/*
 * Copyright (c) 2001, 2018, Oracle and/or its affiliates. All rights reserved.
 * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
 *
 * This code is free software; you can redistribute it and/or modify it
 * under the terms of the GNU General Public License version 2 only, as
 * published by the Free Software Foundation.  Oracle designates this
 * particular file as subject to the "Classpath" exception as provided
 * by Oracle in the LICENSE file that accompanied this code.
 *
 * This code is distributed in the hope that it will be useful, but WITHOUT
 * ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
 * FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
 * version 2 for more details (a copy is included in the LICENSE file that
 * accompanied this code).
 *
 * You should have received a copy of the GNU General Public License version
 * 2 along with this work; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
 *
 * Please contact Oracle, 500 Oracle Parkway, Redwood Shores, CA 94065 USA
 * or visit www.oracle.com if you need additional information or have any
 * questions.
 */

package java.nio.charset;

import java.nio.BufferOverflowException;
import java.nio.BufferUnderflowException;
import java.util.concurrent.ConcurrentHashMap;
import java.util.Map;

A description of the result state of a coder.
 A charset coder, that is, either a decoder or an encoder, consumes bytes
(or characters) from an input buffer, translates them, and writes the
resulting characters (or bytes) to an output buffer.  A coding process
terminates for one of four categories of reasons, which are described by
instances of this class:

  
 Underflow is reported when there is no more input to be processed, or there is insufficient input and additional input is required. This condition is represented by the unique result object UNDERFLOW, whose isUnderflow method returns true. 
  
 Overflow is reported when there is insufficient room remaining in the output buffer. This condition is represented by the unique result object OVERFLOW, whose 
  isOverflow method returns true. 
  
 A malformed-input error is reported when a sequence of input units is not well-formed. Such errors are described by instances of this class whose isMalformed method returns true and whose length method returns the length of the malformed sequence. There is one unique instance of this class for all malformed-input errors of a given length. 
  
 An unmappable-character error is reported when a sequence of input units denotes a character that cannot be represented in the output charset. Such errors are described by instances of this class whose isUnmappable method returns true and whose length method returns the length of the input sequence denoting the unmappable character. There is one unique instance of this class for all unmappable-character errors of a given length. 

 For convenience, the isError method returns true for result objects that describe malformed-input and unmappable-character errors but false for those that describe underflow or overflow conditions. 
Author:
Mark Reinhold, JSR-51 Expert Group
Since:
1.4/**
 * A description of the result state of a coder.
 *
 * <p> A charset coder, that is, either a decoder or an encoder, consumes bytes
 * (or characters) from an input buffer, translates them, and writes the
 * resulting characters (or bytes) to an output buffer.  A coding process
 * terminates for one of four categories of reasons, which are described by
 * instances of this class:
 *
 * <ul>
 *
 *   <li><p> <i>Underflow</i> is reported when there is no more input to be
 *   processed, or there is insufficient input and additional input is
 *   required.  This condition is represented by the unique result object
 *   {@link #UNDERFLOW}, whose {@link #isUnderflow() isUnderflow} method
 *   returns {@code true}.  </p></li>
 *
 *   <li><p> <i>Overflow</i> is reported when there is insufficient room
 *   remaining in the output buffer.  This condition is represented by the
 *   unique result object {@link #OVERFLOW}, whose {@link #isOverflow()
 *   isOverflow} method returns {@code true}.  </p></li>
 *
 *   <li><p> A <i>malformed-input error</i> is reported when a sequence of
 *   input units is not well-formed.  Such errors are described by instances of
 *   this class whose {@link #isMalformed() isMalformed} method returns
 *   {@code true} and whose {@link #length() length} method returns the length
 *   of the malformed sequence.  There is one unique instance of this class for
 *   all malformed-input errors of a given length.  </p></li>
 *
 *   <li><p> An <i>unmappable-character error</i> is reported when a sequence
 *   of input units denotes a character that cannot be represented in the
 *   output charset.  Such errors are described by instances of this class
 *   whose {@link #isUnmappable() isUnmappable} method returns {@code true} and
 *   whose {@link #length() length} method returns the length of the input
 *   sequence denoting the unmappable character.  There is one unique instance
 *   of this class for all unmappable-character errors of a given length.
 *   </p></li>
 *
 * </ul>
 *
 * <p> For convenience, the {@link #isError() isError} method returns {@code true}
 * for result objects that describe malformed-input and unmappable-character
 * errors but {@code false} for those that describe underflow or overflow
 * conditions.  </p>
 *
 *
 * @author Mark Reinhold
 * @author JSR-51 Expert Group
 * @since 1.4
 */

