feat: add NullCollector

collector.v

@@ -44,7 +44,7 @@ pub fn (mut c DefaultCollector) counter_register(value u64, metric Metric) {
 	}
 }
 
-pub fn (mut c DefaultCollector) counter_increment(metric Metric) {
+pub fn (c &DefaultCollector) counter_increment(metric Metric) {
 	rlock c.counters {
 		entry := c.counter_indexes[metric.str()]
 
@@ -52,7 +52,7 @@ pub fn (mut c DefaultCollector) counter_increment(metric Metric) {
 	}
 }
 
-pub fn (mut c DefaultCollector) counter_decrement(metric Metric) {
+pub fn (c &DefaultCollector) counter_decrement(metric Metric) {
 	rlock c.counters {
 		entry := c.counter_indexes[metric.str()]
 
@@ -60,7 +60,7 @@ pub fn (mut c DefaultCollector) counter_decrement(metric Metric) {
 	}
 }
 
-pub fn (mut c DefaultCollector) counter_get(metric Metric) ?u64 {
+pub fn (c &DefaultCollector) counter_get(metric Metric) ?u64 {
 	return rlock c.counters {
 		entry := c.counter_indexes[metric.str()] or { return none }
 
@@ -77,7 +77,7 @@ pub fn (mut c DefaultCollector) histogram_register(metric Metric) {
 	}
 }
 
-pub fn (mut c DefaultCollector) histogram_add(value f64, metric Metric) {
+pub fn (c &DefaultCollector) histogram_add(value f64, metric Metric) {
 	entry := rlock c.histograms {
 		c.histograms[metric.str()]
 	}
@@ -87,7 +87,7 @@ pub fn (mut c DefaultCollector) histogram_add(value f64, metric Metric) {
 	}
 }
 
-pub fn (mut c DefaultCollector) histogram_get(metric Metric) ?[]f64 {
+pub fn (c &DefaultCollector) histogram_get(metric Metric) ?[]f64 {
 	entry := rlock c.histograms {
 		c.histograms[metric.str()] or { return none }
 	}

null.v

@@ -0,0 +1,26 @@
+module metrics
+
+[heap]
+struct NullCollector {}
+
+pub fn new_null_collector() &NullCollector {
+	return &NullCollector{}
+}
+
+pub fn (c &NullCollector) counter_register(value u64, metric Metric) {}
+
+pub fn (c &NullCollector) counter_increment(metric Metric) {}
+
+pub fn (c &NullCollector) counter_decrement(metric Metric) {}
+
+pub fn (c &NullCollector) counter_get(metric Metric) ?u64 {
+	return none
+}
+
+pub fn (c &NullCollector) histogram_register(metric Metric) {}
+
+pub fn (c &NullCollector) histogram_add(value f64, metric Metric) {}
+
+pub fn (c &NullCollector) histogram_get(metric Metric) ?[]f64 {
+	return none
+}