Fix InputView position and deletion

- Fixes #856

spring-shell-core/src/main/java/org/springframework/shell/component/view/control/InputView.java

@@ -67,8 +67,8 @@ public class InputView extends BoxView {
 		String s = getInputText();
 		screen.writerBuilder().build().text(s, rect.x(), rect.y());
 		screen.setShowCursor(hasFocus());
-		int sum = text.stream().limit(cursorIndex).mapToInt(text -> text.length()).sum();
-		screen.setCursorPosition(new Position(rect.x() + sum, rect.y()));
+		int cPos = cursorPosition();
+		screen.setCursorPosition(new Position(rect.x() + cPos, rect.y()));
 		super.drawInternal(screen);
 	}
 
@@ -81,8 +81,12 @@ public class InputView extends BoxView {
 		return text.stream().collect(Collectors.joining());
 	}
 
+	private int cursorPosition() {
+		return text.stream().limit(cursorIndex).mapToInt(text -> text.length()).sum();
+	}
+
 	private void add(String data) {
-		text.add(data);
+		text.add(cursorIndex, data);
 		moveCursor(1);
 	}
 
@@ -94,7 +98,9 @@ public class InputView extends BoxView {
 	}
 
 	private void delete() {
-		text.remove(cursorIndex);
+		if (cursorIndex < text.size()) {
+			text.remove(cursorIndex);
+		}
 	}
 
 	private void moveCursor(int index) {

spring-shell-core/src/test/java/org/springframework/shell/component/view/control/AbstractViewTests.java

@@ -132,6 +132,10 @@ public class AbstractViewTests {
 		return getField(object, field, String.class);
 	}
 
+	protected static int getIntField(Object object, String field) {
+		return getField(object, field, int.class);
+	}
+
 	protected static Runnable getRunnableField(Object object, String field) {
 		return getField(object, field, Runnable.class);
 	}
@@ -141,4 +145,13 @@ public class AbstractViewTests {
 		return (T) ReflectionTestUtils.getField(object, field);
 	}
 
+	protected static int callIntMethod(Object object, String method) {
+		return callMethod(int.class, object, method);
+	}
+
+	@SuppressWarnings("unchecked")
+	protected static <T> T callMethod(Class<T> type, Object object, String method, Object... args) {
+		return (T) ReflectionTestUtils.invokeMethod(object, method, args);
+	}
+
 }

spring-shell-core/src/test/java/org/springframework/shell/component/view/control/InputViewTests.java

@@ -28,6 +28,7 @@ import static org.assertj.core.api.Assertions.assertThat;
 class InputViewTests extends AbstractViewTests {
 
 	private static final String CURSOR_INDEX_FIELD = "cursorIndex";
+	private static final String CURSOR_POSITION_METHOD = "cursorPosition";
 
 	@Nested
 	class Input {
@@ -135,16 +136,49 @@ class InputViewTests extends AbstractViewTests {
 			configure(view);
 		}
 
-		int cursorIndex() {
-			return (Integer) ReflectionTestUtils.getField(view, CURSOR_INDEX_FIELD);
-		}
-
 		@Test
 		void addEmojiAndBackspace() {
 			handleKey(view, "😂");
-			assertThat(cursorIndex()).isEqualTo(1);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(1);
 			handleKey(view, Key.Backspace);
-			assertThat(cursorIndex()).isEqualTo(0);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(0);
+		}
+
+		@Test
+		void deleteFromLastPosition() {
+			handleKey(view, Key.Delete);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(0);
+			handleKey(view, Key.a);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(1);
+		}
+
+	}
+
+	@Nested
+	class MoveAndMods {
+
+		InputView view;
+
+		@BeforeEach
+		void setup() {
+			view = new InputView();
+			configure(view);
+		}
+
+		@Test
+		void shouldAddToCursorPosition() {
+			assertThat(callIntMethod(view, CURSOR_POSITION_METHOD)).isEqualTo(0);
+			handleKey(view, Key.a);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(1);
+			assertThat(view.getInputText()).isEqualTo("a");
+			assertThat(callIntMethod(view, CURSOR_POSITION_METHOD)).isEqualTo(1);
+
+			handleKey(view, Key.CursorLeft);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(0);
+
+			handleKey(view, Key.b);
+			assertThat(getIntField(view, CURSOR_INDEX_FIELD)).isEqualTo(1);
+			assertThat(view.getInputText()).isEqualTo("ba");
 		}
 
 	}