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/*
 * Copyright (c) 1997, 2023 Oracle and/or its affiliates. All rights reserved.
 *
 * This program and the accompanying materials are made available under the
 * terms of the Eclipse Public License v. 2.0, which is available at
 * http://www.eclipse.org/legal/epl-2.0.
 *
 * This Source Code may also be made available under the following Secondary
 * Licenses when the conditions for such availability set forth in the
 * Eclipse Public License v. 2.0 are satisfied: GNU General Public License,
 * version 2 with the GNU Classpath Exception, which is available at
 * https://www.gnu.org/software/classpath/license.html.
 *
 * SPDX-License-Identifier: EPL-2.0 OR GPL-2.0 WITH Classpath-exception-2.0
 */

package org.eclipse.angus.mail.util;

import java.io.FilterOutputStream;
import java.io.IOException;
import java.io.OutputStream;
import java.io.PrintStream;

/**
 * This class implements a UUEncoder. It is implemented as
 * a FilterOutputStream, so one can just wrap this class around
 * any output stream and write bytes into this filter. The Encoding
 * is done as the bytes are written out.
 *
 * @author John Mani
 */

public class UUEncoderStream extends FilterOutputStream {
    private byte[] buffer;    // cache of bytes that are yet to be encoded
    private int bufsize = 0;    // size of the cache
    private boolean wrotePrefix = false;
    private boolean wroteSuffix = false;

    private String name;    // name of file
    private int mode;        // permissions mode

    /**
     * Create a UUencoder that encodes the specified input stream
     *
     * @param out the output stream
     */
    public UUEncoderStream(OutputStream out) {
        this(out, "encoder.buf", 0644);
    }

    /**
     * Create a UUencoder that encodes the specified input stream
     *
     * @param out  the output stream
     * @param name Specifies a name for the encoded buffer
     */
    public UUEncoderStream(OutputStream out, String name) {
        this(out, name, 0644);
    }

    /**
     * Create a UUencoder that encodes the specified input stream
     *
     * @param out  the output stream
     * @param name Specifies a name for the encoded buffer
     * @param mode Specifies permission mode for the encoded buffer
     */
    public UUEncoderStream(OutputStream out, String name, int mode) {
        super(out);
        this.name = name;
        this.mode = mode;
        buffer = new byte[45];
    }

    /**
     * Set up the buffer name and permission mode.
     * This method has any effect only if it is invoked before
     * you start writing into the output stream
     *
     * @param    name    the buffer name
     * @param    mode    the permission mode
     */
    public void setNameMode(String name, int mode) {
        this.name = name;
        this.mode = mode;
    }

    @Override
    public void write(byte[] b, int off, int len) throws IOException {
        for (int i = 0; i < len; i++)
            write(b[off + i]);
    }

    @Override
    public void write(byte[] data) throws IOException {
        write(data, 0, data.length);
    }

    @Override
    public void write(int c) throws IOException {
        /* buffer up characters till we get a line's worth, then encode
         * and write them out. Max number of characters allowed per
         * line is 45.
         */
        buffer[bufsize++] = (byte) c;
        if (bufsize == 45) {
            writePrefix();
            encode();
            bufsize = 0;
        }
    }

    @Override
    public void flush() throws IOException {
        if (bufsize > 0) { // If there's unencoded characters in the buffer
            writePrefix();
            encode();      // .. encode them
            bufsize = 0;
        }
        writeSuffix();
        out.flush();
    }

    @Override
    public void close() throws IOException {
        flush();
        out.close();
    }

    /**
     * Write out the prefix: "begin  "
     */
    private void writePrefix() throws IOException {
        if (!wrotePrefix) {
            // name should be ASCII, but who knows...
            PrintStream ps = new PrintStream(out, false, "utf-8");
            ps.format("begin %o %s%n", mode, name);
            ps.flush();
            wrotePrefix = true;
        }
    }

    /**
     * Write a single line containing space and the suffix line
     * containing the single word "end" (terminated by a newline)
     */
    private void writeSuffix() throws IOException {
        if (!wroteSuffix) {
            PrintStream ps = new PrintStream(out, false, "us-ascii");
            ps.println(" \nend");
            ps.flush();
            wroteSuffix = true;
        }
    }

    /**
     * Encode a line.
     * Start off with the character count, followed by the encoded atoms
     * and terminate with LF. (or is it CRLF or the local line-terminator ?)
     * Take three bytes and encodes them into 4 characters
     * If bufsize if not a multiple of 3, the remaining bytes are filled
     * with '1'. This insures that the last line won't end in spaces
     * and potentiallly be truncated.
     */
    private void encode() throws IOException {
        byte a, b, c;
        int c1, c2, c3, c4;
        int i = 0;

        // Start off with the count of characters in the line
        out.write((bufsize & 0x3f) + ' ');

        while (i < bufsize) {
            a = buffer[i++];
            if (i < bufsize) {
                b = buffer[i++];
                if (i < bufsize)
                    c = buffer[i++];
                else // default c to 1
                    c = 1;
            } else { // default b & c to 1
                b = 1;
                c = 1;
            }

            c1 = (a >>> 2) & 0x3f;
            c2 = ((a << 4) & 0x30) | ((b >>> 4) & 0xf);
            c3 = ((b << 2) & 0x3c) | ((c >>> 6) & 0x3);
            c4 = c & 0x3f;
            out.write(c1 + ' ');
            out.write(c2 + ' ');
            out.write(c3 + ' ');
            out.write(c4 + ' ');
        }
        // Terminate with LF. (should it be CRLF or local line-terminator ?)
        out.write('\n');
    }

    /**** begin TEST program *****
     public static void main(String argv[]) throws Exception {
     FileInputStream infile = new FileInputStream(argv[0]);
     UUEncoderStream encoder = new UUEncoderStream(System.out);
     int c;

     while ((c = infile.read()) != -1)
     encoder.write(c);
     encoder.close();
     }
     **** end TEST program *****/
}