Save history even when calculation doesn't happen on-the-fly

app/src/main/java/org/solovyev/android/calculator/Calculator.java

@@ -102,17 +102,12 @@ public class Calculator implements SharedPreferences.OnSharedPreferenceChangeLis
 
     public void evaluate() {
         final EditorState state = editor.getState();
-        evaluate(JsclOperation.numeric, state.getTextString());
+        evaluate(JsclOperation.numeric, state.getTextString(), state.sequence);
     }
 
     public void simplify() {
         final EditorState state = editor.getState();
-        evaluate(JsclOperation.simplify, state.getTextString());
-    }
-
-    public long evaluate(@Nonnull final JsclOperation operation,
-            @Nonnull final String expression) {
-        return evaluate(operation, expression, nextSequence());
+        evaluate(JsclOperation.simplify, state.getTextString(), state.sequence);
     }
 
     public long evaluate(@Nonnull final JsclOperation operation, @Nonnull final String expression,
@@ -343,5 +338,4 @@ public class Calculator implements SharedPreferences.OnSharedPreferenceChangeLis
     public static long nextSequence() {
         return SEQUENCER.incrementAndGet();
     }
-
 }

app/src/main/java/org/solovyev/android/calculator/history/History.java

@@ -254,8 +254,9 @@ public class History {
             // don't add empty states to empty history
             return;
         }
-        recent.add(state);
-        onRecentChanged(new AddedEvent(state, true));
+        if (recent.add(state)) {
+            onRecentChanged(new AddedEvent(state, true));
+        }
     }
 
     public void updateSaved(@Nonnull HistoryState state) {

app/src/main/java/org/solovyev/android/calculator/history/RecentHistory.java

@@ -2,7 +2,6 @@ package org.solovyev.android.calculator.history;
 
 import android.support.annotation.NonNull;
 import android.support.annotation.Nullable;
-
 import org.solovyev.android.Check;
 
 import java.util.Collections;
@@ -17,10 +16,13 @@ public class RecentHistory {
     private final List<HistoryState> list = new LinkedList<>();
     private int current = -1;
 
-    public void add(@NonNull HistoryState state) {
+    public boolean add(@NonNull HistoryState state) {
         Check.isMainThread();
         if (isCurrent(state)) {
-            return;
+            return false;
+        }
+        if (updateState(state)) {
+            return true;
         }
         while (current != list.size() - 1) {
             list.remove(list.size() - 1);
@@ -28,6 +30,20 @@ public class RecentHistory {
         list.add(state);
         current++;
         trim();
+        return true;
+    }
+
+    private boolean updateState(@NonNull HistoryState state) {
+        if (current == -1) {
+            return false;
+        }
+        final HistoryState old = list.get(current);
+        if (old.display.sequence == state.display.sequence && old.editor.sequence == state.editor.sequence) {
+            // if recalculation is taking place we need to update current history item
+            list.set(current, state);
+            return true;
+        }
+        return false;
     }
 
     private void trim() {

app/src/test/java/org/solovyev/android/calculator/BaseCalculatorTest.java

@@ -32,7 +32,7 @@ public abstract class BaseCalculatorTest {
     }
 
     protected final void assertError(@NonNull String expression) {
-        calculator.evaluate(numeric, expression);
+        calculator.evaluate(numeric, expression, 0);
         verify(calculator.bus, atLeastOnce()).post(argThat(failed()));
     }
 
@@ -55,7 +55,7 @@ public abstract class BaseCalculatorTest {
     }
 
     protected final void assertEval(@NonNull final String expected, @NonNull final String expression, final JsclOperation operation) {
-        calculator.evaluate(operation, expression);
+        calculator.evaluate(operation, expression, 0);
         verify(calculator.bus, atLeastOnce()).post(finishedEvent(expected, expression, operation));
     }