package bluej.parser;

import java.io.Reader;

import javax.swing.text.Document;
import javax.swing.text.Segment;

import bluej.editor.moe.MoeSyntaxDocument;
import bluej.utility.Debug;
import threadchecker.OnThread;
import threadchecker.Tag;




| An efficient reader which reads directly from the supplied Document.
|
| @author Davin McCall
|
public class DocumentReader
extends Reader{    
   private Segment buffer;
   
   private MoeSyntaxDocument document;
   
   private int bufpos;
   
   private int docPosition;
   
   private int docLength;
    
   
   


| Construct a DocumentReader to read an entire document.
|
public DocumentReader(MoeSyntaxDocument document)
   {
      this(document, 0);     
      }
    
   
   


| Construct a DocumentReader to read a document starting from the given position.
|
public DocumentReader(MoeSyntaxDocument document, int position)
   {        
      buffer = new Segment();
      buffer.setPartialReturn(true);
       
      this.document = document;
       
      docPosition = position;
      docLength = document.getLength();
      fillBuffer();     
      }
    
   
   


| Construct a new DocumentReader to read text between the two
| given document positions.
|
public DocumentReader(MoeSyntaxDocument document, int position, int endpos)
   {        
      buffer = new Segment();
      buffer.setPartialReturn(true);
       
      this.document = document;
       
      docPosition = position;
       
      docLength = endpos;
      if (docLength > document.getLength())
           
      throw new IllegalArgumentException("Trying to construct DocumentReader to look up to " + endpos + " in a document of length: " + document.getLength());
      fillBuffer();     
      }
    
   
   @Override
   @OnThread(value = Tag.FXPlatform,ignoreParent = true)
   
   public void close()
   {        
           
      }

   
   @Override
   @OnThread(value = Tag.FXPlatform,ignoreParent = true)
   
   public int read()
   {
      if (bufpos == buffer.getEndIndex()) {
         if (docPosition == docLength) {                
            return -1;             
            }
         fillBuffer();         
         }
        
       
      return buffer.array[bufpos++];     
      }
    
   
   @Override
   @OnThread(value = Tag.FXPlatform,ignoreParent = true)
   
   public int read(char[] cbuf, int off, int len)
   {
      int docAvail = Math.min(len, docLength - docPosition + buffer.getEndIndex() - bufpos);
        
      if (docAvail == 0) {            
         return -1;         
         }
        
      len = Math.min(len, docAvail);
       
      int remaining = len;
        
      while (remaining > 0){
         int avail = Math.min(buffer.getEndIndex() - bufpos, remaining);
         if (avail == 0) {
            fillBuffer();
            avail = Math.min(buffer.getEndIndex() - bufpos, remaining);             
            }
         System.arraycopy(buffer.array, bufpos, cbuf, off, avail);
           
         off += avail;
           
         bufpos += avail;
           
         remaining -= avail;         
         }
        
       
      return len;     
      }

   
   private void fillBuffer()
   {        
      int docAvail = docLength - docPosition;
      document.getText(docPosition, docAvail, buffer);
      docPosition += (buffer.getEndIndex() - buffer.getBeginIndex());
      bufpos = buffer.getBeginIndex();     
      } 
   }