package fr.xephi.authme.command;

import fr.xephi.authme.permission.DefaultPermission;
import fr.xephi.authme.permission.PermissionNode;
import fr.xephi.authme.util.CollectionUtils;
import fr.xephi.authme.util.StringUtils;

import java.util.ArrayList;
import java.util.List;

import static com.google.common.base.Preconditions.checkArgument;
import static java.util.Arrays.asList;

/**
 * Command description - defines which labels ("names") will lead to a command and points to the
 * {@link ExecutableCommand} implementation that executes the logic of the command.
 *
 * CommandDescription instances are built hierarchically and have one parent or {@code null} for base commands
 * (main commands such as /authme) and may have multiple children extending the mapping of the parent: e.g. if
 * /authme has a child whose label is "register", then "/authme register" is the command that the child defines.
 */
public class CommandDescription {

    /**
     * Defines the labels to execute the command. For example, if labels are "register" and "r" and the parent is
     * the command for "/authme", then both "/authme register" and "/authme r" will be handled by this command.
     */
    private List<String> labels;
    /**
     * Short description of the command.
     */
    private String description;
    /**
     * Detailed description of what the command does.
     */
    private String detailedDescription;
    /**
     * The executable command instance described by this object.
     */
    private ExecutableCommand executableCommand;
    /**
     * The parent command.
     */
    private CommandDescription parent;
    /**
     * The child commands that extend this command.
     */
    private List<CommandDescription> children = new ArrayList<>();
    /**
     * The arguments the command takes.
     */
    private List<CommandArgumentDescription> arguments;
    /**
     * Command permissions required to execute this command.
     */
    private CommandPermissions permissions;

    /**
     * Private constructor. Use {@link CommandDescription#builder()} to create instances of this class.
     * <p />
     * Note for developers: Instances should be created with {@link CommandDescription#createInstance} to be properly
     * registered in the command tree.
     */
    private CommandDescription() {
    }

    /**
     * Create an instance.
     *
     * @param labels              List of command labels.
     * @param description         Command description.
     * @param detailedDescription Detailed comment description.
     * @param executableCommand   The executable command, or null.
     * @param parent              Parent command.
     * @param arguments           Command arguments.
     * @param permissions         The permissions required to execute this command.
     *
     * @return The created instance
     * @see CommandDescription#builder()
     */
    private static CommandDescription createInstance(List<String> labels, String description,
                                                 String detailedDescription, ExecutableCommand executableCommand,
                                                 CommandDescription parent, List<CommandArgumentDescription> arguments,
                                                 CommandPermissions permissions) {
        CommandDescription instance = new CommandDescription();
        instance.labels = labels;
        instance.description = description;
        instance.detailedDescription = detailedDescription;
        instance.executableCommand = executableCommand;
        instance.parent = parent;
        instance.arguments = arguments;
        instance.permissions = permissions;

        if (parent != null) {
            parent.addChild(instance);
        }
        return instance;
    }

    private void addChild(CommandDescription command) {
        children.add(command);
    }

    /**
     * Get all relative labels of this command. For example, if this object describes "/authme register" and
     * "/authme r", then "r" and "register" are the relative labels, whereas "authme" is the label of the parent.
     *
     * @return All relative labels.
     */
    public List<String> getLabels() {
        return labels;
    }

    /**
     * Check whether this command description has a specific command.
     *
     * @param commandLabel The label to check for.
     *
     * @return {@code true} if this command contains the given label, {@code false} otherwise.
     */
    public boolean hasLabel(String commandLabel) {
        for (String label : labels) {
            if (label.equalsIgnoreCase(commandLabel)) {
                return true;
            }
        }
        return false;
    }

    /**
     * Return the {@link ExecutableCommand} instance defined by the command description.
     *
     * @return The executable command object.
     */
    public ExecutableCommand getExecutableCommand() {
        return executableCommand;
    }

    /**
     * Return the parent.
     *
     * @return The parent command, or null for base commands.
     */
    public CommandDescription getParent() {
        return parent;
    }

    /**
     * Return the number of parents that precede the command description.
     *
     * @return The number of parents, e.g. for "/authme abc def" the parent count is 2 ("/authme abc", "/authme")
     */
    public int getParentCount() {
        if (parent == null) {
            return 0;
        }
        return parent.getParentCount() + 1;
    }

    /**
     * Return all command children.
     *
     * @return Command children.
     */
    public List<CommandDescription> getChildren() {
        return children;
    }

    /**
     * Return all arguments the command takes.
     *
     * @return Command arguments.
     */
    public List<CommandArgumentDescription> getArguments() {
        return arguments;
    }

    /**
     * Return a short description of the command.
     *
     * @return Command description.
     */
    public String getDescription() {
        return description;
    }

    /**
     * Return a detailed description of the command.
     *
     * @return Detailed description.
     */
    public String getDetailedDescription() {
        return detailedDescription;
    }

    /**
     * Return the permissions required to execute the command.
     *
     * @return The command permissions, or null if none are required to execute the command.
     */
    public CommandPermissions getCommandPermissions() {
        return permissions;
    }

    /**
     * Return a builder instance to create a new command description.
     *
     * @return The builder
     */
    public static CommandBuilder builder() {
        return new CommandBuilder();
    }

    /**
     * Builder for initializing CommandDescription objects.
     */
    public static final class CommandBuilder {
        private List<String> labels;
        private String description;
        private String detailedDescription;
        private ExecutableCommand executableCommand;
        private CommandDescription parent;
        private List<CommandArgumentDescription> arguments = new ArrayList<>();
        private CommandPermissions permissions;

        /**
         * Build a CommandDescription from the builder or throw an exception if a mandatory
         * field has not been set.
         *
         * @return The generated CommandDescription object
         */
        public CommandDescription build() {
            checkArgument(!CollectionUtils.isEmpty(labels), "Labels may not be empty");
            checkArgument(!StringUtils.isEmpty(description), "Description may not be empty");
            checkArgument(!StringUtils.isEmpty(detailedDescription), "Detailed description may not be empty");
            checkArgument(executableCommand != null, "Executable command must be set");
            // parents and permissions may be null; arguments may be empty

            return createInstance(labels, description, detailedDescription, executableCommand,
                                  parent, arguments, permissions);
        }

        public CommandBuilder labels(List<String> labels) {
            this.labels = labels;
            return this;
        }

        public CommandBuilder labels(String... labels) {
            return labels(asList(labels));
        }

        public CommandBuilder description(String description) {
            this.description = description;
            return this;
        }

        public CommandBuilder detailedDescription(String detailedDescription) {
            this.detailedDescription = detailedDescription;
            return this;
        }

        public CommandBuilder executableCommand(ExecutableCommand executableCommand) {
            this.executableCommand = executableCommand;
            return this;
        }

        public CommandBuilder parent(CommandDescription parent) {
            this.parent = parent;
            return this;
        }

        /**
         * Add an argument that the command description requires. This method can be called multiples times to add
         * multiple arguments.
         *
         * @param label The label of the argument (single word name of the argument)
         * @param description The description of the argument
         * @param isOptional True if the argument is optional, false if it is mandatory
         *
         * @return The builder
         */
        public CommandBuilder withArgument(String label, String description, boolean isOptional) {
            arguments.add(new CommandArgumentDescription(label, description, isOptional));
            return this;
        }

        public CommandBuilder permissions(DefaultPermission defaultPermission,
                                          PermissionNode... permissionNodes) {
            this.permissions = new CommandPermissions(asList(permissionNodes), defaultPermission);
            return this;
        }
    }

}