Adds an inefficient implementation of #1

Adds a technically working dial command whose tab completion is too horrendously slow to be usable

src/main/java/net/knarcraft/stargatecommand/command/DialTabCompleter.java

@@ -0,0 +1,95 @@
+package net.knarcraft.stargatecommand.command;
+
+import net.TheDgtl.Stargate.api.StargateAPI;
+import net.TheDgtl.Stargate.manager.PermissionManager;
+import net.TheDgtl.Stargate.network.Network;
+import net.TheDgtl.Stargate.network.RegistryAPI;
+import net.TheDgtl.Stargate.network.portal.Portal;
+import net.TheDgtl.Stargate.network.portal.RealPortal;
+import org.bukkit.command.Command;
+import org.bukkit.command.CommandSender;
+import org.bukkit.command.TabCompleter;
+import org.bukkit.entity.Player;
+import org.jetbrains.annotations.NotNull;
+import org.jetbrains.annotations.Nullable;
+
+import java.util.ArrayList;
+import java.util.Collection;
+import java.util.HashMap;
+import java.util.LinkedList;
+import java.util.List;
+import java.util.Map;
+
+/**
+ * A tab completer for the /sgc dial command
+ */
+public class DialTabCompleter implements TabCompleter {
+
+    private final StargateAPI stargateAPI;
+
+    /**
+     * Instantiates a new dial tab completer
+     *
+     * @param stargateAPI <p>A reference to the Stargate API</p>
+     */
+    public DialTabCompleter(StargateAPI stargateAPI) {
+        this.stargateAPI = stargateAPI;
+    }
+
+    @Nullable
+    @Override
+    public List<String> onTabComplete(@NotNull CommandSender commandSender, @NotNull Command command, @NotNull String s,
+                                      @NotNull String[] args) {
+        if (!(commandSender instanceof Player player)) {
+            commandSender.sendMessage("This command can only be used by players");
+            return new ArrayList<>();
+        }
+
+        List<String> availableNetworks = new ArrayList<>();
+        Map<Network, List<String>> availablePortals = new HashMap<>();
+        RegistryAPI registryAPI = stargateAPI.getRegistry();
+        PermissionManager permissionManager = stargateAPI.getPermissionManager(player);
+
+        //Populate the collections with available networks and portals
+        populateNetworksAndPortals(permissionManager, availableNetworks, availablePortals);
+
+        if (args.length > 1) {
+            Network network = registryAPI.getNetwork(args[0], false);
+            if (network != null && availablePortals.containsKey(network)) {
+                return availablePortals.get(network);
+            } else {
+                return new ArrayList<>();
+            }
+        } else {
+            return availableNetworks;
+        }
+    }
+
+    /**
+     * Populates the given collections with available networks and portals
+     *
+     * @param permissionManager <p>The permission manager to use to check for availability</p>
+     * @param availableNetworks <p>The list to store available networks to</p>
+     * @param availablePortals  <p>The map to store available portals to</p>
+     */
+    private void populateNetworksAndPortals(PermissionManager permissionManager, List<String> availableNetworks,
+                                            Map<Network, List<String>> availablePortals) {
+        List<Network> networks = new LinkedList<>(stargateAPI.getRegistry().getNetworkMap().values());
+        //Get all available networks and portals
+        for (Network network : networks) {
+            Collection<Portal> portals = network.getAllPortals();
+            for (Portal portal : portals) {
+                if (permissionManager.hasAccessPermission((RealPortal) portal)) {
+                    //Add an empty list if the network has not been encountered before
+                    if (!availablePortals.containsKey(network)) {
+                        availablePortals.put(network, new LinkedList<>());
+                    }
+                    availablePortals.get(network).add(portal.getName());
+                }
+            }
+        }
+        //Add only the network names with portals available to the player
+        availablePortals.keySet().forEach((item) -> availableNetworks.add(item.getName()));
+    }
+
+}