HistoryManager.java :  » UnTagged » and-bible » net » bible » service » history » Android Open Source

package net.bible.service.history;

import java.util.ArrayList;
import java.util.Collections;
import java.util.List;
import java.util.Stack;

import net.bible.android.control.page.CurrentBiblePage;
import net.bible.android.control.page.CurrentPage;
import net.bible.android.control.page.CurrentPageManager;

import org.crosswire.jsword.book.Book;
import org.crosswire.jsword.passage.Key;

import android.util.Log;

public class HistoryManager {

  private static int MAX_HISTORY = 20;
  private Stack<KeyHistoryItem> history = new Stack<KeyHistoryItem>();
  private static HistoryManager singleton = new HistoryManager();

  private boolean isGoingBack = false;
  
  private static final String TAG = "HistoryManager";
  
  public static HistoryManager getInstance() {
    return singleton;
  }
  
  public boolean canGoBack() {
    return history.size()>0;
  }
  
  /**
   *  called when a verse is changed
   */
  public void beforePageChange() {
    // if we cause the change by requesting Back then ignore it
    if (!isGoingBack) {
      KeyHistoryItem item = createHistoryItem();
      add(history, item);
    }
  }
  private KeyHistoryItem createHistoryItem() {
    CurrentPage currentPage = CurrentPageManager.getInstance().getCurrentPage();
    Book doc = currentPage.getCurrentDocument();
    if (currentPage.getKey()==null) {
      return null;
    }
    
    Key key = currentPage.getSingleKey();
    KeyHistoryItem historyItem = new KeyHistoryItem(doc, key);
    
    return historyItem;
  }
  
  //not used just keep a list of verse changes for now
  public void documentChanged() {
  }
  
  public void goBack() {
    if (history.size()>0) {
      try {
        Log.d(TAG, "History size:"+history.size());
        isGoingBack = true;
  
        // pop the previous item
        KeyHistoryItem previousItem = history.pop();
  
        if (previousItem!=null) {
          Log.d(TAG, "Going back to:"+previousItem);
          previousItem.revertTo();
        }
      } finally {
        isGoingBack = false;
      }
    }
  }
  
  public List<HistoryItem> getHistory() {
    List<HistoryItem> allHistory = new ArrayList<HistoryItem>(history);
    // reverse so most recent items are at top rather than end
    Collections.reverse(allHistory);
    return allHistory;
  }
  
  /** add item and check size of stack
   * 
   * @param stack
   * @param item
   */
  private synchronized void add(Stack<KeyHistoryItem> stack, KeyHistoryItem item) {
    if (item!=null) {
      Log.d(TAG, "Adding "+item.getKey()+" to history");
      Log.d(TAG, "Stack size:"+stack.size());
      
      stack.push(item);
      
      while (stack.size()>MAX_HISTORY) {
        Log.d(TAG, "Shrinking large stack");
        stack.remove(0);
      }
    }
  }
}