From 079a597be475bc637be599ea14bebc223fd7b8ff Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Sebastian=20D=C3=B6ll?= <sebastian@katallaxie.dev>
Date: Fri, 25 Oct 2024 20:00:16 +0000
Subject: [PATCH] feat: filter channel

---
 channels/channels.go      | 16 ++++++++++++++++
 channels/channels_test.go | 22 ++++++++++++++++++++++
 2 files changed, 38 insertions(+)

diff --git a/channels/channels.go b/channels/channels.go
index f0f4d1e..d5ad8e2 100644
--- a/channels/channels.go
+++ b/channels/channels.go
@@ -55,3 +55,19 @@ func Drain[T any](input <-chan T) {
 		}
 	}()
 }
+
+// Filter filters the channel with the given function.
+func Filter[T any](input <-chan T, fn func(T) bool) <-chan T {
+	c := make(chan T)
+
+	go func() {
+		defer close(c)
+		for v := range input {
+			if fn(v) {
+				c <- v
+			}
+		}
+	}()
+
+	return c
+}
diff --git a/channels/channels_test.go b/channels/channels_test.go
index f74fbb8..be051a6 100644
--- a/channels/channels_test.go
+++ b/channels/channels_test.go
@@ -41,3 +41,25 @@ func TestDrain(t *testing.T) {
 
 	require.Empty(t, in, 0)
 }
+
+func TestFilter(t *testing.T) {
+	in := make(chan int)
+	out := Filter(in, func(v int) bool {
+		return v%2 == 0
+	})
+
+	go func() {
+		in <- 1
+		in <- 2
+		in <- 3
+		close(in)
+	}()
+
+	el := []int{}
+
+	for v := range out {
+		el = append(el, v)
+	}
+
+	assert.Equal(t, []int{2}, el)
+}