Add defensive checks to prevent crash with zero-dimension elevation grids

Co-authored-by: louis-e <[email protected]>

Author: Copilot

src/elevation_data.rs

@@ -83,8 +83,9 @@ pub fn fetch_elevation_data(
     let tiles: Vec<(u32, u32)> = get_tile_coordinates(bbox, zoom);
 
     // Match grid dimensions with Minecraft world size
-    let grid_width: usize = scale_factor_x as usize;
-    let grid_height: usize = scale_factor_z as usize;
+    // Ensure minimum grid size of 1 to prevent division by zero and indexing errors
+    let grid_width: usize = (scale_factor_x as usize).max(1);
+    let grid_height: usize = (scale_factor_z as usize).max(1);
 
     // Initialize height grid with proper dimensions
     let mut height_grid: Vec<Vec<f64>> = vec![vec![f64::NAN; grid_width]; grid_height];
@@ -376,6 +377,11 @@ fn get_tile_coordinates(bbox: &LLBBox, zoom: u8) -> Vec<(u32, u32)> {
 }
 
 fn apply_gaussian_blur(heights: &[Vec<f64>], sigma: f64) -> Vec<Vec<f64>> {
+    // Guard against empty input
+    if heights.is_empty() || heights[0].is_empty() {
+        return heights.to_owned();
+    }
+    
     let kernel_size: usize = (sigma * 3.0).ceil() as usize * 2 + 1;
     let kernel: Vec<f64> = create_gaussian_kernel(kernel_size, sigma);
 
@@ -445,6 +451,11 @@ fn create_gaussian_kernel(size: usize, sigma: f64) -> Vec<f64> {
 }
 
 fn fill_nan_values(height_grid: &mut [Vec<f64>]) {
+    // Guard against empty grid
+    if height_grid.is_empty() || height_grid[0].is_empty() {
+        return;
+    }
+    
     let height: usize = height_grid.len();
     let width: usize = height_grid[0].len();
 
@@ -485,6 +496,11 @@ fn fill_nan_values(height_grid: &mut [Vec<f64>]) {
 }
 
 fn filter_elevation_outliers(height_grid: &mut [Vec<f64>]) {
+    // Guard against empty grid
+    if height_grid.is_empty() || height_grid[0].is_empty() {
+        return;
+    }
+    
     let height = height_grid.len();
     let width = height_grid[0].len();
 

src/ground.rs

@@ -75,6 +75,10 @@ impl Ground {
     /// Converts game coordinates to elevation data coordinates
     #[inline(always)]
     fn get_data_coordinates(&self, coord: XZPoint, data: &ElevationData) -> (f64, f64) {
+        // Guard against division by zero for edge cases
+        if data.width == 0 || data.height == 0 {
+            return (0.0, 0.0);
+        }
         let x_ratio: f64 = coord.x as f64 / data.width as f64;
         let z_ratio: f64 = coord.z as f64 / data.height as f64;
         (x_ratio.clamp(0.0, 1.0), z_ratio.clamp(0.0, 1.0))
@@ -83,8 +87,17 @@ impl Ground {
     /// Interpolates height value from the elevation grid
     #[inline(always)]
     fn interpolate_height(&self, x_ratio: f64, z_ratio: f64, data: &ElevationData) -> i32 {
+        // Guard against out of bounds access
+        if data.width == 0 || data.height == 0 || data.heights.is_empty() {
+            return self.ground_level;
+        }
         let x: usize = ((x_ratio * (data.width - 1) as f64).round() as usize).min(data.width - 1);
         let z: usize = ((z_ratio * (data.height - 1) as f64).round() as usize).min(data.height - 1);
+        
+        // Additional safety check for row length
+        if z >= data.heights.len() || x >= data.heights[z].len() {
+            return self.ground_level;
+        }
         data.heights[z][x]
     }