SelectItemsUtils.java

/*
 * Copyright OmniFaces
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not use this file except in compliance with
 * the License. You may obtain a copy of the License at
 *
 *     https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software distributed under the License is distributed on
 * an "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the License for the
 * specific language governing permissions and limitations under the License.
 */
package org.omnifaces.util.selectitems;

import static org.omnifaces.util.Utils.isEmpty;

import java.util.ArrayList;
import java.util.Iterator;
import java.util.List;
import java.util.NoSuchElementException;
import java.util.Objects;

import jakarta.faces.component.UIComponent;
import jakarta.faces.context.FacesContext;
import jakarta.faces.convert.Converter;
import jakarta.faces.model.SelectItem;
import jakarta.faces.model.SelectItemGroup;

/**
 * Collection of utility methods for working with {@link SelectItem} or data represented by them.
 *
 * @author Arjan Tijms
 *
 */
public final class SelectItemsUtils {

    private SelectItemsUtils() {}

    /**
     * Finds an object value in the {@link SelectItem} instances associated with the given component by means of matching its converted value with
     * the given string value.
     *
     * @param context The involved faces context.
     * @param component the component with which {@link SelectItem}s should be associated that are used to search in.
     * @param value a string that should match the string representation of one of the values held by the {@link SelectItem}s.
     * @param converter the faces {@link Converter} used to generate String representations for the values held by the {@link SelectItem}s.
     *
     * @return the Object representation of the value where its string representation matches the input value.
     */
    public static Object findValueByStringConversion(FacesContext context, UIComponent component, String value, Converter<Object> converter) {
        return findValueByStringConversion(context, component, SelectItemsCollector.collectFromParent(context, component).iterator(), value, converter);
    }

    private static Object findValueByStringConversion(FacesContext context, UIComponent component, Iterator<SelectItem> items, String value, Converter<Object> converter) {
        while (items.hasNext()) {
            SelectItem item = items.next();

            if (item instanceof SelectItemGroup) {
                SelectItem[] groupItems = ((SelectItemGroup) item).getSelectItems();
                Object object = findValueByStringConversion(context, component, groupItems, value, converter);

                if (object != null) {
                    return object;
                }
            }
            else if (!item.isNoSelectionOption()) {
                Object itemValue = item.getValue();
                String convertedItemValue = converter.getAsString(context, component, itemValue);

                if (Objects.equals(value, convertedItemValue)) {
                    return itemValue;
                }
            }
        }

        return null;
    }

    private static Object findValueByStringConversion(FacesContext context, UIComponent component, SelectItem[] items, String value, Converter<Object> converter) {
        return isEmpty(items) ? null : findValueByStringConversion(context, component, new ArrayIterator(items), value, converter);
    }

    /**
     * Collects all values associated with all {@link SelectItem} instances associated with the given component.
     * <p>
     * Note that values from recursively scanned {@link SelectItemGroup} instances are included.
     *
     * @param context The involved faces context.
     * @param component the component with which {@link SelectItem} instances should be associated
     * @return List of all values hold by {@link SelectItem} instances
     */
    public static List<Object> collectAllValuesFromSelectItems(FacesContext context, UIComponent component) {
        List<Object> values = new ArrayList<>();
        collect(SelectItemsCollector.collectFromParent(context, component).iterator(), values);

        return values;
    }

    private static void collect(Iterator<SelectItem> items, List<Object> values) {
        while (items.hasNext()) {
            SelectItem item = items.next();
            if (item instanceof SelectItemGroup) {
                SelectItem[] subitems = ((SelectItemGroup) item).getSelectItems();
                if (!isEmpty(subitems)) {
                    collect(new ArrayIterator(subitems), values);
                }
            } else if (!item.isNoSelectionOption()) {
                values.add(item.getValue());
            }
        }
    }

    /**
     * Exposes an Array via an <code>Iterator</code>
     */
    static class ArrayIterator implements Iterator<SelectItem> {

        private SelectItem[] items;
        private int index = 0;

        public ArrayIterator(SelectItem[] items) {
            this.items = items;
        }

        @Override
        public boolean hasNext() {
            return (index < items.length);
        }

        @Override
        public SelectItem next() {
            if (hasNext()) {
                return items[index++];
            }
            else {
                throw new NoSuchElementException();
            }
        }

        @Override
        public void remove() {
            throw new UnsupportedOperationException();
        }

    }

}