/*
 * 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
 *
 * http://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 com.addthis.hydra.data.filter.value;

import com.addthis.bundle.core.Bundle;
import com.addthis.bundle.util.AutoField;
import com.addthis.bundle.util.AutoParam;
import com.addthis.bundle.util.ValueUtil;
import com.addthis.bundle.value.ValueArray;
import com.addthis.bundle.value.ValueObject;

import com.fasterxml.jackson.annotation.JsonProperty;

/**
 * This {@link AbstractValueFilter ValueFilter} <span class="hydra-summary">returns the <i>i</i><sup>th</sup> element of an array</span>.
 * <p/>
 * <p>The {@link #index index} specifies the 0-based offset of the element to retrieve.
 * A negative value for the index will retrieve the (-i) value from the opposite end of the array.
 * If {@link #toNull toNull} is true, then a null value is returned when the index is out of bounds.
 * If toNull is false, then the entire array is returned when the index is out of bounds.
 * <p/>
 * <p>Example:</p>
 * <pre>
 *      {from:"FOO_2_BAR", to:"FOO", filter:[{split:"="}, {index:0}]}
 * </pre>
 *
 * @user-reference
 * @exclude-fields once
 */
public class ValueFilterIndex extends AbstractValueFilterContextual {

    /** The array offset of the element to return. */
    @AutoParam private AutoField index;

    /** If true, then return null when the index is out of bounds. Default is true. */
    @JsonProperty private boolean toNull = true;

    @Override public ValueObject filter(ValueObject value, Bundle context) {
        ValueObject nullReturn = toNull ? null : value;
        if (ValueUtil.isEmpty(value)) {
            return nullReturn;
        }
        if (value.getObjectType() == ValueObject.TYPE.ARRAY) {
            ValueArray arr = value.asArray();
            if (arr.isEmpty()) {
                return nullReturn;
            }
            int i = index.getInt(context).getAsInt();
            while (i < 0) {
                i = arr.size() + i;
            }
            return (arr.size() > i) ? arr.get(i) : nullReturn;
        }
        return nullReturn;
    }

    /** required to override by contract -- not used */
    @Override public ValueObject filterValue(ValueObject value, Bundle context) {
        throw new UnsupportedOperationException("only filter should be called");
    }
}