/**
*******************************************************************************
* Copyright (C) 2006, International Business Machines Corporation and    *
* others. All Rights Reserved.                                                *
*******************************************************************************
*
*******************************************************************************
*/ 
package com.ibm.icu.charset;

import java.nio.ByteBuffer;
import java.nio.CharBuffer;
import java.nio.IntBuffer;
import java.nio.charset.CharsetDecoder;
import java.nio.charset.CharsetEncoder;
import java.nio.charset.CoderResult;

import com.ibm.icu.text.UTF16;

class CharsetUTF16 extends CharsetICU {
    
    protected byte[] fromUSubstitution = new byte[]{(byte)0xff, (byte)0xfd};
   
    public CharsetUTF16(String icuCanonicalName, String javaCanonicalName, String[] aliases){
        super(icuCanonicalName, javaCanonicalName, aliases);
        maxBytesPerChar = 4;
        minBytesPerChar = 2;
        maxCharsPerByte = 1;
    }
    class CharsetDecoderUTF16 extends CharsetDecoderICU{

        public CharsetDecoderUTF16(CharsetICU cs) {
            super(cs);
        }

        protected CoderResult decodeLoop(ByteBuffer source, CharBuffer target, IntBuffer offsets, boolean flush){
            CoderResult cr = CoderResult.UNDERFLOW;
            if(!source.hasRemaining() && toUnicodeStatus==0) {
                /* no input, nothing to do */
                return cr;
            }
            if(!target.hasRemaining()) {
                return CoderResult.OVERFLOW;
            }
        
            int sourceIndex=0, count=0, length, sourceArrayIndex;
            char c=0, trail;
            length = source.remaining();
            sourceArrayIndex = source.position();

            /* complete a partial UChar or pair from the last call */
            if(toUnicodeStatus!=0) {
                /*
                 * special case: single byte from a previous buffer,
                 * where the byte turned out not to belong to a trail surrogate
                 * and the preceding, unmatched lead surrogate was put into toUBytes[]
                 * for error handling
                 */
                toUBytesArray[toUBytesBegin+0]=(byte)toUnicodeStatus;
                toULength=1;
                toUnicodeStatus=0;
            }
            if((count=toULength)!=0) {
                byte[] pArray=toUBytesArray;
                int pArrayIndex = toUBytesBegin;
                do {
                    pArray[count++]=source.get(sourceArrayIndex++);
                    ++sourceIndex;
                    --length;
                    if(count==2) {
                        c=(char)(((pArray[pArrayIndex+0]&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(pArray[pArrayIndex+1]&UConverterConstants.UNSIGNED_BYTE_MASK));
                        if(!UTF16.isSurrogate(c)) {
                            /* output the BMP code point */
                            target.put(c);
                            if(offsets!=null) {
                                offsets.put(-1);
                            }
                            count=0;
                            c=0;
                            break;
                        } else if(UTF16.isLeadSurrogate(c)) {
                            /* continue collecting bytes for the trail surrogate */
                            c=0; /* avoid unnecessary surrogate handling below */
                        } else {
                            /* fall through to error handling for an unmatched trail surrogate */
                            break;
                        }
                    } else if(count==4) {
                        c=(char)(((pArray[pArrayIndex+0]&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(pArray[pArrayIndex+1]&UConverterConstants.UNSIGNED_BYTE_MASK));
                        trail=(char)(((pArray[pArrayIndex+2]&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(pArray[pArrayIndex+3]&UConverterConstants.UNSIGNED_BYTE_MASK));
                        if(UTF16.isTrailSurrogate(trail)) {
                            /* output the surrogate pair */
                            target.put(c);
                            if(target.remaining()>=1) {
                                target.put(trail);
                                if(offsets!=null) {
                                    offsets.put(-1);
                                    offsets.put(-1);
                                }
                            } else /* targetCapacity==1 */ {
                                charErrorBufferArray[charErrorBufferBegin+0]=trail;
                                charErrorBufferLength=1;
                                return CoderResult.OVERFLOW;
                            }
                            count=0;
                            c=0;
                            break;
                        } else {
                            /* unmatched lead surrogate, handle here for consistent toUBytes[] */
        
