Moving bulk of console runner into library func

conway/conways-game-of-life/main.go

@@ -4,7 +4,6 @@ import (
 	"flag"
 	"fmt"
 	"os"
-	"time"
 )
 
 import (
@@ -22,37 +21,10 @@ var (
 func main() {
 	flag.Parse()
 
-	game := NewGameOfLife(*height, *width)
-	err := game.ImportRandomState()
+	retCode, err := RunConsoleGame(*height, *width, *sleepMs, *mutate)
 	if err != nil {
-		fmt.Fprintf(os.Stderr, "WHAT IN FAIL?: %v\n", err)
-		os.Exit(2)
+		fmt.Fprintf(os.Stderr, "ERROR: %v\n", err)
 	}
 
-	genTicks, err := game.Generations()
-	if err != nil {
-		fmt.Fprintf(os.Stderr, "No generations?: %v\n", err)
-		os.Exit(3)
-	}
-
-	sleepInterval := time.Duration(*sleepMs * 1000 * 1000)
-	for genTick := range genTicks {
-		fmt.Printf("\nGeneration %v\n%v\n", genTick.N, time.Now())
-		fmt.Println(game)
-
-		if genTick.Error != nil {
-			fmt.Fprintf(os.Stderr, "%s: %s\n", genTick.Message, genTick.Error)
-			os.Exit(4)
-		}
-
-		if len(genTick.Message) > 0 {
-			fmt.Println(genTick.Message)
-		}
-
-		if *mutate && genTick.N%2 == 0 {
-			game.Mutate()
-		}
-
-		time.Sleep(sleepInterval)
-	}
+	os.Exit(retCode)
 }

conway/game_of_life.go

@@ -15,6 +15,42 @@ type GameOfLife struct {
 	State *GameState
 }
 
+func RunConsoleGame(height, width, sleepMs int, mutate bool) (int, error) {
+	sleepInterval := time.Duration(sleepMs * 1000 * 1000)
+
+	game := NewGameOfLife(height, width)
+	err := game.ImportRandomState()
+	if err != nil {
+		return 2, err
+	}
+
+	genTicks, err := game.Generations()
+	if err != nil {
+		return 3, err
+	}
+
+	for genTick := range genTicks {
+		fmt.Printf("\nGeneration %v\n%v\n", genTick.N, time.Now())
+		fmt.Println(game)
+
+		if genTick.Error != nil {
+			return 4, genTick.Error
+		}
+
+		if len(genTick.Message) > 0 {
+			fmt.Println(genTick.Message)
+		}
+
+		if mutate && genTick.N%2 == 0 {
+			game.Mutate()
+		}
+
+		time.Sleep(sleepInterval)
+	}
+
+	return 0, nil
+}
+
 func (game *GameOfLife) Mutate() error {
 	return game.State.Mutate()
 }