// This file is part of the 64k demo project.
// It implements the ShaderComposer class.

#include "gpu/effects/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) {
  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) {
    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";
  ResolveRecursive(main_code, ss, included);

  return ss.str();
}