package bjc.utils.cli;

import java.util.TreeMap;
import java.util.function.BiConsumer;
import java.util.function.Consumer;

import bjc.utils.funcdata.FunctionalMap;
import bjc.utils.funcdata.IMap;

/**
 * A general command mode, with a customizable set of commands.
 *
 * There is a small set of commands which is handled by default. The first is
 * 'list', which lists all the commands the user can input. The second is
 * 'alias', which allows the user to bind a new name to a command.
 *
 * @author ben
 */
public class GenericCommandMode implements CommandMode {
	/* Contains the commands this mode handles. */
	private final IMap<String, Command> commandHandlers;
	/* Commands to execute in every mode. */
	private final IMap<String, Command> defaultHandlers;

	/* Contains help topics without an associated command */
	private final IMap<String, CommandHelp> helpTopics;

	/* The action to execute upon encountering an unknown command */
	private BiConsumer<String, String[]> unknownCommandHandler;

	/* The functions to use for input/output */
	private final Consumer<String> errorOutput;
	private final Consumer<String> normalOutput;

	/* The name of this command mode, or null if it is unnamed */
	private String modeName;

	/* The custom prompt to use, or null if none is specified */
	private String customPrompt;

	/**
	 * Create a new generic command mode
	 *
	 * @param normalOutput
	 *        The function to use for normal output.
	 *
	 * @param errorOutput
	 *        The function to use for error output.
	 */
	public GenericCommandMode(final Consumer<String> normalOutput, final Consumer<String> errorOutput) {
		if(normalOutput == null)
			throw new NullPointerException("Normal output source must be non-null");
		else if(errorOutput == null) throw new NullPointerException("Error output source must be non-null");

		this.normalOutput = normalOutput;
		this.errorOutput = errorOutput;

		/* Initialize maps so that they sort in alphabetical order. */
		commandHandlers = new FunctionalMap<>(new TreeMap<>());
		defaultHandlers = new FunctionalMap<>(new TreeMap<>());
		helpTopics = new FunctionalMap<>(new TreeMap<>());

		/* Setup default commands. */
		setupDefaultCommands();
	}

	/**
	 * Add an alias to an existing command.
	 *
	 * @param commandName
	 *        The name of the command to add an alias for.
	 *
	 * @param aliasName
	 *        The new alias for the command.
	 *
	 * @throws IllegalArgumentException
	 *         If the specified command doesn't have a bound handler, or if
	 *         the alias name already has a bound value.
	 */
	public void addCommandAlias(final String commandName, final String aliasName) {
		if(commandName == null) {
			throw new NullPointerException("Command name must not be null");
		} else if(aliasName == null) {
			String msg = "Alias name must not be null";
			throw new NullPointerException(msg);
		} else if(!commandHandlers.containsKey(commandName) && !defaultHandlers.containsKey(commandName)) {
			String msg = String.format("Cannot alias non-existant command '%s'", commandName);
			throw new IllegalArgumentException(msg);
		} else if(commandHandlers.containsKey(aliasName) || defaultHandlers.containsKey(aliasName)) {
			String msg = String.format("Cannot bind alias '%s' to an already bound command.", aliasName);
			throw new IllegalArgumentException(msg);
		} else {
			/* The command that will be aliased. */
			Command aliasedCommand;

			/* Get the alias. */
			if(defaultHandlers.containsKey(commandName)) {
				aliasedCommand = defaultHandlers.get(commandName).aliased();
			} else {
				aliasedCommand = commandHandlers.get(commandName).aliased();
			}

			commandHandlers.put(aliasName, aliasedCommand);
		}
	}

	/**
	 * Add a command to this command mode.
	 *
	 * @param command
	 *        The name of the command to add.
	 *
	 * @param handler
	 *        The handler to use for the specified command.
	 *
	 * @throws IllegalArgumentException
	 *         If the specified command already has a handler registered.
	 */
	public void addCommandHandler(final String command, final Command handler) {
		if(command == null) {
			throw new NullPointerException("Command must not be null");
		} else if(handler == null) {
			throw new NullPointerException("Handler must not be null");
		} else if(canHandle(command)) {
			String msg = String.format("Command '%s' already has a registered handler");
			throw new IllegalArgumentException(msg);
		} else {
			commandHandlers.put(command, handler);
		}
	}

	/**
	 * Add a help topic to this command mode that isn't tied to a command.
	 *
	 * @param topicName
	 *        The name of the topic.
	 *
	 * @param topic
	 *        The contents of the topic.
	 */
	public void addHelpTopic(final String topicName, final CommandHelp topic) {
		helpTopics.put(topicName, topic);
	}

