[Refactor] Implement in-memory VFS cache.

Refactors VFS to use a cetralised, in memory caching on the server. This
resolves performance and state sync issues from the previous
implementation.

common/src/command_processor.cpp

@@ -3,10 +3,9 @@
 
 #include "command_processor.h"
 #include "db/database_manager.h"
-#include "vfs.h"
+#include "i_network_bridge.h"
 #include "lua_api.h"
 #include "lua_processor.h"
-#include "machine_manager.h"
 #include "machine.h"
 
 
@@ -24,20 +23,19 @@ vfs_node* find_node_by_id(vfs_node* root, long long id) {
 }
 
 CommandProcessor::CommandProcessor(Machine* home_machine,
-                                   std::map<std::string, Machine*>& world_machines,
                                    DatabaseManager* db_manager,
-                                   MachineManager* machine_manager) :
+                                   MachineManager* machine_manager,
+                                   INetworkBridge* network_bridge) :
     _machine_manager(machine_manager),
     _db_manager(db_manager),
+    _network_bridge(network_bridge),
     _home_machine(home_machine),
-    _session_machine(home_machine),
+    _session_machine(home_machine) {
-    _world_machines(world_machines) {
+
-  _lua = new LuaProcessor();
+  if(home_machine) _current_dir = home_machine->vfs_root;
-  _current_dir = _session_machine->vfs_root;
 }
 
 CommandProcessor::~CommandProcessor(void) {
-  delete _lua;
 }
 
 vfs_node* CommandProcessor::get_current_dir(void) {
@@ -47,11 +45,6 @@ vfs_node* CommandProcessor::get_current_dir(void) {
 Machine* CommandProcessor::get_home_machine(void)     { return _home_machine; }
 Machine* CommandProcessor::get_session_machine(void)  { return _session_machine; }
 
-std::map<std::string, Machine*>&
-CommandProcessor::get_world_machines(void) {
-  return _world_machines;
-}
-
 DatabaseManager* CommandProcessor::get_db_manager(void) {
   return _db_manager;
 }
@@ -60,6 +53,10 @@ MachineManager* CommandProcessor::get_machine_manager(void) {
   return _machine_manager;
 }
 
+INetworkBridge* CommandProcessor::get_network_bridge(void) {
+  return _network_bridge;
+}
+
 void CommandProcessor::set_current_dir(vfs_node* node) {
   _current_dir = node;
 }
@@ -72,6 +69,12 @@ void CommandProcessor::set_session_machine(Machine* machine) {
 }
 
 std::string CommandProcessor::process_command(const std::string& command) {
+  /*
+   * Creating the Lua processor on-demand to ensure it exists on the same
+   * thread that will execute the script.
+   */
+  LuaProcessor lua(*this);
+
   /* Trim trailing whitespace. */
   std::string cmd = command;
   size_t end = cmd.find_last_not_of(" \t\n\r");
@@ -104,7 +107,7 @@ std::string CommandProcessor::process_command(const std::string& command) {
 
   if(script_id > 0) {
     bool is_remote = (_session_machine != _home_machine);
-    sol::object result = _lua->execute(script_content, *this, args, is_remote);
+    sol::object result = lua.execute(script_content, *this, args, is_remote);
     return result.is<std::string>() ? result.as<std::string>() : "[Script returned an unexpected type]";
   }
   return "Unknown command: " + command_name + "\n";

common/src/command_processor.h

@@ -1,18 +1,18 @@
 #pragma once
 
-#include <lua_processor.h>
 #include <string>
-#include <map>
 
 #include "db/database_manager.h"
+#include "i_network_bridge.h"
 #include "machine.h"
 #include "machine_manager.h"
-#include "vfs.h"
+
+class LuaProcessor;
 
 class CommandProcessor {
 public:
-  CommandProcessor(Machine* home_machine, std::map<std::string, Machine*>& world_machines,
+  CommandProcessor(Machine* home_machine, DatabaseManager* db_manager,
-                   DatabaseManager* db_manager, MachineManager* machine_manager);
+                   MachineManager* machine_manager, INetworkBridge* network_bridge);
   ~CommandProcessor(void);
 
