/*======================================================================
  FILE: icalcomponent.c
  CREATOR: eric 28 April 1999
  
  $Id: icalcomponent.c,v 1.64 2008-01-30 20:28:42 dothebart Exp $

 (C) COPYRIGHT 2000, Eric Busboom, http://www.softwarestudio.org

 This program is free software; you can redistribute it and/or modify
 it under the terms of either: 

    The LGPL as published by the Free Software Foundation, version
    2.1, available at: http://www.fsf.org/copyleft/lesser.html

  Or:

    The Mozilla Public License Version 1.0. You may obtain a copy of
    the License at http://www.mozilla.org/MPL/

  The original code is icalcomponent.c

======================================================================*/


#ifdef HAVE_CONFIG_H
#include "config.h"
#endif

#include "icalcomponent.h"
#include "pvl.h" /* "Pointer-to-void list" */
#include "icalerror.h"
#include "icalmemory.h"
#include "icalenums.h"
#include "icaltime.h"
#include "icalarray.h"
#include "icaltimezone.h"
#include "icalduration.h"
#include "icalperiod.h"
#include "icalparser.h"
#include "icalrestriction.h"

#include <stdlib.h>  /* for malloc */
#include <stdarg.h> /* for va_list, etc */
#include <errno.h>
#include <assert.h>
#include <stdio.h> /* for fprintf */
#include <string.h> /* for strdup */
#include <limits.h> /* for INT_MAX */

#ifdef WIN32
#define strncasecmp      strnicmp
#if defined(_MSC_VER) && (_MSC_VER < 1900)
#define snprintf _snprintf
#endif
#endif

struct icalcomponent_impl 
{
	char id[5];
	icalcomponent_kind kind;
	char* x_name;
	pvl_list properties;
	pvl_elem property_iterator;
	pvl_list components;
	pvl_elem component_iterator;
	icalcomponent* parent;

	/** An array of icaltimezone structs. We use this so we can do fast
	   lookup of timezones using binary searches. timezones_sorted is
	   set to 0 whenever we add a timezone, so we remember to sort the
	   array before doing a binary search. */
	icalarray* timezones;
	int timezones_sorted;
};

/* icalproperty functions that only components get to use */
void icalproperty_set_parent(icalproperty* property,
			     icalcomponent* component);
icalcomponent* icalproperty_get_parent(icalproperty* property);
void icalcomponent_add_children(icalcomponent *impl,va_list args);
static icalcomponent* icalcomponent_new_impl (icalcomponent_kind kind);

static void icalcomponent_merge_vtimezone (icalcomponent *comp,
					   icalcomponent *vtimezone,
					   icalarray *tzids_to_rename);
static void icalcomponent_handle_conflicting_vtimezones (icalcomponent *comp,
							 icalcomponent *vtimezone,
							 icalproperty *tzid_prop,
							 const char *tzid,
							 icalarray *tzids_to_rename);
static unsigned int icalcomponent_get_tzid_prefix_len (const char *tzid);
static void icalcomponent_rename_tzids(icalcomponent* comp,
				       icalarray* rename_table);
static void icalcomponent_rename_tzids_callback(icalparameter *param,
						void *data);
static int icalcomponent_compare_vtimezones (icalcomponent	*vtimezone1,
					     icalcomponent	*vtimezone2);
static int icalcomponent_compare_timezone_fn	(const void	*elem1,
						 const void	*elem2);
static struct icaltimetype
icalcomponent_get_datetime(icalcomponent *comp, icalproperty *prop);


void icalcomponent_add_children(icalcomponent *impl, va_list args)
{
    void* vp;
    
    while((vp = va_arg(args, void*)) != 0) {

	assert (icalcomponent_isa_component(vp) != 0 ||
		icalproperty_isa_property(vp) != 0 ) ;

	if (icalcomponent_isa_component(vp) != 0 ){
	  icalcomponent_add_component(impl, (icalcomponent*)vp);

	} else if (icalproperty_isa_property(vp) != 0 ){
	    icalcomponent_add_property(impl, (icalproperty*)vp);
	}
    }    
}

static icalcomponent*
icalcomponent_new_impl (icalcomponent_kind kind)
{
    icalcomponent* comp;

    if (!icalcomponent_kind_is_valid(kind))
	return NULL;

    if ( ( comp = (icalcomponent*) malloc(sizeof(icalcomponent))) == 0) {
	icalerror_set_errno(ICAL_NEWFAILED_ERROR);
	return 0;
    }
    
    strcpy(comp->id,"comp");

    comp->kind = kind;
    comp->properties = pvl_newlist();
    comp->property_iterator = 0;
    comp->components = pvl_newlist();
    comp->component_iterator = 0;
    comp->x_name = 0;
    comp->parent = 0;
    comp->timezones = NULL;
    comp->timezones_sorted = 1;

    return comp;
}

/** @brief Constructor
 */
icalcomponent*
icalcomponent_new (icalcomponent_kind kind)
{
   return icalcomponent_new_impl(kind);
}

/** @brief Constructor
 */
icalcomponent*
icalcomponent_vanew (icalcomponent_kind kind, ...)
{
   va_list args;

   icalcomponent *impl = icalcomponent_new_impl(kind);

    if (impl == 0){
	return 0;
    }

   va_start(args,kind);
   icalcomponent_add_children(impl, args);
   va_end(args);

   return impl;
}

/** @brief Constructor
 */
icalcomponent* icalcomponent_new_from_string(const char* str)
{
    return icalparser_parse_string(str);
}

/** @brief Constructor
 */
icalcomponent* icalcomponent_new_clone(icalcomponent* old)
{
    icalcomponent *new;
    icalproperty *p;
    icalcomponent *c;
    pvl_elem itr;

    icalerror_check_arg_rz( (old!=0), "component");

    new = icalcomponent_new_impl(old->kind);

    if (new == 0){
	return 0;
    }

    
    for( itr = pvl_head(old->properties);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	p = (icalproperty*)pvl_data(itr);
	icalcomponent_add_property(new,icalproperty_new_clone(p));
    }
   
   
    for( itr = pvl_head(old->components);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	c = (icalcomponent*)pvl_data(itr);
	icalcomponent_add_component(new,icalcomponent_new_clone(c));
    }

   return new;

}

/** @brief Constructor
 */
icalcomponent*
icalcomponent_new_x (const char* x_name)
{
    icalcomponent* comp = icalcomponent_new_impl(ICAL_X_COMPONENT);
    if (!comp) {
       return 0;
    }
    comp->x_name = icalmemory_strdup(x_name);
    return comp;
}

/*** @brief Destructor
 */
void
icalcomponent_free (icalcomponent* c)
{
    icalproperty* prop;
    icalcomponent* comp;

    icalerror_check_arg_rv( (c!=0), "component");

