//
// VinilRuntime.java  
// 

package vinil;

// Imports here
import java.util.*;

/**
 * class VinilRuntime
 * A VinilExtension which provides basic run-time services
 */
public class VinilRuntime implements VinilExtension
{
  /** Call correct function */
  public VinilElement doFunction(String name, VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    if (name.equals("sto"))
      return VinilRuntime.sto(env, parameters);
    else if (name.equals("set"))
      return VinilRuntime.set(env, parameters);
    else if (name.equals("ret"))
      return VinilRuntime.ret(env, parameters);
    else if (name.equals("equ"))
      return VinilRuntime.equ(env, parameters);
    else if (name.equals("+"))
      return VinilRuntime.plus(env, parameters);
    else if (name.equals("*"))
      return VinilRuntime.times(env, parameters);
    else if (name.equals("if"))
      return VinilRuntime.vIf(env, parameters);
    else if (name.equals("while"))
      return VinilRuntime.vWhile(env, parameters);
    else
      throw new VinilException("internal error: extension function not found");
  }
  
  public Vector getNames()
  {
    Vector v = new Vector();
    v.addElement("sto");
    v.addElement("ret");
    v.addElement("set");
    v.addElement("equ");
    v.addElement("+");
    v.addElement("*");
    v.addElement("if");
    v.addElement("while");
    return v;
  }

  static VinilElement vWhile(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    VinilElement vBool, vCode;
    try
      {
	// Sort out condition, then and else statements
	if(parameters instanceof VinilList) // it is a list
	  {
	    VinilList l=(VinilList)parameters;
	    if(l.size()!=2)
	      throw new VinilException("While takes two parameters");
	    vBool = l.elementAt(0);
	    vCode = l.elementAt(1);
	  }
	else if(parameters instanceof VinilDictionary) // it is a dictionary
	  {
	    VinilDictionary d=(VinilDictionary)parameters;
	    vBool=d.get(new VinilString("bool"));
	    vCode=d.get(new VinilString("code"));
	  }
	else // it is neither a list nor a dictionary
	  throw new VinilException("While requires list or dictionary");

	boolean looper=true;
	VinilElement tempBool;
	VinilBoolean vb;
	VinilList retval=new VinilList();

	while(looper)
	  {
	    // if the boolean is code, run it
	    tempBool=env.interpret(vBool);

	    // If it ain't a boolean, throw an exception
	    if(!(tempBool instanceof VinilBoolean))
	      throw new VinilException("While requires a boolean");

	    // Evaluate value
	    vb=(VinilBoolean)tempBool;
	    if(vb.getValue()==true)
	      retval.addTail(env.interpret(vCode));
	    else
	      looper=false;
	  }
	return retval;
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: "+e.toString());
      }
  }

  static VinilElement vIf(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    VinilElement vBool, vThen, vElse, retval;
    try
      {
	// Sort out condition, then and else statements
	if(parameters instanceof VinilList) // it is a list
	  {
	    VinilList l=(VinilList)parameters;
	    if((l.size()!=2)&&(l.size()!=3))
	      throw new VinilException("If takes a list of 2 or 3 items");
	    vBool = l.elementAt(0);
	    vThen = l.elementAt(1);
	    if(l.size()==3)
	      vElse = l.elementAt(2);
	    else 
	      vElse = new VinilNull();
	  }
	else if(parameters instanceof VinilDictionary) // it is a dictionary
	  {
	    VinilDictionary d=(VinilDictionary)parameters;
	    vBool=d.get(new VinilString("cond"));
	    vThen=d.get(new VinilString("then"));
	    vElse=d.get(new VinilString("else"));
	  }
	else // it is neither a list nor a dictionary
	  throw new VinilException("If requires list or dictionary");

	// if the boolean is code, run it
	vBool=env.interpret(vBool);

	// If it ain't a boolean, throw an exception
	if(!(vBool instanceof VinilBoolean))
	  throw new VinilException("If requires a boolean");

	// Evaluate value
	VinilBoolean vb=(VinilBoolean)vBool;
	if(vb.getValue()==true)
	  retval=vThen;
	else
	  retval=vElse;

	// If the result is code, run it
        retval=env.interpret(retval);

	return retval;
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: "+e.toString());
      }
  }

  static VinilElement sto(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    try
      {
	if ((parameters == null) || 
	    (!parameters.getClass().equals(Class.forName("vinil.VinilList"))) ||
	    (((VinilList)parameters).size() != 2))
	  throw new VinilException("sto takes two parameters");
	
