first commit

store/db/sqlite/functions.go

@@ -0,0 +1,44 @@
+// Package sqlite provides SQLite driver implementation with custom functions.
+// Custom functions are registered globally on first use to extend SQLite's
+// limited ASCII-only text operations with proper Unicode support.
+package sqlite
+
+import (
+	"database/sql/driver"
+	"sync"
+
+	"golang.org/x/text/cases"
+	msqlite "modernc.org/sqlite"
+)
+
+var (
+	registerUnicodeLowerOnce sync.Once
+	registerUnicodeLowerErr  error
+	// unicodeFold provides Unicode case folding for case-insensitive comparisons.
+	// It's safe to use concurrently and reused across all function calls.
+	unicodeFold = cases.Fold()
+)
+
+// ensureUnicodeLowerRegistered registers the memos_unicode_lower custom function
+// with SQLite. This function provides proper Unicode case folding for case-insensitive
+// text comparisons, overcoming modernc.org/sqlite's lack of ICU extension.
+//
+// The function is registered once globally and is safe to call multiple times.
+func ensureUnicodeLowerRegistered() error {
+	registerUnicodeLowerOnce.Do(func() {
+		registerUnicodeLowerErr = msqlite.RegisterScalarFunction("memos_unicode_lower", 1, func(_ *msqlite.FunctionContext, args []driver.Value) (driver.Value, error) {
+			if len(args) == 0 || args[0] == nil {
+				return nil, nil
+			}
+			switch v := args[0].(type) {
+			case string:
+				return unicodeFold.String(v), nil
+			case []byte:
+				return unicodeFold.String(string(v)), nil
+			default:
+				return v, nil
+			}
+		})
+	})
+	return registerUnicodeLowerErr
+}