#ifdef ICAL_FREE_ON_LIST_IS_ERROR
    icalerror_assert( (c->parent ==0),"Tried to free a component that is still attached to a parent component");
#else
    if(c->parent != 0){
	return;
    }
#endif

    if(c != 0 ){
       
		if ( c->properties != 0 )
		{
		   while( (prop=pvl_pop(c->properties)) != 0){
		   assert(prop != 0);
			   icalproperty_set_parent(prop,0);
		   icalproperty_free(prop);
		   }
	        pvl_free(c->properties);
		}
      

       while( (comp=pvl_data(pvl_head(c->components))) != 0){
	   assert(comp!=0);
	   icalcomponent_remove_component(c,comp);
	   icalcomponent_free(comp);
       }
       
       pvl_free(c->components);

	if (c->x_name != 0) {
	    free(c->x_name);
	}

	if (c->timezones)
	    icaltimezone_array_free (c->timezones);

	c->kind = ICAL_NO_COMPONENT;
	c->properties = 0;
	c->property_iterator = 0;
	c->components = 0;
	c->component_iterator = 0;
	c->x_name = 0;	
	c->id[0] = 'X';
	c->timezones = NULL;

	free(c);
    }
}


char*
icalcomponent_as_ical_string (icalcomponent* impl)
{
	char *buf;
	buf = icalcomponent_as_ical_string_r(impl);
	icalmemory_add_tmp_buffer(buf);
	return buf;
}


char*
icalcomponent_as_ical_string_r (icalcomponent* impl)
{
   char* buf;
   char* tmp_buf;
   size_t buf_size = 1024;
   char* buf_ptr = 0;
    pvl_elem itr;
   /* RFC 2445 explicitly says that the newline is *ALWAYS* a \r\n (CRLF)!!!! */
   const char newline[] = "\r\n";
   
   icalcomponent *c;
   icalproperty *p;
   icalcomponent_kind kind = icalcomponent_isa(impl);

   const char* kind_string;

   icalerror_check_arg_rz( (impl!=0), "component");
   icalerror_check_arg_rz( (kind!=ICAL_NO_COMPONENT), "component kind is ICAL_NO_COMPONENT");
   
   if (kind != ICAL_X_COMPONENT) {
       kind_string  = icalcomponent_kind_to_string(kind);
   } else {
       kind_string = impl->x_name;
   }

   icalerror_check_arg_rz( (kind_string!=0),"Unknown kind of component");

   buf = icalmemory_new_buffer(buf_size);
   buf_ptr = buf; 

   icalmemory_append_string(&buf, &buf_ptr, &buf_size, "BEGIN:");
   icalmemory_append_string(&buf, &buf_ptr, &buf_size, kind_string);
   icalmemory_append_string(&buf, &buf_ptr, &buf_size, newline);
   


   for( itr = pvl_head(impl->properties);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	p = (icalproperty*)pvl_data(itr);
	
	icalerror_assert((p!=0),"Got a null property");
	tmp_buf = icalproperty_as_ical_string_r(p);
	
	icalmemory_append_string(&buf, &buf_ptr, &buf_size, tmp_buf);
	free(tmp_buf);
    }
   
   
   for( itr = pvl_head(impl->components);
	itr != 0;
	itr = pvl_next(itr))
   {	
       c = (icalcomponent*)pvl_data(itr);
       
       tmp_buf = icalcomponent_as_ical_string_r(c);
       
       icalmemory_append_string(&buf, &buf_ptr, &buf_size, tmp_buf);
       free(tmp_buf);
       
   }
   
   icalmemory_append_string(&buf, &buf_ptr, &buf_size, "END:");
   icalmemory_append_string(&buf, &buf_ptr, &buf_size, 
			    icalcomponent_kind_to_string(kind));
   icalmemory_append_string(&buf, &buf_ptr, &buf_size, newline);

   return buf;
}


int
icalcomponent_is_valid (icalcomponent* component)
{
    if ( (strcmp(component->id,"comp") == 0) &&
	 component->kind != ICAL_NO_COMPONENT){
	return 1;
    } else {
	return 0;
    }

}


icalcomponent_kind
icalcomponent_isa (const icalcomponent* component)
{
   icalerror_check_arg_rx( (component!=0), "component", ICAL_NO_COMPONENT);

   if(component != 0)
   {
       return component->kind;
   }
   return ICAL_NO_COMPONENT;
}


int
icalcomponent_isa_component (void* component)
{
    icalcomponent *impl = component;

    icalerror_check_arg_rz( (component!=0), "component");

    if (strcmp(impl->id,"comp") == 0) {
	return 1;
    } else {
	return 0;
    }

}

void
icalcomponent_add_property (icalcomponent* component, icalproperty* property)
{
    icalerror_check_arg_rv( (component!=0), "component");
    icalerror_check_arg_rv( (property!=0), "property");

    icalerror_assert( (!icalproperty_get_parent(property)),"The property has already been added to a component. Remove the property with icalcomponent_remove_property before calling icalcomponent_add_property");

    icalproperty_set_parent(property,component);

    pvl_push(component->properties,property);
}


void
icalcomponent_remove_property (icalcomponent* component, icalproperty* property)
{
    pvl_elem itr, next_itr;

    icalerror_check_arg_rv( (component!=0), "component");
    icalerror_check_arg_rv( (property!=0), "property");
    
    icalerror_assert( (icalproperty_get_parent(property)),"The property is not a member of a component");

    
    for( itr = pvl_head(component->properties);
	 itr != 0;
	 itr = next_itr)
    {
	next_itr = pvl_next(itr);
	
	if( pvl_data(itr) == (void*)property ){

	   if (component->property_iterator == itr){
	       component->property_iterator = pvl_next(itr);
	   }

	   pvl_remove( component->properties, itr); 
	  icalproperty_set_parent(property,0);
	}
    }	
}

int
icalcomponent_count_properties (icalcomponent* component, 
				icalproperty_kind kind)
{
    int count=0;
    pvl_elem itr;

    icalerror_check_arg_rz( (component!=0), "component");

    for( itr = pvl_head(component->properties);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	if(kind == icalproperty_isa((icalproperty*)pvl_data(itr)) ||
	    kind == ICAL_ANY_PROPERTY){
	    count++;
	}
    }


    return count;

}

icalproperty* icalcomponent_get_current_property (icalcomponent* component)
{
   icalerror_check_arg_rz( (component!=0),"component");

   if ((component->property_iterator==0)){
       return 0;
   }

   return (icalproperty*) pvl_data(component->property_iterator);
}

icalproperty*
icalcomponent_get_first_property (icalcomponent* c, icalproperty_kind kind)
{
   icalerror_check_arg_rz( (c!=0),"component");
  
   for( c->property_iterator = pvl_head(c->properties);
	c->property_iterator != 0;
	c->property_iterator = pvl_next(c->property_iterator)) {
	    
       icalproperty *p =  (icalproperty*) pvl_data(c->property_iterator);
	
	   if (icalproperty_isa(p) == kind || kind == ICAL_ANY_PROPERTY) {
	       
	       return p;
	   }
   }
   return 0;
}

icalproperty*
icalcomponent_get_next_property (icalcomponent* c, icalproperty_kind kind)
{
   icalerror_check_arg_rz( (c!=0),"component");

   if (c->property_iterator == 0){
       return 0;
   }

   for( c->property_iterator = pvl_next(c->property_iterator);
	c->property_iterator != 0;
	c->property_iterator = pvl_next(c->property_iterator)) {
	    
       icalproperty *p =  (icalproperty*) pvl_data(c->property_iterator);
	   
       if (icalproperty_isa(p) == kind || kind == ICAL_ANY_PROPERTY) {
	   
	   return p;
       }
   }

   return 0;
}


icalproperty**
icalcomponent_get_properties (icalcomponent* component, icalproperty_kind kind);


void
icalcomponent_add_component (icalcomponent* parent, icalcomponent* child)
{
    icalerror_check_arg_rv( (parent!=0), "parent");
    icalerror_check_arg_rv( (child!=0), "child");
    
    if (child->parent !=0) {
        icalerror_set_errno(ICAL_USAGE_ERROR);
    }

    child->parent = parent;

    /* Fix for Mozilla - bug 327602 */
    if (child->kind != ICAL_VTIMEZONE_COMPONENT) {
        pvl_push(parent->components, child);
    } else {
        /* VTIMEZONES should be first in the resulting VCALENDAR. */
        pvl_unshift(parent->components, child);

