refactor and improve algo

Author: danielchalmers

DesktopClock.Tests/PixelShifterTests.cs

@@ -13,8 +13,8 @@ public void ShiftX_ShouldNotExceedMaxTotalShift(int shiftAmount, int maxTotalShi
     {
         var shifter = new PixelShifter
         {
-            ShiftAmount = shiftAmount,
-            MaxTotalShift = maxTotalShift,
+            PixelsPerShift = shiftAmount,
+            MaxPixelOffset = maxTotalShift,
         };
 
         double totalShiftX = 0;
@@ -37,8 +37,8 @@ public void ShiftY_ShouldNotExceedMaxTotalShift(int shiftAmount, int maxTotalShi
     {
         var shifter = new PixelShifter
         {
-            ShiftAmount = shiftAmount,
-            MaxTotalShift = maxTotalShift,
+            PixelsPerShift = shiftAmount,
+            MaxPixelOffset = maxTotalShift,
         };
 
         double totalShiftY = 0;

DesktopClock/Utilities/PixelShifter.cs

@@ -11,38 +11,46 @@ public class PixelShifter
     /// <summary>
     /// The number of pixels that will be shifted each time.
     /// </summary>
-    public int ShiftAmount { get; set; } = 2;
+    public int PixelsPerShift { get; set; } = 1;
 
     /// <summary>
     /// The maximum amount of drift that can occur in each direction.
     /// </summary>
-    public int MaxTotalShift { get; set; } = 4;
+    public int MaxPixelOffset { get; set; } = 4;
 
     public double ShiftX()
     {
-        var shift = _random.Next(-ShiftAmount, ShiftAmount + 1);
-        var newTotalShiftX = _totalShiftX + shift;
-
-        if (Math.Abs(newTotalShiftX) <= MaxTotalShift)
-        {
-            _totalShiftX = newTotalShiftX;
-            return shift;
-        }
-
-        return 0;
+        double pixelsToMoveBy = GetRandomShift();
+        pixelsToMoveBy = GetFinalShiftAmount(_totalShiftX, pixelsToMoveBy, MaxPixelOffset);
+        _totalShiftX += pixelsToMoveBy;
+        return pixelsToMoveBy;
     }
 
     public double ShiftY()
     {
-        var shift = _random.Next(-ShiftAmount, ShiftAmount + 1);
-        var newTotalShiftY = _totalShiftY + shift;
+        double pixelsToMoveBy = GetRandomShift();
+        pixelsToMoveBy = GetFinalShiftAmount(_totalShiftY, pixelsToMoveBy, MaxPixelOffset);
+        _totalShiftY += pixelsToMoveBy;
+        return pixelsToMoveBy;
+    }
+
+    private int GetRandomShift() => _random.Next(-PixelsPerShift, PixelsPerShift + 1);
 
-        if (Math.Abs(newTotalShiftY) <= MaxTotalShift)
+    private double GetFinalShiftAmount(double current, double offset, double max)
+    {
+        var newTotal = current + offset;
+
+        if (newTotal > max)
         {
-            _totalShiftY = newTotalShiftY;
-            return shift;
+            return max - current;
+        }
+        else if (newTotal < -max)
+        {
+            return -max - current;
+        }
+        else
+        {
+            return offset;
         }
-
-        return 0;
     }
 }