   std::string process_command(const std::string& command);
@@ -23,9 +23,9 @@ public:
   vfs_node* get_current_dir(void);
   Machine* get_home_machine(void);
   Machine* get_session_machine(void);
-  std::map<std::string, Machine*>& get_world_machines(void);
   DatabaseManager* get_db_manager(void);
   MachineManager* get_machine_manager(void);
+  INetworkBridge* get_network_bridge(void);
  
   void set_current_dir(vfs_node* node);
   void set_session_machine(Machine* machine);
@@ -33,9 +33,9 @@ public:
 private:
   MachineManager* _machine_manager;
   DatabaseManager* _db_manager;
+  INetworkBridge* _network_bridge;
   Machine* _home_machine;
   Machine* _session_machine;
   vfs_node* _current_dir;
-  std::map<std::string, Machine*>& _world_machines;
   LuaProcessor* _lua;
 };

common/src/db/database_manager.cpp

@@ -8,13 +8,7 @@ DatabaseManager::DatabaseManager(const std::string& db_path) :
   _machine_repository = std::make_unique<MachineRepository>(_db);
   _service_repository = std::make_unique<ServiceRepository>(_db);
   _vfs_repository     = std::make_unique<VFSRepository>(_db);
-}
 
-DatabaseManager::~DatabaseManager(void) {
-  /* db is auto closed when _db goes out of scope. */
-}
-
-void DatabaseManager::init(void) {
   _db <<  "CREATE TABLE IF NOT EXISTS players("
           "id INTEGER PRIMARY KEY AUTOINCREMENT,"
           "username TEXT NOT NULL UNIQUE,"
@@ -46,6 +40,10 @@ void DatabaseManager::init(void) {
           ");";
 }
 
+DatabaseManager::~DatabaseManager(void) {
+  /* db is auto closed when _db goes out of scope. */
+}
+
 bool DatabaseManager::create_player(const std::string& username, const std::string& password,
                                     const std::string& hostname, vfs_node* vfs_template) {
   long long player_id   = 0;

common/src/db/database_manager.h

@@ -15,8 +15,6 @@ public:
   DatabaseManager(const std::string& db_path);
   ~DatabaseManager(void);
 
-  void init(void);
-
   /* Return true on success, false if user already exists. */
   bool create_player(const std::string& username, const std::string& password,
                      const std::string& hostname, vfs_node* vfs_template);

common/src/db/machine_repository.cpp

@@ -31,6 +31,15 @@ std::vector<MachineData> MachineRepository::get_all_npcs(void) {
   return machines;
 }
 
+std::vector<MachineData> MachineRepository::get_all(void) {
+  std::vector<MachineData> machines;
+  _db << "SELECT id, ip_address FROM machines;"
+      >> [&](long long id, std::string ip_address) {
+      machines.push_back({id, ip_address});
+    };
+  return machines;
+}
+
 std::string MachineRepository::get_hostname(long long machine_id) {
   std::string hostname;
   _db << "SELECT hostname FROM machines WHERE id = ?;"

common/src/db/machine_repository.h

@@ -19,6 +19,7 @@ public:
                    const std::string& ip_address);
   int get_npc_count(void);
   std::vector<MachineData> get_all_npcs(void);
+  std::vector<MachineData> get_all(void);
   std::string get_hostname(long long machine_id);
 
 private:

common/src/i_network_bridge.h

@@ -0,0 +1,11 @@
+#pragma once
+
+#include <string>
+
+class Machine;
+
+class INetworkBridge {
+public:
+  virtual Machine* get_machine_by_ip(const std::string& ip) = 0;
+  virtual void release_machine(long long machine_id) = 0;
+};

common/src/lua_api.cpp

@@ -1,9 +1,9 @@
 #include <sol/types.hpp>
 #include <sstream>
 
+#include "i_network_bridge.h"
 #include "lua_api.h"
 #include "command_processor.h"
-#include "db/database_manager.h"
 #include "machine.h"
 #include "vfs.h"
 