    /* Add the VTIMEZONE to our array. */
	/* FIXME: Currently we are also creating this array when loading in
	   a builtin VTIMEZONE, when we don't need it. */
	if (!parent->timezones)
	    parent->timezones = icaltimezone_array_new ();

	icaltimezone_array_append_from_vtimezone (parent->timezones, child);

	/* Flag that we need to sort it before doing any binary searches. */
	parent->timezones_sorted = 0;
    }
}


void
icalcomponent_remove_component (icalcomponent* parent, icalcomponent* child)
{
   pvl_elem itr, next_itr;

   icalerror_check_arg_rv( (parent!=0), "parent");
   icalerror_check_arg_rv( (child!=0), "child");
   
    /* If the component is a VTIMEZONE, remove it from our array as well. */
    if (child->kind == ICAL_VTIMEZONE_COMPONENT) {
	icaltimezone *zone;
	int i, num_elements;

	num_elements = parent->timezones ? parent->timezones->num_elements : 0;
        for (i = 0; i < num_elements; i++) {
	    zone = icalarray_element_at (parent->timezones, i);
	    if (icaltimezone_get_component (zone) == child) {
		icaltimezone_free (zone, 0);
	        icalarray_remove_element_at (parent->timezones, i);
		break;
	    }
	}
    }

   for( itr = pvl_head(parent->components);
	itr != 0;
	itr = next_itr)
   {
       next_itr = pvl_next(itr);
       
       if( pvl_data(itr) == (void*)child ){

	   if (parent->component_iterator == itr){
	       /* Don't let the current iterator become invalid */

	       /* HACK. The semantics for this are troubling. */
	       parent->component_iterator = 
		   pvl_next(parent->component_iterator);
	          
	   }
	   pvl_remove( parent->components, itr); 
	   child->parent = 0;
	   break;
       }
   }	
}


int
icalcomponent_count_components (icalcomponent* component, 
				icalcomponent_kind kind)
{
    int count=0;
    pvl_elem itr;

    icalerror_check_arg_rz( (component!=0), "component");

    for( itr = pvl_head(component->components);
	 itr != 0;
	 itr = pvl_next(itr))
    {
	if(kind == icalcomponent_isa((icalcomponent*)pvl_data(itr)) ||
	    kind == ICAL_ANY_COMPONENT){
	    count++;
	}
    }

    return count;
}

icalcomponent*
icalcomponent_get_current_component(icalcomponent* component)
{
   icalerror_check_arg_rz( (component!=0),"component");

   if (component->component_iterator == 0){
       return 0;
   }

   return (icalcomponent*) pvl_data(component->component_iterator);
}

icalcomponent*
icalcomponent_get_first_component (icalcomponent* c, 
				   icalcomponent_kind kind)
{
   icalerror_check_arg_rz( (c!=0),"component");
  
   for( c->component_iterator = pvl_head(c->components);
	c->component_iterator != 0;
	c->component_iterator = pvl_next(c->component_iterator)) {
	    
       icalcomponent *p =  (icalcomponent*) pvl_data(c->component_iterator);
	
	   if (icalcomponent_isa(p) == kind || kind == ICAL_ANY_COMPONENT) {
	       
	       return p;
	   }
   }

   return 0;
}


icalcomponent*
icalcomponent_get_next_component (icalcomponent* c, icalcomponent_kind kind)
{
   icalerror_check_arg_rz( (c!=0),"component");
  
   if (c->component_iterator == 0){
       return 0;
   }

   for( c->component_iterator = pvl_next(c->component_iterator);
	c->component_iterator != 0;
	c->component_iterator = pvl_next(c->component_iterator)) {
	    
       icalcomponent *p =  (icalcomponent*) pvl_data(c->component_iterator);
	
	   if (icalcomponent_isa(p) == kind || kind == ICAL_ANY_COMPONENT) {
	       
	       return p;
	   }
   }

   return 0;
}

icalcomponent* icalcomponent_get_first_real_component(icalcomponent *c)
{
    icalcomponent *comp;

    for(comp = icalcomponent_get_first_component(c,ICAL_ANY_COMPONENT);
	comp != 0;
	comp = icalcomponent_get_next_component(c,ICAL_ANY_COMPONENT)){

	icalcomponent_kind kind = icalcomponent_isa(comp);

	if(kind == ICAL_VEVENT_COMPONENT ||
	   kind == ICAL_VTODO_COMPONENT ||
	   kind == ICAL_VJOURNAL_COMPONENT ||
	   kind == ICAL_VFREEBUSY_COMPONENT ||
	   kind == ICAL_VQUERY_COMPONENT ||
	   kind == ICAL_VAGENDA_COMPONENT){
	    return comp;
	}
    }
    return 0;
}


/**	@brief Get the timespan covered by this component, in UTC
 *	(deprecated)
 *
 *      see icalcomponent_foreach_recurrence() for a better way to
 *      extract spans from an component.
 *
 *	This method can be called on either a VCALENDAR or any real
 *	component. If the VCALENDAR contains no real component, but
 *	contains a VTIMEZONE, we return that span instead.
 *	This might not be a desirable behavior; we keep it for now
 *	for backward compatibility, but it might be deprecated at a
 *	future time.
 *
 *	FIXME this API needs to be clarified. DTEND is defined as the
 *	first available time after the end of this event, so the span
 *	should actually end 1 second before DTEND.
 */

icaltime_span icalcomponent_get_span(icalcomponent* comp)
{
    icalcomponent *inner;
    icalcomponent_kind kind;
    icaltime_span span;
    struct icaltimetype start, end;

    span.start = 0;
    span.end = 0;
    span.is_busy= 1;

    /* initial Error checking */
    if (comp == NULL) {
	return span;
    }

    /* FIXME this might go away */
    kind  = icalcomponent_isa(comp);
    if(kind == ICAL_VCALENDAR_COMPONENT){
	inner = icalcomponent_get_first_real_component(comp);

	/* Maybe there is a VTIMEZONE in there */
	if (inner == 0){
	    inner = icalcomponent_get_first_component(comp,
			       ICAL_VTIMEZONE_COMPONENT);
	}

    } else {
	inner = comp;
    }

    if (inner == 0){
	icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
	/*icalerror_warn("icalcomponent_get_span: no component specified, or empty VCALENDAR component");*/
	return span; 
    }
    
    kind  = icalcomponent_isa(inner);

    if( !( kind == ICAL_VEVENT_COMPONENT ||
	   kind == ICAL_VJOURNAL_COMPONENT ||
	   kind == ICAL_VTODO_COMPONENT ||	   
	   kind == ICAL_VFREEBUSY_COMPONENT )) {
	icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
	/*icalerror_warn("icalcomponent_get_span: no component specified, or empty VCALENDAR component");*/
	return span; 
	
    }

    /* Get to work. starting with DTSTART */
    start = icalcomponent_get_dtstart(comp);
    if (icaltime_is_null_time(start)) {
	return span;
    }
    span.start = icaltime_as_timet_with_zone(start,
	icaltimezone_get_utc_timezone());

    /* The end time could be specified as either a DTEND or a DURATION */
    /* icalcomponent_get_dtend takes care of these cases. */
    end = icalcomponent_get_dtend(comp);
    if (icaltime_is_null_time(end)) {
	if (!icaltime_is_date(start)) {
	    /* If dtstart is a DATE-TIME and there is no DTEND nor DURATION
	       it takes no time */
	    span.start = 0;
	    return span;
	} else {
	    end = start;
	}
    }

    span.end = icaltime_as_timet_with_zone(end,
	icaltimezone_get_utc_timezone());
    if (icaltime_is_date(start)) {
	/* Until the end of the day*/
	span.end += 60*60*24 - 1;
    }

    return span;

