fix: Behaviour change in the Snowflake animation

fix: Guard against zero framesCount to avoid modulo by zero in SnowFlakeAnimation

fix: blicking illusion back

fix: added input validation

Author: samruddhi-Rahegaonkar

lib/badge_animation/ani_snowflake.dart

@@ -2,29 +2,76 @@ import 'package:badgemagic/badge_animation/animation_abstract.dart';
 
 class SnowFlakeAnimation extends BadgeAnimation {
   @override
-  void processAnimation(int badgeHeight, int badgeWidth, int animationIndex,
-      List<List<bool>> processGrid, List<List<bool>> canvas) {
+  void processAnimation(
+    int badgeHeight,
+    int badgeWidth,
+    int animationIndex,
+    List<List<bool>> processGrid,
+    List<List<bool>> canvas,
+  ) {
+    if (processGrid.isEmpty ||
+        processGrid.any((row) => row.length != processGrid[0].length)) {
+      throw ArgumentError(
+        'processGrid must be a non-empty rectangular 2D list',
+      );
+    }
     int newGridHeight = processGrid.length;
     int newGridWidth = processGrid[0].length;
-    for (int i = 0; i < badgeHeight; i++) {
-      for (int j = 0; j < badgeWidth; j++) {
-        // Calculate the total number of frames that fit the badge width
-        int framesCount = (newGridWidth / badgeWidth).ceil();
 
-        // Determine the current frame based on the animation value
-        int currentcountFrame = animationIndex ~/ badgeWidth % framesCount;
+    if (canvas.length < badgeHeight ||
+        canvas.any((row) => row.length < badgeWidth)) {
+      throw ArgumentError(
+        'canvas must have at least $badgeHeight rows and $badgeWidth columns',
+      );
+    }
+    int framesCount = (newGridWidth / badgeWidth).ceil();
+    framesCount = framesCount == 0 ? 1 : framesCount;
+
+    int currentFrame = (animationIndex ~/ badgeWidth) % framesCount;
 
-        // Calculate the starting column for the current frame in newGrid
-        int startCol = currentcountFrame * badgeWidth;
+    int startCol = currentFrame * badgeWidth;
+    if (startCol + badgeWidth > newGridWidth) {
+      startCol = newGridWidth - badgeWidth;
+      if (startCol < 0) startCol = 0;
+    }
+
+    List<List<bool>> tempFrame = List.generate(
+      badgeHeight,
+      (_) => List.filled(badgeWidth, false),
+    );
+
+    for (int i = 0; i < badgeHeight; i++) {
+      for (int j = 0; j < badgeWidth; j++) {
+        int gridCol = startCol + j;
+        bool isValid = i < newGridHeight && gridCol < newGridWidth;
+        tempFrame[i][j] = isValid ? processGrid[i][gridCol] : false;
+      }
+    }
 
-        bool isNewGridCell = i < newGridHeight && (startCol + j) < newGridWidth;
+    int shiftLeftBy =
+        _countLeadingEmptyCols(tempFrame, badgeHeight, badgeWidth);
 
-        // Update the grid based on the current frame's data
-        bool snowflakeCondition =
-            (isNewGridCell && processGrid[i][startCol + j]);
+    for (int i = 0; i < badgeHeight; i++) {
+      for (int j = 0; j < badgeWidth; j++) {
+        int sourceCol = j + shiftLeftBy;
+        canvas[i][j] = sourceCol < badgeWidth ? tempFrame[i][sourceCol] : false;
+      }
+    }
+  }
 
-        canvas[i][j] = snowflakeCondition;
+  int _countLeadingEmptyCols(List<List<bool>> frame, int height, int width) {
+    for (int col = 0; col < width; col++) {
+      bool isColEmpty = true;
+      for (int row = 0; row < height; row++) {
+        if (frame[row][col]) {
+          isColEmpty = false;
+          break;
+        }
+      }
+      if (!isColEmpty) {
+        return col;
       }
     }
+    return 0;
   }
 }