@@ -15,45 +15,34 @@ vfs_node* get_current_dir(CommandProcessor& context) {
 
 std::string rm(CommandProcessor& context, const std::string& filename) {
   vfs_node* current_dir = context.get_current_dir();
-  DatabaseManager* db = context.get_db_manager();
+  auto it = current_dir->children.find(filename);
 
-  /* find the file in the database. */
+  if(it == current_dir->children.end()) {
-  long long file_id = 0;
-  int file_type = 0;
-  db->_db << "SELECT id, type FROM vfs_nodes WHERE parent_id = ? AND name = ?;"
-          << current_dir->id << filename
-          >> std::tie(file_id, file_type);
-
-  if(file_id == 0) {
     return "rm: cannot remove '" + filename + "': No such file or directory.";
   }
-  if(file_type == DIR_NODE) {
+  if(it->second->type == DIR_NODE) {
     return "rm: cannot remove '" + filename + "': Is a directory.";
   }
 
-  db->_db << "DELETE FROM vfs_nodes WHERE id = ?;" << file_id;
+  delete it->second; /* Free the memory for the node. */
-  /* Also remove from in-mem VFS. */
+  current_dir->children.erase(it); /* Remove from map. */
-  delete current_dir->children[filename];
-  current_dir->children.erase(filename);
-
   return "";
 }
 
 std::string write_file(CommandProcessor& context, const std::string& filename,
                        const std::string& content) {
   vfs_node* current_dir = context.get_current_dir();
-  DatabaseManager* db = context.get_db_manager();
+  auto it = current_dir->children.find(filename);
 
-  if(current_dir->children.count(filename)) {
+  if(it != current_dir->children.end()) {
-    vfs_node* target_node = current_dir->children[filename];
+    /* File exists, update content. */
-    db->_db << "UPDATE vfs_nodes SET content = ? WHERE id = ?;"
+    if(it->second->type == DIR_NODE) {
-            << content << target_node->id;
+      return "write: " + filename + ": Is a directory.";
-    target_node->content = content;
+    }
+    it->second->content = content;
   } else {
-    db->_db << "INSERT INTO vfs_nodes (machine_id, parent_id, name, type, content) VALUES (?, ?, ?, ?, ?);"
+    /* File does not exist, create it. */
-            << context.get_session_machine()->id << current_dir->id << filename << FILE_NODE << content;
     vfs_node* new_file = new_node(filename, FILE_NODE, current_dir);
-    new_file->id = db->_db.last_insert_rowid();
     new_file->content = content;
     current_dir->children[filename] = new_file;
   }
@@ -62,24 +51,15 @@ std::string write_file(CommandProcessor& context, const std::string& filename,
 
 std::string cd(CommandProcessor& context, const std::string& path) {
   vfs_node* current_dir = context.get_current_dir();
-  DatabaseManager* db = context.get_db_manager();
 
   if(path == "..") {
     if(current_dir->parent) {
       context.set_current_dir(current_dir->parent);
     }
   } else {
-    long long target_id = 0;
+    auto it = current_dir->children.find(path);
-    db->_db << "SELECT id FROM vfs_nodes WHERE parent_id = ? AND name = ? AND type = 1;"
+    if(it != current_dir->children.end() && it->second->type == DIR_NODE) {
-            << current_dir->id << path
+      context.set_current_dir(it->second);
-            >> target_id;
-
-    if(target_id > 0) {
-      /* Inefficient, I know. */
-      Machine* reloaded_machine =
-        context.get_machine_manager()->load_machine(context.get_session_machine()->id, db);
-      vfs_node* new_dir = find_node_by_id(reloaded_machine->vfs_root, target_id);
-      context.set_current_dir(new_dir);
     } else {
       return "cd: no such file or directory: " + path;
     }
@@ -89,52 +69,59 @@ std::string cd(CommandProcessor& context, const std::string& path) {
 
