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package com.qcloud.cos.internal;

import java.io.InputStream;
import java.util.EnumMap;

/**
 * Client request options such as client markers for individual
 * {@link QcloudWebServiceRequest}s.
 */
public final class RequestClientOptions {
    /**
     * Used to enable mark-and-reset for
     * non-mark-and-resettable non-file input stream for up to 128K memory
     * buffering by default. Add 1 to get around an implementation quirk of
     * BufferedInputStream.
     *
     * Retries after reading {@link #DEFAULT_STREAM_BUFFER_SIZE} bytes would
     * fail to reset the underlying input stream as the mark position would
     * have been invalidated.
     *
     */
    public static final int DEFAULT_STREAM_BUFFER_SIZE = (1 << 17)+1;
    public static enum Marker {
        /**
         * Used to specify the http user_agent value.
         * This marker is intended only for internal use by the COS SDK.
         */
        USER_AGENT,
        ;
    }

    private final EnumMap markers = new EnumMap(Marker.class);
    /**
     * Used for mark-and-reset purposes during retry.
     */
    private int readLimit = DEFAULT_STREAM_BUFFER_SIZE;

    /**
     * Returns the value of the specified marker; or null if there is no such
     * value.
     */
    public String getClientMarker(Marker marker) {
        return markers.get(marker);
    }

    /**
     * Associates the given value with the given marker.
     * Note the {@link Marker#USER_AGENT} is only intended for internal use
     * by the COS SDK.
     */
    public void putClientMarker(Marker marker, String value) {
        markers.put(marker, value);
    }

    /**
     * Appends a user agent to the USER_AGENT client marker.
     * This method is intended only for internal use by the COS SDK.
     */
    public void appendUserAgent(String userAgent) {
        String marker = markers.get(Marker.USER_AGENT);
        if (marker == null)
            marker = "";
        marker = createUserAgentMarkerString(marker, userAgent);
        putClientMarker(Marker.USER_AGENT, marker);
    }

    /**
     * Appends the given client marker string to the existing one and returns it.
     */
    private String createUserAgentMarkerString(final String marker, String userAgent) {
        return marker.contains(userAgent) ? marker : marker + " " + userAgent;
    }

    /**
     * Returns the mark-and-reset read limit; defaults to
     * {@value #DEFAULT_STREAM_BUFFER_SIZE}.
     *
     * @see InputStream#mark(int)
     */
    public final int getReadLimit() {
        return readLimit;
    }

    /**
     * Sets the optional mark-and-reset read limit used for signing and retry
     * purposes.
     *
     * @see InputStream#mark(int)
     */
    public final void setReadLimit(int readLimit) {
        this.readLimit = readLimit;
    }

    /**
     * Copy the internal states of this RequestClientOptions to the
     * target RequestClientOptions.
     */
    void copyTo(RequestClientOptions target) {
        target.setReadLimit(getReadLimit());
        for (Marker marker: Marker.values())
            target.putClientMarker(marker, getClientMarker(marker));
    }
}