Refactor c/beer-song/beer_song.c

c/beer-song/src/beer_song.c

@@ -1,7 +1,7 @@
 #include <stdio.h>
 
 int verse(char* response, int bottles) {
-  if (bottles < 0) {
+	if (response == NULL || bottles < 0) {
 		return 0;
 	}
 
@@ -39,19 +39,21 @@ int verse(char* response, int bottles) {
 }
 
 void sing(char *response, int start, int finish) {
+	if (response == NULL || start < 0 || finish < 0 || start <= finish) {
+		return;
+	}
+
 	char *origin = response;
 
 	for (int bottles = start; bottles >= finish; bottles--) {
-    int charsAdded = verse(response, bottles);
-    response += charsAdded;
+		int charsAdded = verse(origin, bottles);
+		origin += charsAdded;
 
 		// Add a newline between verses,
 		// except for the last verse.
 		if (bottles != finish) {
-      sprintf(response, "\n");
-      response += 1;
+			sprintf(origin, "\n");
+			origin += 1;
 		}
 	}
-
-  response = origin;
 }