 std::string ls(CommandProcessor& context) {
   vfs_node* dir = context.get_current_dir();
-  printf("DEBUG: ls command called for directory_id: %lld\n", dir->id);
   if(dir->type != DIR_NODE) {
     return "ls: not a directory";
   }
 
   std::stringstream ss;
-
+  for(auto const& [name, node] : dir->children) {
-  context.get_db_manager()->_db << "SELECT name, type FROM vfs_nodes WHERE parent_id = ?;"
+    ss << name;
-                                << dir->id
+    if(node->type == DIR_NODE) {
-                                >> [&](std::string name, int type) {
+      ss << "/";
-      ss << name;
+    }
-      if(type == DIR_NODE) ss << "/";
+    ss << "   ";
-      ss << "   ";
+  }
-    };
-
   return ss.str();
 }
 
 std::string ssh(CommandProcessor& context, const std::string& ip) {
-  if(context.get_world_machines().count(ip)) {
+  INetworkBridge* bridge = context.get_network_bridge();
-    context.set_session_machine(context.get_world_machines().at(ip));
+  Machine* target_machine = bridge->get_machine_by_ip(ip);
+
+  if(target_machine) {
+    context.set_session_machine(target_machine);
     return "Connected to " + ip;
+  } else {
+    return "ssh: Could not resolve hostname " + ip + ": Name or service not found";
   }
-  return "ssh: Could not resolve hostname " + ip + ": Name or service not found";
 }
 
 std::string nmap(CommandProcessor& context, const std::string& ip) {
-  if(!context.get_world_machines().count(ip)) {
+  long long machine_id = context.get_machine_manager()->get_machine_id_by_ip(ip);
+  if(machine_id == 0) {
     return "nmap: Could not resolve host: " + ip;
   }
+  auto services = context.get_db_manager()->services().get_for_machine(machine_id);
 
-  Machine* target_machine = context.get_world_machines().at(ip);
+  if(services.empty()) {
-  if(target_machine->services.empty()) {
     return "No open ports for " + ip;
   }
 
   std::stringstream ss;
   ss << "Host: " << ip << "\n";
   ss << "PORT\tSTATE\tSERVICE\n";
-  for(auto const& [port, service_name] : target_machine->services) {
+  for(auto const& [port, service_name] : services) {
     ss << port << "/tcp\t" << "open\t" << service_name << "\n";
   }
   return ss.str();
 }
 
 std::string disconnect(CommandProcessor& context) {
+  Machine* current_machine = context.get_session_machine();
+  if(current_machine != context.get_home_machine()) {
+    INetworkBridge* bridge = context.get_network_bridge();
+    bridge->release_machine(current_machine->id);
+  }
   context.set_session_machine(context.get_home_machine());
   return "Connection closed.";
 }

common/src/lua_api.h

@@ -4,6 +4,7 @@
 #include "vfs.h"
 
 class CommandProcessor;
+class NetworkManager;
 
 namespace api {
 

common/src/lua_processor.cpp

@@ -4,11 +4,11 @@
 #include <sol/raii.hpp>
 
 #include "lua_processor.h"
-#include "vfs.h"
 #include "lua_api.h"
 #include "command_processor.h"
+#include "vfs.h"
 
-LuaProcessor::LuaProcessor(void) {
+LuaProcessor::LuaProcessor(CommandProcessor& context) {
   _lua.open_libraries(sol::lib::base, sol::lib::string, sol::lib::io, sol::lib::table);
 
   /* Expose vfs_node struct members to Lua. */
@@ -23,15 +23,15 @@ LuaProcessor::LuaProcessor(void) {
 
