core/sis-feature/src/main/java/org/apache/sis/filter/Node.java

/*
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF licenses this file to You 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 org.apache.sis.filter;

import java.util.Map;
import java.util.IdentityHashMap;
import java.util.Collection;
import java.io.Serializable;
import java.util.Collections;
import org.apache.sis.feature.DefaultAttributeType;
import org.apache.sis.util.collection.DefaultTreeTable;
import org.apache.sis.util.collection.TableColumn;
import org.apache.sis.util.collection.TreeTable;
import org.apache.sis.util.resources.Vocabulary;
import org.apache.sis.util.logging.Logging;
import org.apache.sis.internal.system.Loggers;

// Branch-dependent imports
import org.opengis.feature.AttributeType;
import org.opengis.filter.BinaryLogicOperator;


/**
 * Base class of Apache SIS implementation of OGC expressions, comparators or filters.
 * {@code Node} instances are associated together in a tree, which can be formatted
 * by {@link #toString()}.
 *
 * @author  Johann Sorel (Geomatys)
 * @author  Martin Desruisseaux (Geomatys)
 * @version 1.1
 * @since   1.1
 * @module
 */
abstract class Node implements Serializable {
    /**
     * For cross-version compatibility.
     */
    private static final long serialVersionUID = -749201100175374658L;

    /**
     * Creates a new expression, operator or filter.
     */
    protected Node() {
    }

    /**
     * Creates an attribute type for values of the given type and name.
     * The attribute is mandatory, unbounded and has no default value.
     *
     * @param  type  type of values in the attribute.
     * @param  name  name of the attribute to create.
     * @return an attribute of the given type and name.
     */
    static <T> AttributeType<T> createType(final Class<T> type, final Object name) {
        return new DefaultAttributeType<>(Collections.singletonMap(DefaultAttributeType.NAME_KEY, name),
                                          type, 1, 1, null, (AttributeType<?>[]) null);
    }

    /**
     * Returns the mathematical symbol for this binary function.
     * For comparison operators, the symbol should be one of {@literal < > ≤ ≥ = ≠}.
     * For arithmetic operators, the symbol should be one of {@literal + − × ÷}.
     *
     * @return the mathematical symbol, or 0 if none.
     */
    protected char symbol() {
        return (char) 0;
    }

    /**
     * Returns a name or symbol for this node. This is used for information purpose,
     * for example in order to build a string representation.
     *
     * @return the name of this node.
     */
    protected abstract String getName();

    /**
     * Returns the children of this node, or an empty collection if none. This is used
     * for information purpose, for example in order to build a string representation.
     *
     * <p>The name of this method is the same as {@link BinaryLogicOperator#getChildren()}
     * in order to have only one method to override.</p>
     *
     * @return the children of this node, or an empty collection if none.
     */
    protected abstract Collection<?> getChildren();

    /**
     * Builds a tree representation of this node, including all children. This method expects an
     * initially empty node, which will be set to the {@linkplain #getName() name} of this node.
     * Then all children will be appended recursively, with a check against cyclic graph.
     *
     * @param  root     where to create a tree representation of this node.
     * @param  visited  nodes already visited. This method will write in this map.
     */
    private void toTree(final TreeTable.Node root, final Map<Object,Boolean> visited) {
        root.setValue(TableColumn.VALUE, getName());
        for (final Object child : getChildren()) {
            final TreeTable.Node node = root.newChild();
            final String value;
            if (child instanceof Node) {
                if (visited.putIfAbsent(child, Boolean.TRUE) == null) {
                    ((Node) child).toTree(node, visited);
                    continue;
                } else {
                    value = Vocabulary.format(Vocabulary.Keys.CycleOmitted);
                }
            } else {
                value = String.valueOf(child);
            }
            node.setValue(TableColumn.VALUE, value);
        }
    }

    /**
     * Returns a string representation of this node. This representation can be printed
     * to the {@linkplain System#out standard output stream} (for example) if it uses a
     * monospaced font and supports Unicode.
     *
     * @return a string representation of this filter.
     */
    @Override
    public final String toString() {
        final DefaultTreeTable table = new DefaultTreeTable(TableColumn.VALUE);
        toTree(table.getRoot(), new IdentityHashMap<>());
        return table.toString();
    }

    /**
     * Returns a hash code value computed from the class and the children.
     */
    @Override
    public int hashCode() {
        return getClass().hashCode() + 37 * getChildren().hashCode();
    }

    /**
     * Returns {@code true} if the given object is an instance of the same class with the equal children.
     */
    @Override
    public boolean equals(final Object other) {
        if (other != null && other.getClass() == getClass()) {
            return getChildren().equals(((Node) other).getChildren());
        }
        return false;
    }

    /**
     * Reports that an operation failed because of the given exception.
     * This method assumes that the warning occurred in an {@code evaluate(…)} method.
     *
     * @todo Consider defining a {@code Context} class providing, among other information, listeners where to report warnings.
     *
     * @see <a href="https://issues.apache.org/jira/browse/SIS-460">SIS-460</a>
     */
    final void warning(final Exception e) {
        Logging.recoverableException(Logging.getLogger(Loggers.FILTER), getClass(), "evaluate", e);
    }
}