feat: add counters

collector.v

@@ -0,0 +1,57 @@
+module metrics
+
+import sync.stdatomic
+
+struct CounterEntry {
+	metric Metric
+	index  int
+}
+
+[heap]
+struct DefaultMetricsCollector {
+mut:
+	counters        shared []u64
+	counter_indexes shared map[string]CounterEntry
+}
+
+pub fn new_default_metrics_collector() &DefaultMetricsCollector {
+	return &DefaultMetricsCollector{
+		counters: []u64{}
+		counter_indexes: map[string]CounterEntry{}
+	}
+}
+
+pub fn (mut c DefaultMetricsCollector) counter_register(value u64, metric Metric) {
+	new_index := lock c.counters {
+		c.counters << value
+
+		c.counters.len - 1
+	}
+
+	lock c.counter_indexes {
+		c.counter_indexes[metric.str()] = CounterEntry{
+			metric: metric
+			index: new_index
+		}
+	}
+}
+
+pub fn (mut c DefaultMetricsCollector) counter_increment(metric Metric) {
+	entry := rlock c.counter_indexes {
+		c.counter_indexes[metric.str()]
+	}
+
+	rlock c.counters {
+		stdatomic.add_u64(&c.counters[entry.index], 1)
+	}
+}
+
+pub fn (mut c DefaultMetricsCollector) counter_decrement(metric Metric) {
+	entry := rlock c.counter_indexes {
+		c.counter_indexes[metric.str()]
+	}
+
+	rlock c.counters {
+		stdatomic.sub_u64(&c.counters[entry.index], 1)
+	}
+}

counter_test.v

@@ -0,0 +1,8 @@
+import metrics
+
+fn test_counter_increment() {
+	mut m := new_default_metrics_collector()
+	m.counter_register(0, 'test')
+
+	m.counter_increment('test')
+}

metrics.v

@@ -0,0 +1,26 @@
+module metrics
+
+[params]
+pub struct Metric {
+	name   string      [required]
+	labels [][2]string
+}
+
+[inline]
+fn join_two_array(arr [2]string) string {
+	return arr[0] + '=' + arr[1]
+}
+
+pub fn (m &Metric) str() string {
+	if m.labels.len == 0 {
+		return m.name
+	}
+
+	return '$m.name{${m.labels.map(join_two_array(it)).join(',')}}'
+}
+
+interface MetricsCollector {
+	counter_register(value u64, metric Metric)
+	counter_increment(metric Metric)
+	counter_decrement(metric Metric)
+}