   /* Create the 'bettola' API table. */
   sol::table bettola_api = _lua.create_named_table("bettola");
-  bettola_api["rm"]             = &api::rm;
+  bettola_api.set_function("rm",              &api::rm);
-  bettola_api["ls"]             = &api::ls;
+  bettola_api.set_function("ls",              &api::ls);
-  bettola_api["write_file"]     = &api::write_file;
+  bettola_api.set_function("write_file",      &api::write_file);
-  bettola_api["get_current_dir"]= &api::get_current_dir;
+  bettola_api.set_function("get_current_dir", &api::get_current_dir);
-  bettola_api["cd"]             = &api::cd;
+  bettola_api.set_function("cd",              &api::cd);
-  bettola_api["ssh"]            = &api::ssh;
+  bettola_api.set_function("close_terminal",  &api::close_terminal);
-  bettola_api["nmap"]           = &api::nmap;
+  bettola_api.set_function("ssh",             &api::ssh);
-  bettola_api["disconnect"]     = &api::disconnect;
+  bettola_api.set_function("nmap",            &api::nmap);
-  bettola_api["close_terminal"] = &api::close_terminal;
+  bettola_api.set_function("disconnect",      &api::disconnect);
 }
 
 LuaProcessor::~LuaProcessor(void) {}

common/src/lua_processor.h

@@ -9,7 +9,7 @@ class CommandProcessor;
 
 class LuaProcessor {
 public:
-  LuaProcessor(void);
+  LuaProcessor(CommandProcessor& context);
   ~LuaProcessor(void);
 
   /* Executes a string of lua code and returns result as a string. */

common/src/machine_manager.cpp

@@ -96,7 +96,7 @@ void build_tree(vfs_node* parent, const std::map<long long, vfs_node*>& nodes) {
   }
 }
 
-Machine* MachineManager::load_machine(long long machine_id, DatabaseManager* db_manager) {
+Machine* MachineManager::load_machine(long long machine_id) {
   printf("DEBUG: load_machine called for machine_id: %lld\n", machine_id);
 
   std::string hostname = _db_manager->machines().get_hostname(machine_id);
@@ -107,7 +107,7 @@ Machine* MachineManager::load_machine(long long machine_id, DatabaseManager* db_
   std::map<long long, vfs_node*> node_map;
   vfs_node* root = nullptr;
 
-  auto nodes = db_manager->vfs().get_nodes_for_machine(machine_id);
+  auto nodes = _db_manager->vfs().get_nodes_for_machine(machine_id);
   for(vfs_node* node : nodes) {
     node_map[node->id] = node;
     if(node->name == "/") {
@@ -123,3 +123,17 @@ Machine* MachineManager::load_machine(long long machine_id, DatabaseManager* db_
   }
   return machine;
 }
+
+long long MachineManager::get_machine_id_by_ip(const std::string& ip) {
+  if(_ip_to_id_map.count(ip)) {
+    return _ip_to_id_map[ip];
+  }
+  return 0;
+}
+
+void MachineManager::init(void) {
+  auto all_machines = _db_manager->machines().get_all();
+  for(const auto& machine_data : all_machines) {
+    _ip_to_id_map[machine_data.ip_address] = machine_data.id;
+  }
+}

common/src/machine_manager.h

@@ -1,5 +1,6 @@
 #pragma once
 
+#include <map>
 #include <string>
 
 #include "db/database_manager.h"
@@ -16,12 +17,20 @@ public:
 
   Machine* create_machine(uint32_t id, const std::string& hostname,
                           const std::string& system_type);
-  Machine* load_machine(long long machine_id, DatabaseManager* db_manager);
+  Machine* load_machine(long long machine_id);
+  void init(void);
 
   vfs_node* get_vfs_template(void) { return _vfs_template_root; }
 
+  /* Machine lookup. */
+  long long get_machine_id_by_ip(const std::string& ip);
+
 private:
   DatabaseManager* _db_manager;
   vfs_node* _vfs_template_root;
+
+  /* In memory cache of all machines, loaded or not. */
+  std::map<std::string, long long> _ip_to_id_map;
+  std::map<long long, Machine*> _world_machines;
 };
 

server/src/network_manager.cpp

@@ -16,26 +16,18 @@
 #include "vfs.h"
 
 NetworkManager::NetworkManager(const std::string& db_path) :
+    _io_context(),
     _db_manager(std::make_unique<DatabaseManager>(db_path)),
     _acceptor(_io_context),
     _machine_manager(_db_manager.get()) {
 
