From d4791f3d357634daf506fb8f91cc5332a794c421 Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <me@liz.coffee>
Date: Fri, 20 Jun 2025 14:53:38 -0700
Subject: Move to nodejs

---
 u/fn/either.ts | 180 ++++++++++++++++++++++++++-------------------------------
 1 file changed, 83 insertions(+), 97 deletions(-)

(limited to 'u/fn/either.ts')

diff --git a/u/fn/either.ts b/u/fn/either.ts
index ffe8033..8c47b64 100644
--- a/u/fn/either.ts
+++ b/u/fn/either.ts
@@ -1,114 +1,100 @@
-import { type Mapper, type Supplier, isObject } from "@emprespresso/pengueno";
+import { type Mapper, type Supplier, isObject } from '@emprespresso/pengueno';
 
-type IEitherTag = "IEither";
-const iEitherTag: IEitherTag = "IEither";
+type IEitherTag = 'IEither';
+const iEitherTag: IEitherTag = 'IEither';
 
 export interface _Either<LeftT, RightT, T> {
-  readonly isLeft: LeftT;
-  readonly isRight: RightT;
-  readonly value: T;
+    readonly isLeft: LeftT;
+    readonly isRight: RightT;
+    readonly value: T;
 }
 export type Left<E> = _Either<true, false, E>;
 export type Right<T> = _Either<false, true, T>;
 
 export interface IEither<E, T> {
-  readonly _tag: IEitherTag;
-
-  mapBoth: <_E, _T>(
-    errBranch: Mapper<E, _E>,
-    okBranch: Mapper<T, _T>,
-  ) => IEither<_E, _T>;
-  fold: <_T>(folder: Mapper<Left<E> | Right<T>, _T>) => _T;
-  moveRight: <_T>(t: _T) => IEither<E, _T>;
-  mapRight: <_T>(mapper: Mapper<T, _T>) => IEither<E, _T>;
-  mapLeft: <_E>(mapper: Mapper<E, _E>) => IEither<_E, T>;
-  flatMap: <_T>(mapper: Mapper<T, IEither<E, _T>>) => IEither<E, _T>;
-  flatMapAsync: <_T>(
-    mapper: Mapper<T, Promise<IEither<E, _T>>>,
-  ) => Promise<IEither<E, _T>>;
+    readonly _tag: IEitherTag;
+
+    mapBoth: <_E, _T>(errBranch: Mapper<E, _E>, okBranch: Mapper<T, _T>) => IEither<_E, _T>;
+    fold: <_T>(folder: Mapper<Left<E> | Right<T>, _T>) => _T;
+    moveRight: <_T>(t: _T) => IEither<E, _T>;
+    mapRight: <_T>(mapper: Mapper<T, _T>) => IEither<E, _T>;
+    mapLeft: <_E>(mapper: Mapper<E, _E>) => IEither<_E, T>;
+    flatMap: <_T>(mapper: Mapper<T, IEither<E, _T>>) => IEither<E, _T>;
+    flatMapAsync: <_T>(mapper: Mapper<T, Promise<IEither<E, _T>>>) => Promise<IEither<E, _T>>;
 }
 
