From a054cb04fe590f9dfbf26bc9062abff6dc560d6e Mon Sep 17 00:00:00 2001
From: Tim <hello@timsmart.co>
Date: Wed, 7 Feb 2024 17:36:42 +1300
Subject: [PATCH] add releaseAll api to Semaphore

---
 .changeset/chilly-birds-eat.md                |  8 +++++
 packages/effect/src/Effect.ts                 |  1 +
 .../effect/src/internal/effect/circular.ts    | 32 ++++++++++++-------
 packages/effect/test/Effect/semaphore.test.ts |  8 +++++
 4 files changed, 38 insertions(+), 11 deletions(-)
 create mode 100644 .changeset/chilly-birds-eat.md

diff --git a/.changeset/chilly-birds-eat.md b/.changeset/chilly-birds-eat.md
new file mode 100644
index 0000000000..4ff61292fd
--- /dev/null
+++ b/.changeset/chilly-birds-eat.md
@@ -0,0 +1,8 @@
+---
+"effect": patch
+---
+
+add releaseAll api to Semaphore
+
+You can use `semphore.releaseAll` to atomically release all the permits of a
+Semaphore.
diff --git a/packages/effect/src/Effect.ts b/packages/effect/src/Effect.ts
index 4ec45641f8..029b31c602 100644
--- a/packages/effect/src/Effect.ts
+++ b/packages/effect/src/Effect.ts
@@ -4689,6 +4689,7 @@ export interface Semaphore {
   withPermits(permits: number): <R, E, A>(self: Effect<R, E, A>) => Effect<R, E, A>
   take(permits: number): Effect<never, never, number>
   release(permits: number): Effect<never, never, void>
+  releaseAll: Effect<never, never, void>
 }
 
 /**
diff --git a/packages/effect/src/internal/effect/circular.ts b/packages/effect/src/internal/effect/circular.ts
index 1f0221ee80..f35a41a706 100644
--- a/packages/effect/src/internal/effect/circular.ts
+++ b/packages/effect/src/internal/effect/circular.ts
@@ -35,7 +35,7 @@ import * as supervisor from "../supervisor.js"
 
 /** @internal */
 class Semaphore {
-  public waiters = new Array<() => void>()
+  public waiters = new Array<() => boolean>()
   public taken = 0
 
   constructor(readonly permits: number) {}
@@ -48,14 +48,16 @@ class Semaphore {
     core.asyncEither<never, never, number>((resume) => {
       if (this.free < n) {
         const observer = () => {
-          if (this.free >= n) {
-            const observerIndex = this.waiters.findIndex((cb) => cb === observer)
-            if (observerIndex !== -1) {
-              this.waiters.splice(observerIndex, 1)
-            }
-            this.taken += n
-            resume(core.succeed(n))
+          if (this.free < n) {
+            return false
+          }
+          const observerIndex = this.waiters.findIndex((cb) => cb === observer)
+          if (observerIndex !== -1) {
+            this.waiters.splice(observerIndex, 1)
           }
+          this.taken += n
+          resume(core.succeed(n))
+          return true
         }
         this.waiters.push(observer)
         return Either.left(core.sync(() => {
@@ -69,15 +71,23 @@ class Semaphore {
       return Either.right(core.succeed(n))
     })
 
-  readonly release = (n: number): Effect.Effect<never, never, void> =>
+  readonly updateTaken = (f: (n: number) => number): Effect.Effect<never, never, void> =>
     core.withFiberRuntime<never, never, void>((fiber) => {
-      this.taken -= n
+      this.taken = f(this.taken)
       fiber.getFiberRef(currentScheduler).scheduleTask(() => {
-        this.waiters.forEach((wake) => wake())
+        while (this.waiters.length > 0) {
+          if (this.waiters[0]() === false) {
+            break
+          }
+        }
       }, fiber.getFiberRef(core.currentSchedulingPriority))
       return core.unit
     })
 
+  readonly release = (n: number): Effect.Effect<never, never, void> => this.updateTaken((taken) => taken - n)
+
+  readonly releaseAll: Effect.Effect<never, never, void> = this.updateTaken((_) => 0)
+
   readonly withPermits = (n: number) => <R, E, A>(self: Effect.Effect<R, E, A>) =>
     core.uninterruptibleMask((restore) =>
       core.flatMap(
diff --git a/packages/effect/test/Effect/semaphore.test.ts b/packages/effect/test/Effect/semaphore.test.ts
index d2fa9b851d..386af6b650 100644
--- a/packages/effect/test/Effect/semaphore.test.ts
+++ b/packages/effect/test/Effect/semaphore.test.ts
@@ -34,4 +34,12 @@ describe("Effect", () => {
       yield* $(TestClock.adjust(D.seconds(3)))
       assert.equal(messages.length, 8)
     }))
+
+  it.effect("releaseAll", () =>
+    Effect.gen(function*(_) {
+      const sem = yield* _(Effect.makeSemaphore(4))
+      yield* _(sem.take(4))
+      yield* _(sem.releaseAll)
+      yield* _(sem.take(1))
+    }))
 })