Bugfix: Scroll away from invalid dates (#280)

* initial working version

* fix native variant issue

* cleanup

* cleanup

android/src/main/java/com/henninghall/date_picker/ui/WheelChangeListenerImpl.java

@@ -13,7 +13,6 @@ import com.henninghall.date_picker.wheels.Wheel;
 import java.text.ParseException;
 import java.text.SimpleDateFormat;
 import java.util.Calendar;
-import java.util.Date;
 import java.util.TimeZone;
 
 public class WheelChangeListenerImpl implements WheelChangeListener {
@@ -30,33 +29,96 @@ public class WheelChangeListenerImpl implements WheelChangeListener {
         this.rootView = rootView;
     }
 
+    private SimpleDateFormat getDateFormat(){
+        TimeZone timeZone = state.getTimeZone();
+        SimpleDateFormat dateFormat = uiManager.getDateFormat();
+        dateFormat.setTimeZone(timeZone);
+        return dateFormat;
+    }
+
     @Override
     public void onChange(Wheel picker) {
         if(wheels.hasSpinningWheel()) return;
 
-        WritableMap event = Arguments.createMap();
-        TimeZone timeZone = state.getTimeZone();
-        SimpleDateFormat dateFormat = uiManager.getDateFormat();
+        if(!exists()){
+            Calendar closestExistingDate = getClosestExistingDateInPast();
+            if(closestExistingDate != null) {
+                uiManager.animateToDate(closestExistingDate);
+            }
+            return;
+        }
+
+        Calendar selectedDate = getSelectedDate();
+        if(selectedDate == null) return;
+
         Calendar minDate = state.getMinimumDate();
+        if (minDate != null && selectedDate.before(minDate)) {
+            uiManager.animateToDate(minDate);
+            return;
+        }
+
         Calendar maxDate = state.getMaximumDate();
+        if (maxDate != null && selectedDate.after(maxDate)) {
+            uiManager.animateToDate(maxDate);
+            return;
+        }
+
+        emitDateChangeEvent(selectedDate);
+    }
+
+    // Example: Jan 1 returns true, April 31 returns false.
+    private boolean exists(){
+        SimpleDateFormat dateFormat = getDateFormat();
+        String toParse = wheels.getDateTimeString();
         try {
-            dateFormat.setTimeZone(timeZone);
-            Calendar date = Calendar.getInstance(timeZone);
-            String toParse = wheels.getDateString();
-            Date newDate = dateFormat.parse(toParse);
-            date.setTime(newDate);
-            String dateString = Utils.dateToIso(date);
-            if (minDate != null && date.before(minDate)) uiManager.animateToDate(minDate);
-            else if (maxDate != null && date.after(maxDate)) uiManager.animateToDate(maxDate);
-            else {
-                event.putString("date", dateString);
-                event.putString("dateString", uiManager.getDisplayValueString());
-                DatePickerManager.context.getJSModule(RCTEventEmitter.class)
-                        .receiveEvent(rootView.getId(), "dateChange", event);
-            }
+            dateFormat.setLenient(false); // disallow parsing invalid dates
+            dateFormat.parse(toParse);
+            return true;
+        } catch (ParseException e) {
+            return false;
+        }
+    }
+
+    private Calendar getSelectedDate(){
+        SimpleDateFormat dateFormat = getDateFormat();
+        String toParse = wheels.getDateTimeString();
+        TimeZone timeZone = state.getTimeZone();
+        Calendar date = Calendar.getInstance(timeZone);
+        try {
+            dateFormat.setLenient(true); // allow parsing invalid dates
+            date.setTime(dateFormat.parse(toParse));
+            return date;
         } catch (ParseException e) {
             e.printStackTrace();
         }
+        return null;
+    }
+
+    private Calendar getClosestExistingDateInPast(){
+        SimpleDateFormat dateFormat = getDateFormat();
+        dateFormat.setLenient(false); // disallow parsing invalid dates
+
+        int maxDaysInPastToCheck = 10;
+        for (int i = 0; i < maxDaysInPastToCheck; i++){
+            try {
+                String toParse = wheels.getDateTimeString(i);
+                Calendar calendar = Calendar.getInstance(state.getTimeZone());
+                calendar.setTime(dateFormat.parse(toParse));
+                return calendar;
+            } catch (ParseException ignored) {
+                // continue checking if exception (which means invalid date)
+            }
+        }
+        return null;
+    }
+
+    private void emitDateChangeEvent(Calendar date) {
+        WritableMap event = Arguments.createMap();
+        String dateString = Utils.dateToIso(date);
+        event.putString("date", dateString);
+        event.putString("dateString", uiManager.getDisplayValueString());
+        DatePickerManager.context.getJSModule(RCTEventEmitter.class)
+                .receiveEvent(rootView.getId(), "dateChange", event);
     }
 
 }

android/src/main/java/com/henninghall/date_picker/ui/Wheels.java

@@ -6,7 +6,6 @@ import com.henninghall.date_picker.models.Variant;
 import com.henninghall.date_picker.pickers.Picker;
 import com.henninghall.date_picker.R;
 import com.henninghall.date_picker.State;
-import com.henninghall.date_picker.Utils;
 import com.henninghall.date_picker.models.WheelType;
 import com.henninghall.date_picker.models.Mode;
 import com.henninghall.date_picker.wheelFunctions.SetDividerHeight;
@@ -112,19 +111,41 @@ public class Wheels {
         return wheelPerWheelType.get(type);
     }
 
