/*
 * 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.xml;

import java.util.Map;
import java.util.HashMap;
import java.util.Iterator;
import java.util.Collections;
import org.apache.sis.internal.xml.LegacyNamespaces;


/**
 * The target version of standards for {@link Transformer}.
 *
 * @author  Martin Desruisseaux (Geomatys)
 * @author  Cullen Rombach (Image Matters)
 * @version 1.0
 *
 * @see Transformer
 *
 * @since 0.4
 * @module
 */
final class TransformVersion {
    /**
     * Metadata using the legacy ISO 19139:2007 schema (replaced by ISO 19115-3).
     */
    static final TransformVersion ISO19139 = new TransformVersion(42, 2);
    static {
        ISO19139.addSurjectives(new String[] {
                Namespaces.CAT,
                Namespaces.CIT,
                Namespaces.DQC,
                Namespaces.FCC,
                Namespaces.GEX,
                Namespaces.GMW,
                Namespaces.LAN,
                Namespaces.MAC,
                Namespaces.MAS,
                Namespaces.MCC,
                Namespaces.MCO,
                Namespaces.MD1,
                Namespaces.MD2,
                Namespaces.MDA,
                Namespaces.MDB,
                Namespaces.MDQ,
                Namespaces.MDS,
                Namespaces.MDT,
                Namespaces.MEX,
                Namespaces.MMI,
                Namespaces.MPC,
                Namespaces.MRC,
                Namespaces.MRD,
                Namespaces.MRI,
                Namespaces.MRL,
                Namespaces.MRS,
                Namespaces.MSR,
                Namespaces.RCE
            }, LegacyNamespaces.GMD);
        /*
         * For the way back from legacy ISO 19139:2007 to new ISO 19115-3:2016, we must rely on TransformingReader
         * (do NOT declare entries in 'imports', because some namespaces must be left unchanged). An exception to
         * this rule is the "gco" namespace, because our reader renames only element namespaces while we need to
         * rename also attributes in "gco" namespace (e.g. "gco:nilReason").
         */
        ISO19139.addSurjective (Namespaces.SRV, LegacyNamespaces.SRV);
        ISO19139.addSurjective (Namespaces.GCX, LegacyNamespaces.GMX);
        ISO19139.addBijective  (Namespaces.GCO, LegacyNamespaces.GCO);
        ISO19139.addAlias(LegacyNamespaces.GMI, LegacyNamespaces.GMI_ALIAS);
    }

    /**
     * GML using the legacy {@code "http://www.opengis.net/gml"} namespace.
     * Note that the use of GML 3.2 implies the use of ISO 19139:2007.
     */
    static final TransformVersion GML31 = new TransformVersion(ISO19139);
    static {
        GML31.addBijective(Namespaces.GML, LegacyNamespaces.GML);
    }

    /**
     * Apply all known namespace replacements. This can be used only at unmarshalling time,
     * for replacing all namespaces by the namespaces declared in Apache SIS JAXB annotations.
     */
    static final TransformVersion ALL = GML31;

    /**
     * The URI replacements to apply when going from the model implemented by Apache SIS
     * to the transforming reader/writer. Keys are the URIs as declared in JAXB annotations,
     * and values are the URIs to write instead of the actual ones.
     *
     * <p>This map shall not be modified after construction.
     * We do not wrap in {@link Collections#unmodifiableMap(Map)} for efficiency.</p>
     *
     * @see #exports()
     */
    private final Map<String,String> exports;

    /**
     * The URI replacements to apply when going from the transforming reader/writer to
     * the model implemented by Apache SIS. This map is the converse of {@link #exports}.
     * It does not contain the map of properties to rename because that map is handled
     * by {@link TransformingReader} instead, as part of {@value TransformingReader#FILENAME} file.
     *
     * <p>This map shall not be modified after construction.
     * We do not wrap in {@link Collections#unmodifiableMap(Map)} for efficiency.</p>
     */
    private final Map<String,String> imports;

    /**
     * Creates a new enumeration initialized to the given capacity.
     *
     * @param  ec  exports capacity.
     * @param  ic  imports capacity.
     */
    private TransformVersion(final int ec, final int ic) {
        exports = new HashMap<>(ec);
        imports = new HashMap<>(ic);
    }

    /**
     * Creates an enumeration initialized to a copy of the given enumeration.
     * This construction should be followed by calls to {@code add(…)} methods.
     */
    private TransformVersion(final TransformVersion first) {
        exports = new HashMap<>(first.exports);
        imports = new HashMap<>(first.imports);
    }

    /**
     * Adds a namespace to be considered as an alias of another namespace.
     * The aliases are usually non-official URL and should not be used in exports.
     */
    private void addAlias(final String standard, final String alias) {
        imports.put(alias, standard);
    }

    /**
     * Adds a two-directional association between a namespace used in JAXB annotation and a namespace
     * used in XML document. A bijective association means that the renaming is reversible.
     */
    private void addBijective(final String jaxb, final String xml) {
        exports.put(jaxb, xml);
        imports.put(xml, jaxb);
    }

    /**
     * Adds a one-way association from JAXB namespace to XML namespace. Many JAXB namespaces may map
     * to the same XML namespace. For example most ISO 19115-3:2016 namespaces map to the same legacy
     * ISO 19139:2007 namespace. Consequently this association is not easily reversible.
     */
    private void addSurjective(final String jaxb, final String xml) {
        exports.put(jaxb, xml);
    }

    /**
     * Adds one-way associations from JAXB namespaces to a single XML namespace.
     * This method is used when the legacy schema (the {@code xml} one) was one large monolithic schema,
     * and the new schema (represented by {@code jaxb}) has been separated in many smaller modules.
     */
    private void addSurjectives(final String[] jaxb, final String xml) {
        for (final String e : jaxb) {
            exports.put(e, xml);
        }
    }

    /**
     * Converts a namespace used in JAXB annotation to the namespace used in XML document.
     * Returns the same URI if there is no replacement.
     */
    final String exportNS(final String uri) {
        return exports.getOrDefault(uri, uri);
    }

    /**
     * Converts a namespace used in XML document to the namespace used in JAXB annotation.
     * Returns the same URI if there is no replacement.
     */
    final String importNS(final String uri) {
        return imports.getOrDefault(uri, uri);
    }

    /**
     * Returns the URI replacements to apply when going from the model implemented by Apache SIS to the
     * transforming reader/writer. Used only for more sophisticated work than what {@link #exportNS(String)} does.
     * Returned as an iterator for avoiding to expose modifiable map; do not invoke {@link Iterator#remove()}.
     */
    final Iterator<Map.Entry<String,String>> exports() {
        return exports.entrySet().iterator();
    }
}
