/**
    * Copyright (C) 2010-14 pvmanager developers. See COPYRIGHT.TXT
    * All rights reserved. Use is subject to license terms. See LICENSE.TXT
    */
   package org.epics.pvmanager;
   
   import java.util.Collection;
   import java.util.HashMap;
   import java.util.HashSet;
  import java.util.Map;
  import java.util.Set;
  
  /**
   *
   * @author carcassi
   */
  class WritePlanner {
      
      private Map<String, ChannelHandler> channels = new HashMap<String, ChannelHandler>();
      private Map<String, Object> values = new HashMap<String, Object>();
      private Map<String, Set<String>> preceding = new HashMap<String, Set<String>>();
      private Map<String, Set<String>> succeeding = new HashMap<String, Set<String>>();
      private Set<String> leafs = new HashSet<String>();
      
      void addChannel(ChannelHandler channel, Object value, Collection<String> precedingChannels) {
          channels.put(channel.getChannelName(), channel);
          values.put(channel.getChannelName(), value);
          preceding.put(channel.getChannelName(), new HashSet<String>(precedingChannels));
          for (String precedingChannel : precedingChannels) {
              Set<String> succeedingChannels = succeeding.get(precedingChannel);
              if (succeedingChannels ==  null) {
                  succeedingChannels = new HashSet<String>();
                  succeeding.put(precedingChannel, succeedingChannels);
              }
              succeedingChannels.add(channel.getChannelName());
          }
          if (precedingChannels.isEmpty()) {
              leafs.add(channel.getChannelName());
          }
      }
      
      void removeChannel(String channelName) {
          channels.remove(channelName);
          values.remove(channelName);
          preceding.remove(channelName);
          Set<String> succeedingChannels = succeeding.remove(channelName);
          if (succeedingChannels != null) {
              for (String succeedingChannel : succeedingChannels) {
                  Set<String> precedingChannels = preceding.get(succeedingChannel);
                  precedingChannels.remove(channelName);
                  if (precedingChannels.isEmpty())
                      leafs.add(succeedingChannel);
              }
          }
      }
  
      Map<ChannelHandler, Object> nextChannels() {
          Map<ChannelHandler, Object> nextChannels = new HashMap<ChannelHandler, Object>();
          for (String channelName : leafs) {
              nextChannels.put(channels.get(channelName), values.get(channelName));
          }
          leafs.clear();
          return nextChannels;
      }
      
      boolean isDone() {
          return channels.isEmpty();
      }
      
  }