From 95d5acc8c7e60255b19e7084e374eb26cc5d0ba3 Mon Sep 17 00:00:00 2001
From: Roland Reichwein <mail@reichwein.it>
Date: Sat, 4 Apr 2020 13:21:59 +0200
Subject: Versioned plugins

---
 plugin.cpp         | 48 ++++++++++++++++++++++++++++++++++++++++--------
 plugin.h           | 18 +++++++++++++++++-
 plugin_interface.h |  3 +++
 webserver.cpp      |  8 +++++++-
 4 files changed, 67 insertions(+), 10 deletions(-)

diff --git a/plugin.cpp b/plugin.cpp
index 9c47ed2..c0a01fc 100644
--- a/plugin.cpp
+++ b/plugin.cpp
@@ -1,21 +1,22 @@
 #include "plugin.h"
 
 #include <boost/dll/import.hpp>
-#include <boost/shared_ptr.hpp>
 #include <boost/filesystem.hpp>
 
 #include <iostream>
 #include <filesystem>
 
-#include "plugin_interface.h"
-
 namespace dll = boost::dll;
 namespace fs = std::filesystem;
 using namespace std::string_literals;
 
-void load_plugins(Config& config)
+PluginLoader::PluginLoader(Config& config): m_config{config}
+{
+}
+
+void PluginLoader::load_plugins()
 {
- const auto& plugin_directories{config.PluginDirectories()};
+ const auto& plugin_directories{m_config.PluginDirectories()};
 
  for (const auto& dir: plugin_directories) {
   for (auto& path: fs::recursive_directory_iterator(dir)) {
@@ -23,14 +24,45 @@ void load_plugins(Config& config)
 
     dll::fs::path lib_path{path.path()};
 
+    try {
     boost::shared_ptr<webserver_plugin_interface> plugin = dll::import<webserver_plugin_interface>(lib_path, "webserver_plugin", dll::load_mode::append_decorations);
-    if (!plugin)
-     throw std::runtime_error("Can't load plugin");
+    if (plugin) {
+     if (plugin->version() != webserver_plugin_interface::interface_version)
+      throw std::runtime_error("Bad interface version for "s + path.path().generic_string() + ": "s + std::to_string(plugin->version()) + " vs. "s + std::to_string(webserver_plugin_interface::interface_version));
 
-    std::cout << "Plugin: " << plugin->generate_page("a") << std::endl;
+     if (m_plugins.contains(plugin->name()))
+      throw std::runtime_error("Plugin already exists: "s + plugin->name());
+
+     m_plugins.emplace(plugin->name(), plugin);
+
+     std::cout << "Found plugin: " << plugin->name() << std::endl;
+    } else
+     std::cout << "Can't load plugin from " << path.path().generic_string() << std::endl;
+    } catch (const std::exception& ex) {
+     std::cout << "Can't load plugin from " << path.path().generic_string() << ": " << ex.what() << std::endl;
+    }
    }
   }
  }
 
 }
 
+bool PluginLoader::validate_config()
+{
+ const auto& sites{m_config.Sites()};
+
+ for (const auto& site: sites) {
+  for (const auto& path: site.paths) {
+   if (path.type == Plugin) {
+    std::string plugin {path.params.at("plugin")};
+
+    if (!m_plugins.contains(plugin)) {
+     std::cout << "Configured plugin " << plugin << " not found" << std::endl;
+     return false;
+    }
+   }
+  }
+ }
+ return true;
+}
+
diff --git a/plugin.h b/plugin.h
index 1c88ff9..cc68524 100644
--- a/plugin.h
+++ b/plugin.h
@@ -1,5 +1,21 @@
 #pragma once
 
 #include "config.h"
+#include "plugin_interface.h"
 
-void load_plugins(Config& config);
+#include <boost/shared_ptr.hpp>
+
+#include <memory>
+#include <unordered_map>
+
+class PluginLoader
+{
+ Config& m_config;
+ std::unordered_map<std::string, boost::shared_ptr<webserver_plugin_interface>> m_plugins;
+
+public:
+ PluginLoader(Config& config);
+
+ void load_plugins(); // Load all plugins from configured paths
+ bool validate_config(); // Check if all configured plugins exist
+};
diff --git a/plugin_interface.h b/plugin_interface.h
index 72da0b9..e67d20a 100644
--- a/plugin_interface.h
+++ b/plugin_interface.h
@@ -6,6 +6,9 @@
 
 class BOOST_SYMBOL_VISIBLE webserver_plugin_interface {
 public:
+ static const int interface_version {1};
+ virtual int version() { return interface_version; }
+ virtual std::string name() = 0;
  virtual std::string generate_page(std::string path) = 0;
  virtual ~webserver_plugin_interface(){}
 };
diff --git a/webserver.cpp b/webserver.cpp
index 2574272..3f7a2a3 100644
--- a/webserver.cpp
+++ b/webserver.cpp
@@ -33,7 +33,13 @@ int main(int argc, char* argv[])
 
  try {
   Config config{config_filename};
-  load_plugins(config);
+  
+  PluginLoader plugin_loader(config);
+  plugin_loader.load_plugins();
+
+  if (!plugin_loader.validate_config())
+   throw std::runtime_error("Couldn't find all configured plugins.");
+
   return http_server(argc, argv);
  } catch (const std::exception& ex) {
   std::cout << "Error: " << ex.what() << std::endl;
-- 
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