import java.util.List;
import java.util.ArrayList;
import java.io.IOException;

/**
 * This is a placeholder for the fully working Backend that will be developed
 * by one of your teammates this week and then integrated with your role code
 * in a future week.  It is designed to help develop and test the functionality
 * of your own Frontend role code this week.  Note the limitations described
 * below.
 */
public class Backend_Placeholder implements BackendInterface {

    // Presumably this placeholder is using a placeholder tree that is itself
    // not fully functional.  The future working Backend will be making use of
    // a fully working tree.
    IterableSortedCollection<Song> tree;

    public Backend_Placeholder(IterableSortedCollection<Song> tree) {
        this.tree = tree;
    }

    // when this method is called, an extra song is added to this backend
    public void readData(String filename) throws IOException {
        tree.insert(new Song("DJ Got Us Fallin' In Love (feat. Pitbull)",
                             "Usher","atl hip hop",2010,120,86,66,-3,8));
    }

    // these filters should work on the limited list of hard-coded songs in tree
    public List<String> getAndSetRange(Integer low, Integer high) {
        String lowString = (char)('A'+(low==null?0:low))+" string";
        Song lowSong = new Song(lowString,lowString,lowString,
                                low,low,low,low,low,low);
        String highString = (char)('A'+(high==null?0:high))+" string";
        Song highSong = new Song(highString,highString,highString,
                                 high,high,high,high,high,high);
        tree.setIteratorMin(lowSong);
        tree.setIteratorMax(highSong);
        return fiveMost();
    }

    // filters are being completely ignored here, and the fivemost danceable
    // songs are really the five only
    public List<String> applyAndSetFilter(Integer threshold) {
        return fiveMost();
    }

    public List<String> fiveMost() {
        List<String> titles = new ArrayList<>();
        for(Song song : tree) {
            titles.add(song.getTitle());
        }
        return titles;
    }
}