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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.util

import nl.adaptivity.xmlutil.*
import nl.adaptivity.xmlutil.XmlDelegatingReader
import nl.adaptivity.xmlutil.core.impl.multiplatform.Reader
import nl.adaptivity.xmlutil.core.impl.multiplatform.StringReader
import nl.adaptivity.xmlutil.util.impl.CombiningReader
import nl.adaptivity.xmlutil.util.impl.FragmentNamespaceContext

/**
 * This streamreader allows for reading document fragments. It does so by wrapping the reader into a
 * pair of wrapper elements, and then ignoring those on reading.
 *
 * Created by pdvrieze on 04/11/15.
 */
public actual class XMLFragmentStreamReader private constructor(delegate: XmlReader) :
    XmlDelegatingReader(delegate) {

    override val delegate: XmlReader get() = super.delegate

    private var localNamespaceContext: FragmentNamespaceContext =
        FragmentNamespaceContext(null, emptyArray(), emptyArray())

    public constructor(reader: Reader, namespaces: Iterable) : this(getDelegate(reader, namespaces)) {
        if (delegate.isStarted && delegate.eventType === EventType.START_ELEMENT) extendNamespace()
    }

    override fun getNamespaceURI(prefix: String): String? {
        if (WRAPPERPPREFIX.contentEquals(prefix)) return null

        return super.getNamespaceURI(prefix)
    }

    override fun getNamespacePrefix(namespaceUri: String): String? {
        if (WRAPPERNAMESPACE.contentEquals(namespaceUri)) return null

        return super.getNamespacePrefix(namespaceUri)
    }

    override fun next(): EventType {
        return when (val delegateNext = delegate.next()) {
            EventType.END_DOCUMENT -> delegateNext
            EventType.START_DOCUMENT,
            EventType.PROCESSING_INSTRUCTION,
            EventType.DOCDECL -> next()

            EventType.START_ELEMENT -> {
                if (WRAPPERNAMESPACE.contentEquals(delegate.namespaceURI)) {
                    // Special case the wrapping namespace, dropping the element.
                    next()
                } else {
                    extendNamespace()
                    delegateNext
                }
            }

            EventType.END_ELEMENT -> if (WRAPPERNAMESPACE.contentEquals(delegate.namespaceURI)) {
                // Drop the closing tag of the wrapper as well
                delegate.next()
            } else {
                localNamespaceContext = localNamespaceContext.parent ?: localNamespaceContext
                delegateNext
            }

            else -> delegateNext
        }
    }

    override val namespaceContext: IterableNamespaceContext get() = localNamespaceContext

    public actual companion object {

        public const val WRAPPERPPREFIX: String = "SDFKLJDSF"
        public const val WRAPPERNAMESPACE: String = "http://wrapperns"

        private fun getDelegate(
            reader: Reader,
            wrapperNamespaceContext: Iterable
        ): XmlReader {
            val wrapper = buildString {
                append("<$WRAPPERPPREFIX:wrapper xmlns:$WRAPPERPPREFIX=\"$WRAPPERNAMESPACE\"")
                for (ns in wrapperNamespaceContext) {
                    val prefix = ns.prefix
                    val uri = ns.namespaceURI
                    if (XMLConstants.DEFAULT_NS_PREFIX == prefix) {
                        append(" xmlns")
                    } else {
                        append(" xmlns:").append(prefix)
                    }
                    append("=\"").append(uri.xmlEncode()).append('"')
                }
                append(" >")
            }

            val actualInput = CombiningReader(StringReader(wrapper), reader, StringReader(""))
            return xmlStreaming.newGenericReader(actualInput)
        }

        public fun from(reader: Reader, namespaceContext: Iterable): XMLFragmentStreamReader {
            return XMLFragmentStreamReader(reader, namespaceContext)
        }

        public fun from(reader: Reader): XMLFragmentStreamReader {
            return XMLFragmentStreamReader(reader, emptyList())
        }

        public actual fun from(fragment: ICompactFragment): XMLFragmentStreamReader {
            return XMLFragmentStreamReader(StringReader(fragment.contentString), fragment.namespaces)
        }
    }

    private fun extendNamespace() {
        val namespaceDecls = delegate.namespaceDecls
        val nscount = namespaceDecls.size
        val prefixes = Array(nscount) { idx -> namespaceDecls[idx].prefix }
        val namespaces = Array(nscount) { idx -> namespaceDecls[idx].namespaceURI }

        localNamespaceContext = FragmentNamespaceContext(localNamespaceContext, prefixes, namespaces)
    }


}