}

/**
 * Decide if this recurrance is acceptable
 * 
 * @param comp       A valid icalcomponent.
 * @param dtstart    The base dtstart value for this component.
 * @param recurtime  The time to test against.
 *
 * @return true if the recurrence value is excluded, false otherwise.
 *
 * This function decides if a specific recurrence value is
 * excluded by EXRULE or EXDATE properties.
 *
 * It's not the most efficient code.  You might get better performance
 * if you assume that recurtime is always increasing for each
 * call. Then you could:
 *
 *   - sort the EXDATE values
 *   - save the state of each EXRULE iterator for the next call.
 * 
 * In this case though you don't need to worry how you call this
 * function.  It will always return the correct result.
 */

int icalproperty_recurrence_is_excluded(icalcomponent *comp,
				       struct icaltimetype *dtstart,
				       struct icaltimetype *recurtime) {
  icalproperty *exdate, *exrule;
  pvl_elem property_iterator;

  if (comp == NULL || 
      dtstart == NULL || 
      recurtime == NULL ||
      icaltime_is_null_time(*recurtime))
    /* BAD DATA */
    return 1;
    
  property_iterator = comp->property_iterator;

  /** first test against the exdate values **/
  for (exdate = icalcomponent_get_first_property(comp,ICAL_EXDATE_PROPERTY);
       exdate != NULL;
       exdate = icalcomponent_get_next_property(comp,ICAL_EXDATE_PROPERTY)) {
	 
    struct icaltimetype exdatetime = icalcomponent_get_datetime(comp, exdate);

    if (icaltime_compare(*recurtime, exdatetime) == 0) {
      /** MATCHED **/
        
      comp->property_iterator = property_iterator;
      return 1;
    }
  }

  /** Now test against the EXRULEs **/
  for (exrule = icalcomponent_get_first_property(comp,ICAL_EXRULE_PROPERTY);
       exrule != NULL;
       exrule = icalcomponent_get_next_property(comp,ICAL_EXRULE_PROPERTY)) {
	 
    struct icalrecurrencetype recur = icalproperty_get_exrule(exrule);
    icalrecur_iterator *exrule_itr  = icalrecur_iterator_new(recur, *dtstart);
    struct icaltimetype exrule_time;

    while (exrule_itr) {
      int result;
      exrule_time = icalrecur_iterator_next(exrule_itr);

      if (icaltime_is_null_time(exrule_time))
	break;

      result = icaltime_compare(*recurtime, exrule_time);
      if (result == 0) {
	icalrecur_iterator_free(exrule_itr);
        comp->property_iterator = property_iterator;
	return 1; /** MATCH **/
      }
      if (result == 1)
	break;    /** exrule_time > recurtime **/
    }

    icalrecur_iterator_free(exrule_itr);
  }
  comp->property_iterator = property_iterator; 

  return 0;  /** no matches **/
}

/**
 * @brief Return the busy status based on the TRANSP property.
 *
 * @param comp   A valid icalcomponent.
 *
 * @return 1 if the event is a busy item, 0 if it is not.
 */

static int icalcomponent_is_busy(icalcomponent *comp) {
  icalproperty *transp;
  enum icalproperty_status status;
  int ret = 1;

  /** @todo check access control here, converting busy->free if the
     permissions do not allow access... */

  /* Is this a busy time?  Check the TRANSP property */
  transp = icalcomponent_get_first_property(comp, ICAL_TRANSP_PROPERTY);
  
  if (transp) {
    icalvalue *transp_val = icalproperty_get_value(transp);

    switch (icalvalue_get_transp(transp_val)) {
    case ICAL_TRANSP_OPAQUE:
    case ICAL_TRANSP_OPAQUENOCONFLICT:
    case ICAL_TRANSP_NONE:
      ret = 1;
      break;
    case ICAL_TRANSP_TRANSPARENT:
    case ICAL_TRANSP_TRANSPARENTNOCONFLICT:
      ret = 0;
      break;
    default:
      ret = 0;
      break;
    }
  }
  status = icalcomponent_get_status(comp);
  if (ret && status) {
     switch (status) {
     case ICAL_STATUS_CANCELLED:
     case ICAL_STATUS_TENTATIVE:
        ret = 0;
	break;
    default:
	break;
    }
  }
  return(ret);
}




/**
 * @brief cycle through all recurrances of an event
 *
 * @param comp           A valid VEVENT component
 * @param start          Ignore timespans before this
 * @param end            Ignore timespans after this
 * @param callback       Function called for each timespan within the range
 * @param callback_data  Pointer passed back to the callback function
 *
 * This function will call the specified callback function for once
 * for the base value of DTSTART, and foreach recurring date/time
 * value.
 *
 * It will filter out events that are specified as an EXDATE or an EXRULE.
 *
 * @todo We do not filter out duplicate RRULES/RDATES
 * @todo We do not handle RDATEs with explicit periods
 */

void icalcomponent_foreach_recurrence(icalcomponent* comp,
				      struct icaltimetype start,
				      struct icaltimetype end,
			void (*callback)(icalcomponent *comp, 
                                         struct icaltime_span *span, 
                                         void *data),
				void *callback_data)
{
  struct icaltimetype dtstart, dtend;
  icaltime_span recurspan, basespan, limit_span;
  time_t limit_start, limit_end;
  int dtduration;
  icalproperty *rrule, *rdate;
  struct icaldurationtype dur;
  pvl_elem property_iterator;	/* for saving the iterator */
  
  if (comp == NULL || callback == NULL)
    return;
  
  dtstart = icalcomponent_get_dtstart(comp);
  
  if (icaltime_is_null_time(dtstart))
    return;			


  /* The end time could be specified as either a DTEND or a DURATION */
  /* icalcomponent_get_dtend takes care of these cases. */
  dtend = icalcomponent_get_dtend(comp);

  /* Now set up the base span for this item, corresponding to the 
     base DTSTART and DTEND */
  basespan = icaltime_span_new(dtstart, dtend, 1);

  basespan.is_busy = icalcomponent_is_busy(comp);


  /** Calculate the ceiling and floor values.. **/
  limit_start = icaltime_as_timet_with_zone(start, icaltimezone_get_utc_timezone());
  if (!icaltime_is_null_time(end))
    limit_end   = icaltime_as_timet_with_zone(end, icaltimezone_get_utc_timezone());
  else
    limit_end   = INT_MAX;  /* max 32 bit time_t */

  limit_span.start = limit_start;
  limit_span.end   = limit_end;


  /* Do the callback for the initial DTSTART entry */

  if (!icalproperty_recurrence_is_excluded(comp, &dtstart, &dtstart)) {
    /** call callback action **/
    if (icaltime_span_overlaps(&basespan, &limit_span))
    (*callback) (comp, &basespan, callback_data);
  }

  recurspan = basespan;
  dtduration = basespan.end - basespan.start;
  
  /* Now cycle through the rrule entries */
  for (rrule = icalcomponent_get_first_property(comp,ICAL_RRULE_PROPERTY);
       rrule != NULL;
       rrule = icalcomponent_get_next_property(comp,ICAL_RRULE_PROPERTY)) {

    struct icalrecurrencetype recur = icalproperty_get_rrule(rrule);
    icalrecur_iterator *rrule_itr  = icalrecur_iterator_new(recur, dtstart);
    struct icaltimetype rrule_time;
    if(rrule_itr)  
        rrule_time = icalrecur_iterator_next(rrule_itr);
    /** note that icalrecur_iterator_next always returns dtstart
	the first time.. **/

    while (rrule_itr) {
      rrule_time = icalrecur_iterator_next(rrule_itr);

      if (icaltime_is_null_time(rrule_time)) 
	break;

      dur = icaltime_subtract(rrule_time, dtstart);

      recurspan.start = basespan.start + icaldurationtype_as_int(dur);
      recurspan.end   = recurspan.start + dtduration;

      /** save the iterator ICK! **/
      property_iterator = comp->property_iterator;

      if (!icalproperty_recurrence_is_excluded(comp, &dtstart, &rrule_time)) {
	/** call callback action **/
	if (icaltime_span_overlaps(&recurspan, &limit_span))
	(*callback) (comp, &recurspan, callback_data);
      }
      comp->property_iterator = property_iterator;
    } /* end of iteration over a specific RRULE */

    icalrecur_iterator_free(rrule_itr);
  } /* end of RRULE loop */


  /** Now process RDATE entries **/
  for (rdate = icalcomponent_get_first_property(comp,ICAL_RDATE_PROPERTY);
       rdate != NULL;
       rdate = icalcomponent_get_next_property(comp,ICAL_RDATE_PROPERTY)) {

    struct icaldatetimeperiodtype rdate_period = icalproperty_get_rdate(rdate);

    /** RDATES can specify raw datetimes, periods, or dates.
	we only support raw datetimes for now.. 

