import java.io.PrintWriter;
import java.io.StringWriter;
import java.lang.annotation.ElementType;
import java.lang.annotation.Retention;
import java.lang.annotation.RetentionPolicy;
import java.lang.annotation.Target;
import java.lang.reflect.Constructor;
import java.lang.reflect.Field;
import java.lang.reflect.InvocationTargetException;
import java.lang.reflect.Method;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.HashMap;
import java.util.List;
import java.util.Map.Entry;
import java.util.TreeMap;
import java.util.regex.Matcher;
import java.util.regex.Pattern;

import org.apache.commons.lang.StringUtils;
import org.apache.commons.lang.time.StopWatch;
import org.bukkit.Bukkit;
import org.bukkit.ChatColor;
import org.bukkit.OfflinePlayer;
import org.bukkit.command.Command;
import org.bukkit.command.CommandExecutor;
import org.bukkit.command.CommandMap;
import org.bukkit.command.CommandSender;
import org.bukkit.command.PluginCommand;
import org.bukkit.command.TabCompleter;
import org.bukkit.entity.Player;
import org.bukkit.plugin.Plugin;
import org.bukkit.plugin.java.JavaPlugin;

import net.md_5.bungee.api.chat.ClickEvent;
import net.md_5.bungee.api.chat.ComponentBuilder;
import net.md_5.bungee.api.chat.HoverEvent;

/**
 * Register a command with the command system!
 * <br><br>
 * Handles arguments, argument type handling, predictions, tab completion, sub-sub-sub-commands, error handling, help pages, and more!
 * <br><br>
 * CommandManager manager = new CommandManager(plugin, "Help Tag", "command", "permission node");
 *
 * @author Stumblinbear
 */
public class CommandManager implements TabCompleter, CommandExecutor {
	static boolean GLOBAL_DEBUG = false;
	@Cmd(cmd = "debug",
			args = "[bool]",
			argTypes = { Arg.ArgBoolean.class },
			help = "Toggle debug mode.",
			longhelp = "Toggle debug mode. Shows information on command usage.",
			only = CommandOnly.OP,
			permission = "debug")
	public static CommandFinished cmdToggleDebugMode(CommandSender sender, Object[] args) {
		GLOBAL_DEBUG = (args.length != 0 ? (Boolean)args[0] : !GLOBAL_DEBUG);
		sender.sendMessage(ChatColor.YELLOW + "Debug mode is now: " + (GLOBAL_DEBUG ? ChatColor.GREEN + "ON" : ChatColor.RED + "OFF"));
		return CommandFinished.DONE;
	}

	private static HashMap<Class<? extends AbstractArg<?>>, AbstractArg<?>> argInstances = new HashMap<Class<? extends AbstractArg<?>>, AbstractArg<?>>();

	private ArrayList<Cmd> commands = new ArrayList<Cmd>();
	private ArrayList<Method> commandMethods = new ArrayList<Method>();

	String tag;
	String command;
	String permissionScheme;

	public CommandManager(JavaPlugin plugin, String tag, String permissionScheme, String command, String... aliases) {
		this.tag = tag;
		this.command = command;
		this.permissionScheme = permissionScheme;

		// Used to inject the command without using plugin.yml
		try {
			final Field bukkitCommandMap = Bukkit.getServer().getClass().getDeclaredField("commandMap");

			bukkitCommandMap.setAccessible(true);
			CommandMap commandMap = (CommandMap)bukkitCommandMap.get(Bukkit.getServer());

			Constructor<PluginCommand> c = PluginCommand.class.getDeclaredConstructor(String.class, Plugin.class);
			c.setAccessible(true);

			PluginCommand pluginCommand = c.newInstance(command, plugin);
			pluginCommand.setTabCompleter(this);
			pluginCommand.setExecutor(this);
			if(aliases.length > 0)
				pluginCommand.setAliases(Arrays.asList(aliases));
			commandMap.register(command, pluginCommand);

			loadCommandClass(this.getClass());
		} catch(Exception e) { e.printStackTrace(); }
	}

