From ef51b25e4388cbdf3a27e23d9f1fa381ae20a5ad Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <lizhunt@amazon.com>
Date: Fri, 16 May 2025 16:17:13 -0700
Subject: snapshot

---
 u/fn/callable.ts                |   4 ++
 u/fn/either.ts                  |  28 +++++++---
 u/server/activity/fourohfour.ts |  30 +++++++++++
 u/server/activity/health.ts     |  12 +++--
 u/server/activity/mod.ts        |  13 +++--
 u/server/filter/json.ts         |  37 +++++++------
 u/server/filter/method.ts       |  38 +++++++-------
 u/server/filter/mod.ts          |   2 +-
 u/server/metrics.ts             | 112 ++++++++++++++++++++++++++++++++++++++++
 u/server/mod.ts                 |   3 +-
 u/server/request.ts             |  27 ++++++++++
 u/server/response.ts            |  44 ++++++++++++++++
 12 files changed, 299 insertions(+), 51 deletions(-)
 create mode 100644 u/server/activity/fourohfour.ts
 create mode 100644 u/server/metrics.ts
 create mode 100644 u/server/request.ts
 create mode 100644 u/server/response.ts

(limited to 'u')

diff --git a/u/fn/callable.ts b/u/fn/callable.ts
index 2749947..a087928 100644
--- a/u/fn/callable.ts
+++ b/u/fn/callable.ts
@@ -13,3 +13,7 @@ export interface SideEffect<T> extends Callable<void, T> {
 export interface Mapper<T, U> extends Callable<U, T> {
   (t: T): U;
 }
+
+export interface BiMapper<T, U, R> extends Callable {
+  (t: T, u: U): R;
+}
diff --git a/u/fn/either.ts b/u/fn/either.ts
index 916bb71..9dc1027 100644
--- a/u/fn/either.ts
+++ b/u/fn/either.ts
@@ -1,10 +1,16 @@
-import type { Mapper, Supplier } from "@emprespresso/pengueno";
+import type { BiMapper, Mapper, Supplier } from "@emprespresso/pengueno";
+import { isObject } from "../leftpadesque/mod.ts";
+
+type IEitherTag = "IEither";
+const iEitherTag: IEitherTag = "IEither";
 
 export interface IEither<E, T> {
+  readonly _tag: IEitherTag;
   mapBoth: <Ee, Tt>(
     errBranch: Mapper<E, Ee>,
     okBranch: Mapper<T, Tt>,
   ) => IEither<Ee, Tt>;
+  fold: <Tt>(folder: BiMapper<E | null, T | null, Tt>) => Tt;
   moveRight: <Tt>(t: Tt) => IEither<E, Tt>;
   mapRight: <Tt>(mapper: Mapper<T, Tt>) => IEither<E, Tt>;
   mapLeft: <Ee>(mapper: Mapper<E, Ee>) => IEither<Ee, T>;
@@ -15,14 +21,20 @@ export interface IEither<E, T> {
 }
 
 export class Either<E, T> implements IEither<E, T> {
-  private constructor(private readonly err?: E, private readonly ok?: T) {}
+  private constructor(
+    private readonly err?: E,
+    private readonly ok?: T,
+    public readonly _tag: IEitherTag = iEitherTag,
+  ) {}
 
-  public moveRight<Tt>(
-    t: Tt,
-  ) {
+  public moveRight<Tt>(t: Tt) {
     return this.mapRight(() => t);
   }
 
+  public fold<R>(folder: BiMapper<E | null, T | null, R>): R {
+    return folder(this.err ?? null, this.ok ?? null);
+  }
+
   public mapBoth<Ee, Tt>(
     errBranch: Mapper<E, Ee>,
     okBranch: Mapper<T, Tt>,
@@ -37,7 +49,7 @@ export class Either<E, T> implements IEither<E, T> {
   }
 
   public mapRight<Tt>(mapper: Mapper<T, Tt>): IEither<E, Tt> {
-    if (this.ok !== undefined) return Either.right(mapper(this.ok));
+    if (this.ok !== undefined) return Either.right<E, Tt>(mapper(this.ok));
     return Either.left<E, Tt>(this.err!);
   }
 