public class CoderResult {

    private static final int CR_UNDERFLOW  = 0;
    private static final int CR_OVERFLOW   = 1;
    private static final int CR_ERROR_MIN  = 2;
    private static final int CR_MALFORMED  = 2;
    private static final int CR_UNMAPPABLE = 3;

    private static final String[] names
        = { "UNDERFLOW", "OVERFLOW", "MALFORMED", "UNMAPPABLE" };

    private final int type;
    private final int length;

    private CoderResult(int type, int length) {
        this.type = type;
        this.length = length;
    }

    
Returns a string describing this coder result.
Returns:
 A descriptive string/**
     * Returns a string describing this coder result.
     *
     * @return  A descriptive string
     */
    public String toString() {
        String nm = names[type];
        return isError() ? nm + "[" + length + "]" : nm;
    }

    
Tells whether or not this object describes an underflow condition.
Returns:
 true if, and only if, this object denotes underflow/**
     * Tells whether or not this object describes an underflow condition.
     *
     * @return  {@code true} if, and only if, this object denotes underflow
     */
    public boolean isUnderflow() {
        return (type == CR_UNDERFLOW);
    }

    
Tells whether or not this object describes an overflow condition.
Returns:
 true if, and only if, this object denotes overflow/**
     * Tells whether or not this object describes an overflow condition.
     *
     * @return  {@code true} if, and only if, this object denotes overflow
     */
    public boolean isOverflow() {
        return (type == CR_OVERFLOW);
    }

    
Tells whether or not this object describes an error condition.
Returns:
 true if, and only if, this object denotes either a malformed-input error or an unmappable-character error/**
     * Tells whether or not this object describes an error condition.
     *
     * @return  {@code true} if, and only if, this object denotes either a
     *          malformed-input error or an unmappable-character error
     */
    public boolean isError() {
        return (type >= CR_ERROR_MIN);
    }

    
Tells whether or not this object describes a malformed-input error.
Returns:
 true if, and only if, this object denotes a malformed-input error/**
     * Tells whether or not this object describes a malformed-input error.
     *
     * @return  {@code true} if, and only if, this object denotes a
     *          malformed-input error
     */
    public boolean isMalformed() {
        return (type == CR_MALFORMED);
    }

    
Tells whether or not this object describes an unmappable-character
error.
Returns:
 true if, and only if, this object denotes an unmappable-character error/**
     * Tells whether or not this object describes an unmappable-character
     * error.
     *
     * @return  {@code true} if, and only if, this object denotes an
     *          unmappable-character error
     */
    public boolean isUnmappable() {
        return (type == CR_UNMAPPABLE);
    }

    
Returns the length of the erroneous input described by this
object  (optional operation).
Throws:
UnsupportedOperationException –  If this object does not describe an error condition, that is, if the isError does not return true
Returns:
 The length of the erroneous input, a positive integer/**
     * Returns the length of the erroneous input described by this
     * object&nbsp;&nbsp;<i>(optional operation)</i>.
     *
     * @return  The length of the erroneous input, a positive integer
     *
     * @throws  UnsupportedOperationException
     *          If this object does not describe an error condition, that is,
     *          if the {@link #isError() isError} does not return {@code true}
     */
    public int length() {
        if (!isError())
            throw new UnsupportedOperationException();
        return length;
    }

