clipboard watcher

go.mod

@@ -1 +1 @@
-module github.com/atotto/clipboard
+module github.com/tehsphinx/clipboard

watcher.go

@@ -0,0 +1,42 @@
+package clipboard
+
+import (
+	"context"
+	"time"
+)
+
+// Watch returns a channel for new clipboard content whenever it changes.
+// It will return current clipboard content if not empty when initialized.
+// Interval is the time between clipboard checks. Take into account that clickboard
+// checks need a few milliseconds as well.
+func Watch(interval time.Duration) (<-chan string, context.CancelFunc) {
+	var (
+		ch          = make(chan string)
+		lastContent string
+		ctx, cancel = context.WithCancel(context.Background())
+	)
+
+	go func() {
+		defer close(ch)
+
+		for {
+			time.Sleep(interval)
+
+			select {
+			case <-ctx.Done():
+				return
+			default:
+			}
+
+			content, err := ReadAll()
+			if err != nil || content == "" || content == lastContent {
+				continue
+			}
+
+			lastContent = content
+			ch <- content
+		}
+	}()
+
+	return ch, cancel
+}

watcher_test.go

@@ -0,0 +1,44 @@
+package clipboard
+
+import (
+	"fmt"
+	"testing"
+	"time"
+)
+
+func TestChange(t *testing.T) {
+	testStrings := []string{
+		"content 1",
+		"content 2",
+		"content 3",
+	}
+
+	WriteAll("")
+	ch, cancel := Watch(20 * time.Millisecond)
+
+	go func() {
+		for _, c := range testStrings {
+			WriteAll(c)
+			time.Sleep(100 * time.Millisecond)
+		}
+
+		// check if rewriting the same content doesn't affect the test
+		WriteAll("content 3")
+		time.Sleep(100 * time.Millisecond)
+
+		cancel()
+	}()
+
+	var i int
+	for c := range ch {
+		fmt.Println(i, testStrings[i], c)
+		if c != testStrings[i] {
+			t.Errorf("want %s, got %s", testStrings[i], c)
+		}
+		i++
+	}
+
+	if i != 3 {
+		t.Errorf("want %d, got %d", 3, i)
+	}
+}