//
//  ========================================================================
//  Copyright (c) 1995-2019 Mort Bay Consulting Pty. Ltd.
//  ------------------------------------------------------------------------
//  All rights reserved. This program and the accompanying materials
//  are made available under the terms of the Eclipse Public License v1.0
//  and Apache License v2.0 which accompanies this distribution.
//
//      The Eclipse Public License is available at
//      http://www.eclipse.org/legal/epl-v10.html
//
//      The Apache License v2.0 is available at
//      http://www.opensource.org/licenses/apache2.0.php
//
//  You may elect to redistribute this code under either of these licenses.
//  ========================================================================
//

package org.eclipse.jetty.server;

import java.util.ArrayList;
import java.util.Enumeration;
import java.util.Iterator;
import java.util.List;
import java.util.StringTokenizer;

import org.eclipse.jetty.util.log.Log;
import org.eclipse.jetty.util.log.Logger;

/* ------------------------------------------------------------ */
/** Byte range inclusive of end points.
 * <PRE>
 * 
 *   parses the following types of byte ranges:
 * 
 *       bytes=100-499
 *       bytes=-300
 *       bytes=100-
 *       bytes=1-2,2-3,6-,-2
 *
 *   given an entity length, converts range to string
 * 
 *       bytes 100-499/500
 * 
 * </PRE>
 * 
 * Based on RFC2616 3.12, 14.16, 14.35.1, 14.35.2
 * <p>
 * And yes the spec does strangely say that while 10-20, is bytes 10 to 20 and 10- is bytes 10 until the end that -20 IS NOT bytes 0-20, but the last 20 bytes of the content.
 * 
 * @version $version$
 * 
 */
public class InclusiveByteRange 
{
    private static final Logger LOG = Log.getLogger(InclusiveByteRange.class);

    private long first;
    private long last;    

    public InclusiveByteRange(long first, long last)
    {
        this.first = first;
        this.last = last;
    }
    
    public long getFirst()
    {
        return first;
    }

    public long getLast()
    {
        return last;
    }    


    /* ------------------------------------------------------------ */
    private void coalesce(InclusiveByteRange r)
    {
        first = Math.min(first,r.first);
        last = Math.max(last,r.last);
    }

    /* ------------------------------------------------------------ */
    private boolean overlaps(InclusiveByteRange range)
    {
        return  (range.first>=this.first && range.first<=this.last)
                ||
                (range.last>=this.first && range.last<=this.last)
                ||
                (range.first<this.first && range.last>this.last);
    }

    /* ------------------------------------------------------------ */
    public long getSize()
    {
        return last-first+1;
    }

    /* ------------------------------------------------------------ */
    public String toHeaderRangeString(long size)
    {
        StringBuilder sb = new StringBuilder(40);
        sb.append("bytes ");
        sb.append(first);
        sb.append('-');
        sb.append(last);
        sb.append("/");
        sb.append(size);
        return sb.toString();
    }

    /* ------------------------------------------------------------ */
    @Override
    public int hashCode()
    {
        return (int)(first ^ last);
    }
    
    /* ------------------------------------------------------------ */
    @Override
    public boolean equals( Object obj )
    {
        if(obj == null)
            return false;

        if(!(obj instanceof InclusiveByteRange))
            return false;

        return ((InclusiveByteRange)obj).first == this.first &&
            ((InclusiveByteRange)obj).last == this.last;
    }

    /* ------------------------------------------------------------ */
    @Override
    public String toString()
    {
        StringBuilder sb = new StringBuilder(60);
        sb.append(Long.toString(first));
        sb.append(":");
        sb.append(Long.toString(last));
        return sb.toString();
    }
    
    
    /* ------------------------------------------------------------ */
    /** 
     * @param headers Enumeration of Range header fields.
     * @param size Size of the resource.
     * @return List of satisfiable ranges
     */
    public static List<InclusiveByteRange> satisfiableRanges(Enumeration<String> headers, long size)
    {
        List<InclusiveByteRange> ranges = null;
        final long end = size-1;
        
        // walk through all Range headers
        while (headers.hasMoreElements())
        {
            String header = headers.nextElement();
            StringTokenizer tok = new StringTokenizer(header,"=,",false);
            String t=null;
            try
            {
                // read all byte ranges for this header 
                while (tok.hasMoreTokens())
                {
                    try
                    {
                        t = tok.nextToken().trim();
                        if ("bytes".equals(t))
                            continue;

                        long first = -1;
                        long last = -1;
                        int dash = t.indexOf('-');
                        if (dash < 0 || t.indexOf("-",dash + 1) >= 0)
                        {
                            LOG.warn("Bad range format: {}",t);
                            break;
                        }
                        
                        if (dash>0)
                            first = Long.parseLong(t.substring(0,dash).trim());
                        if (dash<(t.length()-1))
                            last = Long.parseLong(t.substring(dash + 1).trim());
                        
                        if (first==-1)
                        {
                            if (last==-1)
                            {
                                LOG.warn("Bad range format: {}",t);
                                break;
                            }
                            
                            if (last==0)
                                continue;
                            
                            // This is a suffix range
                            first = Math.max(0,size-last);
                            last = end;
                        } 
                        else 
                        {
                            // Range starts after end
                            if (first>=size)
                                continue;
                            
                            if (last==-1)
                                last = end;
                            else if (last>=end)
                                last = end;
                        }

                        if (last<first)
                        {
                            LOG.warn("Bad range format: {}",t);
                            break;
                        }

                        InclusiveByteRange range = new InclusiveByteRange(first,last);
                        if (ranges==null)
                            ranges = new ArrayList<>();
                        
                        boolean coalesced = false;
                        for (Iterator<InclusiveByteRange> i = ranges.listIterator(); i.hasNext();)
                        {
                            InclusiveByteRange r = i.next();
                            if (range.overlaps(r))
                            {
                                coalesced =  true;
                                r.coalesce(range);
                                while(i.hasNext())
                                {
                                    InclusiveByteRange r2 = i.next();

                                    if (r2.overlaps(r))
                                    {
                                        r.coalesce(r2);
                                        i.remove();
                                    }
                                }
                            }
                        }
                        
                        if (!coalesced)
                            ranges.add(range);

                    }
                    catch (NumberFormatException e)
                    {
                        LOG.warn("Bad range format: {}",t);
                        LOG.ignore(e);
                    }
                }
            }
            catch(Exception e)
            {
                LOG.warn("Bad range format: {}",t);
                LOG.ignore(e);
            }    
        }
        
        return ranges;
    }

    /* ------------------------------------------------------------ */
    public static String to416HeaderRangeString(long size)
    {
        StringBuilder sb = new StringBuilder(40);
        sb.append("bytes */");
        sb.append(size);
        return sb.toString();
    }


}