@@ -79,3 +91,7 @@ export class Either<E, T> implements IEither<E, T> {
     }
   }
 }
+
+export const isEither = <E, T>(o: unknown): o is IEither<E, T> => {
+  return isObject(o) && "_tag" in o && o._tag === "IEither";
+};
diff --git a/u/server/activity/fourohfour.ts b/u/server/activity/fourohfour.ts
new file mode 100644
index 0000000..698dacd
--- /dev/null
+++ b/u/server/activity/fourohfour.ts
@@ -0,0 +1,30 @@
+import {
+  type ITraceable,
+  JsonResponse,
+  TraceUtil,
+} from "@emprespresso/pengueno";
+
+export enum HealthCheckInput {
+  CHECK,
+}
+export enum HealthCheckOutput {
+  YAASQUEEN,
+}
+
+const messages = [
+  "(≧ω≦)ゞ Oopsie! This endpoint has gone a-404-dable!",
+  "｡ﾟ(｡ﾉωヽ｡)ﾟ｡ Meow-t found! Your API call ran away!",
+  "404-bidden! But like...in a cute way (・`ω´・) !",
+  "(=①ω①=) This endpoint is hiss-terically missing!",
+  "┐(´∀｀)┌ Whoopsie fluff! No API here!",
+  "(つ≧▽≦)つ Your data went on a paw-sible vacation!",
+  "(ꈍᴗꈍ) Uwu~ not found, but found our hearts instead!",
+  "ヽ(；▽；)ノ Eep! This route has ghosted you~",
+];
+export const FourOhFourActivity = <Trace>(req: ITraceable<Request, Trace>) =>
+  req.bimap(TraceUtil.withFunctionTrace(FourOhFourActivity))
+    .map(() =>
+      new JsonResponse(messages[Math.random() * messages.length], {
+        status: 404,
+      })
+    );
diff --git a/u/server/activity/health.ts b/u/server/activity/health.ts
index 7ee6629..98acbb8 100644
--- a/u/server/activity/health.ts
+++ b/u/server/activity/health.ts
@@ -27,15 +27,19 @@ export const HealthCheckActivity = <Trace>(
       health.mapBoth((e) => {
         trace.addTrace(LogLevel.ERROR).trace(`${e}`);
         return new Response(
-          "oh no, i need to eat more vegetables (｡•́︿•̀｡)...\n",
-          { status: 500 },
+          JSON.stringify({
+            message: "oh no, i need to eat more vegetables (｡•́︿•̀｡)...",
+          }),
+          { status: 500, headers: { "Content-Type": "application/json" } },
         );
       }, (_healthy) => {
         const msg = `think im healthy!! (✿˘◡˘) ready to do work~`;
         trace.trace(msg);
         return new Response(
-          msg + "\n",
-          { status: 200 },
+          JSON.stringify({
+            message: "oh no, i need to eat more vegetables (｡•́︿•̀｡)...",
+          }),
+          { status: 500, headers: { "Content-Type": "application/json" } },
         );
       });
     }));
diff --git a/u/server/activity/mod.ts b/u/server/activity/mod.ts
index 9d05d3c..f0cbed2 100644
--- a/u/server/activity/mod.ts
+++ b/u/server/activity/mod.ts
@@ -1,10 +1,15 @@
-import type { RequestFilter } from "@emprespresso/pengueno";
+import { JsonResponse, type RequestFilter } from "@emprespresso/pengueno";
 
-export class r200 extends Response {
-  public override readonly status = 200;
+export enum StatusOK {
+  FOLLOW = 300,
+  OK = 200,
+}
+export interface ActivityOk {
+  readonly status: StatusOK;
 }
 