	/**
	 * Parses classes for @Cmd annotations.
	 */
	public CommandManager loadCommandClass(Class<?> commandClass) {
		try {
			for(Method method : commandClass.getMethods()) {
				if(method.isAnnotationPresent(Cmd.class)) {
					Cmd cmd = method.getAnnotation(Cmd.class);
					commands.add(cmd);
					commandMethods.add(method);
				}
			}
		} catch(SecurityException e) {
			e.printStackTrace();
		}

		return this;
	}

	@Override
	public List<String> onTabComplete(CommandSender sender, Command command, String alias, String[] args) {
		List<String> predictions = new ArrayList<String>();
		String token = (args.length == 0 ? "" : args[args.length - 1]);

		for(Cmd c : commands) {
			List<String> cmdPredictions = getPredicted(c, token, args.length - 1);
			// Prevent duplicate entries
			if(cmdPredictions != null) {
				for(String str : cmdPredictions) {
					if(!predictions.contains(str))
						predictions.add(str);
				}
			}
		}

		return predictions;
	}

	/**
	 * Get a prediction of the next command argument.
	 */
	private List<String> getPredicted(Cmd c, String token, int i) {
		String[] cmdArg = c.cmd().split(" ");
		// If no token, return all possible commands.
		if(token == "")
			return Arrays.asList(new String[] { cmdArg[0] });
		// If the amount of args is more than available, or it doesn't start with the token.
		if(i >= cmdArg.length) {
			int argNum = i - cmdArg.length;
			if(argNum >= c.argTypes().length)
				return null;
			else{
				if(!argInstances.containsKey(c.argTypes()[argNum]))
					try {
						argInstances.put(c.argTypes()[argNum], c.argTypes()[argNum].newInstance());
					} catch (Exception e) { }
				AbstractArg<?> absArg = argInstances.get(c.argTypes()[argNum]);
				return absArg.getPredictions();
			}
		// If it doesn't start with the token.
		}else if(!cmdArg[i].startsWith(token))
			return null;
		// It must be a match!
		return Arrays.asList(new String[] { cmdArg[i] });
	}

	@Override
	public boolean onCommand(CommandSender sender, Command cmd, String label, String[] args) {
		StopWatch sw = null;
		if(GLOBAL_DEBUG) {
			sw = new StopWatch();
			sw.start();
		}

		CommandFinished finishedType = runCommand(sender, args);
		if(finishedType.shouldPrint()) {
			sender.sendMessage(ChatColor.RED + finishedType.getErrorString());

			// Do our best to predict which command was going to be used.
			if(finishedType == CommandFinished.COMMAND) {
				// TreeMaps automatically sort by numbers.
				TreeMap<Double, Cmd> possible = new TreeMap<Double, Cmd>();
				for(Cmd c : commands) {
					// Reduce arg array to the shortest one.
					String[] fixedArgs = new String[c.cmd().split(" ").length];
					for(int i = 0; i < (args.length > fixedArgs.length ? fixedArgs.length : args.length); i++)
						fixedArgs[i] = args[i];

					// Combine the arguments.
					String cmdArgs = StringUtils.join(fixedArgs, " ");

					// Use Levenshtein Distance to get how similar the two strings are to each other. Calculate percentage with the value returned.
					possible.put((1D - (StringUtils.getLevenshteinDistance(cmdArgs, c.cmd()) / (Math.max(cmdArgs.length(), c.cmd().length()) * 1D))) * 100D, c);
				}

				// Are there even any predictions?
				if(possible.size() > 0) {
					// Get the last entry. (The one with the highest possibility)
					Entry<Double, Cmd> entry = possible.pollLastEntry();
					sender.sendMessage("");
					// Allow players to click the command in chat to add it to their chat input.
					if(sender instanceof Player) {
						((Player)sender).spigot().sendMessage(new ComponentBuilder("   Did you mean: ").color(net.md_5.bungee.api.ChatColor.GOLD)
					    		.append("/" + label + " " + entry.getValue().cmd()).color(net.md_5.bungee.api.ChatColor.GRAY)
					    		.event(new HoverEvent(HoverEvent.Action.SHOW_TEXT, new ComponentBuilder(StringUtils.join((entry.getValue().longhelp().equals("") ? entry.getValue().help() : entry.getValue().longhelp()).split("(?<=\\G.........................)"), "\n")).create()))
					    		.event(new ClickEvent(ClickEvent.Action.SUGGEST_COMMAND, "/" + label + " " + entry.getValue().cmd()))
					    		.append("? We're " + ((int)(entry.getKey() * 10) / 10D) + "% sure.").reset().color(net.md_5.bungee.api.ChatColor.GOLD).create());
					}else
						sender.sendMessage(ChatColor.GOLD + "   Did you mean: " + ChatColor.GRAY + "/" + label + " " + entry.getValue().cmd() + ChatColor.GOLD + "? We're " + ((int)(entry.getKey() * 10) / 10D) + "% sure.");
					sender.sendMessage("");
				}
			}
		}

