feat: added gauge type & some tests

.gitignore

@@ -0,0 +1,2 @@
+*.c
+*.so

collector.v

@@ -2,12 +2,12 @@ module metrics
 
 import sync.stdatomic
 
-struct CounterEntry {
+struct Counter {
 	metric Metric
-	index  int
+	data   u64
 }
 
-struct HistogramEntry {
+struct FloatSeries {
 	metric Metric
 pub mut:
 	data shared []f64
@@ -16,47 +16,41 @@ pub mut:
 [heap]
 struct DefaultCollector {
 mut:
-	// The mutex for counters also applies to counter_indexes. Both data
-	// structuress are only ever updated together. Note that only registering a
-	// new metric actually changes these; all operations on already existing
-	// metrics use atomic operations on the elements of the counters array.
-	counters        shared []u64
-	counter_indexes map[string]CounterEntry
-	histograms      shared map[string]HistogramEntry
+	counters   shared map[string]&Counter
+	histograms shared map[string]&FloatSeries
+	gauges     shared map[string]&FloatSeries
 }
 
 pub fn new_default_collector() &DefaultCollector {
 	return &DefaultCollector{
-		counters: []u64{}
-		counter_indexes: map[string]CounterEntry{}
-		histograms: map[string]HistogramEntry{}
+		counters: map[string]&Counter{}
+		histograms: map[string]&FloatSeries{}
+		gauges: map[string]&FloatSeries{}
 	}
 }
 
 pub fn (mut c DefaultCollector) counter_register(value u64, metric Metric) {
 	lock c.counters {
-		c.counters << value
-
-		c.counter_indexes[metric.str()] = CounterEntry{
+		c.counters[metric.str()] = &Counter{
 			metric: metric
-			index: c.counters.len - 1
+			data: value
 		}
 	}
 }
 
 pub fn (c &DefaultCollector) counter_increment(metric Metric) {
 	rlock c.counters {
-		entry := c.counter_indexes[metric.str()]
+		entry := c.counters[metric.str()]
 
-		stdatomic.add_u64(&c.counters[entry.index], 1)
+		stdatomic.add_u64(&entry.data, 1)
 	}
 }
 
 pub fn (c &DefaultCollector) counter_get(metric Metric) ?u64 {
 	return rlock c.counters {
-		entry := c.counter_indexes[metric.str()] or { return none }
+		entry := c.counters[metric.str()] or { return none }
 
-		stdatomic.load_u64(&c.counters[entry.index])
+		stdatomic.load_u64(&entry.data)
 	}
 }
 
@@ -64,7 +58,7 @@ pub fn (c &DefaultCollector) counters() []Metric {
 	mut metrics := []Metric{}
 
 	rlock c.counters {
-        for _, entry in c.counter_indexes {
+		for _, entry in c.counters {
 			metrics << entry.metric
 		}
 	}
@@ -74,14 +68,14 @@ pub fn (c &DefaultCollector) counters() []Metric {
 
 pub fn (mut c DefaultCollector) histogram_register(metric Metric) {
 	lock c.histograms {
-		c.histograms[metric.str()] = HistogramEntry{
+		c.histograms[metric.str()] = &FloatSeries{
 			metric: metric
 			data: []f64{}
 		}
 	}
 }
 
-pub fn (c &DefaultCollector) histogram_add(value f64, metric Metric) {
+pub fn (c &DefaultCollector) histogram_record(value f64, metric Metric) {
 	entry := rlock c.histograms {
 		c.histograms[metric.str()]
 	}
@@ -102,3 +96,52 @@ pub fn (c &DefaultCollector) histogram_get(metric Metric) ?[]f64 {
 		entry.data.clone()
 	}
 }
+
+pub fn (mut c DefaultCollector) gauge_register(value f64, metric Metric) {
+	lock c.gauges {
+		c.gauges[metric.str()] = &FloatSeries{
+			metric: metric
+			data: [value]
+		}
+	}
+}
+
+pub fn (c &DefaultCollector) gauge_add(value f64, metric Metric) {
+	entry := rlock c.gauges {
+		c.gauges[metric.str()]
+	}
+
+	lock entry.data {
+		entry.data[0] += value
+	}
+}
+
+pub fn (c &DefaultCollector) gauge_sub(value f64, metric Metric) {
+	entry := rlock c.gauges {
+		c.gauges[metric.str()]
+	}
+
+	lock entry.data {
+		entry.data[0] -= value
+	}
+}
+
+pub fn (c &DefaultCollector) gauge_set(value f64, metric Metric) {
+	entry := rlock c.gauges {
+		c.gauges[metric.str()]
+	}
+
+	lock entry.data {
+		entry.data[0] = value
+	}
+}
+
+pub fn (c &DefaultCollector) gauge_get(metric Metric) ?f64 {
+	entry := rlock c.gauges {
+		c.gauges[metric.str()]
+	}
+
+	return rlock entry.data {
+		entry.data[0]
+	}
+}

