1 files changed, 72 insertions, 0 deletions
diff --git a/u/trace/itrace.ts b/u/trace/itrace.ts
new file mode 100644
index 0000000..b483067
--- /dev/null
+++ b/u/trace/itrace.ts
@@ -0,0 +1,72 @@
+import { Mapper, SideEffect } from "../fn/mod.ts";
+
+export interface ITrace<TracingW> {
+  addTrace: Mapper<TracingW, ITrace<TracingW>>;
+  trace: SideEffect<TracingW>;
+}
+
+export type ITraceableTuple<T, Trace> = [T, Trace];
+export type ITraceableMapper<T, Trace, U, W = ITraceable<T, Trace>> = (
+  w: W,
+) => U;
+
+export interface ITraceable<T, Trace> {
+  readonly item: T;
+  readonly trace: ITrace<Trace>;
+
+  move<U>(u: U): ITraceable<U, Trace>;
+  map: <U>(
+    mapper: ITraceableMapper<T, Trace, U>,
+  ) => ITraceable<U, Trace>;
+  bimap: <U>(
+    mapper: ITraceableMapper<T, Trace, ITraceableTuple<U, Trace>>,
+  ) => ITraceable<U, Trace>;
+  peek: (peek: ITraceableMapper<T, Trace, void>) => ITraceable<T, Trace>;
+  flatMap: <U>(
+    mapper: ITraceableMapper<T, Trace, ITraceable<U, Trace>>,
+  ) => ITraceable<U, Trace>;
+  flatMapAsync<U>(
+    mapper: ITraceableMapper<T, Trace, Promise<ITraceable<U, Trace>>>,
+  ): ITraceable<Promise<U>, Trace>;
+}
+
+export class TraceableImpl<T, L> implements ITraceable<T, L> {
+  protected constructor(
+    readonly item: T,
+    readonly trace: ITrace<L>,
+  ) {}
+
+  public map<U>(mapper: ITraceableMapper<T, L, U>) {
+    const result = mapper(this);
+    return new TraceableImpl(result, this.trace);
+  }
+
+  public flatMap<U>(
+    mapper: ITraceableMapper<T, L, ITraceable<U, L>>,
+  ): ITraceable<U, L> {
+    return mapper(this);
+  }
+
+  public flatMapAsync<U>(
+    mapper: ITraceableMapper<T, L, Promise<ITraceable<U, L>>>,
+  ): ITraceable<Promise<U>, L> {
+    return new TraceableImpl(
+      mapper(this).then(({ item }) => item),
+      this.trace,
+    );
+  }
+
+  public peek(peek: ITraceableMapper<T, L, void>) {
+    peek(this);
+    return this;
+  }
+
+  public move<Tt>(t: Tt): ITraceable<Tt, L> {
+    return this.map(() => t);
+  }
+
+  public bimap<U>(mapper: ITraceableMapper<T, L, ITraceableTuple<U, L>>) {
+    const [item, trace] = mapper(this);
+    return new TraceableImpl(item, this.trace.addTrace(trace));
+  }
+}