LuaScript/src/main/java/org/openautonomousconnection/luascript/hosts/HostServices.java

package org.openautonomousconnection.luascript.hosts;

import java.util.Objects;
import java.util.Optional;

/**
 * Service container holding optional host capabilities.
 *
 * <p>This avoids one huge "bridge" interface.</p>
 */
public final class HostServices {

    private final ConsoleHost console;
    private final DomHost dom;
    private final EventHost events;
    private final ResourceHost resources;
    private final UiHost ui;

    private HostServices(Builder b) {
        this.console = b.console;
        this.ui = b.ui;
        this.dom = b.dom;
        this.events = b.events;
        this.resources = b.resources;
    }

    /**
     * @return optional DomHost capability
     */
    public Optional<DomHost> dom() {
        return Optional.ofNullable(dom);
    }

    /**
     * @return optional EventHost capability
     */
    public Optional<EventHost> events() {
        return Optional.ofNullable(events);
    }

    /**
     * @return optional ResourceHost capability
     */
    public Optional<ResourceHost> resources() {
        return Optional.ofNullable(resources);
    }

    /** @return optional console host */
    public Optional<ConsoleHost> console() {
        return Optional.ofNullable(console);
    }

    /** @return optional ui host */
    public Optional<UiHost> ui() {
        return Optional.ofNullable(ui);
    }

    /** @return builder */
    public static Builder builder() {
        return new Builder();
    }

    /**
     * Builder for HostServices.
     */
    public static final class Builder {
        private ConsoleHost console;
        private DomHost dom;
        private EventHost events;
        private ResourceHost resources;
        private UiHost ui;

        public Builder console(ConsoleHost console) {
            this.console = Objects.requireNonNull(console, "console");
            return this;
        }

        public Builder ui(UiHost ui) {
            this.ui = Objects.requireNonNull(ui, "ui");
            return this;
        }

        /**
         * Provides dom capability.
         *
         * @param dom dom host
         * @return this
         */
        public Builder dom(DomHost dom) {
            this.dom = Objects.requireNonNull(dom, "dom");
            return this;
        }

        /**
         * Provides event subscription capability.
         *
         * @param events event host
         * @return this
         */
        public Builder events(EventHost events) {
            this.events = Objects.requireNonNull(events, "events");
            return this;
        }

        /**
         * Provides resource loading capability.
         *
         * @param resources resource host
         * @return this
         */
        public Builder resources(ResourceHost resources) {
            this.resources = Objects.requireNonNull(resources, "resources");
            return this;
        }

        public HostServices build() {
            return new HostServices(this);
        }
    }
}