1 files changed, 112 insertions, 0 deletions
diff --git a/u/server/metrics.ts b/u/server/metrics.ts
new file mode 100644
index 0000000..05df967
--- /dev/null
+++ b/u/server/metrics.ts
@@ -0,0 +1,112 @@
+import {
+  type BiMapper,
+  Either,
+  type IEither,
+  type ITraceable,
+  type Mapper,
+  type Supplier,
+} from "@emprespresso/pengueno";
+
+export enum Unit {
+  COUNT,
+  MILLISECONDS,
+}
+
+export interface IMetric<MetricT extends string, TUnit extends Unit> {
+  readonly metric: MetricT;
+  readonly unit: TUnit;
+  readonly value: number;
+  readonly emissionTimestamp: Date;
+}
+
+export type BaseMetricT = string;
+export interface CountMetric<MetricT extends BaseMetricT>
+  extends IMetric<MetricT, Unit.COUNT> {
+  readonly unit: Unit.COUNT;
+}
+
+export interface TimeMetric<MetricT extends BaseMetricT>
+  extends IMetric<MetricT, Unit.MILLISECONDS> {
+  readonly unit: Unit.MILLISECONDS;
+}
+
+export interface IMetricsData<
+  MetricT extends BaseMetricT,
+  Tracing,
+  TraceW,
+> {
+  addCount: BiMapper<MetricT, number, CountMetric<MetricT>>;
+
+  stopwatch: BiMapper<
+    MetricT,
+    ITraceable<Tracing, TraceW>,
+    ITraceable<MetricT, TraceW>
+  >;
+  endStopwatch: Mapper<
+    ITraceable<MetricT, TraceW>,
+    IEither<Error, TimeMetric<MetricT>>
+  >;
+
+  flush: Supplier<Array<IMetric<MetricT, Unit>>>;
+}
+
+export class TraceableMetricsData<MetricT extends BaseMetricT, Tracing, Trace>
+  implements IMetricsData<MetricT, Tracing, Trace> {
+  private readonly timers: Map<ITraceable<MetricT, Trace>, Date> = new Map();
+  private metricBuffer: Array<IMetric<MetricT, Unit>> = [];
+
+  private constructor() {}
+
+  private addMetric<TUnit extends Unit>(
+    metric: MetricT,
+    unit: TUnit,
+    value: number,
+  ): IMetric<MetricT, TUnit> {
+    const _metric = {
+      metric,
+      unit,
+      value,
+      emissionTimestamp: new Date(),
+    };
+    this.metricBuffer.push(_metric);
+    return _metric;
+  }
+
+  public flush() {
+    const metrics = [...this.metricBuffer];
+    this.metricBuffer = [];
+    return metrics;
+  }
+
+  public addCount(
+    metric: MetricT,
+    count: number,
+  ): CountMetric<MetricT> {
+    return this.addMetric(metric, Unit.COUNT, count);
+  }
+
+  public stopwatch(metric: MetricT, traceable: ITraceable<Tracing, Trace>) {
+    const timer = traceable.move(metric);
+    this.timers.set(timer, new Date());
+    return timer;
+  }
+
+  public endStopwatch(
+    stopwatch: ITraceable<MetricT, Trace>,
+  ): IEither<Error, TimeMetric<MetricT>> {
+    const now = new Date();
+    if (this.timers.has(stopwatch)) {
+      const timer = this.timers.get(stopwatch)!;
+      const diff = now.getTime() - timer.getTime();
+      this.timers.delete(stopwatch);
+      return Either.right<Error, TimeMetric<MetricT>>(
+        this.addMetric(stopwatch.item, Unit.MILLISECONDS, diff) as TimeMetric<
+          MetricT
+        >,
+      );
+    }
+    return Either.left<Error, TimeMetric<MetricT>>(
+      new Error("cannot stop stopwatch before starting it"),
+    );
+  }
+}