		if(GLOBAL_DEBUG && sw != null) {
			sw.stop();
			sender.sendMessage(ChatColor.YELLOW + "Command took " + sw.getTime() + " milliseconds to complete.");
		}
		return true;
	}

	/**
	 * Find the best command to run and do so.
	 */
	public CommandFinished runCommand(CommandSender sender, String[] args) {
		try {
			// Display help if no args, or they use the help command
			if(args.length == 0 || args[0].equalsIgnoreCase("help"))
				return displayHelp(sender, args.length == 0 ? null : args);
			else{
				Cmd bestFit = null;
				int bestFit_i = 0;
				int bestFit_args = -1;

				// Loop through commands until a suitable one is found
				for(int i = 0; i < commands.size(); i++) {
					Cmd cmd = commands.get(i);

					// Split the base command and check for a match
					String[] cmds = cmd.cmd().split(" ");
					if(args.length >= cmds.length) {
						boolean valid = true;
						for(int j = 0; j < cmds.length; j++) {
							if(!cmds[j].equalsIgnoreCase(args[j])) {
								valid = false;
								break;
							}
						}

						if(!valid)
							continue;
					}else
						continue;

					// Check if it's better than the best fit.
					if(cmd.cmd().split(" ").length > bestFit_args) {
						bestFit = cmd;
						bestFit_i = i;
						bestFit_args = cmd.cmd().split(" ").length;
					}else
						continue;
				}

				if(bestFit != null) {
					// Check the "only" argument
					if(sender instanceof Player) {
						if(bestFit.only() == CommandOnly.CONSOLE)
							return CommandFinished.NOPLAYER;
					}else if(bestFit.only() == CommandOnly.PLAYER)
						return CommandFinished.NOCONSOLE;

					// Check for the "op" argument and permission argument
					if((bestFit.only() == CommandOnly.OP ? !sender.isOp() : false) ||
							(bestFit.permission() != "" ? !sender.hasPermission(permissionScheme + "." + bestFit.permission()) : false))
						return CommandFinished.PERMISSION;

					// Split up the args; arguments in quotes count as a single argument.
					List<Object> cmdArgList = new ArrayList<Object>();
					Matcher m = Pattern.compile("(?:([^\"]\\S*)|\"(.+?)\")\\s*").matcher(StringUtils.join(args, " ").replaceFirst(bestFit.cmd(), "").trim());
					for(int j = 0; m.find(); j++) {
						// Apply the requested argument type.
						Class<? extends AbstractArg<?>> requestedType = (j < bestFit.argTypes().length ? bestFit.argTypes()[j] : Arg.ArgString.class);
						// Cache the instance.
						if(!argInstances.containsKey(requestedType))
							argInstances.put(requestedType, requestedType.newInstance());
						AbstractArg<?> absArg = argInstances.get(requestedType);
						try {
							Object arg = absArg.parseArg(m.group(1) != null ? m.group(1) : m.group(2));
							if(arg == null)
								// Some argument parsers don't throw an exception. Just an extra precaution.
								throw new CommandException(absArg.getFailure() + " (" + m.group(1) != null ? m.group(1) : m.group(2) + ")");
							cmdArgList.add(arg);
						} catch(Exception e) {
							return CommandFinished.CUSTOM.replace(absArg.getFailure() + " (" + (m.group(1) != null ? m.group(1) : m.group(2)) + ")");
						}
					}

					// Check that all the required arguments have been fulfilled.
					Object[] cmdArgsPassed = cmdArgList.toArray(new Object[cmdArgList.size()]);
					if(StringUtils.countMatches(bestFit.args(), "<") > cmdArgsPassed.length)
						return CommandFinished.BADCOMMAND.replace(command + " " + bestFit.cmd() + " " + bestFit.args());