    
Result object indicating underflow, meaning that either the input buffer
has been completely consumed or, if the input buffer is not yet empty,
that additional input is required.
/**
     * Result object indicating underflow, meaning that either the input buffer
     * has been completely consumed or, if the input buffer is not yet empty,
     * that additional input is required.
     */
    public static final CoderResult UNDERFLOW
        = new CoderResult(CR_UNDERFLOW, 0);

    
Result object indicating overflow, meaning that there is insufficient
room in the output buffer.
/**
     * Result object indicating overflow, meaning that there is insufficient
     * room in the output buffer.
     */
    public static final CoderResult OVERFLOW
        = new CoderResult(CR_OVERFLOW, 0);

    private static final class Cache {
        static final Cache INSTANCE = new Cache();
        private Cache() {}

        final Map<Integer, CoderResult> unmappable = new ConcurrentHashMap<>();
        final Map<Integer, CoderResult> malformed  = new ConcurrentHashMap<>();
    }

    private static final CoderResult[] malformed4 = new CoderResult[] {
        new CoderResult(CR_MALFORMED, 1),
        new CoderResult(CR_MALFORMED, 2),
        new CoderResult(CR_MALFORMED, 3),
        new CoderResult(CR_MALFORMED, 4),
    };

    
Static factory method that returns the unique object describing a
malformed-input error of the given length.
Params:
length – 
         The given length
Returns:
 The requested coder-result object/**
     * Static factory method that returns the unique object describing a
     * malformed-input error of the given length.
     *
     * @param   length
     *          The given length
     *
     * @return  The requested coder-result object
     */
    public static CoderResult malformedForLength(int length) {
        if (length <= 0)
            throw new IllegalArgumentException("Non-positive length");
        if (length <= 4)
            return malformed4[length - 1];
        return Cache.INSTANCE.malformed.computeIfAbsent(length,
                n -> new CoderResult(CR_MALFORMED, n));
    }

    private static final CoderResult[] unmappable4 = new CoderResult[] {
        new CoderResult(CR_UNMAPPABLE, 1),
        new CoderResult(CR_UNMAPPABLE, 2),
        new CoderResult(CR_UNMAPPABLE, 3),
        new CoderResult(CR_UNMAPPABLE, 4),
    };

    
Static factory method that returns the unique result object describing
an unmappable-character error of the given length.
Params:
length – 
         The given length
Returns:
 The requested coder-result object/**
     * Static factory method that returns the unique result object describing
     * an unmappable-character error of the given length.
     *
     * @param   length
     *          The given length
     *
     * @return  The requested coder-result object
     */
    public static CoderResult unmappableForLength(int length) {
        if (length <= 0)
            throw new IllegalArgumentException("Non-positive length");
        if (length <= 4)
            return unmappable4[length - 1];
        return Cache.INSTANCE.unmappable.computeIfAbsent(length,
                n -> new CoderResult(CR_UNMAPPABLE, n));
    }

    
Throws an exception appropriate to the result described by this object.
Throws:
BufferUnderflowException –  If this object is UNDERFLOW
BufferOverflowException –  If this object is OVERFLOW
MalformedInputException – 
         If this object represents a malformed-input error; the
         exception's length value will be that of this object
UnmappableCharacterException – 
         If this object represents an unmappable-character error; the
         exceptions length value will be that of this object/**
     * Throws an exception appropriate to the result described by this object.
     *
     * @throws  BufferUnderflowException
     *          If this object is {@link #UNDERFLOW}
     *
     * @throws  BufferOverflowException
     *          If this object is {@link #OVERFLOW}
     *
     * @throws  MalformedInputException
     *          If this object represents a malformed-input error; the
     *          exception's length value will be that of this object
     *
     * @throws  UnmappableCharacterException
     *          If this object represents an unmappable-character error; the
     *          exceptions length value will be that of this object
     */
    public void throwException()
        throws CharacterCodingException
    {
        switch (type) {
        case CR_UNDERFLOW:   throw new BufferUnderflowException();
        case CR_OVERFLOW:    throw new BufferOverflowException();
        case CR_MALFORMED:   throw new MalformedInputException(length);
        case CR_UNMAPPABLE:  throw new UnmappableCharacterException(length);
        default:
            assert false;
        }
    }

}