input.New refactor and test

src/device/input/input.go

@@ -3,6 +3,7 @@ package input
 import (
 	"context"
 	"os"
+	"syscall"
 )
 
 type Input interface {
@@ -11,19 +12,46 @@ type Input interface {
 }
 
 func New(ctx context.Context) Input {
-	foo := randomCharFromRange('a', 'g')
-	if p, ok := os.LookupEnv("INPUT_RANDOM_WEIGHT_FILE"); ok && len(p) > 0 {
-		foo = randomCharFromWeightFile(p)
-	}
-	var result Input = NewRandom(foo)
-	if os.Getenv("INPUT_KEYBOARD") == "true" {
-		result = NewKeyboard()
-	}
-	if os.Getenv("INPUT_BUFFERED") == "true" {
-		result = NewBuffered(ctx, result)
-	}
-	if p, ok := os.LookupEnv("INPUT_REMAP_FILE"); ok && len(p) > 0 {
-		result = NewRemapFromFile(result, p)
-	}
-	return result
+	return newNew(ctx)()
+}
+
+func newNew(ctx context.Context) func() Input {
+	maker := newSourceFunc()
+
+	if os.Getenv("INPUT_BUFFERED") == "true" {
+		oldMaker := maker
+		maker = func() Input {
+			return NewBuffered(ctx, oldMaker())
+		}
+	}
+	if p := os.Getenv("INPUT_REMAP_FILE"); p != "" {
+		oldMaker := maker
+		maker = func() Input {
+			return NewRemapFromFile(oldMaker(), p)
+		}
+	}
+	if os.Getenv("INPUT_REFRESH_ON_SIGUSR1") != "" {
+		oldMaker := maker
+		c := NewRefreshCh(syscall.SIGUSR1)
+		maker = func() Input {
+			return NewRefresh(oldMaker, c)
+		}
+	}
+	return maker
+}
+
+func newSourceFunc() func() Input {
+	if os.Getenv("INPUT_KEYBOARD") == "true" {
+		singletonKeyboard := NewKeyboard()
+		return func() Input {
+			return singletonKeyboard
+		}
+	}
+	return func() Input {
+		generator := randomCharFromRange('a', 'g')
+		if p, ok := os.LookupEnv("INPUT_RANDOM_WEIGHT_FILE"); ok && len(p) > 0 {
+			generator = randomCharFromWeightFile(p)
+		}
+		return NewRandom(generator)
+	}
 }