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Component of the XMLUtil library
There is a newer version: 0.90.0-RC3
/*
 * Copyright (c) 2024.
 *
 * This file is part of xmlutil.
 *
 * This file is licenced to you under the Apache License, Version 2.0 (the
 * "License"); you may not use this file except in compliance
 * with the License.  You should have received a copy of the license with the source distribution.
 * Alternatively, 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 nl.adaptivity.xmlutil

import kotlinx.serialization.ExperimentalSerializationApi
import kotlinx.serialization.KSerializer
import kotlinx.serialization.descriptors.SerialDescriptor
import kotlinx.serialization.descriptors.SerialKind

/**
 * Combined interface for custom serializers that support special casing by the XML Format.
 */
@ExperimentalXmlUtilApi
public interface XmlSerializer : KSerializer, XmlSerializationStrategy, XmlDeserializationStrategy

/**
 * Helper function that allows the XML format to use a different descriptor for the given type. This
 * is intended for use with custom serializers implementing [XmlSerializer] to handle xml
 * serialization specially.
 * @receiver The "normal"/default descriptor
 * @param xmlDescriptor The descriptor to use in case of XML (not overridden by default).
 * @param serialQName The name of the type as if specified by annotation. By default `null` (no name given)
 * @return A subtype of the serializer that is recognized by the xml format and allows dynamic
 *          descriptions dependent on the format.
 */
@ExperimentalXmlUtilApi
public fun SerialDescriptor.xml(
    xmlDescriptor: SerialDescriptor = this,
    serialQName: QName? = null
): XmlSerialDescriptor {
    return XmlSerialDescriptorImpl(this, xmlDescriptor, serialQName)
}

/**
 * Marker to signify that the descriptor is an xmlSerialDescriptor and the delegate
 * can be retrieved through getElementDescriptor with negative value.
 */
@XmlUtilInternal
public annotation class XmlSerialDescriptorMarker

/**
 * Serial Descriptor delegate that supports special casing by the XML format. This means
 * that the descriptor can be different for non-xml and xml serialization. (Used by the QName
 * serializer).
 */
@ExperimentalXmlUtilApi
public interface XmlSerialDescriptor : SerialDescriptor {
    public val delegate: SerialDescriptor
    public val xmlDescriptor: SerialDescriptor
    public val serialQName: QName? get() = null

    @ExperimentalSerializationApi
    override val elementsCount: Int get() = delegate.elementsCount

    @ExperimentalSerializationApi
    override val kind: SerialKind get() = delegate.kind

    @ExperimentalSerializationApi
    override val serialName: String get() = delegate.serialName

    @ExperimentalSerializationApi
    override fun getElementAnnotations(index: Int): List = delegate.getElementAnnotations(index)

    @ExperimentalSerializationApi
    override fun getElementDescriptor(index: Int): SerialDescriptor = when {
        index < 0 -> xmlDescriptor
        else -> delegate.getElementDescriptor(index)
    }

    @ExperimentalSerializationApi
    override fun getElementIndex(name: String): Int = delegate.getElementIndex(name)

    @ExperimentalSerializationApi
    override fun getElementName(index: Int): String = delegate.getElementName(index)

    @ExperimentalSerializationApi
    override fun isElementOptional(index: Int): Boolean {
        return delegate.isElementOptional(index)
    }

    @ExperimentalSerializationApi
    override val annotations: List get() =
        listOf(XmlSerialDescriptorMarker()) + delegate.annotations

    override val isInline: Boolean get() = delegate.isInline

    @ExperimentalSerializationApi
    override val isNullable: Boolean get() = delegate.isNullable
}

private class XmlSerialDescriptorImpl(
    override val delegate: SerialDescriptor,
    xmlDescriptor: SerialDescriptor = delegate,
    serialQName: QName? = null
) : XmlSerialDescriptor {
    override val serialQName: QName? get() = xmlDescriptor.serialQName

    override val xmlDescriptor: XmlSerialDescriptor = object : XmlSerialDescriptor {
        override val delegate: SerialDescriptor = xmlDescriptor

        override val xmlDescriptor: SerialDescriptor get() = this
        override val serialQName: QName? = serialQName
    }

}