001/*
002 * SPDX-License-Identifier: Apache-2.0
003 *
004 * Copyright 2024-2026 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.mediatype;
019
020import com.google.common.io.ByteSource;
021
022import org.slf4j.Logger;
023import org.slf4j.LoggerFactory;
024
025import java.io.IOException;
026import java.net.URI;
027import java.nio.charset.Charset;
028import java.util.Optional;
029
030// TODO Increase test coverage... (this currently only used by YamlMediaType)
031public abstract class ResourceCharsetDetectorSPI implements ResourceCharsetDetector {
032
033    private static final Logger LOG = LoggerFactory.getLogger(ResourceCharsetDetectorSPI.class);
034
035    @Override
036    public abstract Optional<Charset> detectCharset(URI uri, ByteSource source);
037
038    /**
039     * Peeks at the first N bytes of a resource.
040     *
041     * @return byte array of length up to N bytes, or shorter if the resource had less bytes, or
042     *     there was an error reading from it
043     */
044    protected final byte[] peek(int n, URI uri, ByteSource source) {
045        try {
046            return source.slice(0, n).read();
047        } catch (IOException e) {
048            LOG.warn("Failed to peek at the first {} bytes", n, uri, e);
049            return EMPTY; // skipcq: JAVA-S1049
050        }
051    }
052
053    private static final byte[] EMPTY = new byte[0];
054}