package net.sf.okapi.steps.paraaligner;
   
   import java.util.Iterator;
   import java.util.LinkedList;
   import java.util.List;
   
   import net.sf.okapi.common.LocaleId;
   import net.sf.okapi.common.resource.ISegments;
   import net.sf.okapi.common.resource.ITextUnit;
  import net.sf.okapi.common.resource.Segment;
  import net.sf.okapi.common.resource.TextContainer;
  
  class AlignedParagraphs {
  	private List<List<ITextUnit>> sourceParas;
  	private List<List<ITextUnit>> targetParas;
  	private List<ITextUnit> alignedParas;
  	private LocaleId targetLocale;
  
  	public AlignedParagraphs(LocaleId targetLocale) {
  		this.sourceParas = new LinkedList<>();
  		this.targetParas = new LinkedList<>();
  		this.alignedParas = new LinkedList<>();
  		this.targetLocale = targetLocale;
  	}
  
  	public void addAlignment(ITextUnit srcTu, ITextUnit trgTu) {
  		List<ITextUnit> srcParas = new LinkedList<>();
  		if (srcTu != null) {
  			srcParas.add(srcTu);
  		}
  		List<ITextUnit> trgParas = new LinkedList<>();
  		if (trgTu != null) {
  			trgParas.add(trgTu);
  		}
  		sourceParas.add(srcParas);
  		targetParas.add(trgParas);
  	}
  
  	public void addAlignment(List<ITextUnit> srcTus, List<ITextUnit> trgTus) {
  		sourceParas.add(srcTus);
  		targetParas.add(trgTus);
  	}
  
  	public List<ITextUnit> align() {
  		// source and target lists are guaranteed to have the same number of elements, though some will be null
  		for (List<ITextUnit> stus : sourceParas) {
  			ITextUnit stu = null;
  			List<ITextUnit> ttus = targetParas.remove(0);
  			
  			if (stus != null && !stus.isEmpty()) {
  				stu = combineTextUnits(stus);
  				if (stu != null && ttus != null && !ttus.isEmpty()) {
  					ITextUnit combinedTarget = combineTextUnits(ttus);
  					if (combinedTarget != null) {
  						stu = addTargetTextUnitAsTarget(stu, combinedTarget, targetLocale);
  					}
  				}
  			} else {
  				if (ttus != null && !ttus.isEmpty()) {
  					// source is null, use target tu (target content is source in this TU)
  					ITextUnit tempTarget = combineTextUnits(ttus);
  					if (tempTarget != null) {
  						tempTarget.createTarget(targetLocale, true, ITextUnit.COPY_ALL);	
  						// remove the source
  						tempTarget.setSource(null);
  						stu = tempTarget;
  					}
  				}
  			}
  			
  			// Only add non-null aligned paragraphs
  			if (stu != null) {
  				alignedParas.add(stu);
  			}
  		}
  		
  		return alignedParas;
  	}
  
  	private ITextUnit combineTextUnits(List<ITextUnit> tus) {
  		// Guard against null or empty list to prevent NoSuchElementException
  		if (tus == null || tus.isEmpty()) {
  			return null;
  		}
  		
  		Iterator<ITextUnit> its = tus.iterator();
  		ITextUnit tuNew = its.next().clone();
  		TextContainer tcAligned = tuNew.getSource();
  		
  		while (its.hasNext()) {
  			ITextUnit tu2combin = its.next();
  			TextContainer tcSource = tu2combin.getSource();
  			tcSource.joinAll(); // joins all data parts and segments into one
  			ISegments segs2add = tcSource.getSegments();
  			Iterator<Segment> itSeg = segs2add.iterator();
  			while (itSeg.hasNext()) {
  				String cLast;
  				String sCurNoTrim = tcAligned.toString();
  				String sCur = sCurNoTrim.trim();
 				int lonny = sCur.length();
 				if (lonny > 0) {
 					cLast = sCur.substring(lonny - 1);
 					if (sCur.equals(sCurNoTrim)) {
 						if (cLast.equals("!") || cLast.equals(".") || cLast.equals("?")) {
 							// append two spaces so previous punc will be a break point
 							tcAligned.append(" "); 
 						}
 							
 						else {
 							// didn't end with whitespace, so force a sentence break
 							tcAligned.append(". "); 
 						}
 					}
 				}
 				
 				// this combines content from next text unit
 				tcAligned.append(itSeg.next().getContent()); 
 			}
 		}
 		tcAligned.joinAll(); // join new parts together as one
 		return tuNew;
 	}
 
 	private ITextUnit addTargetTextUnitAsTarget(ITextUnit tuSource, ITextUnit tuTarget, LocaleId targetLocale) {
 		tuSource.setTarget(targetLocale, tuTarget.getSource());
 		return tuSource;
 	}
 }