 export class Either<E, T> implements IEither<E, T> {
-  private readonly self: Left<E> | Right<T>;
-
-  private constructor(
-    init: { err?: E; ok?: T },
-    public readonly _tag: IEitherTag = iEitherTag,
-  ) {
-    this.self = <Left<E> | Right<T>>{
-      isLeft: "err" in init,
-      isRight: "ok" in init,
-      value: init.err ?? init.ok!,
-    };
-  }
-
-  public moveRight<_T>(t: _T) {
-    return this.mapRight(() => t);
-  }
-
-  public fold<_T>(folder: Mapper<Left<E> | Right<T>, _T>): _T {
-    return folder(this.self);
-  }
-
-  public mapBoth<_E, _T>(
-    errBranch: Mapper<E, _E>,
-    okBranch: Mapper<T, _T>,
-  ): IEither<_E, _T> {
-    if (this.self.isLeft) return Either.left(errBranch(this.self.value));
-    return Either.right(okBranch(this.self.value));
-  }
-
-  public flatMap<_T>(mapper: Mapper<T, IEither<E, _T>>): IEither<E, _T> {
-    if (this.self.isRight) return mapper(this.self.value);
-    return Either.left<E, _T>(this.self.value);
-  }
-
-  public mapRight<_T>(mapper: Mapper<T, _T>): IEither<E, _T> {
-    if (this.self.isRight) return Either.right<E, _T>(mapper(this.self.value));
-    return Either.left<E, _T>(this.self.value);
-  }
-
-  public mapLeft<_E>(mapper: Mapper<E, _E>): IEither<_E, T> {
-    if (this.self.isLeft) return Either.left<_E, T>(mapper(this.self.value));
-    return Either.right<_E, T>(this.self.value);
-  }
-
-  public async flatMapAsync<_T>(
-    mapper: Mapper<T, Promise<IEither<E, _T>>>,
-  ): Promise<IEither<E, _T>> {
-    if (this.self.isLeft) {
-      return Promise.resolve(Either.left<E, _T>(this.self.value));
+    private readonly self: Left<E> | Right<T>;
+
+    private constructor(
+        init: { err?: E; ok?: T },
+        public readonly _tag: IEitherTag = iEitherTag,
+    ) {
+        this.self = <Left<E> | Right<T>>{
+            isLeft: 'err' in init,
+            isRight: 'ok' in init,
+            value: init.err ?? init.ok!,
+        };
     }
-    return await mapper(this.self.value).catch((err) =>
-      Either.left<E, _T>(err),
-    );
-  }
-
-  static left<E, T>(e: E): IEither<E, T> {
-    return new Either<E, T>({ err: e });
-  }
-
-  static right<E, T>(t: T): IEither<E, T> {
-    return new Either<E, T>({ ok: t });
-  }
-
-  static fromFailable<E, T>(s: Supplier<T>): IEither<E, T> {
-    try {
-      return Either.right<E, T>(s());
-    } catch (e) {
-      return Either.left<E, T>(e as E);
+
+    public moveRight<_T>(t: _T) {
+        return this.mapRight(() => t);
+    }
+
+    public fold<_T>(folder: Mapper<Left<E> | Right<T>, _T>): _T {
+        return folder(this.self);
+    }
+
+    public mapBoth<_E, _T>(errBranch: Mapper<E, _E>, okBranch: Mapper<T, _T>): IEither<_E, _T> {
+        if (this.self.isLeft) return Either.left(errBranch(this.self.value));
+        return Either.right(okBranch(this.self.value));
+    }
+
+    public flatMap<_T>(mapper: Mapper<T, IEither<E, _T>>): IEither<E, _T> {
+        if (this.self.isRight) return mapper(this.self.value);
+        return Either.left<E, _T>(this.self.value);
+    }
+
+    public mapRight<_T>(mapper: Mapper<T, _T>): IEither<E, _T> {
+        if (this.self.isRight) return Either.right<E, _T>(mapper(this.self.value));
+        return Either.left<E, _T>(this.self.value);
+    }
+
+    public mapLeft<_E>(mapper: Mapper<E, _E>): IEither<_E, T> {
+        if (this.self.isLeft) return Either.left<_E, T>(mapper(this.self.value));
+        return Either.right<_E, T>(this.self.value);
+    }
+
+    public async flatMapAsync<_T>(mapper: Mapper<T, Promise<IEither<E, _T>>>): Promise<IEither<E, _T>> {
+        if (this.self.isLeft) {
+            return Promise.resolve(Either.left<E, _T>(this.self.value));
+        }
+        return await mapper(this.self.value).catch((err) => Either.left<E, _T>(err));
+    }
+
+    static left<E, T>(e: E): IEither<E, T> {
+        return new Either<E, T>({ err: e });
+    }
+
+    static right<E, T>(t: T): IEither<E, T> {
+        return new Either<E, T>({ ok: t });
+    }
+
+    static fromFailable<E, T>(s: Supplier<T>): IEither<E, T> {
+        try {
+            return Either.right<E, T>(s());
+        } catch (e) {
+            return Either.left<E, T>(e as E);
+        }
+    }
+
+    static async fromFailableAsync<E, T>(s: Supplier<Promise<T>> | Promise<T>): Promise<IEither<E, T>> {
+        return await (typeof s === 'function' ? s() : s)
+            .then((t: T) => Either.right<E, T>(t))
+            .catch((e: E) => Either.left<E, T>(e));
     }
-  }
-
-  static async fromFailableAsync<E, T>(
-    s: Supplier<Promise<T>>,
-  ): Promise<IEither<E, T>> {
-    return await s()
-      .then((t: T) => Either.right<E, T>(t))
-      .catch((e: E) => Either.left<E, T>(e));
-  }
 }
 
 export const isEither = <E, T>(o: unknown): o is IEither<E, T> => {
-  return isObject(o) && "_tag" in o && o._tag === "IEither";
+    return isObject(o) && '_tag' in o && o._tag === 'IEither';
 };
-- 
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