Usernames are now case-insensitive

This fixes a UX issue, where if you accidentally capitalized a letter
in the username when logging in, it would instead create a new account.

The behavior was confusing, since to the user it looks as if their
characters were deleted or progress was not saved.

In order for this to work, duplicate accounts (e.g. username and USERNAME)
need to be deleted/renamed. The server will *detect* if any duplicates
exist. If any are found, it will direct the server operator to a pruning
script, or they can choose to resolve the duplicates manually.

src/db/Database.hpp

@@ -5,7 +5,7 @@
 #include <string>
 #include <vector>
 
-#define DATABASE_VERSION 3
+#define DATABASE_VERSION 4
 
 namespace Database {
 

src/db/init.cpp

@@ -9,6 +9,37 @@
 std::mutex dbCrit;
 sqlite3 *db;
 
+/*
+ * When migrating from DB version 3 to 4, we change the username column
+ * to be case-insensitive. This function ensures there aren't any
+ * duplicates, e.g. username and USERNAME, before doing the migration.
+ * I handled this in the code itself rather than the migration file just so
+ * we can have a more detailed error message than what SQLite provides.
+ */
+static void checkCaseSensitiveDupes() {
+    const char* sql = "SELECT Login, COUNT(*) FROM Accounts GROUP BY LOWER(Login) HAVING COUNT(*) > 1;";
+
+    sqlite3_stmt* stmt;
+    sqlite3_prepare_v2(db, sql, -1, &stmt, NULL);
+    int stat = sqlite3_step(stmt);
+
+    if (stat == SQLITE_DONE) {
+        // no rows returned, so we're good
+        sqlite3_finalize(stmt);
+        return;
+    } else if (stat != SQLITE_ROW) {
+        std::cout << "[FATAL] Failed to check for duplicate accounts: " << sqlite3_errmsg(db) << std::endl;
+        sqlite3_finalize(stmt);
+        exit(1);
+    }
+
+    std::cout << "[FATAL] Case-sensitive duplicates detected in the Login column." << std::endl;
+    std::cout << "Either manually delete/rename the offending accounts, or run the pruning script:" << std::endl;
+    std::cout << "https://github.com/OpenFusionProject/scripts/tree/main/db_migration/caseinsens.py" << std::endl;
+    sqlite3_finalize(stmt);
+    exit(1);
+}
+
 static void createMetaTable() {
     std::lock_guard<std::mutex> lock(dbCrit); // XXX
 
@@ -143,6 +174,10 @@ static void checkMetaTable() {
     }
 
     while (dbVersion != DATABASE_VERSION) {
+        // need to run this before we do any migration logic
+        if (dbVersion == 3)
+            checkCaseSensitiveDupes();
+
         // db migrations
         std::cout << "[INFO] Migrating Database to Version " << dbVersion + 1 << std::endl;