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/*
 * 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.tika.detect;

import java.io.IOException;
import java.io.InputStream;
import java.io.Serializable;

import org.apache.tika.metadata.Metadata;
import org.apache.tika.mime.MediaType;

/**
 * Content type detector. Implementations of this interface use various
 * heuristics to detect the content type of a document based on given
 * input metadata or the first few bytes of the document stream.
 *
 * @since Apache Tika 0.3
 */
public interface Detector extends Serializable {

    /**
     * Detects the content type of the given input document. Returns
     * application/octet-stream if the type of the document
     * can not be detected.
     * 
     * If the document input stream is not available, then the first
     * argument may be null. Otherwise the detector may
     * read bytes from the start of the stream to help in type detection.
     * The given stream is guaranteed to support the
     * {@link InputStream#markSupported() mark feature} and the detector
     * is expected to {@link InputStream#mark(int) mark} the stream before
     * reading any bytes from it, and to {@link InputStream#reset() reset}
     * the stream before returning. The stream must not be closed by the
     * detector.
     * 
     * The given input metadata is only read, not modified, by the detector.
     *
     * @param input document input stream, or null
     * @param metadata input metadata for the document
     * @return detected media type, or application/octet-stream
     * @throws IOException if the document input stream could not be read
     */
    MediaType detect(InputStream input, Metadata metadata) throws IOException;

}