        @todo Add support for other types **/
    
    if (icaltime_is_null_time(rdate_period.time)) 
      continue;

    dur = icaltime_subtract(rdate_period.time, dtstart);

    recurspan.start = basespan.start + icaldurationtype_as_int(dur);
    recurspan.end   = recurspan.start + dtduration;

    /** save the iterator ICK! **/
    property_iterator = comp->property_iterator;

    if (!icalproperty_recurrence_is_excluded(comp, &dtstart, &rdate_period.time)) {
      /** call callback action **/
      (*callback) (comp, &recurspan, callback_data);
    }
    comp->property_iterator = property_iterator;
  }
}



int icalcomponent_check_restrictions(icalcomponent* comp){
    icalerror_check_arg_rz(comp!=0,"comp");
    return icalrestriction_check(comp);
}

/** @brief returns the number of errors encountered parsing the data
 *
 * This function counts the number times the X-LIC-ERROR occurs
 * in the data structure.
 */

int icalcomponent_count_errors(icalcomponent* component)
{
    int errors = 0;
    icalproperty *p;
    icalcomponent *c;
    pvl_elem itr;

    for( itr = pvl_head(component->properties);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	p = (icalproperty*)pvl_data(itr);
	
	if(icalproperty_isa(p) == ICAL_XLICERROR_PROPERTY)
	{
	    errors++;
	}
    }


    for( itr = pvl_head(component->components);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	c = (icalcomponent*)pvl_data(itr);
	
	errors += icalcomponent_count_errors(c);
	
    }

    return errors;
}


void icalcomponent_strip_errors(icalcomponent* component)
{
    icalproperty *p;
    icalcomponent *c;
    pvl_elem itr, next_itr;

   for( itr = pvl_head(component->properties);
	 itr != 0;
	 itr = next_itr)
    {	
	p = (icalproperty*)pvl_data(itr);
	next_itr = pvl_next(itr);

	if(icalproperty_isa(p) == ICAL_XLICERROR_PROPERTY)
	{
	    icalcomponent_remove_property(component,p);
	    icalproperty_free(p);
	    p = NULL;
	}
    }
    
    for( itr = pvl_head(component->components);
	 itr != 0;
	 itr = pvl_next(itr))
    {	
	c = (icalcomponent*)pvl_data(itr);
	icalcomponent_strip_errors(c);
    }
}

/* Hack. This will change the state of the iterators */
void icalcomponent_convert_errors(icalcomponent* component)
{
    icalproperty *p, *next_p;
    icalcomponent *c;

    for(p = icalcomponent_get_first_property(component,ICAL_ANY_PROPERTY);
	p != 0;
	p = next_p){
	
	next_p = icalcomponent_get_next_property(component,ICAL_ANY_PROPERTY);

	if(icalproperty_isa(p) == ICAL_XLICERROR_PROPERTY)
	{
	    struct icalreqstattype rst;
	    icalparameter *param  = icalproperty_get_first_parameter
		(p,ICAL_XLICERRORTYPE_PARAMETER);

	    rst.code = ICAL_UNKNOWN_STATUS;
	    rst.desc = 0;

	    switch(icalparameter_get_xlicerrortype(param)){

		case  ICAL_XLICERRORTYPE_PARAMETERNAMEPARSEERROR: {
		    rst.code = ICAL_3_2_INVPARAM_STATUS;
		    break;
		}
		case  ICAL_XLICERRORTYPE_PARAMETERVALUEPARSEERROR: {
		    rst.code = ICAL_3_3_INVPARAMVAL_STATUS;
		    break;
		}
		case  ICAL_XLICERRORTYPE_PROPERTYPARSEERROR: {		    
		    rst.code = ICAL_3_0_INVPROPNAME_STATUS;
		    break;
		}
		case  ICAL_XLICERRORTYPE_VALUEPARSEERROR: {
		    rst.code = ICAL_3_1_INVPROPVAL_STATUS;
		    break;
		}
		case  ICAL_XLICERRORTYPE_COMPONENTPARSEERROR: {
		    rst.code = ICAL_3_4_INVCOMP_STATUS;
		    break;
		}

		default: {
		    break;
		}
	    }
	    if (rst.code != ICAL_UNKNOWN_STATUS){
		
		rst.debug = icalproperty_get_xlicerror(p);
		icalcomponent_add_property(component,
					   icalproperty_new_requeststatus(rst));
		
		icalcomponent_remove_property(component,p);
		icalproperty_free(p);
		p = NULL;
	    }
	}
    }

    for(c = icalcomponent_get_first_component(component,ICAL_ANY_COMPONENT);
	c != 0;
	c = icalcomponent_get_next_component(component,ICAL_ANY_COMPONENT)){
	
	icalcomponent_convert_errors(c);
    }
}


icalcomponent* icalcomponent_get_parent(icalcomponent* component)
{
   return component->parent;
}

void icalcomponent_set_parent(icalcomponent* component, icalcomponent* parent)
{
   component->parent = parent;
}

icalcompiter icalcompiter_null = {ICAL_NO_COMPONENT,0};


struct icalcomponent_kind_map {
	icalcomponent_kind kind;
	char name[20];
};

  

static const struct icalcomponent_kind_map component_map[] = 
{
    { ICAL_VEVENT_COMPONENT, "VEVENT" },
    { ICAL_VTODO_COMPONENT, "VTODO" },
    { ICAL_VJOURNAL_COMPONENT, "VJOURNAL" },
    { ICAL_VCALENDAR_COMPONENT, "VCALENDAR" },
    { ICAL_VAGENDA_COMPONENT, "VAGENDA" },
    { ICAL_VFREEBUSY_COMPONENT, "VFREEBUSY" },
    { ICAL_VTIMEZONE_COMPONENT, "VTIMEZONE" },
    { ICAL_VALARM_COMPONENT, "VALARM" },
    { ICAL_XSTANDARD_COMPONENT, "STANDARD" }, /*These are part of RFC2445 */
    { ICAL_XDAYLIGHT_COMPONENT, "DAYLIGHT" }, /*but are not really components*/
    { ICAL_X_COMPONENT, "X" },
    { ICAL_VSCHEDULE_COMPONENT, "SCHEDULE" },

    /* CAP components */
    { ICAL_VCAR_COMPONENT, "VCAR" },  
    { ICAL_VCOMMAND_COMPONENT, "VCOMMAND" },  
    { ICAL_VQUERY_COMPONENT, "VQUERY" },  
    { ICAL_VREPLY_COMPONENT, "VREPLY" },

