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package framework;

import java.io.Serializable;
import java.util.Collection;
import java.util.LinkedHashMap;
import java.util.Map;
import java.util.Optional;
import java.util.Set;
import java.util.stream.Collectors;
import java.util.stream.Stream;

/**
 * session scoped object
 * 
 * @param  value type
 */
public interface Attributes extends Map, Serializable {
    /**
     * @return attribute names
     */
    Stream names();

    /**
     * @param  value type
     * @param name attribute name
     * @return attribute value
     */
     Optional getAttr(String name);

    /**
     * @param name attribute name
     * @param value attribute value
     */
    void setAttr(String name, ValueType value);

    /**
     * @param name attribute name
     */
    void removeAttr(String name);

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#size()
     */
    @Override
    default int size() {
        return (int) names().count();
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#isEmpty()
     */
    @Override
    default boolean isEmpty() {
        return !names().findAny()
            .isPresent();
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#containsKey(java.lang.Object)
     */
    @Override
    default boolean containsKey(Object key) {
        return names().anyMatch(key::equals);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#containsValue(java.lang.Object)
     */
    @Override
    default boolean containsValue(Object value) {
        return values().contains(value);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#get(java.lang.Object)
     */
    @Override
    default ValueType get(Object key) {
        return getAttr((String) key).orElse(null);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#put(java.lang.Object, java.lang.Object)
     */
    @Override
    default ValueType put(String key, ValueType value) {
        ValueType old = getAttr(key).orElse(null);
        setAttr(key, value);
        return old;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#remove(java.lang.Object)
     */
    @Override
    default ValueType remove(Object key) {
        ValueType old = getAttr((String) key).orElse(null);
        removeAttr((String) key);
        return old;
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#putAll(java.util.Map)
     */
    @Override
    default void putAll(Map m) {
        m.forEach((k, v) -> setAttr(k, v));
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#clear()
     */
    @Override
    default void clear() {
        names().forEach(this::removeAttr);
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#keySet()
     */
    @Override
    default Set keySet() {
        return names().collect(Collectors.toSet());
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#values()
     */
    @Override
    default Collection values() {
        return names().map(i -> getAttr(i).orElse(null))
            .collect(Collectors.toList());
    }

    /*
     * (non-Javadoc)
     * 
     * @see java.util.Map#entrySet()
     */
    @Override
    default Set> entrySet() {
        return names().map(i -> Tuple.of(i, getAttr(i).orElse(null)))
            .collect(Collectors.toSet());
    }

    /**
     * get and remove value from session
     * 
     * @param key session key
     * @return text
     */
    default String flash(String key) {
        String value = Tool.string(get(key))
            .orElse("");
        removeAttr(key);
        return value;
    }

    /**
     * Simple implementation
     *
     * @param  Value type
     */
    @SuppressWarnings("serial")
    public static class Impl implements Attributes {

        /**
         * Map
         */
        final LinkedHashMap map = new LinkedHashMap<>();

        @Override
        public Stream names() {
            return map.keySet()
                .stream();
        }

        @SuppressWarnings("unchecked")
        @Override
        public  Optional getAttr(String name) {
            return Optional.ofNullable((T) map.get(name));
        }

        @Override
        public void setAttr(String name, V value) {
            map.put(name, value);
        }

        @Override
        public void removeAttr(String name) {
            map.remove(name);
        }

    }
}