3 files changed, 125 insertions, 0 deletions
diff --git a/u/server/filter/json.ts b/u/server/filter/json.ts
new file mode 100644
index 0000000..4a2961e
--- /dev/null
+++ b/u/server/filter/json.ts
@@ -0,0 +1,51 @@
+import {
+  Either,
+  type IEither,
+  type ITraceable,
+  LogLevel,
+  Metric,
+  PenguenoError,
+  type PenguenoRequest,
+  type RequestFilter,
+  type ServerTrace,
+  TraceUtil,
+} from "@emprespresso/pengueno";
+
+export interface JsonTransformer<R, ParsedJson = unknown> {
+  (json: ITraceable<ParsedJson, ServerTrace>): IEither<PenguenoError, R>;
+}
+
+const ParseJsonMetric = Metric.fromName("JsonParse");
+export const jsonModel = <MessageT>(
+  jsonTransformer: JsonTransformer<MessageT>,
+): RequestFilter<MessageT> =>
+(r: ITraceable<PenguenoRequest, ServerTrace>) =>
+  r.bimap(TraceUtil.withMetricTrace(ParseJsonMetric))
+    .map((j) =>
+      Either.fromFailableAsync<Error, MessageT>(j.get().json())
+        .then((either) =>
+          either.mapLeft((errReason) => {
+            j.trace.addTrace(LogLevel.WARN).trace(`${errReason}`);
+            return new PenguenoError(
+              "seems to be invalid JSON (>//<) can you fix?",
+              400,
+            );
+          })
+        )
+    )
+    .peek(
+      TraceUtil.promiseify((traceableEither) =>
+        traceableEither.get().mapBoth(
+          () => traceableEither.trace.trace(ParseJsonMetric.failure),
+          () => traceableEither.trace.trace(ParseJsonMetric.success),
+        )
+      ),
+    )
+    .map(
+      TraceUtil.promiseify((traceableEitherJson) =>
+        traceableEitherJson.get()
+          .mapRight(traceableEitherJson.move)
+          .flatMap(jsonTransformer)
+      ),
+    )
+    .get();
diff --git a/u/server/filter/method.ts b/u/server/filter/method.ts
new file mode 100644
index 0000000..6b0419d
--- /dev/null
+++ b/u/server/filter/method.ts
@@ -0,0 +1,41 @@
+import {
+  Either,
+  type ITraceable,
+  LogLevel,
+  PenguenoError,
+  type PenguenoRequest,
+  type RequestFilter,
+  type ServerTrace,
+  TraceUtil,
+} from "@emprespresso/pengueno";
+
+type HttpMethod =
+  | "POST"
+  | "GET"
+  | "HEAD"
+  | "PUT"
+  | "DELETE"
+  | "CONNECT"
+  | "OPTIONS"
+  | "TRACE"
+  | "PATCH";
+
+export const requireMethod = (
+  methods: Array<HttpMethod>,
+): RequestFilter<HttpMethod> =>
+(req: ITraceable<PenguenoRequest, ServerTrace>) =>
+  req.bimap(TraceUtil.withFunctionTrace(requireMethod))
+    .move(Promise.resolve(req.get()))
+    .map(TraceUtil.promiseify((t) => {
+      const { method: _method } = t.get();
+      const method = <HttpMethod> _method;
+      if (!methods.includes(method)) {
+        const msg = "that's not how you pet me (⋟﹏⋞)~";
+        t.trace.addTrace(LogLevel.WARN).trace(msg);
+        return Either.left<PenguenoError, HttpMethod>(
+          new PenguenoError(msg, 405),
+        );
+      }
+      return Either.right<PenguenoError, HttpMethod>(method);
+    }))
+    .get();
diff --git a/u/server/filter/mod.ts b/u/server/filter/mod.ts
new file mode 100644
index 0000000..bbf37df
--- /dev/null
+++ b/u/server/filter/mod.ts
@@ -0,0 +1,33 @@
+import {
+  type IEither,
+  type ITraceable,
+  LogLevel,
+  type PenguenoRequest,
+  type ServerTrace,
+} from "@emprespresso/pengueno";
+
+export enum ErrorSource {
+  USER = LogLevel.WARN,
+  SYSTEM = LogLevel.ERROR,
+}
+
+export class PenguenoError extends Error {
+  public readonly source: ErrorSource;
+  constructor(message: string, public readonly status: number) {
+    super(message);
+    this.source = Math.floor(status / 100) === 4
+      ? ErrorSource.USER
+      : ErrorSource.SYSTEM;
+  }
+}
+
+export interface RequestFilter<
+  T,
+  Err extends PenguenoError = PenguenoError,
+  RIn = ITraceable<PenguenoRequest, ServerTrace>,
+> {
+  (req: RIn): Promise<IEither<Err, T>>;
+}
+
+export * from "./method.ts";
+export * from "./json.ts";