package ch.egsolutions.tutorial;
import java.util.ArrayList;
import java.util.Collections;
import java.util.HashMap;
import java.util.Iterator;
import java.util.List;
import java.util.Random;
import java.util.Set;

import android.app.Activity;
import android.content.Context;
import android.os.Bundle;
import android.util.Log;
import android.widget.ArrayAdapter;
import android.widget.ListView;
import android.widget.SectionIndexer;

public class AlphabetIndexer extends Activity {
        ListView myListView;
        ArrayList<String> elements;

        @Override
        public void onCreate(Bundle savedInstanceState) {
                super.onCreate(savedInstanceState);
                setContentView(R.layout.main);

                // elements
                String s = "QWERTZUIOPASDFGHJKLYXCVBNM";
                Random r = new Random();
                elements = new ArrayList<String>();
                for (int i = 0; i < 300; i++) {

                        elements.add(s.substring(r.nextInt(s.length())));

                }
                Collections.sort(elements); // Must be sorted!

                // listview
                myListView = (ListView) findViewById(R.id.myListView);
                myListView.setFastScrollEnabled(true);
                MyIndexerAdapter<String> adapter = new MyIndexerAdapter<String>(
                                getApplicationContext(), android.R.layout.simple_list_item_1,
                                elements);
                myListView.setAdapter(adapter);

        }

        class MyIndexerAdapter<T> extends ArrayAdapter<T> implements SectionIndexer {

                ArrayList<String> myElements;
                HashMap<String, Integer> alphaIndexer;

                String[] sections;

                public MyIndexerAdapter(Context context, int textViewResourceId,
                                List<T> objects) {
                        super(context, textViewResourceId, objects);
                        myElements = (ArrayList<String>) objects;
                        // here is the tricky stuff
                        alphaIndexer = new HashMap<String, Integer>();
                        // in this hashmap we will store here the positions for
                        // the sections

                        int size = elements.size();
                        for (int i = size - 1; i >= 0; i--) {
                                String element = elements.get(i);
                                alphaIndexer.put(element.substring(0, 1), i);
                        //We store the first letter of the word, and its index.
                        //The Hashmap will replace the value for identical keys are putted in
                        }

                        // now we have an hashmap containing for each first-letter
                        // sections(key), the index(value) in where this sections begins

                        // we have now to build the sections(letters to be displayed)
                        // array .it must contains the keys, and must (I do so...) be
                        // ordered alphabetically

                        Set<String> keys = alphaIndexer.keySet(); // set of letters ...sets
                        // cannot be sorted...

                        Iterator<String> it = keys.iterator();
                        ArrayList<String> keyList = new ArrayList<String>(); // list can be
                        // sorted

                        while (it.hasNext()) {
                                String key = it.next();
                                keyList.add(key);
                        }

                        Collections.sort(keyList);

                        sections = new String[keyList.size()]; // simple conversion to an
                        // array of object
                        keyList.toArray(sections);

                        // ooOO00K !

                }

                @Override
                public int getPositionForSection(int section) {
                        // Log.v("getPositionForSection", ""+section);
                        String letter = sections[section];

                        return alphaIndexer.get(letter);
                }

                @Override
                public int getSectionForPosition(int position) {

                        // you will notice it will be never called (right?)
                        Log.v("getSectionForPosition", "called");
                        return 0;
                }

                @Override
                public Object[] getSections() {

                        return sections; // to string will be called each object, to display
                        // the letter
                }

        }
}