    /* libical private components */
    { ICAL_XLICINVALID_COMPONENT, "X-LIC-UNKNOWN" },  
    { ICAL_XLICMIMEPART_COMPONENT, "X-LIC-MIME-PART" },  
    { ICAL_ANY_COMPONENT, "ANY" },  
    { ICAL_XROOT_COMPONENT, "XROOT" },  

    /* End of list */
    { ICAL_NO_COMPONENT, "" },
};


int icalcomponent_kind_is_valid(const icalcomponent_kind kind)
{
    int i = 0;
    do {
      if (component_map[i].kind == kind)
	return 1;
    } while (component_map[i++].kind != ICAL_NO_COMPONENT);

    return 0;
}

const char* icalcomponent_kind_to_string(icalcomponent_kind kind)
{
    int i;

    for (i=0; component_map[i].kind != ICAL_NO_COMPONENT; i++) {
	if (component_map[i].kind == kind) {
	    return component_map[i].name;
	}
    }

    return 0;

}

icalcomponent_kind icalcomponent_string_to_kind(const char* string)
{
    int i;

    if (string ==0 ) { 
	return ICAL_NO_COMPONENT;
    }

    for (i=0; component_map[i].kind  != ICAL_NO_COMPONENT; i++) {
	if (strncasecmp(string, component_map[i].name, strlen(component_map[i].name)) == 0) {
	    return component_map[i].kind;
	}
    }

    return ICAL_NO_COMPONENT;
}



icalcompiter 
icalcomponent_begin_component(icalcomponent* component,icalcomponent_kind kind)
{
    icalcompiter itr;
    pvl_elem i;

    itr.kind = kind;
    itr.iter = NULL;

    icalerror_check_arg_re(component!=0,"component",icalcompiter_null);

    for( i = pvl_head(component->components); i != 0; i = pvl_next(i)) {
	
	icalcomponent *c =  (icalcomponent*) pvl_data(i);
	
	if (icalcomponent_isa(c) == kind || kind == ICAL_ANY_COMPONENT) {
	    
	    itr.iter = i;

	    return itr;
	}
    }

    return icalcompiter_null;
}

icalcompiter
icalcomponent_end_component(icalcomponent* component,icalcomponent_kind kind)
{
    icalcompiter itr; 
    pvl_elem i;

    itr.kind = kind;

    icalerror_check_arg_re(component!=0,"component",icalcompiter_null);

    for( i = pvl_tail(component->components); i != 0; i = pvl_prior(i)) {
	
	icalcomponent *c =  (icalcomponent*) pvl_data(i);
	
	if (icalcomponent_isa(c) == kind || kind == ICAL_ANY_COMPONENT) {
	    
	    itr.iter = pvl_next(i);

	    return itr;
	}
    }

    return icalcompiter_null;;
}


icalcomponent* icalcompiter_next(icalcompiter* i)
{
   if (i->iter == 0){
       return 0;
   }

   icalerror_check_arg_rz( (i!=0),"i");

   for( i->iter = pvl_next(i->iter);
	i->iter != 0;
	i->iter = pvl_next(i->iter)) {
	    
       icalcomponent *c =  (icalcomponent*) pvl_data(i->iter);
	
	   if (icalcomponent_isa(c) == i->kind 
	       || i->kind == ICAL_ANY_COMPONENT) {
	       
	       return icalcompiter_deref(i);;
	   }
   }

   return 0;

}

icalcomponent* icalcompiter_prior(icalcompiter* i)
{
   if (i->iter == 0){
       return 0;
   }

   for( i->iter = pvl_prior(i->iter);
	i->iter != 0;
	i->iter = pvl_prior(i->iter)) {
	    
       icalcomponent *c =  (icalcomponent*) pvl_data(i->iter);
	
	   if (icalcomponent_isa(c) == i->kind 
	       || i->kind == ICAL_ANY_COMPONENT) {
	       
	       return icalcompiter_deref(i);;
	   }
   }

   return 0;

}
icalcomponent* icalcompiter_deref(icalcompiter* i)
{
    if(i->iter ==0){
	return 0;
    }

    return pvl_data(i->iter);
}

icalcomponent* icalcomponent_get_inner(icalcomponent* comp)
{
    if (icalcomponent_isa(comp) == ICAL_VCALENDAR_COMPONENT){
	return icalcomponent_get_first_real_component(comp);
    } else {
	return comp;
    }
}

/** @brief sets the METHOD property to the given method
 */

void icalcomponent_set_method(icalcomponent* comp, icalproperty_method method)
{
    icalproperty *prop 
	= icalcomponent_get_first_property(comp, ICAL_METHOD_PROPERTY);


    if (prop == 0){
	prop = icalproperty_new_method(method);
	icalcomponent_add_property(comp, prop);
    }
    
    icalproperty_set_method(prop,method);

}

/** @brief returns the METHOD property 
 */

icalproperty_method icalcomponent_get_method(icalcomponent* comp)
{
    icalproperty *prop 
	= icalcomponent_get_first_property(comp,ICAL_METHOD_PROPERTY);

    if (prop == 0){
	return ICAL_METHOD_NONE;
    }
    
    return icalproperty_get_method(prop);
}

#define ICALSETUPSET(p_kind) \
    icalcomponent *inner; \
    icalproperty *prop; \
    icalerror_check_arg_rv(comp!=0,"comp");\
    inner = icalcomponent_get_inner(comp); \
    if(inner == 0){\
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);\
        return;\
    }\
    prop = icalcomponent_get_first_property(inner, p_kind);
 

/**	@brief Set DTSTART property to given icaltime
 *
 *	This method respects the icaltime type (DATE vs DATE-TIME) and
 *	timezone (or lack thereof).
 */
void icalcomponent_set_dtstart(icalcomponent* comp, struct icaltimetype v)
{
    const char *tzid;
    ICALSETUPSET(ICAL_DTSTART_PROPERTY);

    if (prop == 0){
	prop = icalproperty_new_dtstart(v);
	icalcomponent_add_property(inner, prop);
    } else {
        icalproperty_remove_parameter_by_kind(prop, ICAL_TZID_PARAMETER);
    }
    
    icalproperty_set_dtstart(prop,v);

    if ((tzid = icaltime_get_tzid(v)) != NULL && !icaltime_is_utc(v)) {
	icalproperty_add_parameter(prop, icalparameter_new_tzid(tzid));
    }
}

/**	@brief Get a DATE or DATE-TIME property as an icaltime
 *
 *	If the property is a DATE-TIME with a timezone parameter and a
 *	corresponding VTIMEZONE is present in the component, the
 *	returned component will already be in the correct timezone;
 *	otherwise the caller is responsible for converting it.
 *
 *	FIXME this is useless until we can flag the failure
 */
static struct icaltimetype
icalcomponent_get_datetime(icalcomponent *comp, icalproperty *prop) {

    icalcomponent      *c;
    icalparameter      *param;
    struct icaltimetype	ret;

    ret = icalvalue_get_datetime(icalproperty_get_value(prop));

    if ((param = icalproperty_get_first_parameter(prop, ICAL_TZID_PARAMETER))
	!= NULL) {
	const char     *tzid = icalparameter_get_tzid(param);
	icaltimezone   *tz = NULL;

	for (c = comp; c != NULL; c = icalcomponent_get_parent(c)) {
	    tz = icalcomponent_get_timezone(c, tzid);
	    if (tz != NULL)
		break;
	}

	if (tz == NULL)
	    tz = icaltimezone_get_builtin_timezone_from_tzid(tzid);

