(new): add threshold-based log level filtering and docs

- add threshold-aware LogLevel constructors
- add Logger.SetThresholdMode and SameThreshold
- preserve legacy SameLevel behavior for compatibility
- extend tests for threshold mode and compatibility
- update README and release notes for v2.2.0

logger_test.go

@@ -120,6 +120,77 @@ func TestLoggerPrintfFormatsMessage(t *testing.T) {
 	}
 }
 
+func TestLoggerUsesSeverityOrderingWhenThresholdModeIsDisabled(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		SetLevel(NewThresholdLogLevel(1, 0, "warn")).
+		AddWriter(writer)
+
+	logger.Print(NewThresholdLogLevel(0, 100, "info"))
+	logger.Print(NewThresholdLogLevel(2, 0, "error"))
+
+	if writer.printCalls != 1 {
+		t.Fatalf("severity mode should allow only lower-or-equal severity levels, got %d writes", writer.printCalls)
+	}
+}
+
+func TestLoggerUsesThresholdOrderingWhenThresholdModeIsEnabled(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		SetLevel(NewThresholdLogLevel(4, 20, "custom")).
+		SetThresholdMode(true).
+		AddWriter(writer)
+
+	logger.Print(NewThresholdLogLevel(4, 10, "debug"))
+	logger.Print(NewThresholdLogLevel(0, 30, "info"))
+
+	if writer.printCalls != 1 {
+		t.Fatalf("threshold mode should allow only entries at or below the configured threshold, got %d writes", writer.printCalls)
+	}
+}
+
+func TestDeprecatedLevelMethodKeepsLegacySeverityBehavior(t *testing.T) {
+	writer := &stubLoggerWriter{}
+	logger := CreateLogger().
+		Level(FATAL).
+		AddWriter(writer)
+
+	logger.Print(INFO, "info")
+	logger.Print(WARN, "warn")
+	logger.Print(ERROR, "error")
+	logger.Print(FATAL, "fatal")
+	logger.Print(DEBUG, "debug")
+
+	if writer.printCalls != 4 {
+		t.Fatalf("Level(FATAL) should keep legacy behavior and allow INFO/WARN/ERROR/FATAL only, got %d writes", writer.printCalls)
+	}
+}
+
+func TestSameLevelIgnoresThresholdDifferencesForCompatibility(t *testing.T) {
+	legacy := NewLogLevel(1, "warn")
+	threshold := NewThresholdLogLevel(1, 20, "warn")
+
+	if !legacy.SameLevel(threshold) {
+		t.Fatalf("SameLevel() should continue comparing only severity index")
+	}
+	if legacy.Equal(threshold) {
+		t.Fatalf("Equal() should distinguish levels with different threshold configuration")
+	}
+}
+
+func TestSameThresholdComparesOnlyThresholdValue(t *testing.T) {
+	first := NewThresholdLogLevel(1, 20, "warn")
+	second := NewThresholdLogLevel(9, 20, "custom")
+	third := NewThresholdLogLevel(1, 30, "warn")
+
+	if !first.SameThreshold(second) {
+		t.Fatalf("SameThreshold() should ignore severity and compare threshold only")
+	}
+	if first.SameThreshold(third) {
+		t.Fatalf("SameThreshold() should detect different threshold values")
+	}
+}
+
 func TestLogLevelForMethodReturnsExpectedLevels(t *testing.T) {
 	tests := []struct {
 		name   string
@@ -150,15 +221,16 @@ func TestLogLevelForMethodReturnsExpectedLevels(t *testing.T) {
 
 func TestNewLevelConstructorsSetExpectedSeverity(t *testing.T) {
 	tests := []struct {
-		name string
-		got  LogLevel
-		want LogLevel
+		name   string
+		got    LogLevel
+		want   LogLevel
+		wantTh uint8
 	}{
-		{name: "info", got: NewInfoLogLevel("custom"), want: INFO},
-		{name: "warn", got: NewWarnLogLevel("custom"), want: WARN},
-		{name: "error", got: NewErrorLogLevel("custom"), want: ERROR},
-		{name: "fatal", got: NewFatalLogLevel("custom"), want: FATAL},
-		{name: "debug", got: NewDebugLogLevel("custom"), want: DEBUG},
+		{name: "info", got: NewInfoLogLevel("custom"), want: INFO, wantTh: 10},
+		{name: "warn", got: NewWarnLogLevel("custom"), want: WARN, wantTh: 20},
+		{name: "error", got: NewErrorLogLevel("custom"), want: ERROR, wantTh: 30},
+		{name: "fatal", got: NewFatalLogLevel("custom"), want: FATAL, wantTh: 40},
+		{name: "debug", got: NewDebugLogLevel("custom"), want: DEBUG, wantTh: 0},
 	}
 
 	for _, tt := range tests {
@@ -166,6 +238,9 @@ func TestNewLevelConstructorsSetExpectedSeverity(t *testing.T) {
 			if tt.got.n != tt.want.n {
 				t.Fatalf("%s severity = %d, want %d", tt.name, tt.got.n, tt.want.n)
 			}
+			if tt.got.th != tt.wantTh {
+				t.Fatalf("%s threshold = %d, want %d", tt.name, tt.got.th, tt.wantTh)
+			}
 			if tt.got.GetName() != "custom" {
 				t.Fatalf("%s constructor should preserve name, got %q", tt.name, tt.got.GetName())
 			}