From 2e34965e5e48175c5ee6016af1a858f7f3f02c1d Mon Sep 17 00:00:00 2001
From: skal <pascal.massimino@gmail.com>
Date: Wed, 4 Feb 2026 11:56:03 +0100
Subject: feat(gpu): Implement recursive WGSL composition and modularize
 shaders (Task #50)

- Updated ShaderComposer to support recursive #include "snippet_name" with cycle detection.
- Extracted granular WGSL snippets: math/sdf_shapes, math/sdf_utils, render/shadows, render/scene_query, render/lighting_utils.
- Refactored Renderer3D to use #include in shaders, simplifying C++ dependency lists.
- Fixed WGPUShaderSourceWGSL usage on macOS to correctly handle composed shader strings.
- Added comprehensive unit tests for recursive composition in test_shader_composer.
- Verified system stability with test_3d_render and full test suite.
- Marked Task #50 as recurrent for future code hygiene.
---
 src/gpu/effects/shader_composer.cc | 48 ++++++++++++++++++++++++++++++++++----
 1 file changed, 43 insertions(+), 5 deletions(-)

(limited to 'src/gpu/effects/shader_composer.cc')

diff --git a/src/gpu/effects/shader_composer.cc b/src/gpu/effects/shader_composer.cc
index 3e08df9..8d66ad7 100644
--- a/src/gpu/effects/shader_composer.cc
+++ b/src/gpu/effects/shader_composer.cc
@@ -2,6 +2,7 @@
 // It implements the ShaderComposer class.
 
 #include "gpu/effects/shader_composer.h"
+#include <set>
 #include <sstream>
 
 ShaderComposer& ShaderComposer::Get() {
@@ -14,22 +15,59 @@ void ShaderComposer::RegisterSnippet(const std::string& name,
   snippets_[name] = code;
 }
 
+void ShaderComposer::ResolveRecursive(const std::string& source,
+                                      std::stringstream& ss,
+                                      std::set<std::string>& included) {
+  std::istringstream stream(source);
+  std::string line;
+  while (std::getline(stream, line)) {
+    // Check for #include "snippet_name"
+    if (line.compare(0, 9, "#include ") == 0) {
+      size_t start = line.find('"');
+      size_t end = line.find('"', start + 1);
+      if (start != std::string::npos && end != std::string::npos) {
+        std::string name = line.substr(start + 1, end - start - 1);
+        if (included.find(name) == included.end()) {
+          included.insert(name);
+          auto it = snippets_.find(name);
+          if (it != snippets_.end()) {
+            ss << "// --- Included: " << name << " ---\n";
+            ResolveRecursive(it->second, ss, included);
+            ss << "// --- End Include: " << name << " ---\n";
+          } else {
+            ss << "// ERROR: Snippet not found: " << name << "\n";
+          }
+        }
+      }
+    } else {
+      ss << line << "\n";
+    }
+  }
+}
+
 std::string
 ShaderComposer::Compose(const std::vector<std::string>& dependencies,
                         const std::string& main_code) {
   std::stringstream ss;
   ss << "// Generated by ShaderComposer\n\n";
 
+  std::set<std::string> included;
+
+  // Process explicit dependencies first
   for (const auto& dep : dependencies) {
-    auto it = snippets_.find(dep);
-    if (it != snippets_.end()) {
-      ss << "// --- Snippet: " << dep << " ---\n";
-      ss << it->second << "\n";
+    if (included.find(dep) == included.end()) {
+      included.insert(dep);
+      auto it = snippets_.find(dep);
+      if (it != snippets_.end()) {
+        ss << "// --- Dependency: " << dep << " ---\n";
+        ResolveRecursive(it->second, ss, included);
+        ss << "\n";
+      }
     }
   }
 
   ss << "// --- Main Code ---\n";
-  ss << main_code;
+  ResolveRecursive(main_code, ss, included);
 
   return ss.str();
 }
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