                            /* back out reading the code unit after it */
                            if((source.position()-sourceArrayIndex)>=2) {
                                sourceArrayIndex-=2;
                            } else {
                                /*
                                 * if the trail unit's first byte was in a previous buffer, then
                                 * we need to put it into a special place because toUBytes[] will be
                                 * used for the lead unit's bytes
                                 */
                                toUnicodeStatus=0x100|pArray[pArrayIndex+2];
                                --sourceArrayIndex;
                            }
                            toULength=2;
                            cr = CoderResult.malformedForLength(sourceArrayIndex);
                            break;
                        }
                    }
                } while(length>0);
                toULength=(byte)count;
            }
        
            /* copy an even number of bytes for complete UChars */
            count=2*target.remaining();
            if(count>length) {
                count=length&~1;
            }
            if(c==0 && count>0) {
                length-=count;
                count>>=1;
                //targetCapacity-=count;
                if(offsets==null) {
                    do {
                        c=(char)(((source.get(sourceArrayIndex+0)&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(source.get(sourceArrayIndex+1)&UConverterConstants.UNSIGNED_BYTE_MASK));
                        sourceArrayIndex+=2;
                        if(!UTF16.isSurrogate(c)) {
                            target.put(c);
                        } else if(UTF16.isLeadSurrogate(c) && count>=2 &&
                                  UTF16.isTrailSurrogate(trail=(char)(((source.get(sourceArrayIndex+0)&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(source.get(sourceArrayIndex+1)&UConverterConstants.UNSIGNED_BYTE_MASK)))
                                 ) {
                            sourceArrayIndex+=2;
                            --count;
                            target.put(c);
                            target.put(trail);
                        } else {
                            break;
                        }
                    } while(--count>0);
                } else {
                    do {
                        c=(char)(((source.get(sourceArrayIndex+0)&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(source.get(sourceArrayIndex+1)&UConverterConstants.UNSIGNED_BYTE_MASK));
                        sourceArrayIndex+=2;
                        if(!UTF16.isSurrogate(c)) {
                            target.put(c);
                            offsets.put(sourceIndex);
                            sourceIndex+=2;
                        } else if(UTF16.isLeadSurrogate(c) && count>=2 &&
                                  UTF16.isTrailSurrogate(trail=(char)(((source.get(sourceArrayIndex+0)&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(source.get(sourceArrayIndex+1)&UConverterConstants.UNSIGNED_BYTE_MASK)))
                        ) {
                            sourceArrayIndex+=2;
                            --count;
                            target.put(c);
                            target.put(trail);
                            offsets.put(sourceIndex);
                            offsets.put(sourceIndex);
                            sourceIndex+=4;
                        } else {
                            break;
                        }
                    } while(--count>0);
                }
        
                if(count==0) {
                    /* done with the loop for complete UChars */
                    c=0;
                } else {
                    /* keep c for surrogate handling, trail will be set there */
                    length+=2*(count-1); /* one more byte pair was consumed than count decremented */
                }
            }
        
            if(c!=0) {
                /*
                 * c is a surrogate, and
                 * - source or target too short
                 * - or the surrogate is unmatched
                 */
                toUBytesArray[toUBytesBegin+0]=(byte)(c>>>8);
                toUBytesArray[toUBytesBegin+1]=(byte)c;
                toULength=2;
        