	VinilElement symbol, value;
	symbol = ((VinilList)parameters).elementAt(0);
	value = ((VinilList)parameters).elementAt(1);
	
	if (!symbol.getClass().equals(Class.forName("vinil.VinilKeyword")))
	  throw new VinilException("improper variable name");
	
	env.put((VinilKeyword)symbol, value);
	return value;
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: VinilList or VinilKeyword not found");
      }
  }
  
  static VinilElement set(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    try
      {
	if ((parameters == null) || 
	    (!parameters.getClass().equals(Class.forName("vinil.VinilList"))) ||
	    (((VinilList)parameters).size() != 2))
	  throw new VinilException("sto takes two parameters");
	
	VinilElement symbol, value;
	symbol = ((VinilList)parameters).elementAt(0);
	value = ((VinilList)parameters).elementAt(1);
	value = value.evaluate(env, null);
	
	if (!symbol.getClass().equals(Class.forName("vinil.VinilKeyword")))
	  throw new VinilException("improper variable name");
	
	env.put((VinilKeyword)symbol, value);
	return value;
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: VinilList or VinilKeyword not found");
      }
  }
  
  static VinilElement ret(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    env.popReturn();
    if (parameters != null)
      env.pushReturn(parameters.evaluate(env, null));
    else
      env.pushReturn(null);
    return parameters;
  }
  
  static VinilElement equ(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    if (parameters == null)
      throw new VinilException("equ operator requires a list of 2 parameters");
    
    try
      {
	parameters = parameters.evaluate(env, null);
	if (Class.forName("vinil.VinilList").equals(parameters.getClass()))
	  {
	    VinilList l = (VinilList)parameters;
	    if (l.size() != 2)
	      throw new VinilException("equ operator requires a list of 2 parameters");
	    
	    VinilElement e = l.elementAt(0);
	    VinilElement f = l.elementAt(1);
	    e = e.evaluate(env, null);
	    f = f.evaluate(env, null);
	    
	    boolean b;
	    if ((e == null) && (f == null))
	      b = true;
	    else if ((f == null) && (e != null))
	      b = e.equals(f);
	    else
	      b = f.equals(e);
	    
	    VinilBoolean ret = new VinilBoolean();
	    ret.setValue(b);
	    
	    return ret;
	  }
	else
	  throw new VinilException("equ operator requires a list of 2 parameters");
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: class VinilList not found");
      }
  }
  
  static VinilElement plus(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    if (parameters == null)
      throw new VinilException("+ operator requires parameters");
    
    float f = 0;
    
    try
      {
	parameters = parameters.evaluate(env, null);
	if (Class.forName("vinil.VinilList").equals(parameters.getClass()))
	  {
	    VinilList l = (VinilList)parameters;
	    for (int i = 0; i < l.size(); i++)
	      {
		VinilElement e = l.elementAt(i);
		e = e.evaluate(env, null);
		if (!Class.forName("vinil.VinilNumber").equals(e.getClass()))
		  throw new VinilException("+ operator operates only on numbers");
		f += ((VinilNumber)e).getValue().floatValue();
	      }
	    VinilNumber n = new VinilNumber();
	    n.setValue(new Float(f));
	    return n;
	  }
	else if (Class.forName("vinil.VinilNumber").equals(parameters.getClass()))
	  {
	    return parameters;
	  }
	else
	  throw new VinilException("+ operator operates only on numbers");
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: VinilList or VinilNumber not found");
      }
  }
  
  static VinilElement times(VinilEnvironment env, VinilElement parameters) throws VinilException
  {
    if (parameters == null)
      throw new VinilException("+ operator requires parameters");
    
    float f = 1;
    
    try
      {
	parameters = parameters.evaluate(env, null);
	if (Class.forName("vinil.VinilList").equals(parameters.getClass()))
	  {
	    VinilList l = (VinilList)parameters;
	    for (int i = 0; i < l.size(); i++)
	      {
		VinilElement e = l.elementAt(i);
		e = e.evaluate(env, null);
		if (!Class.forName("vinil.VinilNumber").equals(e.getClass()))
		  throw new VinilException("+ operator operates only on numbers");
		f *= ((VinilNumber)e).getValue().floatValue();
	      }
	    VinilNumber n = new VinilNumber();
	    n.setValue(new Float(f));
	    return n;
	  }
	else if (Class.forName("vinil.VinilNumber").equals(parameters.getClass()))
	  {
	    return parameters;
	  }
	else
	  throw new VinilException("+ operator operates only on numbers");
      }
    catch (VinilException e)
      {
	throw e;
      }
    catch (Exception e)
      {
	throw new VinilException("internal error: VinilList or VinilNumber not found");
      }
  }
}