From f008c002915ee19b5bf93b6cae648f10ca861a22 Mon Sep 17 00:00:00 2001
From: Elizabeth Hunt <me@liz.coffee>
Date: Thu, 3 Jul 2025 13:14:29 -0700
Subject: Adds join functions to Eithers

---
 u/process/env.ts     | 42 ++++++++++++++++++------------------------
 u/types/fn/either.ts | 21 ++++++++++++++++++++-
 2 files changed, 38 insertions(+), 25 deletions(-)

(limited to 'u')

diff --git a/u/process/env.ts b/u/process/env.ts
index 76961c9..88fb490 100644
--- a/u/process/env.ts
+++ b/u/process/env.ts
@@ -1,33 +1,27 @@
 import { IOptional, Either, Optional, type IEither } from '@emprespresso/pengueno';
 
-export const getEnv = <V extends string>(name: string): IOptional<V> =>
-    Optional.from(<V>process.env[name]).filter((val) => val.trim() !== '');
+export const getEnv = <V extends string>(name: string): IOptional<V> => Optional.from(<V>process.env[name]);
 
 export const getRequiredEnv = <V extends string>(name: string): IEither<Error, V> =>
-    getEnv<V>(name)
-        .map((envVal) => Either.right<Error, V>(<V>envVal))
-        .orSome(() => Either.left<Error, V>(new Error(`environment variable "${name}" is required D:`)))
-        .get();
+    Either.fromFailable(() => getEnv<V>(name).get()).mapLeft(
+        () => new Error(`environment variable "${name}" is required D:`),
+    );
 
 type ObjectFromList<T extends ReadonlyArray<string>, V = string> = {
     [K in T extends ReadonlyArray<infer U> ? U : never]: V;
 };
 
-export const getRequiredEnvVars = <V extends string>(vars: ReadonlyArray<V>) =>
-    vars
-        .map((envVar) => [envVar, getRequiredEnv(envVar)] as [V, IEither<Error, V>])
-        .reduce(
-            (acc: IEither<Error, ObjectFromList<typeof vars>>, x: [V, IEither<Error, V>]) => {
-                const [envVar, eitherVal] = x;
-                return acc.flatMap((args) => {
-                    return eitherVal.mapRight(
-                        (envValue) =>
-                            ({
-                                ...args,
-                                [envVar]: envValue,
-                            }) as ObjectFromList<typeof vars>,
-                    );
-                });
-            },
-            Either.right({} as ObjectFromList<typeof vars>),
-        );
+export const getRequiredEnvVars = <V extends string>(vars: Array<V>) => {
+    type Environment = ObjectFromList<typeof vars>;
+    const emptyEnvironment = Either.right<Error, Environment>(<Environment>{});
+    const addTo = (env: Environment, key: V) => (val: string) =>
+        <Environment>{
+            ...env,
+            [key]: val,
+        };
+    return Either.joinRight<V, Error, Environment>(
+        vars,
+        (envVar: V, environment: Environment) => getRequiredEnv(envVar).mapRight(addTo(environment, envVar)),
+        emptyEnvironment,
+    );
+};
diff --git a/u/types/fn/either.ts b/u/types/fn/either.ts
index 6140ada..aa67d41 100644
--- a/u/types/fn/either.ts
+++ b/u/types/fn/either.ts
@@ -1,4 +1,4 @@
-import { IOptional, type Mapper, Optional, type Supplier, Tagged, isTagged } from '@emprespresso/pengueno';
+import { BiMapper, IOptional, type Mapper, Optional, type Supplier, Tagged, isTagged } from '@emprespresso/pengueno';
 
 export const IEitherTag = 'IEither' as const;
 export type IEitherTag = typeof IEitherTag;
@@ -82,6 +82,25 @@ export class Either<E, T> extends _Tagged implements IEither<E, T> {
         return Optional.none();
     }
 
+    static joinRight<K, E, T>(
+        arr: Array<K>,
+        mapper: BiMapper<K, T, IEither<E, T>>,
+        init: IEither<E, T>,
+    ): IEither<E, T> {
+        return arr.reduce((acc: IEither<E, T>, x: K) => acc.flatMap((t) => mapper(x, t)), init);
+    }
+
+    static joinRightAsync<K, E, T>(
+        arr: Array<K>,
+        mapper: BiMapper<K, T, Promise<IEither<E, T>>>,
+        init: IEither<E, T>,
+    ): Promise<IEither<E, T>> {
+        return arr.reduce(
+            (acc: Promise<IEither<E, T>>, x: K) => acc.then((res) => res.flatMapAsync((t) => mapper(x, t))),
+            Promise.resolve(init),
+        );
+    }
+
     static left<E, T>(e: E): IEither<E, T> {
         return new Either({ err: e, _tag: ELeftTag });
     }
-- 
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