1 files changed, 111 insertions, 0 deletions
diff --git a/utils/trace.ts b/utils/trace.ts
new file mode 100644
index 0000000..737aa60
--- /dev/null
+++ b/utils/trace.ts
@@ -0,0 +1,111 @@
+export interface Logger {
+  log: (...args: unknown[]) => void;
+  debug: (...args: unknown[]) => void;
+  warn: (...args: unknown[]) => void;
+  error: (...args: unknown[]) => void;
+}
+
+type Supplier<T> = () => T;
+type TraceSupplier = Supplier<string>;
+export interface ITraceableLogger<L extends ITraceableLogger<L>>
+  extends Logger {
+  addTracer: (traceSupplier: TraceSupplier) => L;
+}
+
+export type ITraceableTuple<T> = [T, TraceSupplier];
+export type ITraceableMapper<T, L extends ITraceableLogger<L>, U> = (
+  t: ITraceable<T, L>,
+) => U;
+export interface ITraceable<T, L extends ITraceableLogger<L>> {
+  item: T;
+  logger: L;
+
+  map: <U>(mapper: ITraceableMapper<T, L, U>) => ITraceable<U, L>;
+  bimap: <U>(
+    mapper: ITraceableMapper<T, L, ITraceableTuple<U>>,
+  ) => ITraceable<U, L>;
+  peek: (peek: ITraceableMapper<T, L, void>) => ITraceable<T, L>;
+  flatMap: <U>(mapper: ITraceableMapper<T, L, ITraceable<U, L>>) => ITraceable<U, L>;
+  flatMapAsync<U>(mapper: ITraceableMapper<T, L, Promise<ITraceable<U, L>>>): ITraceable<Promise<U>, L>;
+}
+
+export class TraceableLogger
+  implements ITraceableLogger<TraceableLogger> {
+  private readonly logger: Logger = console;
+  constructor(
+    private readonly traces = [() => `[${new Date().toISOString()}]`],
+  ) {
+  }
+
+  public debug(...args: unknown[]) {
+    this.logger.debug("[DEBUG]", ...this.getPrefix(), args);
+  }
+
+  public log(...args: unknown[]) {
+    this.logger.log("[INFO]", ...this.getPrefix(), args);
+  }
+
+  public warn(...args: unknown[]) {
+    this.logger.warn("[WARN]", ...this.getPrefix(), args);
+  }
+
+  public error(...args: unknown[]) {
+    this.logger.error("[ERROR]", ...this.getPrefix(), args);
+  }
+
+  public addTracer(traceSupplier: TraceSupplier) {
+    return new TraceableLogger(this.traces.concat(traceSupplier));
+  }
+
+  private getPrefix() {
+    return this.traces.map((tracer) => tracer());
+  }
+}
+
+export class TraceableImpl<
+  T,
+  L extends ITraceableLogger<L>,
+> implements ITraceable<T, L> {
+  private constructor(readonly item: T, readonly logger: L) {}
+
+  public map<U>(mapper: ITraceableMapper<T, L, U>) {
+    const result = mapper(this);
+    return new TraceableImpl(result, this.logger);
+  }
+
+  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((i) => )
+  }
+
+  public peek(peek: ITraceableMapper<T, L, void>) {
+    peek(this);
+    return this;
+  }
+
+  public bimap<U>(mapper: ITraceableMapper<T, L, ITraceableTuple<U>>) {
+    const [item, trace] = mapper(this);
+    return new TraceableImpl(item, this.logger.addTracer(trace));
+  }
+
+  static promiseify<T, L extends ITraceableLogger<L>, U>(
+    mapper: ITraceableMapper<T, L, U>,
+  ): ITraceableMapper<Promise<T>, L, Promise<U>> {
+    return (traceablePromise) => traceablePromise.map(
+      async ({ item: promise }) => {
+        const t = await promise;
+        return traceablePromise.map(() => t).map(mapper).item;
+      });
+//    return (traceable) =>
+//      traceable.item.then((item) => mapper(new TraceableImpl(item, traceable.logger)));
+  }
+
+  static from<T>(t: T) {
+    return new TraceableImpl(t, new TraceableLogger());
+  }
+}
+
+export interface Traceable<T> extends ITraceable<T, TraceableLogger>