-  _db_manager->init();
   _seed_npc_machines();
-
+  _machine_manager.init();
-  /* Load NPC machines from the database. */
-  auto npc_machines = _db_manager->machines().get_all_npcs();
-  for(const auto& machine_data : npc_machines) {
-    _world_machines[machine_data.ip_address] =
-      _machine_manager.load_machine(machine_data.id, _db_manager.get());
-  }
-
-  fprintf(stderr, "Created world with %zu networks\n", _world_machines.size());
 }
 
 NetworkManager::~NetworkManager(void) {
-  for(auto const& [ip, machine] : _world_machines) {
+  for(auto& pair : _active_machines) {
-    delete machine;
+    _save_machine_vfs(pair.second.machine.get());
   }
   stop();
 }
@@ -76,13 +68,10 @@ void NetworkManager::start_accept(void) {
         auto new_connection =
           std::make_shared<net::TcpConnection>(_io_context, std::move(socket));
 
-        /* Create a new player for this connection. */
+        /* Create a new player for this connection. pendnding authentication.*/
         uint32_t player_id = _next_player_id++;
-        Machine* player_machine = _machine_manager.create_machine(player_id, "player.home",
+        auto new_player = std::make_unique<Player>(player_id, nullptr, _db_manager.get(),
-                                                                  "player");
+                                                  &_machine_manager, this);
-        auto new_player = std::make_unique<Player>(player_id, player_machine,
-                                                   _world_machines, _db_manager.get(),
-                                                   &_machine_manager);
         Player* new_player_ptr = new_player.get();
         _players[player_id] = std::move(new_player);
         new_connection->set_id(player_id);
@@ -123,12 +112,11 @@ void NetworkManager::on_message(std::shared_ptr<net::TcpConnection> connection,
         if(args.size() == 3) {
           if(_db_manager->create_player(args[0], args[1], args[2],
                                       _machine_manager.get_vfs_template())) {
-          long long machine_id = _db_manager->players().get_home_machine_id(args[0]);
+          long long home_machine_id = _db_manager->players().get_home_machine_id(args[0]);
-          Machine* home_machine = _machine_manager.load_machine(machine_id, _db_manager.get());
+          Machine* home_machine = _get_or_load_machine(home_machine_id);
           delete player->cmd_processor; /* Delete old command processor. */
-          player->cmd_processor = new CommandProcessor(home_machine, _world_machines,
+          player->cmd_processor = new CommandProcessor(home_machine, _db_manager.get(),
-                                                       _db_manager.get(),
+                                                       &_machine_manager, this);
-                                                       &_machine_manager);
           player->state = PlayerState::ACTIVE;
           connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_CREATE_ACCOUNT_SUCCESS));
           /* send initial prompt. */
@@ -144,22 +132,20 @@ void NetworkManager::on_message(std::shared_ptr<net::TcpConnection> connection,
       case net_protocol::Opcode::C2S_LOGIN:
         if(args.size() == 2) {
           if(_db_manager->players().authenticate(args[0], args[1])) {
-            long long machine_id = _db_manager->players().get_home_machine_id(args[0]);
+            long long home_machine_id = _db_manager->players().get_home_machine_id(args[0]);
-            printf("DEBUG: Loading machine %lld for player %s\n", machine_id, args[0].c_str());
+            Machine* home_machine = _get_or_load_machine(home_machine_id);
-          Machine* home_machine = _machine_manager.load_machine(machine_id, _db_manager.get());
+            delete player->cmd_processor; /* Delete old command processor. */
-          delete player->cmd_processor; /* Delete old command processor. */
+            player->cmd_processor = new CommandProcessor(home_machine, _db_manager.get(),
-          player->cmd_processor = new CommandProcessor(home_machine, _world_machines,
+                                                         &_machine_manager, this);
-                                                       _db_manager.get(), &_machine_manager);
+            player->state = PlayerState::ACTIVE;
-
-          player->state = PlayerState::ACTIVE;
             connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_LOGIN_SUCCESS));
-          /* Send initial prompt. */
+            /* Send initial prompt. */
-          std::string prompt = "\n" + get_full_path(player->cmd_processor->get_current_dir());
+            std::string prompt = "\n" + get_full_path(player->cmd_processor->get_current_dir());
-          connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_COMMAND_RESPONSE,
+            connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_COMMAND_RESPONSE,
-                                                    {prompt}));
+                                                        {prompt}));
-        } else {
+          } else {
-          connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_LOGIN_FAIL,
+            connection->send(net_protocol::build_message(net_protocol::Opcode::S2C_LOGIN_FAIL,
-                                                       {"Invalid username or password."}));
+                                                        {"Invalid username or password."}));
         }
       }
       break;
@@ -214,6 +200,20 @@ void NetworkManager::on_message(std::shared_ptr<net::TcpConnection> connection,
 
