performance improvements + a good amount of changes

src/backends/file_backend.cpp

@@ -0,0 +1,72 @@
+#include "backend.cpp"
+#include <filesystem>
+
+class file_backend : public backend {
+private:
+  unordered_map<string, string> file_cache;
+  bool cache_enabled;
+
+  unique_ptr<http_response> handle_request_nocache(http_request& req) {
+     string filename = req.path() == "/" ? "index.html" : req.path();
+     filename = "./www/" + filename;
+     ifstream stream(filename);
+
+     int status = 200;
+     if (!stream.is_open()) {
+         status = 404;
+         filename = "./error_pages/404.html";
+         stream = ifstream(filename);
+     }
+
+     stringstream buffer;
+     buffer << stream.rdbuf();
+     return make_unique<http_response>(buffer.str(), status);
+  }
+
+  unique_ptr<http_response> handle_request_cache(http_request& req) {
+     string filename = req.path() == "/" ? "/index.html" : req.path();
+     filename = "./www" + filename;
+     auto file_info = file_cache.find(filename);
+
+     int status = 200;
+     if (file_info == file_cache.end()) {
+         status = 404;
+         filename = "./error_pages/404.html";
+         file_info = file_cache.find(filename);
+     }
+
+     return make_unique<http_response>(file_info->second, status);
+  }
+
+  void populate_cache_dir(string dir) {
+    filesystem::recursive_directory_iterator cur = begin(filesystem::recursive_directory_iterator(dir));
+    filesystem::recursive_directory_iterator fin = end(filesystem::recursive_directory_iterator(dir));
+
+    while (cur != fin) {
+        auto p = cur->path();
+        string filename = p.string();
+        stringstream buffer;
+        ifstream stream(filename);
+        buffer << stream.rdbuf();
+        file_cache[filename] = buffer.str();
+        cout << "File at " << filename << " cached (" << file_cache[filename].size() << " bytes)" << endl;
+        ++cur;
+    }
+  }
+
+  void populate_cache() {
+    populate_cache_dir("./www/");
+    populate_cache_dir("./error_pages/");
+  }
+
+public:
+  file_backend(bool enable_cache) : cache_enabled(enable_cache) {
+    if(cache_enabled) {
+      populate_cache(); 
+    }
+  }
+
+  unique_ptr<http_response> handle_request(http_request& req) override {
+    return cache_enabled ? handle_request_cache(req) : handle_request_nocache(req);
+  }
+};