	if (tz != NULL)
	    ret = icaltime_set_timezone(&ret, tz);
    }

    return ret;
}

/**	@brief Get DTSTART property as an icaltime
 *
 *	If DTSTART is a DATE-TIME with a timezone parameter and a
 *	corresponding VTIMEZONE is present in the component, the
 *	returned component will already be in the correct timezone;
 *	otherwise the caller is responsible for converting it.
 *
 *	FIXME this is useless until we can flag the failure
 */
struct icaltimetype icalcomponent_get_dtstart(icalcomponent* comp)
{
    icalcomponent *inner = icalcomponent_get_inner(comp); 
    icalproperty *prop;

    prop = icalcomponent_get_first_property(inner,ICAL_DTSTART_PROPERTY);
    if (prop == 0){
	return icaltime_null_time();
    }

    return icalcomponent_get_datetime(comp, prop);
}

/**	@brief Get DTEND property as an icaltime
 *
 *	If a DTEND property is not present but a DURATION is, we use
 *	that to determine the proper end.
 *
 *	If DTSTART is a DATE-TIME with a timezone parameter and a
 *	corresponding VTIMEZONE is present in the component, the
 *	returned component will already be in the correct timezone;
 *	otherwise the caller is responsible for converting it.
 *
 *	FIXME this is useless until we can flag the failure
 */
struct icaltimetype icalcomponent_get_dtend(icalcomponent* comp)
{
    icalcomponent *inner = icalcomponent_get_inner(comp); 
    icalproperty *end_prop 
	= icalcomponent_get_first_property(inner,ICAL_DTEND_PROPERTY);
    icalproperty *dur_prop 
	= icalcomponent_get_first_property(inner, ICAL_DURATION_PROPERTY);
    struct icaltimetype	ret = icaltime_null_time();

    if ( end_prop != 0) {
	ret = icalcomponent_get_datetime(comp, end_prop);
    } else if ( dur_prop != 0) { 

	struct icaltimetype start = 
	    icalcomponent_get_dtstart(inner);
	struct icaldurationtype duration = 
	    icalproperty_get_duration(dur_prop);

	struct icaltimetype end = icaltime_add(start,duration);

	ret = end;
    }

    return ret;
}

/**	@brief Set DTEND property to given icaltime
 *
 *	This method respects the icaltime type (DATE vs DATE-TIME) and
 *	timezone (or lack thereof).
 *
 *	This also checks that a DURATION property isn't already there,
 *	and returns an error if it is. It's the caller's responsibility
 *	to remove it.
 */
void icalcomponent_set_dtend(icalcomponent* comp, struct icaltimetype v)
{
    const char *tzid;
    ICALSETUPSET(ICAL_DTEND_PROPERTY);

    if (icalcomponent_get_first_property(inner,ICAL_DURATION_PROPERTY)
	!= NULL) {
	icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
	return;
    }

    if (prop == 0) {
	prop = icalproperty_new_dtend(v);
	icalcomponent_add_property(inner, prop);
    } else {
        icalproperty_remove_parameter_by_kind(prop, ICAL_TZID_PARAMETER);
    }

    icalproperty_set_dtend(prop,v);

    if ((tzid = icaltime_get_tzid(v)) != NULL && !icaltime_is_utc(v)) {
	icalproperty_add_parameter(prop, icalparameter_new_tzid(tzid));
    }
}

/**	@brief Set DURATION property to given icalduration
 *
 *	This method respects the icaltime type (DATE vs DATE-TIME) and
 *	timezone (or lack thereof).
 *
 *	This also checks that a DTEND property isn't already there,
 *	and returns an error if it is. It's the caller's responsibility
 *	to remove it.
 */
void icalcomponent_set_duration(icalcomponent* comp, 
				struct icaldurationtype v)
{
    ICALSETUPSET(ICAL_DURATION_PROPERTY);

    if (icalcomponent_get_first_property(inner,ICAL_DTEND_PROPERTY) != NULL) {
	icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
	return;
    }

    if (prop == 0) {
	prop = icalproperty_new_duration(v);
	icalcomponent_add_property(inner, prop);
    } else {
	icalproperty_set_duration(prop,v);
    }
}

/**	@brief Get DURATION property as an icalduration
 *
 *	If a DURATION property is not present but a DTEND is, we use
 *	that to determine the proper end.
 */
struct icaldurationtype icalcomponent_get_duration(icalcomponent* comp)
{
    icalcomponent *inner = icalcomponent_get_inner(comp); 

    icalproperty *end_prop 
	= icalcomponent_get_first_property(inner,ICAL_DTEND_PROPERTY);

    icalproperty *dur_prop 
	= icalcomponent_get_first_property(inner,ICAL_DURATION_PROPERTY);

    struct icaldurationtype ret = icaldurationtype_null_duration();

    if ( dur_prop != 0 && end_prop == 0) { 
	ret = icalproperty_get_duration(dur_prop);

    } else if ( end_prop != 0 && dur_prop == 0) {
	/**
	 * FIXME
	 * We assume DTSTART and DTEND are not in different time zones.
	 * Does the standard actually guarantee this?
	 */
	struct icaltimetype start = 
	    icalcomponent_get_dtstart(inner);
	struct icaltimetype end = 
	    icalcomponent_get_dtend(inner);

	ret = icaltime_subtract(end, start);
    } else {
	/* Error, both duration and dtend have been specified */
	icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
    }
    return ret;
}

void icalcomponent_set_dtstamp(icalcomponent* comp, struct icaltimetype v)
{

    ICALSETUPSET(ICAL_DTSTAMP_PROPERTY);

    if (prop == 0){
	prop = icalproperty_new_dtstamp(v);
	icalcomponent_add_property(inner, prop);
    }
    
    icalproperty_set_dtstamp(prop,v);

}


struct icaltimetype icalcomponent_get_dtstamp(icalcomponent* comp)
{
    icalcomponent *inner = icalcomponent_get_inner(comp); 
    icalproperty *prop 
	= icalcomponent_get_first_property(inner,ICAL_DTSTAMP_PROPERTY);

    if (prop == 0){
	return icaltime_null_time();
    }
    
    return icalproperty_get_dtstamp(prop);
}


void icalcomponent_set_summary(icalcomponent* comp, const char* v)
{
    ICALSETUPSET(ICAL_SUMMARY_PROPERTY)
 
    if (prop == 0){
	prop = icalproperty_new_summary(v);
	icalcomponent_add_property(inner, prop);
    }
    
    icalproperty_set_summary(prop,v);
}


const char* icalcomponent_get_summary(icalcomponent* comp)
{
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_SUMMARY_PROPERTY);

    if (prop == 0){
	return 0;
    }
    
    return icalproperty_get_summary(prop);

}

void icalcomponent_set_comment(icalcomponent* comp, const char* v)
{
    ICALSETUPSET(ICAL_COMMENT_PROPERTY);

    if (prop == 0){
	prop = icalproperty_new_comment(v);
	icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_summary(prop,v);

}
const char* icalcomponent_get_comment(icalcomponent* comp){
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_COMMENT_PROPERTY);

    if (prop == 0){
	return 0;
    }
    
    return icalproperty_get_comment(prop);
}

void icalcomponent_set_uid(icalcomponent* comp, const char* v)
{
    ICALSETUPSET(ICAL_UID_PROPERTY);

    if (prop == 0){
	prop = icalproperty_new_uid(v);
	icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_summary(prop,v);

}
const char* icalcomponent_get_uid(icalcomponent* comp){
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_UID_PROPERTY);

    if (prop == 0){
	return 0;
    }
    
    return icalproperty_get_uid(prop);
}

void icalcomponent_set_recurrenceid(icalcomponent* comp, struct icaltimetype v)
{
    ICALSETUPSET(ICAL_RECURRENCEID_PROPERTY);

    if (prop == 0){
        prop = icalproperty_new_recurrenceid(v);
        icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_recurrenceid(prop,v);
}
struct icaltimetype icalcomponent_get_recurrenceid(icalcomponent* comp)
{
    icalcomponent *inner;
    icalproperty *prop;
    if (comp == 0) {
	icalerror_set_errno(ICAL_BADARG_ERROR);
        return icaltime_null_time();
    }