-export interface IActivity<Trace> extends RequestFilter<r200, Trace> {
+export interface IActivity<Trace>
+  extends RequestFilter<ActivityOk, Trace, Response> {
 }
 
 export * from "./health.ts";
diff --git a/u/server/filter/json.ts b/u/server/filter/json.ts
index f8e4607..1e05bad 100644
--- a/u/server/filter/json.ts
+++ b/u/server/filter/json.ts
@@ -7,27 +7,30 @@ import {
   TraceUtil,
 } from "@emprespresso/pengueno";
 
-type JsonTransformer<JsonT, R> = (
-  json: ITraceable<JsonT>,
+type JsonTransformer<R, Trace> = (
+  json: ITraceable<unknown, Trace>,
 ) => IEither<Error, R>;
-export const json = <BodyT, Trace, JsonT = unknown>(
-  jsonTransformer: JsonTransformer<JsonT, BodyT>,
-): RequestFilter<BodyT, Trace> =>
+export const json = <BodyT, Trace>(
+  jsonTransformer: JsonTransformer<BodyT, Trace>,
+): RequestFilter<BodyT, Trace, Error> =>
 (r: ITraceable<Request, Trace>) =>
   r.bimap(TraceUtil.withFunctionTrace(json))
-    .map(({ item: request }) => Either.fromFailableAsync(request.json()))
-    .map(
-      TraceUtil.promiseify(({ item: eitherJson, trace }) =>
-        eitherJson.mapLeft((errReason) => {
-          trace.addTrace(LogLevel.WARN).trace(`${errReason}`);
-          const err = "seems to be invalid JSON (>//<) can you fix?";
-          return new Error(err);
-        })
-          .flatMap(jsonTransformer)
-          .mapLeft((err) => {
-            trace.addTrace(LogLevel.WARN).trace(`${err}`);
-            return new Response(err.message, { status: 400 });
+    .map(({ item: request, trace }) =>
+      Either.fromFailableAsync<Error, BodyT>(request.json())
+        .then((either) =>
+          either.mapLeft((errReason) => {
+            trace.addTrace(LogLevel.WARN).trace(`${errReason}`);
+            return new Error("seems to be invalid JSON (>//<) can you fix?");
           })
+        )
+    )
+    .flatMapAsync(
+      TraceUtil.promiseify((traceableEitherJson) =>
+        traceableEitherJson.map(({ item }) =>
+          item.mapRight(traceableEitherJson.move).flatMap(
+            jsonTransformer,
+          )
+        )
       ),
     )
     .item;
diff --git a/u/server/filter/method.ts b/u/server/filter/method.ts
index a1401b4..8d13406 100644
--- a/u/server/filter/method.ts
+++ b/u/server/filter/method.ts
@@ -1,6 +1,7 @@
 import {
   Either,
   type ITraceable,
+  JsonResponse,
   LogLevel,
   type RequestFilter,
   TraceUtil,
@@ -17,22 +18,23 @@ type HttpMethod =
   | "TRACE"
   | "PATCH";
 
-export const requireMethod =
-  <Trace>(methods: Array<HttpMethod>): RequestFilter<HttpMethod, Trace> =>
-  (req: ITraceable<Request, Trace>) =>
-    req.bimap(TraceUtil.withFunctionTrace(requireMethod))
-      .map(({ item }) => Promise.resolve(item))
-      .map(TraceUtil.promiseify(({ item: request, trace }) => {
-        const { method: _method } = request;
-        const method = <HttpMethod> _method;
-        if (!methods.includes(method)) {
-          const msg = "that's not how you pet me (⋟﹏⋞)~";
-          trace.addTrace(LogLevel.WARN).trace(msg);
-          return Either.left<Response, HttpMethod>(
-            new Response(msg + "\n", { status: 405 }),
-          );
-        }
+export const requireMethod = <Trace>(
+  methods: Array<HttpMethod>,
+): RequestFilter<HttpMethod, Trace, JsonResponse> =>
+(req: ITraceable<Request, Trace>) =>
+  req.bimap(TraceUtil.withFunctionTrace(requireMethod))
+    .move(Promise.resolve(req.item))
+    .map(TraceUtil.promiseify(({ item: request, trace }) => {
+      const { method: _method } = request;
+      const method = <HttpMethod> _method;
+      if (!methods.includes(method)) {
+        const msg = "that's not how you pet me (⋟﹏⋞)~";
+        trace.addTrace(LogLevel.WARN).trace(msg);
+        return Either.left<JsonResponse, HttpMethod>(
+          new JsonResponse(msg, { status: 405 }),
+        );
+      }
 