	/* Default command builders */
	/*
	 * @TODO 10/09/17 Ben Culkin :CommandExtraction These command messages
	 * should be extracted into some kind of file-based abstraction.
	 */
	private GenericCommand buildAliasCommand() {
		final String aliasShortHelp = "alias\tAlias one command to another";
		final String aliasLongHelp = "Gives a command another name it can be invoked by."
				+ " Invoke with two arguments: the name of the command to alias"
				+ "followed by the name of the alias to give that command.";

		return new GenericCommand((args) -> {
			doAliasCommands(args);

			return this;
		}, aliasShortHelp, aliasLongHelp);
	}

	private GenericCommand buildClearCommands() {
		final String clearShortHelp = "clear\tClear the screen";
		final String clearLongHelp = "Clears the screen of all the text on it," + " and prints a new prompt.";

		return new GenericCommand((args) -> {
			errorOutput.accept("ERROR: This console doesn't support screen clearing");

			return this;
		}, clearShortHelp, clearLongHelp);
	}

	private GenericCommand buildExitCommand() {
		final String exitShortHelp = "exit\tExit the console";
		final String exitLongHelp = "First prompts the user to make sure they want to"
				+ " exit, then quits if they say they do";

		return new GenericCommand((args) -> {
			errorOutput.accept("ERROR: This console doesn't support auto-exiting");

			return this;
		}, exitShortHelp, exitLongHelp);
	}

	private GenericCommand buildHelpCommand() {
		final String helpShortHelp = "help\tConsult the help system";
		final String helpLongHelp = "Consults the internal help system."
				+ " Invoked in two different ways. Invoking with no arguments"
				+ " causes all the topics you can ask for details on to be list,"
				+ " while invoking with the name of a topic will print the entry" + " for that topic";

		return new GenericCommand((args) -> {
			if(args == null || args.length == 0) {
				/* Invoke general help */
				doHelpSummary();
			} else {
				/* Invoke help for a command */
				doHelpCommand(args[0]);
			}

			return this;
		}, helpShortHelp, helpLongHelp);
	}

	private GenericCommand buildListCommand() {
		final String listShortHelp = "list\tList available commands";
		final String listLongHelp = "Lists all of the commands available in this mode,"
				+ " as well as commands available in any mode";

		return new GenericCommand((args) -> {
			doListCommands();

			return this;
		}, listShortHelp, listLongHelp);
	}

	@Override
	public boolean canHandle(final String command) {
		return commandHandlers.containsKey(command) || defaultHandlers.containsKey(command);
	}

	/* Implement default commands */
	private void doAliasCommands(final String[] args) {
		if(args.length != 2) {
			String msg = String.format(
					"ERROR: Alias requires two arguments. The command name, and the alias for that command. ");
			errorOutput.accept(msg);
		} else {
			final String commandName = args[0];
			final String aliasName = args[1];

			if(!canHandle(commandName)) {
				String msg = String.format("ERROR: '%s' is not a valid command.", commandName);

				errorOutput.accept(msg);
			} else if(canHandle(aliasName)) {
				String msg = String.format("ERROR: Cannot overwrite command '%s'", aliasName);

				errorOutput.accept(msg);
			} else {
				addCommandAlias(commandName, aliasName);
			}
		}
	}

	private void doHelpCommand(final String commandName) {
		if(commandHandlers.containsKey(commandName)) {
			final String desc = commandHandlers.get(commandName).getHelp().getDescription();

			normalOutput.accept("\n" + desc);
		} else if(defaultHandlers.containsKey(commandName)) {
			final String desc = defaultHandlers.get(commandName).getHelp().getDescription();

			normalOutput.accept("\n" + desc);
		} else if(helpTopics.containsKey(commandName)) {
			normalOutput.accept("\n" + helpTopics.get(commandName).getDescription());
		} else {
			String msg = String.format("ERROR: No help available for '%s'", commandName);

			errorOutput.accept(msg);
		}
	}

	private void doHelpSummary() {
		normalOutput.accept("Help topics for this command mode are as follows:\n");

		if(commandHandlers.size() > 0) {
			commandHandlers.forEachValue(command -> {
				if(!command.isAlias()) {
					String comLine = command.getHelp().getSummary();
					String msg = String.format("\t%s\n", comLine);

					normalOutput.accept(msg);
				}
			});
		} else {
			normalOutput.accept("\tNone available\n");
		}

		normalOutput.accept("\nHelp topics available in all command modes are as follows\n");
		if(defaultHandlers.size() > 0) {
			/*
			 * @NOTE This block here should be abstracted out into a
			 * method.
			 */
			defaultHandlers.forEachValue(command -> {
				if(!command.isAlias()) {
					String comLine = command.getHelp().getSummary();
					String msg = String.format("\t%s\n", comLine);

