
@@ -51,11 +56,73 @@ void Database::init()
         ");"};
 
     beginTransaction();
+    exec(sqlCreateKima2);
     exec(sqlCreateSellers);
     exec(sqlCreateArticles);
     endTransaction();
 }
 
+void Database::init()
+{
+    int version = getVersion();
+
+    switch (version) {
+    case 0:
+        createNew();
+        break;
+        // perhaps handle upgrades for db schema here...
+    default:
+        // Do nothing because we are up-to-date.
+        break;
+    }
+}
+
+int Database::getVersion()
+{
+    int retCode{};
+    sqlite3_stmt* stmt;
+
+    // Check if there's already a kima2 table available.
+    // If not, return version == 0.
+    retCode = sqlite3_prepare_v2(
+        db_, "SELECT count(*) FROM sqlite_master WHERE type='table' AND name='kima2';", -1, &stmt,
+        nullptr);
+    if (retCode != SQLITE_OK)
+        throw std::string(sqlite3_errmsg(db_));
+    retCode = sqlite3_step(stmt);
+    if (retCode != SQLITE_ROW && retCode != SQLITE_DONE) {
+        std::string errMsg(sqlite3_errmsg(db_));
+        sqlite3_finalize(stmt);
+        throw errMsg;
+    } else if (retCode != SQLITE_DONE) {
+        int count = sqlite3_column_int(stmt, 0);
+        sqlite3_finalize(stmt);
+        if (count == 0)
+            return 0; // no kima2 table, so version is 0
+    }
+
+    // Now that we know that the kima2 table is present, read and return the schema version.
+    retCode = sqlite3_prepare_v2(db_, "SELECT version FROM kima2", -1, &stmt, nullptr);
+    if (retCode != SQLITE_OK)
+        throw std::string(sqlite3_errmsg(db_));
+
+    retCode = sqlite3_step(stmt);
+
+    if (retCode != SQLITE_ROW && retCode != SQLITE_DONE) {
+        std::string errMsg(sqlite3_errmsg(db_));
+        sqlite3_finalize(stmt);
+        throw errMsg;
+    } else if (retCode == SQLITE_DONE) {
+        sqlite3_finalize(stmt);
+        return 0; // no version entry, so version is 0
+    }
+
+    int version = sqlite3_column_int(stmt, 0);
+    sqlite3_finalize(stmt);
+
+    return version;
+}
+
 void Database::beginTransaction() { exec("BEGIN TRANSACTION"); }
 
 void Database::endTransaction() { exec("END TRANSACTION"); }

src/core/database.h

@@ -16,8 +16,11 @@ public:
     void init();
 private:
     sqlite3 *db_;
+    std::string dbname_;
     void beginTransaction();
     void endTransaction();
+    void createNew();
+    int getVersion();
 };
 
 #endif // DATABASE_H