					// Run the command :D
					return (CommandFinished)commandMethods.get(bestFit_i).invoke(null, new Object[] { sender, (cmdArgsPassed != null ? cmdArgsPassed : null) });
				}
			}
		} catch(InvocationTargetException e) {
			e.getCause().printStackTrace();
			if(e.getCause() instanceof CommandException)
				return CommandFinished.CUSTOM.replace(e.getCause().getMessage());
			if(GLOBAL_DEBUG)
				Bukkit.broadcastMessage(ChatColor.RED + "Error: " + getTrace(e));
			return CommandFinished.EXCEPTION;
		} catch (Exception e) {
			e.printStackTrace();
			if(GLOBAL_DEBUG)
				Bukkit.broadcastMessage(ChatColor.RED + "Error: " + getTrace(e));
			return CommandFinished.EXCEPTION;
		}

		return CommandFinished.COMMAND.replace(command);
	}

	/**
	 * Display the help menu.
	 */
	public CommandFinished displayHelp(CommandSender sender, String[] args) {
		ArrayList<String> helpList = new ArrayList<String>(); // The help message buffer
		boolean specific = false; // If "help <command>"
		int perPage = 8; // How many commands to show per page
		int page = 0; // Which page

		if(args != null && args.length != 1) {
			try {
				page = Integer.parseInt(args[1]) - 1;
				if(page < 0) // Negative pages are bad juju.
					page = 0;
			} catch(Exception e) { specific = true; } // If this fails, it's probably a string. Check for a specific command.
		}

		String cmdLabel = null; // The label of the specific command.

		if(specific && args.length != 1) {
			perPage = 4; // Reduce the amount to show per page.
			cmdLabel = StringUtils.join(args, " ").split(" ", 2)[1]; // Because args = "help <command>" cut out "help".
		}

		for(Cmd cmd : commands) {
			// If looking for specific commands and it isn't the one we're looking for
			if(specific && !cmd.cmd().startsWith(cmdLabel))
				continue;

			// Should it even show?
			if(cmd.showInHelp()) {
				// If it can't be used, don't show it! Simple! :D
				boolean canUse = cmd.permission().equals("") ? true : (sender.hasPermission(permissionScheme + "." + cmd.permission()));

				// Is it op-only?
				if(cmd.only() == CommandOnly.OP)
					canUse = (cmd.permission().equals("") ? sender.isOp() : canUse);

				if(canUse)
					helpList.add(ChatColor.GOLD + "/" + command + " " + cmd.cmd() + (cmd.args() != "" ? " " + cmd.args() : "") + ": " + ChatColor.WHITE + (specific ? (cmd.longhelp().equals("") ? cmd.help() : cmd.longhelp()) : cmd.help()));
			}
		}

		// Make sure there's something to show.
		boolean badPage = true;
		if(helpList.size() >= page * perPage) {
			for(int j = 0; j < perPage; j++) {
				if(helpList.size() > (j + page * perPage)) {
					if(j == 0)
						sender.sendMessage(ChatColor.YELLOW + "--------- " + ChatColor.WHITE + tag + " Help (" + (page + 1) + "/" + (int)Math.ceil(helpList.size() / (perPage * 1F)) + ")" + ChatColor.YELLOW + " ---------------------");
					sender.sendMessage(helpList.get((j + page * perPage)));
					badPage = false;
				}
			}
		}

		if(badPage) {
			if(specific)
				return CommandFinished.CUSTOM.replace("Command unrecognized.");
			else
				return CommandFinished.CUSTOM.replace("Page " + (page + 1) + " does not exist in help.");
		}else if(helpList.size() > (page + 1) * perPage)
			sender.sendMessage(ChatColor.WHITE + "Use " + ChatColor.YELLOW + "/" + command + " help " + (page + 2) + ChatColor.WHITE + " to see more help.");
		return CommandFinished.DONE;
	}

	/**
	 * Returns the string version of an exception. Helps with in-game error checking.
	 */
	private String getTrace(Exception e) {
		StringWriter sw = new StringWriter();
		PrintWriter pw = new PrintWriter(sw);
		e.printStackTrace(pw);
		return sw.toString();
	}