 void NetworkManager::on_disconnect(std::shared_ptr<net::TcpConnection> connection) {
   uint32_t player_id = connection->get_id();
+  Player* player = _players[player_id].get();
+
+  if(player && player->cmd_processor) {
+    Machine* home_machine = player->cmd_processor->get_home_machine();
+    Machine* session_machine = player->cmd_processor->get_session_machine();
+
+    if(home_machine) {
+      release_machine(home_machine->id);
+    }
+    if(session_machine && session_machine != home_machine) {
+      release_machine(session_machine->id);
+    }
+  }
+
   fprintf(stderr, "[Player %u] Disconnected.\n", player_id);
   _connections.erase(
     std::remove(_connections.begin(), _connections.end(), connection), _connections.end());
@@ -221,6 +221,67 @@ void NetworkManager::on_disconnect(std::shared_ptr<net::TcpConnection> connectio
   _players.erase(player_id);
 }
 
+Machine* NetworkManager::get_machine_by_ip(const std::string& ip) {
+  long long machine_id = _machine_manager.get_machine_id_by_ip(ip);
+  if(machine_id != 0) {
+    return _get_or_load_machine(machine_id);
+  }
+  return nullptr;
+}
+
+Machine* NetworkManager::_get_or_load_machine(long long machine_id) {
+  if(_active_machines.count(machine_id)) {
+    _active_machines[machine_id].ref_count++;
+    return _active_machines[machine_id].machine.get();
+  }
+
+  /* Machine not in cache, load it. */
+  fprintf(stderr, "Loading machine %lld into cache.\n", machine_id);
+  Machine* loaded_machine = _machine_manager.load_machine(machine_id);
+  _active_machines[machine_id] = {
+    std::unique_ptr<Machine>(loaded_machine), 1
+  };
+  return loaded_machine;
+}
+
+void NetworkManager::release_machine(long long machine_id) {
+  if(!_active_machines.count(machine_id)) {
+    return;
+  }
+
+  _active_machines[machine_id].ref_count--;
+  fprintf(stderr, "Releasing machine %lld, ref count now %d.\n", machine_id,
+          _active_machines[machine_id].ref_count);
+
+  if(_active_machines[machine_id].ref_count <= 0) {
+    fprintf(stderr, "Machine %lld has no more references, saving and evicting from cache.\n",
+            machine_id);
+    _save_machine_vfs(_active_machines[machine_id].machine.get());
+    _active_machines.erase(machine_id);
+  }
+}
+
+void NetworkManager::_recursive_save_vfs(long long machine_id, vfs_node* node, long long* parent_id) {
+  long long current_node_id = _db_manager->vfs().create_node(machine_id, parent_id,
+                                                             node->name, node->type,
+                                                             node->content);
+
+  if(node->type == DIR_NODE) {
+    for(auto const& [name, child] : node->children) {
+      _recursive_save_vfs(machine_id, child, &current_node_id);
+    }
+  }
+}
+
+void NetworkManager::_save_machine_vfs(Machine* machine) {
+  if(!machine || !machine->vfs_root) return;
+
+  _db_manager->_db << "BEGIN;";
+  _db_manager->_db << "DELETE FROM vfs_nodes WHERE machine_id = ?;" << machine->id;
+  _recursive_save_vfs(machine->id, machine->vfs_root, nullptr);
+  _db_manager->_db << "COMMIT;";
+}
+
 void NetworkManager::_seed_npc_machines(void) {
   int npc_count = _db_manager->machines().get_npc_count();
 

server/src/network_manager.h

@@ -10,11 +10,17 @@
 #include "asio/io_context.hpp"
 #include "net/tcp_connection.h"
 #include "player.h"
+#include "i_network_bridge.h"
 #include "machine_manager.h"
 
 class DatabaseManager;
 