collector_test.v

@@ -0,0 +1,112 @@
+module metrics
+
+fn test_implements_interface() {
+	_ := MetricsCollector(new_default_collector())
+}
+
+fn test_null_implements_interface() {
+	_ := MetricsCollector(new_null_collector())
+}
+
+fn test_counter_increment() {
+	mut m := new_default_collector()
+
+	m.counter_register(0, name: 'test')
+	m.counter_increment(name: 'test')
+	assert m.counter_get(name: 'test')? == u64(1)
+
+	m.counter_increment(name: 'test')
+	assert m.counter_get(name: 'test')? == u64(2)
+
+    // Test with labels
+    metric := Metric{
+        name: 'test2'
+        labels: [['hi', 'label']!, ['hi2', 'label2']!]
+    }
+
+    m.counter_register(15, metric)
+	m.counter_increment(metric)
+	assert m.counter_get(metric)? == u64(16)
+}
+
+fn test_histogram() {
+	mut m := new_default_collector()
+
+    m.histogram_register(name: 'test')
+    m.histogram_record(5.0, name: 'test')
+    assert m.histogram_get(name: 'test')? == [5.0]
+
+    m.histogram_record(7.0, name: 'test')
+    assert m.histogram_get(name: 'test')? == [5.0, 7.0]
+
+    // Test with labels
+    metric := Metric{
+        name: 'test2'
+        labels: [['hi', 'label']!, ['hi2', 'label2']!]
+    }
+
+    m.histogram_register(metric)
+    m.histogram_record(5.0, metric)
+    assert m.histogram_get(metric)? == [5.0]
+
+    m.histogram_record(7.0, metric)
+    assert m.histogram_get(metric)? == [5.0, 7.0]
+}
+
+fn test_gauge_add() {
+	mut m := new_default_collector()
+
+    m.gauge_register(0.0, name: 'test')
+    m.gauge_add(5.0, name: 'test')
+    assert m.gauge_get(name: 'test')? == 5.0
+
+    // Test with labels
+    metric := Metric{
+        name: 'test2'
+        labels: [['hi', 'label']!, ['hi2', 'label2']!]
+    }
+
+    m.gauge_register(3.0, metric)
+    m.gauge_add(5.0, metric)
+    assert m.gauge_get(metric)? == 8.0
+}
+
+fn test_gauge_sub() {
+	mut m := new_default_collector()
+
+    m.gauge_register(0.0, name: 'test')
+    m.gauge_sub(5.0, name: 'test')
+    assert m.gauge_get(name: 'test')? == -5.0
+
+    // Test with labels
+    metric := Metric{
+        name: 'test2'
+        labels: [['hi', 'label']!, ['hi2', 'label2']!]
+    }
+
+    m.gauge_register(3.0, metric)
+    m.gauge_sub(5.0, metric)
+    assert m.gauge_get(metric)? == -2.0
+}
+
+fn test_gauge_set() {
+	mut m := new_default_collector()
+
+    m.gauge_register(0.0, name: 'test')
+    m.gauge_set(3.0, name: 'test')
+    assert m.gauge_get(name: 'test')? == 3.0
+    m.gauge_set(5.0, name: 'test')
+    assert m.gauge_get(name: 'test')? == 5.0
+
+    // Test with labels
+    metric := Metric{
+        name: 'test2'
+        labels: [['hi', 'label']!, ['hi2', 'label2']!]
+    }
+
+    m.gauge_register(0.0, metric)
+    m.gauge_set(3.0, metric)
+    assert m.gauge_get(metric)? == 3.0
+    m.gauge_set(5.0, metric)
+    assert m.gauge_get(metric)? == 5.0
+}

counter_test.v

@@ -1,14 +0,0 @@
-module metrics
-
-fn test_counter_increment() {
-	mut m := new_default_collector()
-	m.counter_register(0, name: 'test')
-
-	m.counter_increment(name: 'test')
-
-    assert m.counter_get(name: 'test')? == u64(1)
-
-	m.counter_increment(name: 'test')
-
-    assert m.counter_get(name: 'test')? == u64(2)
-}

exporter/exporter.v

@@ -0,0 +1,10 @@
+module exporter
+
+import io
+import metrics { MetricsCollector }
+
+pub interface MetricsExporter {
+    load(collector MetricsCollector)
+    export_to_writer(writer io.Writer) !
+    export_to_string() string !
+}

exporter/prometheus.v

@@ -0,0 +1,4 @@
+module exporter
+
+pub struct PrometheusExporter {
+}

metrics.v

@@ -20,11 +20,17 @@ pub fn (m &Metric) str() string {
 }
 
 pub interface MetricsCollector {
-	counter_register(value u64, metric Metric)
 	counter_increment(metric Metric)
 	counter_get(metric Metric) ?u64
 	counters() []Metric
+	histogram_record(value f64, metric Metric)
+	histogram_get(metric Metric) ?[]f64
+	gauge_add(value f64, metric Metric)
+	gauge_sub(value f64, metric Metric)
+	gauge_set(value f64, metric Metric)
+	gauge_get(metric Metric) ?f64
+mut:
+	counter_register(value u64, metric Metric)
 	histogram_register(metric Metric)
-	histogram_add(value f64, metric Metric)
-	histogram_get(metric Metric) ?
+	gauge_register(value f64, metric Metric)
 }

null.v

@@ -15,12 +15,26 @@ pub fn (c &NullCollector) counter_get(metric Metric) ?u64 {
 	return none
 }
 
-pub fn (c &NullCollector) counters() []Metric { return [] }
+pub fn (c &NullCollector) counters() []Metric {
+	return []
+}
 
 pub fn (c &NullCollector) histogram_register(metric Metric) {}
 
-pub fn (c &NullCollector) histogram_add(value f64, metric Metric) {}
+pub fn (c &NullCollector) histogram_record(value f64, metric Metric) {}
 
 pub fn (c &NullCollector) histogram_get(metric Metric) ?[]f64 {
 	return none
 }
+
+pub fn (c &NullCollector) gauge_register(value f64, metric Metric) {}
+
+pub fn (c &NullCollector) gauge_add(value f64, metric Metric) {}
+
+pub fn (c &NullCollector) gauge_sub(value f64, metric Metric) {}
+
+pub fn (c &NullCollector) gauge_set(value f64, metric Metric) {}
+
+pub fn (c &NullCollector) gauge_get(metric Metric) ?f64 {
+	return none
+}