Add API for shop command and sub commands

api/src/main/java/de/epiceric/shopchest/api/ShopChest.java

@@ -3,6 +3,7 @@ package de.epiceric.shopchest.api;
 import org.bukkit.entity.Player;
 import org.bukkit.plugin.java.JavaPlugin;
 
+import de.epiceric.shopchest.api.command.ShopCommand;
 import de.epiceric.shopchest.api.player.ShopPlayer;
 
 /**
@@ -34,4 +35,11 @@ public abstract class ShopChest extends JavaPlugin {
      * @return the formatted amount
      */
     public abstract String formatEconomy(double amount);
+
+    /**
+     * Gets the main command of this plugin
+     * 
+     * @return the shop command
+     */
+    public abstract ShopCommand getShopCommand();
 }

api/src/main/java/de/epiceric/shopchest/api/command/ShopCommand.java

@@ -0,0 +1,138 @@
+package de.epiceric.shopchest.api.command;
+
+import java.util.ArrayList;
+import java.util.Arrays;
+import java.util.List;
+import java.util.Locale;
+import java.util.Optional;
+import java.util.stream.Collectors;
+
+import org.bukkit.command.CommandSender;
+
+/**
+ * Represents the plugin's main command
+ * 
+ * @since 1.13
+ */
+public abstract class ShopCommand {
+    private List<SubCommand> subCommands = new ArrayList<>();
+
+    /**
+     * Gets the command's name
+     * 
+     * @return the name
+     * @since 1.13
+     */
+    public abstract String getName();
+
+    /**
+     * Adds a sub command to this command
+     * 
+     * @param subCommand the sub command
+     * @return {@code true} if the sub command has been registered, {@code false} if
+     *         the name has already been taken
+     * @since 1.13
+     */
+    public final boolean addSubCommand(SubCommand subCommand) {
+        boolean nameTaken = subCommands.stream().filter(sub -> sub.getName().equalsIgnoreCase(subCommand.getName()))
+                .findAny().isPresent();
+
+        if (nameTaken) {
+            return false;
+        }
+
+        this.subCommands.add(subCommand);
+        return true;
+    }
+
+    /**
+     * Removes a sub command from this command
+     * 
+     * @param subCommand the sub command
+     * @since 1.13
+     */
+    public final void removeSubCommand(SubCommand subCommand) {
+        this.subCommands.remove(subCommand);
+    }
+
+    /**
+     * Called when this command is executed
+     * <p>
+     * Sub commands are handled here and their respective {@code onExecute} method
+     * is called from here.
+     * <p>
+     * The first argument {@code args[0]} is the name of the sub command (if
+     * entered).
+     * 
+     * @param sender the command sender
+     * @param args   the arguments
+     * @since 1.13
+     */
+    public final void onExecute(CommandSender sender, String... args) {
+        if (args.length > 0) {
+            Optional<SubCommand> optional = subCommands.stream()
+                    .filter(sub -> sub.canExecute(sender) && sub.isPermitted(sender))
+                    .filter(sub -> sub.getName().equalsIgnoreCase(args[0])).findAny();
+
+            if (!optional.isPresent()) {
+                sendUsage(sender);
+                return;
+            }
+
+            optional.ifPresent(sub -> {
+                if (args.length > 1) {
+                    sub.onExecute(sender, Arrays.copyOfRange(args, 1, args.length));
+                } else {
+                    sub.onExecute(sender);
+                }
+            });
+        } else {
+           sendUsage(sender);
+        }
+    }
+
+    /**
+     * Called when a sender tab completes an argument in this command
+     * <p>
+     * Only tab completion for the name of the sub command is handled here.
+     * Everything else has to be implemented in the sub commands respective
+     * {@code onTabComplete} method.
+     * <p>
+     * The first argument {@code args[0]} is the name of the sub command (if
+     * entered).
+     * 
+     * @param sender the command sender
+     * @param args the arguments
+     * @return the tab completions
+     * @since 1.13
+     */
+    public final List<String> onTabComplete(CommandSender sender, String... args) {
+        if (args.length == 1) {
+            return subCommands.stream()
+                    .filter(sub -> sub.canExecute(sender) && sub.isPermitted(sender))
+                    .filter(sub -> sub.getName().toLowerCase(Locale.US).startsWith(args[0].toLowerCase(Locale.US)))
+                    .map(SubCommand::getName).collect(Collectors.toList());
+        } else if (args.length > 1) {
+            return subCommands.stream()
+                    .filter(sub -> sub.canExecute(sender) && sub.isPermitted(sender))
+                    .filter(sub -> sub.getName().equalsIgnoreCase(args[0])).findAny()
+                    .map(sub -> sub.onTabComplete(sender, args))
+                    .orElse(new ArrayList<>());
+        }
+
+        return new ArrayList<>();
+    }
+    
+    /**
+     * Sends the help messages for all sub commands to the given sender
+     * 
+     * @param sender the command sender
+     * @since 1.13
+     */
+    public void sendUsage(CommandSender sender) {
+        String format = "[green] /%s %s [white] - [yellow] %s"; // TODO: i18n
+        subCommands.stream().filter(sub -> sub.canExecute(sender) && sub.isPermitted(sender))
+                .forEach(sub -> sender.sendMessage(String.format(format, sub.getName(), sub.getDescription())));
+    }
+
+}

