/*
 * 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.wicket.util.resource;

import java.io.ByteArrayInputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.Reader;
import java.io.UnsupportedEncodingException;
import java.nio.charset.Charset;
import java.time.Instant;
import org.apache.wicket.util.io.IOUtils;
import org.apache.wicket.util.io.Streams;
import org.apache.wicket.util.lang.Bytes;
import org.apache.wicket.util.string.Strings;


/**
 * Base class for string resources.
 * 
 * @author Jonathan Locke
 */
public abstract class AbstractStringResourceStream extends AbstractResourceStream
        implements
                IStringResourceStream
{
        private static final long serialVersionUID = 1L;

        /** The content-type applied in case the resource stream's default constructor is used */
        public static final String DEFAULT_CONTENT_TYPE = "text";

        /** Charset name for resource */
        private String charsetName;

        /** MIME content type */
        private final String contentType;

        /** The last time this stylesheet was modified */
        private Instant lastModified = null;

        /**
         * Constructor.
         */
        public AbstractStringResourceStream()
        {
                this(DEFAULT_CONTENT_TYPE);
        }

        /**
         * Constructor.
         * 
         * @param contentType
         *            The mime type of this resource, such as "image/jpeg" or "text/html"
         */
        public AbstractStringResourceStream(final String contentType)
        {
                // TODO null for contentType is allowed? or should the default be applied instead?
                this.contentType = contentType;

                lastModified = Instant.now();
        }

        /**
         * @return This resource as a String.
         */
        @Override
        public String asString()
        {
                Reader reader = null;
                try
                {
                        if (charsetName == null)
                        {
                                reader = new InputStreamReader(getInputStream());
                        }
                        else
                        {
                                reader = new InputStreamReader(getInputStream(), getCharset());
                        }
                        return Streams.readString(reader);
                }
                catch (IOException e)
                {
                        throw new RuntimeException("Unable to read resource as String", e);
                }
                catch (ResourceStreamNotFoundException e)
                {
                        throw new RuntimeException("Unable to read resource as String", e);
                }
                finally
                {
                        IOUtils.closeQuietly(reader);
                        IOUtils.closeQuietly(this);
                }
        }

        /**
         * @return Charset for resource
         */
        protected Charset getCharset()
        {
                // java.nio.Charset is not serializable so we can only store the name
                return (charsetName != null) ? Charset.forName(charsetName) : null;
        }

        /**
         * Sets the character set used for reading this resource.
         * 
         * @param charset
         *            Charset for component
         */
        @Override
        public void setCharset(final Charset charset)
        {
                // java.nio.Charset itself is not serializable so we can only store the name
                charsetName = (charset != null) ? charset.name() : null;
        }

        /**
         * @see org.apache.wicket.util.resource.IResourceStream#close()
         */
        @Override
        public void close() throws IOException
        {
        }

        /**
         * @see org.apache.wicket.util.resource.IResourceStream#getContentType()
         */
        @Override
        public String getContentType()
        {
                return contentType;
        }

        /**
         * @see org.apache.wicket.util.resource.IResourceStream#getInputStream()
         */
        @Override
        public InputStream getInputStream() throws ResourceStreamNotFoundException
        {
                final byte[] bytes;
                if (getCharset() != null)
                {
                        try
                        {
                                bytes = getString().getBytes(getCharset().name());
                        }
                        catch (UnsupportedEncodingException e)
                        {
                                throw new ResourceStreamNotFoundException("Could not encode resource", e);
                        }
                }
                else
                {
                        bytes = getString().getBytes();
                }
                return new ByteArrayInputStream(bytes);
        }

        /**
         * @see org.apache.wicket.util.watch.IModifiable#lastModifiedTime()
         */
        @Override
        public Instant lastModifiedTime()
        {
                return lastModified;
        }

        /**
         * @param lastModified
         *            The lastModified to set.
         */
        public void setLastModified(final Instant lastModified)
        {
                this.lastModified = lastModified;
        }

        /**
         * @return The string resource
         */
        protected abstract String getString();

        @Override
        public final Bytes length()
        {
                int lengthInBytes = Strings.lengthInBytes(getString(), getCharset());
                return Bytes.bytes(lengthInBytes);
        }
}