	@Target(ElementType.METHOD)
	@Retention(RetentionPolicy.RUNTIME)
	/**
	 * Attach to a function to denote it as a command. You must register the class it is in as a command class before it will be used.
	 */
	public static @interface Cmd {
		/**
		 * Takes in any amount of subcommands. The command handler always chooses the best-fit command.
		 * <br><br>
		 * Example:
		 * <br>
		 * cmd = "sub1 sub2 sub3 sub4 sub5"
		 */
		String cmd() default "";

		/**
		 * The arguments for the command. Required arguments must be enclosed in <>'s
		 * <br><br>
		 * Example:
		 * <br>
		 * args = "<arg1> <arg2> [arg3]"
		 * <br>
		 * Argument 1 and 2 are required; the third is optional.
		 */
		String args() default "";

		/**
		 * Specifies the type that an argument should be. Default is Arg.ArgString.
		 * <br><br>
		 * Example:
		 * <br>
		 * argTypes = { Arg.ArgInteger, Arg.ArgString, Arg.ArgPlayer }
		 * <ul>
			 * <li>Argument 1 <i>must</i> be an integer.</li>
			 * <li>Argument 2 <i>must</i> be a string(anything).</li>
			 * <li>Argument 3 <i>must</i> be an online player.</li>
		 * </ul>
		 */
		Class<? extends AbstractArg<?>>[] argTypes() default { };

		/**
		 * The text to show next to a command when a user does /cmd help.
		 */
		String help() default "Default help thingy... :(";

		/**
		 * The text to show next to a command when a user does /cmd help <command>.
		 * <br><br>
		 * Use to give more information about the command.
		 */
		String longhelp() default "";

		/**
		 * Should the command be shown in help at all?
		 */
		boolean showInHelp() default true;

		/**
		 * Specifies if the command should be restricted to CONSOLE, OP, or PLAYERS. Otherwise, ALL.
		 */
		CommandOnly only() default CommandOnly.ALL;

		/**
		 * The permission node to use.
		 * <br><br>
		 * Example:
		 * <br>
		 * new CommandManager(plugin, "Test", "testnode", "test");
		 * <br>
		 * permission = "edit"
		 * <br>
		 * This setup would require a player to have testnode.edit to use the command.
		 */
		String permission() default "";
	}

	/**
	 * Used to define who is allowed to use a command.
	 */
	public static enum CommandOnly {
		/**
		 * Only players can use the command.
		 */
		PLAYER,
		/**
		 * Only op players can use the command. Can be overridden by a matched permission.
		 */
		OP,
		/**
		 * Only the console can use the command.
		 */
		CONSOLE,
		/**
		 * Anyone can use the command, given their permissions match.
		 */
		ALL
	}

	/**
	 * This can be used to immediately throw an error without returning a <code>CommandFinished</code>.
	 * It'll display the specified error.
	 */
	public static class CommandException extends Exception {
		private static final long serialVersionUID = 1L;

		public CommandException(String message) {
			super(message);
		}
	}

	/**
	 * A set of command errors.
	 */
	public static enum CommandFinished {
		/** Finished correctly */
		DONE(false, "Done"),
		/** Command does not exist */
		COMMAND(true, "Command does not exist. Use /%s for help."),
		/** Command does not exist */
		BADCOMMAND(true, "Bad command usage: /%s "),
		/** Console not allowed to use */
		NOCONSOLE(true, "This command cannot be run from the console."),
		/** Player not allowed to use */
		NOPLAYER(true, "This command cannot be run by players."),
		/** Player does not exist */
		EXISTPLAYER(true, "That player does not exist."),
		/** Incorrect permissions */
		PERMISSION(true, "Insufficient permissions."),

		HOLDBLOCK(true, "You must be holding a block."),
		HOLDITEM(true, "You must be holding an item."),

		LONGSTRING(true, "String cannot be longer than %s!"),

		/** Custom error */
		CUSTOM(true, "%s"),
		EXCEPTION(true, "An exception occured. Please contact a member of staff and tell them!");

		private boolean shouldPrint;
		private String errorString;
		private String extraString;