					normalOutput.accept(msg);
				}
			});
		} else {
			normalOutput.accept("\tNone available\n");
		}

		normalOutput.accept("\nHelp topics not associated with a command are as follows\n");
		if(helpTopics.size() > 0) {
			helpTopics.forEachValue(topic -> {
				String msg = String.format("\t%s\n", topic.getSummary());

				normalOutput.accept(msg);
			});
		} else {
			normalOutput.accept("\tNone available\n");
		}
	}

	private void doListCommands() {
		normalOutput.accept("The available commands for this mode are as follows:\n");

		commandHandlers.keyList().forEach(commandName -> {
			String msg = String.format("\t%s", commandName);

			normalOutput.accept(msg);
		});

		normalOutput.accept("\nThe following commands are available in all modes:\n");
		defaultHandlers.keyList().forEach(commandName -> {
			String msg = String.format("\t%s", commandName);

			normalOutput.accept(msg);
		});

		normalOutput.accept("\n");
	}

	@Override
	public String getCustomPrompt() {
		if(customPrompt != null) return customPrompt;

		return CommandMode.super.getCustomPrompt();
	}

	@Override
	public String getName() {
		if(modeName != null) return modeName;

		return CommandMode.super.getName();
	}

	@Override
	public boolean isCustomPromptEnabled() {
		return customPrompt != null;
	}

	@Override
	public CommandMode process(final String command, final String[] args) {
		normalOutput.accept("\n");

		if(defaultHandlers.containsKey(command))
			return defaultHandlers.get(command).getHandler().handle(args);
		else if(commandHandlers.containsKey(command))
			return commandHandlers.get(command).getHandler().handle(args);
		else {
			if(args != null) {
				String argString = String.join(", ", args);
				String msg = String.format("ERROR: Unrecognized command %s (arguments %s)", command,
						argString);

				errorOutput.accept(msg);
			} else {
				String msg = String.format("ERROR: Unrecognized command %s", command);

				errorOutput.accept(msg);
			}

			if(unknownCommandHandler == null) {
				String msg = String.format("Command %s is invalid", command);

				throw new UnsupportedOperationException(msg);
			}

			unknownCommandHandler.accept(command, args);
		}

		return this;
	}

	/**
	 * Set the custom prompt for this mode
	 *
	 * @param prompt
	 *        The custom prompt for this mode, or null to disable the custom
	 *        prompt
	 */
	public void setCustomPrompt(final String prompt) {
		customPrompt = prompt;
	}

	/**
	 * Set the name of this mode
	 *
	 * @param name
	 *        The desired name of this mode, or null to use the default name
	 */
	public void setModeName(final String name) {
		modeName = name;
	}

	/**
	 * Set the handler to use for unknown commands
	 *
	 * @param handler
	 *        The handler to use for unknown commands, or null to throw on
	 *        unknown commands
	 */
	public void setUnknownCommandHandler(final BiConsumer<String, String[]> handler) {
		if(handler == null) throw new NullPointerException("Handler must not be null");

		unknownCommandHandler = handler;
	}

	/* Setup default commands. */
	private void setupDefaultCommands() {
		defaultHandlers.put("list", buildListCommand());
		defaultHandlers.put("alias", buildAliasCommand());
		defaultHandlers.put("help", buildHelpCommand());

		/* Help unix people :) */
		addCommandAlias("help", "man");

		/* Add commands handled in a upper layer. */
		/*
		 * @NOTE Figure out a place to put commands that apply across
		 * all modes, but only to a specific application.
		 */
		defaultHandlers.put("clear", buildClearCommands());
		defaultHandlers.put("exit", buildExitCommand());
	}

	/*
	 * (non-Javadoc)
	 *
	 * @see java.lang.Object#toString()
	 */
	@Override
	public String toString() {
		final StringBuilder builder = new StringBuilder();
		builder.append("GenericCommandMode [");

		if(commandHandlers != null) {
			builder.append("commandHandlers=");
			builder.append(commandHandlers);
		}

		if(defaultHandlers != null) {
			builder.append(", ");
			builder.append("defaultHandlers=");
			builder.append(defaultHandlers);
		}

		if(helpTopics != null) {
			builder.append(", ");
			builder.append("helpTopics=");
			builder.append(helpTopics);
		}

		if(modeName != null) {
			builder.append(", ");
			builder.append("modeName=");
			builder.append(modeName);
		}

		if(customPrompt != null) {
			builder.append(", ");
			builder.append("customPrompt=");
			builder.append(customPrompt);
		}

		builder.append("]");

		return builder.toString();
	}
}