1 files changed, 120 insertions, 0 deletions
diff --git a/src/gpu/shader_composer.cc b/src/gpu/shader_composer.cc
new file mode 100644
index 0000000..fce6de4
--- /dev/null
+++ b/src/gpu/shader_composer.cc
@@ -0,0 +1,120 @@
+// This file is part of the 64k demo project.
+// It implements the ShaderComposer class.
+
+#include "gpu/shader_composer.h"
+#include <set>
+#include <sstream>
+
+ShaderComposer& ShaderComposer::Get() {
+  static ShaderComposer instance;
+  return instance;
+}
+
+void ShaderComposer::RegisterSnippet(const std::string& name,
+                                     const std::string& code) {
+  snippets_[name] = code;
+}
+
+void ShaderComposer::ResolveRecursive(const std::string& source,
+                                      std::stringstream& ss,
+                                      std::set<std::string>& included,
+                                      const CompositionMap& substitutions) {
+  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);
+
+        // Apply substitution if available
+        auto sub_it = substitutions.find(name);
+        if (sub_it != substitutions.end()) {
+          name = sub_it->second;
+        }
+
+        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, substitutions);
+            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,
+                        const CompositionMap& substitutions) {
+  std::stringstream ss;
+  ss << "// Generated by ShaderComposer\n\n";
+
+  std::set<std::string> included;
+
+  // Process explicit dependencies first
+  for (const auto& dep : dependencies) {
+    std::string name = dep;
+    auto sub_it = substitutions.find(name);
+    if (sub_it != substitutions.end()) {
+      name = sub_it->second;
+    }
+
+    if (included.find(name) == included.end()) {
+      included.insert(name);
+      auto it = snippets_.find(name);
+      if (it != snippets_.end()) {
+        ss << "// --- Dependency: " << name << " ---\n";
+        ResolveRecursive(it->second, ss, included, substitutions);
+        ss << "\n";
+      }
+    }
+  }
+
+  ss << "// --- Main Code ---\n";
+  ResolveRecursive(main_code, ss, included, substitutions);
+
+  return ss.str();
+}
+
+void ShaderComposer::VerifyIncludes() const {
+#if !defined(STRIP_ALL)
+  // Known placeholders that get substituted at composition time
+  std::set<std::string> known_placeholders = {"render/scene_query_mode"};
+
+  std::set<std::string> missing;
+  for (const auto& [name, code] : snippets_) {
+    std::istringstream stream(code);
+    std::string line;
+    while (std::getline(stream, line)) {
+      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 included = line.substr(start + 1, end - start - 1);
+          if (snippets_.find(included) == snippets_.end() &&
+              known_placeholders.find(included) == known_placeholders.end()) {
+            missing.insert(included);
+          }
+        }
+      }
+    }
+  }
+  if (!missing.empty()) {
+    fprintf(stderr, "WARNING: Unregistered shader snippets:\n");
+    for (const auto& name : missing) {
+      fprintf(stderr, "  - %s\n", name.c_str());
+    }
+  }
+#endif
+}