		CommandFinished(boolean par1ShouldPrint, String par1Error) {
			shouldPrint = par1ShouldPrint;
			errorString = par1Error;
		}

		public boolean shouldPrint() {
			return shouldPrint;
		}

		public String getErrorString() {
			if(extraString != null)
				return errorString.replace("%s", extraString);
			else
				return errorString;
		}

		public CommandFinished replace(String theString) {
			extraString = theString;
			return this;
		}
	}

	/*
	 * Arguments
	 */
	public static interface IArgParse<T> {
		T parseArg(String arg);

		List<String> getPredictions();

		String getFailure();
	}

	public static abstract class AbstractArg<T> implements IArgParse<T> {
		public AbstractArg() { }
	}

	public static class Arg {
		public static class ArgArray extends AbstractArg<List<String>> {
			public List<String> parseArg(String arg) {
				List<String> list = new ArrayList<String>();
				for(String str : arg.split(","))
					list.add(str);
				return list;
			}

			public String getFailure() {
				return "Argument failure.";
			}

			public List<String> getPredictions() { return null; }
		}

		public static class ArgBoolean extends AbstractArg<Boolean> {
			public Boolean parseArg(String arg) {
				if(arg.equalsIgnoreCase("true") || arg.equalsIgnoreCase("yes") || arg.equalsIgnoreCase("on") || arg.equalsIgnoreCase("1"))
					return true;
				if(arg.equalsIgnoreCase("false") || arg.equalsIgnoreCase("no") || arg.equalsIgnoreCase("off") || arg.equalsIgnoreCase("0"))
					return false;
				return null;
			}

			public String getFailure() {
				return "Argument not a valid boolean.";
			}

			public List<String> getPredictions() { return Arrays.asList(new String[] { "true", "false" }); }
		}

		public static class ArgByte extends AbstractArg<Byte> {
			public Byte parseArg(String arg) {
				return Byte.valueOf(arg);
			}

			public String getFailure() {
				return "Argument not a valid byte.";
			}

			public List<String> getPredictions() { return Arrays.asList(new String[] { "0", "1", "2", "3", "4", "5", "6", "7", "8", "9", "10", "11", "12", "13", "14", "15" }); }
		}

		public static class ArgDouble extends AbstractArg<Double> {
			public Double parseArg(String arg) {
				return Double.valueOf(arg);
			}

			public String getFailure() {
				return "Argument not a real number.";
			}

			public List<String> getPredictions() { return null; }
		}

		public static class ArgFloat extends AbstractArg<Float> {
			public Float parseArg(String arg) {
				return Float.valueOf(arg);
			}

			public String getFailure() {
				return "Argument not a floating point number.";
			}

			public List<String> getPredictions() { return null; }
		}

		public static class ArgInteger extends AbstractArg<Integer> {
			public Integer parseArg(String arg) {
				return Integer.valueOf(arg);
			}

			public String getFailure() {
				return "Argument not an integer.";
			}

			public List<String> getPredictions() { return null; }
		}

		public static class ArgPlayer extends AbstractArg<OfflinePlayer> {
			public Player parseArg(String arg) {
				return Bukkit.getPlayer(arg);
			}

			public String getFailure() {
				return CommandFinished.EXISTPLAYER.getErrorString();
			}

			public List<String> getPredictions() {
				List<String> players = new ArrayList<String>();
				for(Player p : Bukkit.getOnlinePlayers())
					players.add(p.getName());
				return players;
			}
		}

		public static class ArgOfflinePlayer extends AbstractArg<OfflinePlayer> {
			@SuppressWarnings("deprecation")
			public OfflinePlayer parseArg(String arg) {
				return Bukkit.getOfflinePlayer(arg);
			}

			public String getFailure() {
				return CommandFinished.EXISTPLAYER.getErrorString();
			}

			public List<String> getPredictions() {
				List<String> players = new ArrayList<String>();
				for(Player p : Bukkit.getOnlinePlayers())
					players.add(p.getName());
				return players;
			}
		}

		public static class ArgString extends AbstractArg<String> {
			public String parseArg(String arg) {
				return arg;
			}

			public String getFailure() {
				return "Could not parse string.";
			}

			public List<String> getPredictions() { return null; }
		}
	}
}