From 5666c895427dea4fe5bfce6d12d2e7ced01d1046 Mon Sep 17 00:00:00 2001
From: LachyFS <100457804+LachyFS@users.noreply.github.com>
Date: Wed, 1 Apr 2026 11:23:42 +1100
Subject: [PATCH] fix: add face validation, constants, and size checks to WASM
 API

- Export FACE_POS_X..FACE_NEG_Z constants for JS consumers
- Return errors for invalid face values instead of silent failures
- Add ChunkNeighbors::size() and validate chunk/neighbor size match
---
 crates/urath-core/src/chunk.rs |  6 +++
 crates/urath-wasm/src/lib.rs   | 93 +++++++++++++++++++++++-----------
 2 files changed, 70 insertions(+), 29 deletions(-)

diff --git a/crates/urath-core/src/chunk.rs b/crates/urath-core/src/chunk.rs
index ebe190a..40cae31 100644
--- a/crates/urath-core/src/chunk.rs
+++ b/crates/urath-core/src/chunk.rs
@@ -303,6 +303,12 @@ pub struct ChunkNeighbors {
 }
 
 impl ChunkNeighbors {
+    /// The chunk size this neighbor set was created for.
+    #[inline]
+    pub fn size(&self) -> usize {
+        self.size
+    }
+
     /// Create neighbors with all faces treated as air.
     pub fn empty(size: usize) -> Self {
         Self {
diff --git a/crates/urath-wasm/src/lib.rs b/crates/urath-wasm/src/lib.rs
index 9dcc0f4..fc1224b 100644
--- a/crates/urath-wasm/src/lib.rs
+++ b/crates/urath-wasm/src/lib.rs
@@ -5,6 +5,51 @@ use urath::{
     TerrainConfig, TerrainGenerator,
 };
 
+pub const FACE_POS_X: u8 = 0;
+pub const FACE_NEG_X: u8 = 1;
+pub const FACE_POS_Y: u8 = 2;
+pub const FACE_NEG_Y: u8 = 3;
+pub const FACE_POS_Z: u8 = 4;
+pub const FACE_NEG_Z: u8 = 5;
+
+/// Face direction constants exported to JavaScript.
+#[wasm_bindgen]
+pub fn face_pos_x() -> u8 {
+    FACE_POS_X
+}
+#[wasm_bindgen]
+pub fn face_neg_x() -> u8 {
+    FACE_NEG_X
+}
+#[wasm_bindgen]
+pub fn face_pos_y() -> u8 {
+    FACE_POS_Y
+}
+#[wasm_bindgen]
+pub fn face_neg_y() -> u8 {
+    FACE_NEG_Y
+}
+#[wasm_bindgen]
+pub fn face_pos_z() -> u8 {
+    FACE_POS_Z
+}
+#[wasm_bindgen]
+pub fn face_neg_z() -> u8 {
+    FACE_NEG_Z
+}
+
+fn face_from_u8(val: u8) -> Result<Face, JsError> {
+    match val {
+        0 => Ok(Face::PosX),
+        1 => Ok(Face::NegX),
+        2 => Ok(Face::PosY),
+        3 => Ok(Face::NegY),
+        4 => Ok(Face::PosZ),
+        5 => Ok(Face::NegZ),
+        _ => Err(JsError::new(&format!("invalid face: {val}, must be 0-5"))),
+    }
+}
+
 /// WASM-exposed chunk that holds voxel data.
 #[wasm_bindgen]
 pub struct WasmChunk {
@@ -73,18 +118,10 @@ impl WasmChunk {
 
     /// Extract the border slice for a given face direction.
     /// Returns a Uint16Array of size² elements.
-    pub fn extract_border(&self, face: u8) -> js_sys::Uint16Array {
-        let f = match face {
-            0 => Face::PosX,
-            1 => Face::NegX,
-            2 => Face::PosY,
-            3 => Face::NegY,
-            4 => Face::PosZ,
-            5 => Face::NegZ,
-            _ => return js_sys::Uint16Array::new_with_length(0),
-        };
+    pub fn extract_border(&self, face: u8) -> Result<js_sys::Uint16Array, JsError> {
+        let f = face_from_u8(face)?;
         let border = self.inner.extract_border(f);
-        js_sys::Uint16Array::from(&border[..])
+        Ok(js_sys::Uint16Array::from(&border[..]))
     }
 
     /// True if all blocks are air. O(1).
@@ -117,15 +154,7 @@ impl WasmChunkNeighbors {
     /// E.g., calling `set_neighbor(0, neighborChunk)` extracts the NegX (x=0) border
     /// from `neighborChunk` and uses it as the PosX neighbor data.
     pub fn set_neighbor(&mut self, face: u8, neighbor_chunk: &WasmChunk) -> Result<(), JsError> {
-        let face = match face {
-            0 => Face::PosX,
-            1 => Face::NegX,
-            2 => Face::PosY,
-            3 => Face::NegY,
-            4 => Face::PosZ,
-            5 => Face::NegZ,
-            _ => return Ok(()),
-        };
+        let face = face_from_u8(face)?;
         let border = neighbor_chunk.inner.extract_border(face.opposite());
         self.inner
             .set_face(face, border)
@@ -135,15 +164,7 @@ impl WasmChunkNeighbors {
     /// Set neighbor border data directly from a Uint16Array (size² elements).
     /// Used by workers that don't have the neighbor WasmChunk.
     pub fn set_neighbor_border(&mut self, face: u8, data: &[u16]) -> Result<(), JsError> {
-        let face = match face {
-            0 => Face::PosX,
-            1 => Face::NegX,
-            2 => Face::PosY,
-            3 => Face::NegY,
-            4 => Face::PosZ,
-            5 => Face::NegZ,
-            _ => return Ok(()),
-        };
+        let face = face_from_u8(face)?;
         self.inner
             .set_face(face, data.to_vec())
             .map_err(|e| JsError::new(&e.to_string()))
@@ -323,6 +344,13 @@ impl WasmGreedyMesher {
         chunk: &WasmChunk,
         neighbors: &WasmChunkNeighbors,
     ) -> Result<WasmMeshResult, JsError> {
+        if neighbors.inner.size() != chunk.inner.size() {
+            return Err(JsError::new(&format!(
+                "neighbor size {} does not match chunk size {}",
+                neighbors.inner.size(),
+                chunk.inner.size()
+            )));
+        }
         let mut opaque = MeshOutput::with_capacity(4096);
         let mut transparent = MeshOutput::with_capacity(1024);
         self.inner
@@ -385,6 +413,13 @@ impl WasmSurfaceNetsMesher {
         chunk: &WasmChunk,
         neighbors: &WasmChunkNeighbors,
     ) -> Result<WasmMeshResult, JsError> {
+        if neighbors.inner.size() != chunk.inner.size() {
+            return Err(JsError::new(&format!(
+                "neighbor size {} does not match chunk size {}",
+                neighbors.inner.size(),
+                chunk.inner.size()
+            )));
+        }
         let mut opaque = MeshOutput::with_capacity(4096);
         let mut transparent = MeshOutput::new();
         self.inner