[Refactor] Shared VFS template for CoW foundation.

Refactors the Virtual file System creation process to improve memory
efficiency at scale. This is laying the ground work for a copy-on-write
system.

Previously, each new VFS instance was a full copy, which won't scale to
a large number of NPC's. Especially now that we are loading in entire
Lua scripts.

- Added VFSManager class which now manages the lifecycle of all VFS
  instances.
- VFSManager creates a single "template" VFS on initilisation. The
  template holds the shared, read-only directories like '/bin' and their
command scripts.
- When a new VFS is created (for a client or NPC), it links it's 'bin'
  directory to the shared template's '/bin' by pointer rather than
creating a copy of it.

this makes sure the content for *all* common command scripts exists in
memory only once, regardless of the number of NPC's we will later
generate.

client/src/terminal.cpp

@@ -20,7 +20,8 @@ Terminal::Terminal(void) {
   _should_close = false;
 
   /* Create local file system for the client. */
-  _local_vfs = vfs_manager::create_root_system("local");
+  VFSManager vfs_manager;
+  _local_vfs = vfs_manager.create_vfs("local");
   _local_cmd_processor = new CommandProcessor(_local_vfs);
   _current_path  = get_full_path(_local_cmd_processor->get_current_dir());
   _scroll_offset = 0;

common/src/vfs_manager.cpp

@@ -10,25 +10,16 @@ vfs_node* new_node(std::string name, vfs_node_type type, vfs_node* parent) {
   return node;
 }
 
-vfs_node* vfs_manager::create_root_system(const std::string& system_type) {
-  /* Rood directory. */
-  vfs_node* root = new_node("/", DIR_NODE, nullptr);
-
-  /* Subdirectories. */
-  vfs_node* home = new_node("home", DIR_NODE, root);
-  vfs_node* bin  = new_node("bin", DIR_NODE, root);
-  root->children["home"]  = home;
-  root->children["bin"]   = bin;
-
-  /* User diractory. */
-  vfs_node* user = new_node("user", DIR_NODE, home);
-  home->children["user"] = user;
-
-  /* Create file. */
-  vfs_node* readme = new_node("readme.txt", FILE_NODE, user);
-  readme->content = "Welcome to your new virtual machine.";
-  user->children["readme.txt"] = readme;
+VFSManager::VFSManager(void) {
+  /* Create template VFS that holds shared, read-only directories. */
+  _vfs_root = new_node("/", DIR_NODE, nullptr);
+  vfs_node* bin = new_node("bin", DIR_NODE, _vfs_root);
+  _vfs_root->children["bin"] = bin;
 
+  /* TODO:
+   * Load all scripts from assets/scripts/bin into the bind node.
+   * We'll create ls.lua manually for now.
+   */
   vfs_node* ls_script = new_node("ls.lua", FILE_NODE, bin);
   ls_script->content = R"lua(-- /bin/ls.lua - Lists files in a directory.
                              local dir = current_dir -- Get directory object from C++.
@@ -46,6 +37,26 @@ vfs_node* vfs_manager::create_root_system(const std::string& system_type) {
                              )lua";
 
   bin->children["ls.lua"] = ls_script;
+}
+
+VFSManager::~VFSManager(void) {
+  /* TODO: Implement recursive deletion of all created VFS nodes.*/
+  //delete _vfs_root;
+}
+
+vfs_node* VFSManager::create_vfs(const std::string& system_type) {
+  vfs_node* root = new_node("/", DIR_NODE, nullptr);
+
+  /* Create directories for this specific VFS. */
+  vfs_node* home = new_node("home", DIR_NODE, root);
+  vfs_node* user = new_node("user", DIR_NODE, home);
+  home->children["user"] = user;
+  vfs_node* readme = new_node("readme.txt", FILE_NODE, user);
+  readme->content = "Welcome to your new virtual machine.";
+  user->children["readme.txt"] = readme;
+
+  /* Link to the shared directories from the template. */
+  root->children["bin"] = _vfs_root->children["bin"];
 
   if(system_type == "npc") {
     vfs_node* npc_file = new_node("npc_system.txt", FILE_NODE, root);

common/src/vfs_manager.h

@@ -1,7 +1,16 @@
 #pragma once
 
+#include <string>
+
 #include "vfs.h"
 
-namespace vfs_manager {
-  vfs_node* create_root_system(const std::string& system_type);
-}
+class VFSManager {
+public:
+  VFSManager(void);
+  ~VFSManager(void); /* TODO: Implement recursive VFS deletion. */
+
+  vfs_node* create_vfs(const std::string& system_type);
+private:
+  vfs_node* _vfs_root;
+};
+

server/src/main.cpp

@@ -9,10 +9,12 @@
 int main(int argc, char** argv) {
   printf("=== Server starting ===\n");
 
+  VFSManager vfs_manager;
+
   /* Create the world map of networks. */
   std::map<std::string, vfs_node*> world_vfs;
-  world_vfs["8.8.8.8"] = vfs_manager::create_root_system("npc"); /* Basic npc system. */
-  world_vfs["10.0.2.15"] = vfs_manager::create_root_system("npc"); /* Another one. */
+  world_vfs["8.8.8.8"] = vfs_manager.create_vfs("npc"); /* Basic npc system. */
+  world_vfs["10.0.2.15"] = vfs_manager.create_vfs("npc"); /* Another one. */
   printf("Created world with %zu networks.\n", world_vfs.size());
 
   /* Network manager now managed the whole world. */