-        return Either.right<Response, HttpMethod>(method);
-      }))
-      .item;
+      return Either.right<JsonResponse, HttpMethod>(method);
+    }))
+    .item;
diff --git a/u/server/filter/mod.ts b/u/server/filter/mod.ts
index 3256d35..78fbd00 100644
--- a/u/server/filter/mod.ts
+++ b/u/server/filter/mod.ts
@@ -3,8 +3,8 @@ import type { IEither, ITraceable } from "@emprespresso/pengueno";
 export interface RequestFilter<
   T,
   Trace,
+  Err,
   RIn = ITraceable<Request, Trace>,
-  Err = Response,
 > {
   (req: RIn): Promise<IEither<Err, T>>;
 }
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"),
+    );
+  }
+}
diff --git a/u/server/mod.ts b/u/server/mod.ts
index 52b26e2..50f82dd 100644
--- a/u/server/mod.ts
+++ b/u/server/mod.ts
@@ -1,2 +1,3 @@
-export * from "./filter/mod.ts";
+export * from "./response.ts";
 export * from "./activity/mod.ts";
+export * from "./filter/mod.ts";
diff --git a/u/server/request.ts b/u/server/request.ts
new file mode 100644
index 0000000..6c4e602
--- /dev/null
+++ b/u/server/request.ts
@@ -0,0 +1,27 @@
+import { ITrace } from "@emprespresso/pengueno";
+import { ITraceWith } from "../trace/mod.ts";
+
+class RequestTraceWith {
+  private constructor(
+    public readonly id: string,
+    public readonly received: Date,
+  ) {
+  }
+
+  public static from() {
+    const id = crypto.randomUUID();
+    const received = new Date();
+    return new RequestTraceWith(id, received);
+  }
+}
+export class RequestTrace implements ITrace<RequestTraceWith> {
+  public readonly requestTrace: RequestTraceWith;
+  constructor(reques);
+
+  public addTrace(_t: ITraceWith<RequestTraceWith>) {
+    return;
+  }
+
+  addTrace: Mapper<ITraceWith<TraceWith>, ITrace<TraceWith>>;
+  trace: SideEffect<ITraceWith<TraceWith>>;
+}
diff --git a/u/server/response.ts b/u/server/response.ts
new file mode 100644
index 0000000..59ca43d
--- /dev/null
+++ b/u/server/response.ts
@@ -0,0 +1,44 @@
+import {
+  type IEither,
+  isEither,
+  type ITraceable,
+} from "@emprespresso/pengueno";
+
+export type ResponseBody = object | string;
+export type TResponseInit = ResponseInit & { status: number };
+const withJsonResponseType = (opts: TResponseInit): TResponseInit => {
+  return {
+    ...opts,
+    headers: {
+      "Content-Type": "application/json",
+      ...(opts?.headers),
+    },
+  };
+};
+
+export class JsonResponse extends Response {
+  constructor(
+    e: ITraceable<IEither<ResponseBody, ResponseBody>>,
+    opts: TResponseInit,
+  ) {
+    const responseOpts = withJsonResponseType(opts);
+    const baseBody = {
+      responseTime: Date.now(),
+    };
+    if (isEither<ResponseBody, ResponseBody>(e)) {
+      super(
+        JSON.stringify(
+          e.fold((err, ok) => err ? ({ error: err! }) : ({ ok: ok! })),
+        ),
+        responseOpts,
+      );
+      return;
+    }
+    super(
+      JSON.stringify(
+        (Math.floor(responseOpts.status / 100) < 4) ? { ok: e } : { error: e },
+      ),
+      responseOpts,
+    );
+  }
+}
-- 
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