api/src/main/java/de/epiceric/shopchest/api/command/SubCommand.java

@@ -0,0 +1,114 @@
+package de.epiceric.shopchest.api.command;
+
+import java.util.List;
+
+import org.bukkit.command.CommandSender;
+import org.bukkit.entity.Player;
+
+/**
+ * Represents a sub command for the plugin's main command
+ * 
+ * @see ShopCommand#addSubCommand(SubCommand)
+ * @since 1.13
+ */
+public abstract class SubCommand {
+    private final String name;
+    private final boolean onlyPlayer;
+
+    /**
+     * Creates a sub command with the given name
+     * <p>
+     * The sub command has to be added to the main command via
+     * {@link ShopCommand#addSubCommand(SubCommand)}.
+     * 
+     * @param name       the name
+     * @param onlyPlayer whether only players can run this sub command
+     * @see ShopCommand#addSubCommand(SubCommand)
+     * @since 1.13
+     */
+    public SubCommand(String name, boolean onlyPlayer) {
+        this.name = name;
+        this.onlyPlayer = onlyPlayer;
+    }
+
+    /**
+     * Gets the name of this sub command
+     * 
+     * @return the name
+     * @since 1.13
+     */
+    public String getName() {
+        return name;
+    }
+
+    /**
+     * Gets the permission the command sender needs to run this sub command
+     * <p>
+     * If no permission is needed, this should return an empty string.
+     * 
+     * @return the permission or an empty string
+     * @since 1.13
+     */
+    public String getPermission() {
+        return "";
+    }
+
+    /**
+     * Gets whether the given sender is permitted to run this sub command
+     * 
+     * @param sender the sender
+     * @return whether the sender is permitted
+     */
+    public boolean isPermitted(CommandSender sender) {
+        return getPermission() == null || getPermission().isEmpty() || sender.hasPermission(getPermission());
+    }
+
+    /**
+     * Gets whether the given sender can run this sub command
+     * <p>
+     * This checks whether the sender is a player if the command can only be run by
+     * players. This does not check for permission.
+     * 
+     * @param sender the sender
+     * @return whether the sender can run this sub command
+     * @since 1.13
+     */
+    public boolean canExecute(CommandSender sender) {
+        return sender instanceof Player || !onlyPlayer;
+    }
+
+    /**
+     * Gets the description of this sub command
+     * 
+     * @return the description
+     * @since 1.13
+     */
+    public abstract String getDescription();
+
+    /**
+     * Called when this sub command is executed
+     * <p>
+     * The first argument {@code args[0]} is not the sub command itself, but the
+     * argument after it (if entered)..
+     * 
+     * @param sender the sender
+     * @param args   the arguments of the sub command
+     * @since 1.13
+     */
+    public abstract void onExecute(CommandSender sender, String... args);
+
+    /**
+     * Called when a sender tab completes an argument in this sub command
+     * <p>
+     * The tab completion for the sub command itself is already handled. The first
+     * argument {@code args[0]} is not the sub command itself, but the argument
+     * after it (if entered)..
+     * 
+     * @param sender the command sender
+     * @param args the arguments of the sub command
+     * @return the tab completions
+     * @since 1.13
+     */
+    public abstract List<String> onTabComplete(CommandSender sender, String... args);
+
+}