-    String getDateString() {
+    String getDateTimeString(int daysToSubtract) {
+        return getDateString(daysToSubtract) + " " + getTimeString();
+    }
+
+    private String getDateModeString(int daysToSubtract) {
         ArrayList<Wheel> wheels = getOrderedVisibleWheels();
-        String dateString = (state.getMode() == Mode.date)
-                ? wheels.get(0).getValue() + " "
-                + wheels.get(1).getValue() + " "
-                + wheels.get(2).getValue()
-                : dayWheel.getValue();
-        return dateString
-                + " " + hourWheel.getValue()
+        StringBuilder sb = new StringBuilder();
+        for (int i = 0; i < 3; i++) {
+            if (i != 0) sb.append(" ");
+            Wheel w = wheels.get(i);
+            if (w instanceof DateWheel) {
+                sb.append(w.getPastValue(daysToSubtract));
+            }
+            else sb.append(w.getValue());
+        }
+        return sb.toString();
+    }
+
+    private String getDateString(int daysToSubtract){
+        if(state.getMode() == Mode.date ){
+            return getDateModeString(daysToSubtract);
+        }
+        return dayWheel.getValue();
+    }
+
+    private String getTimeString(){
+        return hourWheel.getValue()
                 + " " + minutesWheel.getValue()
                 + ampmWheel.getValue();
     }
 
+    String getDateTimeString() {
+        return getDateTimeString(0);
+    }
+
     String getDisplayValue() {
         StringBuilder sb = new StringBuilder();
         for (Wheel wheel: getOrderedVisibleWheels()) {
@@ -137,7 +158,7 @@ public class Wheels {
         ArrayList<WheelType> wheels = state.derived.getOrderedVisibleWheels();
         for (WheelType wheelType : wheels) {
             Wheel wheel = getWheel(wheelType);
-                pickerWrapper.addPicker(wheel.picker.getView());
+            pickerWrapper.addPicker(wheel.picker.getView());
         }
     }
 

android/src/main/java/com/henninghall/date_picker/wheels/DateWheel.java

@@ -19,7 +19,7 @@ public class DateWheel extends Wheel
         Calendar cal = Calendar.getInstance();
         ArrayList<String> values = new ArrayList<>();
         cal.set(Calendar.MONTH, 0);
-        cal.set(Calendar.DATE, 0);
+        cal.set(Calendar.DATE, 1);
         final int maxDate = 31;
         final int minDate = 1;
         for (int i = minDate; i <= maxDate; ++i) {

android/src/main/java/com/henninghall/date_picker/wheels/Wheel.java

@@ -53,6 +53,14 @@ public abstract class Wheel {
         return getValueAtIndex(getIndex());
     }
 
+    public String getPastValue(int subtractIndex) {
+        if(!visible()) return format.format(userSetValue.getTime());
+        int size = values.size();
+        int pastValueIndex = (getIndex() + size - subtractIndex) % size;
+        return getValueAtIndex(pastValueIndex);
+    }
+
+
     private int getIndex() {
         return picker.getValue();
     }

examples/detox/e2e/tests/invalidDates.spec.js

@@ -0,0 +1,52 @@
+const { scrollWheel, expectDate, setDate, setMode, setMaximumDate, setMinimumDate } = require('../utils')
+
+const scrollDays = (days) => scrollWheel(1, days) 
+
+describe('Invalid dates', () => {
+  before(async () => {
+    await device.reloadReactNative()
+    await element(by.text('Advanced')).tap()
+    await setMinimumDate(undefined)
+    await setMaximumDate(undefined)
+    await setMode('date')
+  })
+
+
+  it('scrolls back to last valid date', async () => {
+    await setDate(new Date("2001-02-28 00:00"))
+    await scrollDays(1)
+    await expectDate('2001-02-28 00:00:00')
+  })
+
+  it('scrolls back after scrolling multiple dates', async () => {
+    await setDate(new Date("2001-02-27 00:00"))
+    await scrollDays(2)
+    await expectDate('2001-02-28 00:00:00')
+  })
+
+  it('not scrolling back on unusual valid dates', async () => {
+    await setDate(new Date("2000-02-28 00:00"))
+    await scrollDays(1)
+    await expectDate('2000-02-29 00:00:00')
+  })
+  
+  it('not scrolling back after scrolling past invalid dates', async () => {
+    await setDate(new Date("2001-02-28 00:00"))
+    await scrollDays(4)
+    await expectDate('2001-02-01 00:00:00')
+  })
+  
+  it('works on months with 30 days', async () => {
+    await setDate(new Date("2001-04-30 00:00"))
+    await scrollDays(1)
+    await expectDate('2001-04-30 00:00:00')
+  })
+
+  it('works on months with 31 days', async () => {
+    await setDate(new Date("2001-05-30 00:00"))
+    await scrollDays(1)
+    await expectDate('2001-05-31 00:00:00')
+  })
+
+
+})