                if(UTF16.isLeadSurrogate(c)) {
                    if(length>=2) {
                        if(UTF16.isTrailSurrogate(trail=(char)(((source.get(sourceArrayIndex+0)&UConverterConstants.UNSIGNED_BYTE_MASK)<<8)|(source.get(sourceArrayIndex+1)&UConverterConstants.UNSIGNED_BYTE_MASK)))) {
                            /* output the surrogate pair, will overflow (see conditions comment above) */
                            sourceArrayIndex+=2;
                            length-=2;
                            target.put(c);
                            if(offsets!=null) {
                                offsets.put(sourceIndex);
                            }
                            charErrorBufferArray[charErrorBufferBegin+0]=trail;
                            charErrorBufferLength=1;
                            toULength=0;
                            cr = CoderResult.OVERFLOW;
                        } else {
                            /* unmatched lead surrogate */
                            cr = CoderResult.malformedForLength(sourceArrayIndex);
                        }
                    } else {
                        /* see if the trail surrogate is in the next buffer */
                    }
                } else {
                    /* unmatched trail surrogate */
                    cr = CoderResult.malformedForLength(sourceArrayIndex);
                }
            }
        
           
            /* check for a remaining source byte */
            if(!cr.isError()){
                if(length>0) {
                    if(!target.hasRemaining()) {
                        cr = CoderResult.OVERFLOW;
                    } else {
                        /* it must be length==1 because otherwise the above would have copied more */
                        toUBytesArray[toULength++]=source.get(sourceArrayIndex++);
                    }
                }
            }
            source.position(sourceArrayIndex);

            return cr;
        }
        
    }
    class CharsetEncoderUTF16 extends CharsetEncoderICU{

        public CharsetEncoderUTF16(CharsetICU cs) {
            super(cs, fromUSubstitution);
            implReset();
        }

        private final static int NEED_TO_WRITE_BOM = 1;
        
        protected void implReset() {
            super.implReset();
            fromUnicodeStatus = NEED_TO_WRITE_BOM;
        }
        
        protected CoderResult encodeLoop(CharBuffer source, ByteBuffer target, IntBuffer offsets, boolean flush){
            CoderResult cr = CoderResult.UNDERFLOW;
            if(!source.hasRemaining()) {
                /* no input, nothing to do */
                return cr;
            }
            char c;
            /* write the BOM if necessary */
            if(fromUnicodeStatus==NEED_TO_WRITE_BOM) {
                byte bom[]={ (byte)0xfe, (byte)0xff };
                cr = fromUWriteBytes(this,bom, 0, bom.length, target, offsets, -1);
                if(cr.isError()){
                    return cr;
                }
                fromUnicodeStatus=0;
            }
            
            if(!target.hasRemaining()) {
                return CoderResult.OVERFLOW;
            }
            
            int sourceIndex = 0;
            char trail = 0;
            int length = source.remaining();
            int sourceArrayIndex = source.position();

            /* c!=0 indicates in several places outside the main loops that a surrogate was found */
        
            if((c=(char)fromUChar32)!=0 && UTF16.isTrailSurrogate(trail=source.get(sourceArrayIndex)) && target.remaining()>=4) {
                /* the last buffer ended with a lead surrogate, output the surrogate pair */
                ++sourceArrayIndex;
                --length;
                target.put((byte)(c>>>8));
                target.put((byte)c);
                target.put((byte)(trail>>>8));
                target.put((byte)trail);
                if(offsets!=null && offsets.remaining()>=4) {
                    offsets.put(-1);
                    offsets.put(-1);
                    offsets.put(-1);
                    offsets.put(-1);
                }
                sourceIndex=1;
                fromUChar32=c=0;
            }
            byte overflow[/*4*/] = new byte[4];
            
            if(c==0) {
                /* copy an even number of bytes for complete UChars */
                int count=2*length;
                int targetCapacity = target.remaining();
                if(count>targetCapacity) {
                    count=targetCapacity&~1;
                }           
                /* count is even */
                targetCapacity-=count;
                count>>=1;
                length-=count;

                if(offsets==null) {
                    while(count>0) {
                        c= source.get(sourceArrayIndex++);
                        if(!UTF16.isSurrogate(c)) {
                            target.put((byte)(c>>>8));
                            target.put((byte)c);
                            
