From 75368c8ef8462c9eb60e9ea075982ea5c9634906 Mon Sep 17 00:00:00 2001
From: Eric Rumsey <ehrumsey@gmail.com>
Date: Tue, 27 May 2025 16:31:00 -0500
Subject: [PATCH] Add Do notation for option

---
 src/lib/util/basic/option.ts | 39 +++++++++++++++++++++++++++++++++---
 1 file changed, 36 insertions(+), 3 deletions(-)

diff --git a/src/lib/util/basic/option.ts b/src/lib/util/basic/option.ts
index 165c0c1..a036e00 100644
--- a/src/lib/util/basic/option.ts
+++ b/src/lib/util/basic/option.ts
@@ -10,9 +10,8 @@ export const some = <A>(value: A): Option<A> => ({
 })
 
 // Operations
-export const map =
-  <A, B>(f: (a: A) => B) => (fa: Option<A>): Option<B> =>
-    fa._tag === 'Some' ? some(f(fa.value)) : none
+export const map = <A, B>(f: (a: A) => B) => (fa: Option<A>): Option<B> =>
+  fa._tag === 'Some' ? some(f(fa.value)) : none
 
 export const chain =
   <A, B>(f: (a: A) => Option<B>) => (fa: Option<A>): Option<B> =>
@@ -20,3 +19,37 @@ export const chain =
 
 export const getOrElse = <A>(defaultValue: A) => (fa: Option<A>): A =>
   fa._tag === 'Some' ? fa.value : defaultValue
+
+export class DoOption<T extends Record<string, unknown>> {
+  constructor(private readonly option: Option<T>) {}
+
+  bind<K extends string, A>(key: K, fa: Option<A>): DoOption<T & Record<K, A>> {
+    const newOption = chain((scope: T) =>
+      map((a: A) => ({...scope, [key]: a}))(fa)
+    )(this.option)
+    return new DoOption(newOption as Option<T & Record<K, A>>)
+  }
+
+  return<B>(f: (scope: T) => B): Option<B> {
+    return map(f)(this.option)
+  }
+
+  done(): Option<T> {
+    return this.option
+  }
+  do(fa: Option<unknown>): DoOption<T> {
+    const newOption = chain((scope: T) => map(() => scope)(fa))(this.option)
+    return new DoOption(newOption)
+  }
+
+  doL(f: (scope: T) => Option<unknown>): DoOption<T> {
+    const newOption = chain((scope: T) => map(() => scope)(f(scope)))(
+      this.option,
+    )
+    return new DoOption(newOption)
+  }
+
+  static start(): DoOption<{}> {
+    return new DoOption(some({}))
+  }
+}