-class NetworkManager {
+struct CachedMachine {
+  std::unique_ptr<Machine> machine;
+  int ref_count = 0;
+};
+
+class NetworkManager : public INetworkBridge {
 public:
   NetworkManager(const std::string& db_path);
   ~NetworkManager(void);
@@ -22,11 +28,17 @@ public:
   void start(uint16_t port);
   void stop(void);
 
+  Machine* get_machine_by_ip(const std::string& ip) override;
+  void release_machine(long long machine_id) override;
+
 private:
   void start_accept(void);
   void on_message(std::shared_ptr<net::TcpConnection> connection,
                   const std::string& message);
   void on_disconnect(std::shared_ptr<net::TcpConnection> connection);
+  void _save_machine_vfs(Machine* machine);
+  void _recursive_save_vfs(long long machine_id, vfs_node* node,
+                           long long* parent_id);
 
   void _seed_npc_machines(void);
 
@@ -36,9 +48,12 @@ private:
 
   std::deque<std::shared_ptr<net::TcpConnection>> _connections;
   std::unordered_map<uint32_t, std::unique_ptr<Player>> _players;
+  std::map<long long, CachedMachine> _active_machines;
   uint32_t _next_player_id = 1;
 
-  std::map<std::string, Machine*> _world_machines; /* For NPC's. */
   std::unique_ptr<DatabaseManager> _db_manager;
   MachineManager _machine_manager;
+
+protected:
+  Machine* _get_or_load_machine(long long machine_id);
 };

server/src/player.cpp

@@ -1,25 +1,20 @@
 #include "player.h"
 #include "command_processor.h"
 #include "db/database_manager.h"
+#include "i_network_bridge.h"
 #include "machine.h"
 
 Player::Player(uint32_t new_id, Machine* home_machine,
-               std::map<std::string, Machine*>& world_machines, DatabaseManager* db_manager,
+               DatabaseManager* db_manager,
-               MachineManager* machine_manager) :
+               MachineManager* machine_manager,
+               INetworkBridge* network_bridge) :
     id(new_id),
     state(PlayerState::AUTHENTICATING) {
 
-  cmd_processor = new CommandProcessor(home_machine, world_machines, db_manager, machine_manager);
+  cmd_processor = new CommandProcessor(home_machine, db_manager, machine_manager,
+                                       network_bridge);
 }
 
 Player::~Player(void) {
-  if(cmd_processor) {
+  delete cmd_processor;
-    /*
-     * Player is owner of their own machine. CommandProcessor
-     * holds the most current pointer to it (in case of CoW).
-     * Delete the machine first, then the processor point to it.
-     */
-    delete cmd_processor->get_home_machine();
-    delete cmd_processor;
-  }
 }

server/src/player.h

@@ -1,11 +1,10 @@
 #pragma once
 
 #include <cstdint>
-#include <map>
-#include <string>
 
 #include "db/database_manager.h"
 #include "command_processor.h"
+#include "i_network_bridge.h"
 #include "machine.h"
 #include "machine_manager.h"
 
@@ -16,9 +15,8 @@ enum class PlayerState {
 
 class Player {
 public:
-  Player(uint32_t id, Machine* home_machine, std::map<std::string,
+  Player(uint32_t id, Machine* home_machine, DatabaseManager* db_manager,
-         Machine*>& world_machines, DatabaseManager* db_manager,
+         MachineManager* machine_manager, INetworkBridge* network_bridge);
-         MachineManager* machine_manager);
   ~Player(void);
 
   uint32_t id;