001/*
002 * SPDX-License-Identifier: Apache-2.0
003 *
004 * Copyright 2023-2026 The Enola <https://enola.dev> Authors
005 *
006 * Licensed under the Apache License, Version 2.0 (the "License");
007 * you may not use this file except in compliance with the License.
008 * You may obtain a copy of the License at
009 *
010 *     https://www.apache.org/licenses/LICENSE-2.0
011 *
012 * Unless required by applicable law or agreed to in writing, software
013 * distributed under the License is distributed on an "AS IS" BASIS,
014 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
015 * See the License for the specific language governing permissions and
016 * limitations under the License.
017 */
018package dev.enola.common.io.resource;
019
020import com.google.common.io.ByteSink;
021import com.google.common.io.ByteSource;
022import com.google.common.net.MediaType;
023
024import java.net.URI;
025import java.nio.charset.StandardCharsets;
026
027/**
028 * Resource which ignores writes, and returns an infinite amount of bytes of value 0 on read. This
029 * is a bit like /dev/null on *NIX OS for writing, but not for reading (because /dev/null returns
030 * EOF on read, but this does not).
031 *
032 * @see EmptyResource for an (non-writable) EOF ReadableResource
033 */
034public class NullResource extends BaseResource implements Resource {
035
036    public static class Provider implements ResourceProvider {
037
038        @Override
039        public Resource getResource(URI uri) {
040            if (SCHEME.equals(uri.getScheme())) return NullResource.INSTANCE;
041            else return null;
042        }
043    }
044
045    public static final NullResource INSTANCE =
046            new NullResource(MediaType.OCTET_STREAM.withCharset(StandardCharsets.UTF_8));
047
048    static final String SCHEME = "null";
049
050    public NullResource(MediaType mediaType) {
051        super(uri(mediaType), mediaType);
052    }
053
054    private static URI uri(MediaType mediaType) {
055        // TODO Why URI of MediaType, instead of a single hard-coded fixed one?
056        // TODO Why withoutParameters()? To remove spaces? Just encode!
057        return URI.create(SCHEME + ":" + mediaType.withoutParameters());
058    }
059
060    @Override
061    public ByteSink byteSink() {
062        return NullByteSink.INSTANCE;
063    }
064
065    @Override
066    public ByteSource byteSource() {
067        return NullByteSource.INSTANCE;
068    }
069}