                        } else if(UTF16.isLeadSurrogate(c) && count>=2 && UTF16.isTrailSurrogate(trail=source.get(sourceArrayIndex))) {
                            ++sourceArrayIndex;
                            --count;
                            target.put((byte)(c>>>8));
                            target.put((byte)c);
                            target.put((byte)(trail>>>8));
                            target.put((byte)trail);
                        } else {
                            break;
                        }
                        --count;
                    }
                } else {
                    while(count>0) {
                        c=source.get(sourceArrayIndex++);
                        if(!UTF16.isSurrogate(c)) {
                            target.put((byte)(c>>>8));
                            target.put((byte)c);
                            offsets.put(sourceIndex);
                            offsets.put(sourceIndex++);
                        } else if(UTF16.isLeadSurrogate(c) && count>=2 && UTF16.isTrailSurrogate(trail=source.get(sourceArrayIndex))) {
                            ++sourceArrayIndex;
                            --count;
                            target.put((byte)(c>>>8));
                            target.put((byte)c);
                            target.put((byte)(trail>>>8));
                            target.put((byte)trail);
                            offsets.put(sourceIndex);
                            offsets.put(sourceIndex);
                            offsets.put(sourceIndex);
                            offsets.put(sourceIndex);
                            sourceIndex+=2;
                        } else {
                            break;
                        }
                        --count;
                    }
                }
        
                if(count==0) {
                    /* done with the loop for complete UChars */
                    if(length>0 && targetCapacity>0) {
                        /*
                         * there is more input and some target capacity -
                         * it must be targetCapacity==1 because otherwise
                         * the above would have copied more;
                         * prepare for overflow output
                         */
                        if(!UTF16.isSurrogate(c=source.get(sourceArrayIndex++))) {
                            overflow[0]=(byte)(c>>>8);
                            overflow[1]=(byte)c;
                            length=2; /* 2 bytes to output */
                            c=0;
                        /* } else { keep c for surrogate handling, length will be set there */
                        }
                    } else {
                        length=0;
                        c=0;
                    }
                } else {
                    /* keep c for surrogate handling, length will be set there */
                    targetCapacity+=2*count;
                }
            } else {
                length=0; /* from here on, length counts the bytes in overflow[] */
            }
            
            if(c!=0) {
                /*
                 * c is a surrogate, and
                 * - source or target too short
                 * - or the surrogate is unmatched
                 */
                length=0;
                if(UTF16.isLeadSurrogate(c)) {
                    if(sourceArrayIndex<source.limit()) {
                        if(UTF16.isTrailSurrogate(trail=source.get(sourceArrayIndex))) {
                            /* output the surrogate pair, will overflow (see conditions comment above) */
                            ++sourceArrayIndex;
                            overflow[0]=(byte)(c>>>8);
                            overflow[1]=(byte)c;
                            overflow[2]=(byte)(trail>>>8);
                            overflow[3]=(byte)trail;
                            length=4; /* 4 bytes to output */
                            c=0;
                        } else {
                            /* unmatched lead surrogate */										
                            cr = CoderResult.malformedForLength(sourceArrayIndex);
                        }
                    } else {
                        /* see if the trail surrogate is in the next buffer */
                    }
                } else {
                    /* unmatched trail surrogate */
                    cr = CoderResult.malformedForLength(sourceArrayIndex);
                }
                fromUChar32=c;
            }
            source.position(sourceArrayIndex);
            if(length>0) {
                /* output length bytes with overflow (length>targetCapacity>0) */
                cr = fromUWriteBytes(this, overflow, 0, length, target, offsets, sourceIndex);
            }
            return cr;
        }
    }
    public CharsetDecoder newDecoder() {
        return new CharsetDecoderUTF16(this);
    }

    public CharsetEncoder newEncoder() {
        return new CharsetEncoderUTF16(this);
    }

}