import java.util.ArrayList;
import java.util.List;



/*
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 * and open the template in the editor.
 */

/**
 *
 * @author Mustafa
 */
public class FIFO extends PageReplacement{
    ArrayList<PageTableEntry> validPages = new ArrayList<PageTableEntry>(); // store all the pages in memory
    ArrayList<PageTableEntry> inValidPages = new ArrayList<PageTableEntry>(); // store all the not in memory

    public FIFO(List<PageTableEntry> pageTable, boolean[] memoryFrames) {
        super(pageTable, memoryFrames);

        // add all the valid pages
        for(PageTableEntry pte : super.pageTable) {
            if(pte.isValid()) {
                validPages.add(pte);
            }
        }
        // add all the invalid pages
        for(PageTableEntry pte : super.pageTable) {
            if(!pte.isValid()) {
                inValidPages.add(pte);
            }
        }
    }

    /**
     *
     * @param numberNewPTE
     * @return the page number to be removed from memory
     */
    @Override
    public int getTargetPage(int numberNewPTE) {

        int result = numberNewPTE;
        // if there was a page in memory, remove it and add it to invalid pages
        if(validPages.size() > 0) {
            result = validPages.get(0).getPageFrameNumber();
            inValidPages.add(validPages.remove(0)); // take page on top of memory and add it to tail of inValid pagess
        }

        // now add the page number in virtual space to memory tail
        if(inValidPages.size() > 0) {
            validPages.add(inValidPages.remove(0)); // take page on top of virtual memory and add it to tail of memory pages
        }

        return result;

    }


}