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package com.rabidgremlin.mutters.state;

import java.io.IOException;
import java.io.PrintWriter;
import java.io.Writer;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.HashSet;
import java.util.List;

import com.rabidgremlin.mutters.core.Intent;
import com.rabidgremlin.mutters.core.IntentMatch;
import com.rabidgremlin.mutters.core.session.Session;

public class StateMachine
{

  private HashMap states = new HashMap();

  private State startState;

  private HashMap> transitionMap = new HashMap>();

  private HashSet handledIntents = new HashSet();

  private HashMap preEventActions = new HashMap();

  class Transition
  {
    private State toState;

    private Guard guard;

    Transition(State toState, Guard guard)
    {
      this.toState = toState;
      this.guard = guard;
    }

    public State getToState()
    {
      return toState;
    }

    public void setToState(State toState)
    {
      this.toState = toState;
    }

    public Guard getGuard()
    {
      return guard;
    }

    public void setGuard(Guard guard)
    {
      this.guard = guard;
    }

  }

  public void setStartState(State state)
  {
    this.startState = state;
  }

  private void addState(State state)
  {
    states.put(state.getName(), state);
    if (startState == null)
    {
      startState = state;
    }
  }

  private String makeTransitionKey(String intentName, State state)
  {
    return intentName + '-' + state.getName();
  }

  private String makeGlobalTransitionKey(String intentName)
  {
    return intentName + "-*";
  }

  public void addTransition(String intentName, State fromState, State toState)
  {
    addTransition(intentName, fromState, toState, null);
  }

  public void addPreEventAction(String intentName, State fromState, PreEventAction preEventAction)
  {
    preEventActions.put(makeTransitionKey(intentName, fromState), preEventAction);
  }

  public void addTransition(String intentName, State fromState, State toState, Guard guard)
  {
    if (!states.containsKey(fromState.getName()))
    {
      addState(fromState);
    }

    if (!states.containsKey(toState.getName()))
    {
      addState(toState);
    }

    String key = makeTransitionKey(intentName, fromState);
    List transitionList = transitionMap.get(key);
    if (transitionList == null)
    {
      transitionList = new ArrayList();
      transitionMap.put(key, transitionList);
    }

    transitionList.add(new Transition(toState, guard));

    handledIntents.add(intentName);
  }

  public void addGlobalTransition(String intentName, State toState)
  {
    addGlobalTransition(intentName, toState, null);
  }

  public void addGlobalTransition(String intentName, State toState, Guard guard)
  {

    if (!states.containsKey(toState.getName()))
    {
      addState(toState);
    }

    String key = makeGlobalTransitionKey(intentName);
    List transitionList = transitionMap.get(key);
    if (transitionList == null)
    {
      transitionList = new ArrayList();
      transitionMap.put(key, transitionList);
    }

    transitionList.add(new Transition(toState, guard));

    handledIntents.add(intentName);
  }

  public IntentResponse trigger(final IntentMatch match, final Session session)
  {

    State currentState = startState;

    String currentStateName = (String) session
        .getAttribute("STATE_MACHINE_JLA1974_currentStateName");
    if (currentStateName != null)
    {
      currentState = states.get(currentStateName);
      if (currentState == null)
      {
        throw new IllegalStateException("Illegal current state in session:" + currentStateName);
      }
    }

    Intent intent = match.getIntent();
    String intentName = (intent != null) ? intent.getName() : null;

    if (intentName == null)
    {
      throw new IllegalArgumentException("Request missing intent." + match.toString());
    }

    String key = makeTransitionKey(intentName, currentState);

    // see if we have a pre-evet action and execute it if we have it
    PreEventAction preEventAction = preEventActions.get(key);
    if (preEventAction != null)
    {
      preEventAction.execute(match, session);
    }

    List transitionToStateList = transitionMap.get(key);

    if (transitionToStateList == null)
    {
      key = makeGlobalTransitionKey(intentName);
      transitionToStateList = transitionMap.get(key);

      if (transitionToStateList == null)
      {
        throw new IllegalStateException("Could not find state to transition to. Intent: "
            + intentName + " Current State: " + currentState);
      }
    }

    State transitionToState = null;

    // find first matching to state, checking guards
    for (Transition transition : transitionToStateList)
    {
      if (transition.guard == null)
      {
        transitionToState = transition.toState;
        break;
      }
      else
      {
        if (transition.guard.passes(match, session))
        {
          transitionToState = transition.toState;
          break;
        }
      }
    }

    // didn't find any matching states
    if (transitionToState == null)
    {
      throw new IllegalStateException(
          "Could not find state to transition to. Failed all guards. Intent: " + intentName
              + " Current State: " + currentState);
    }

    IntentResponse response = transitionToState.execute(match, session);

    session.setAttribute("STATE_MACHINE_JLA1974_currentStateName", transitionToState.name);

    return response;
  }

  public boolean canHandleRequest(final IntentMatch request)
  {
    return request.getIntent() != null && handledIntents.contains(request.getIntent().getName());
  }

  public void dump(Writer writer)
    throws IOException
  {
    // dummy state for global transitions
    final State anyState = new State("<>")
    {

      @Override
      public IntentResponse execute(IntentMatch intentMatch, Session session)
      {
        return null;
      }
    };

    PrintWriter out = new PrintWriter(writer);

    out.println("digraph g {");

    out.println("rankdir=LR;");
    out.println("overlap=false;");
    out.println("nodesep=0.25;");

    for (State state : states.values())
    {
      out.print(state.getName());
      out.println(";");
    }

    for (String key : transitionMap.keySet())
    {
      String[] splitKey = key.split("-");
      String intent = splitKey[0];
      State fromState;

      // handle global transitions
      if (splitKey[1].equals("*"))
      {
        fromState = anyState;
      }
      else
      {
        fromState = states.get(splitKey[1]);
      }

      List transitionToStateList = transitionMap.get(key);

      for (Transition transition : transitionToStateList)
      {
        out.print(fromState.getName());
        out.print(" -> ");
        out.print(transition.toState.getName());
        out.print(" [label=\"");
        out.print(intent);

        if (transition.guard != null)
        {
          out.print(" [");
          out.print(transition.guard.getDescription());
          out.print("]");
        }

        out.println("\"];");
      }

    }

    out.println("}");
    out.flush();
  }
}