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return icaltime_null_time();
    }

    prop= icalcomponent_get_first_property(inner, ICAL_RECURRENCEID_PROPERTY);

    if (prop == 0){
        return icaltime_null_time();
    }

    return icalproperty_get_recurrenceid(prop);
}

void icalcomponent_set_description(icalcomponent* comp, const char* v)
{
    ICALSETUPSET(ICAL_DESCRIPTION_PROPERTY);

    if (prop == 0){
        prop = icalproperty_new_description(v);
        icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_description(prop,v);
}
const char* icalcomponent_get_description(icalcomponent* comp)
{
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_DESCRIPTION_PROPERTY);

    if (prop == 0){
        return 0;
    }

    return icalproperty_get_description(prop);
}

void icalcomponent_set_location(icalcomponent* comp, const char* v)
{
    ICALSETUPSET(ICAL_LOCATION_PROPERTY)

    if (prop == 0){
        prop = icalproperty_new_location(v);
        icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_location(prop,v);
}
const char* icalcomponent_get_location(icalcomponent* comp)
{
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp); 

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_LOCATION_PROPERTY);

    if (prop == 0){
        return 0;
    }

    return icalproperty_get_location(prop);
}

void icalcomponent_set_sequence(icalcomponent* comp, int v)
{
    ICALSETUPSET(ICAL_SEQUENCE_PROPERTY);

    if (prop == 0){
        prop = icalproperty_new_sequence(v);
        icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_sequence(prop,v);

}
int icalcomponent_get_sequence(icalcomponent* comp){
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp);

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_SEQUENCE_PROPERTY);

    if (prop == 0){
        return 0;
    }

    return icalproperty_get_sequence(prop);
}


void icalcomponent_set_status(icalcomponent* comp, enum icalproperty_status v)
{
    ICALSETUPSET(ICAL_STATUS_PROPERTY);

    if (prop == 0){
        prop = icalproperty_new_status(v);
        icalcomponent_add_property(inner, prop);
    }

    icalproperty_set_status(prop,v);

}
enum icalproperty_status icalcomponent_get_status(icalcomponent* comp){
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp);

    if(inner == 0){
        icalerror_set_errno(ICAL_MALFORMEDDATA_ERROR);
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_STATUS_PROPERTY);

    if (prop == 0){
        return 0;
    }

    return icalproperty_get_status(prop);
}

icalcomponent* icalcomponent_new_vcalendar(void)
{
    return icalcomponent_new(ICAL_VCALENDAR_COMPONENT);
}
icalcomponent* icalcomponent_new_vevent(void)
{
    return icalcomponent_new(ICAL_VEVENT_COMPONENT);
}
icalcomponent* icalcomponent_new_vtodo(void)
{
    return icalcomponent_new(ICAL_VTODO_COMPONENT);
}
icalcomponent* icalcomponent_new_vjournal(void)
{
    return icalcomponent_new(ICAL_VJOURNAL_COMPONENT);
}
icalcomponent* icalcomponent_new_valarm(void)
{
    return icalcomponent_new(ICAL_VALARM_COMPONENT);
}
icalcomponent* icalcomponent_new_vfreebusy(void)
{
    return icalcomponent_new(ICAL_VFREEBUSY_COMPONENT);
}
icalcomponent* icalcomponent_new_vtimezone(void)
{
    return icalcomponent_new(ICAL_VTIMEZONE_COMPONENT);
}
icalcomponent* icalcomponent_new_xstandard(void)
{
    return icalcomponent_new(ICAL_XSTANDARD_COMPONENT);
}
icalcomponent* icalcomponent_new_xdaylight(void)
{
    return icalcomponent_new(ICAL_XDAYLIGHT_COMPONENT);
}
icalcomponent* icalcomponent_new_vagenda(void)
{
    return icalcomponent_new(ICAL_VAGENDA_COMPONENT);
}
icalcomponent* icalcomponent_new_vquery(void)
{
    return icalcomponent_new(ICAL_VQUERY_COMPONENT);
}
icalcomponent* icalcomponent_new_vreply(void)
{
    return icalcomponent_new(ICAL_VREPLY_COMPONENT);
}

/*
 * Timezone stuff.
 */


/**
 *  This takes 2 VCALENDAR components and merges the second one into the first,
 *  resolving any problems with conflicting TZIDs. comp_to_merge will no
 *  longer exist after calling this function.
 */
void icalcomponent_merge_component(icalcomponent* comp,
				   icalcomponent* comp_to_merge)
{
  icalcomponent *subcomp, *next_subcomp;
  icalarray *tzids_to_rename;
  unsigned int i;

  /* Check that both components are VCALENDAR components. */
  assert (icalcomponent_isa(comp) == ICAL_VCALENDAR_COMPONENT);
  assert (icalcomponent_isa(comp_to_merge) == ICAL_VCALENDAR_COMPONENT);

  /* Step through each subcomponent of comp_to_merge, looking for VTIMEZONEs.
     For each VTIMEZONE found, check if we need to add it to comp and if we
     need to rename it and all TZID references to it. */
  tzids_to_rename = icalarray_new (sizeof (char*), 16);
  subcomp = icalcomponent_get_first_component (comp_to_merge,
					       ICAL_VTIMEZONE_COMPONENT);
  while (subcomp) {
    next_subcomp = icalcomponent_get_next_component (comp_to_merge,
						     ICAL_VTIMEZONE_COMPONENT);
    /* This will add the VTIMEZONE to comp, if necessary, and also update
       the array of TZIDs we need to rename. */
    icalcomponent_merge_vtimezone (comp, subcomp, tzids_to_rename);
    /* FIXME: Handle possible NEWFAILED error. */

    subcomp = next_subcomp;
  }

  /* If we need to do any renaming of TZIDs, do it now. */
  if (tzids_to_rename->num_elements != 0) {
    icalcomponent_rename_tzids (comp_to_merge, tzids_to_rename);
      
    /* Now free the tzids_to_rename array. */
    for (i = 0; i < tzids_to_rename->num_elements; i++) {
      free (icalarray_element_at (tzids_to_rename, i));
    }
  }
  icalarray_free (tzids_to_rename);
  /* Now move all the components from comp_to_merge to comp, excluding
     VTIMEZONE components. */
  subcomp = icalcomponent_get_first_component (comp_to_merge,
					       ICAL_ANY_COMPONENT);
  while (subcomp) {
    next_subcomp = icalcomponent_get_next_component (comp_to_merge,
						     ICAL_ANY_COMPONENT);
    if (icalcomponent_isa(subcomp) != ICAL_VTIMEZONE_COMPONENT) {
      icalcomponent_remove_component (comp_to_merge, subcomp);
      icalcomponent_add_component (comp, subcomp);
    }
    subcomp = next_subcomp;
  }

  /* Free comp_to_merge. We have moved most of the subcomponents over to
     comp now. */
  icalcomponent_free (comp_to_merge);
}


static void icalcomponent_merge_vtimezone (icalcomponent *comp,
					   icalcomponent *vtimezone,
					   icalarray *tzids_to_rename)
{
  icalproperty *tzid_prop;
  const char *tzid;
  char *tzid_copy;
  icaltimezone *existing_vtimezone;

  /* Get the TZID of the VTIMEZONE. */
  tzid_prop = icalcomponent_get_first_property (vtimezone, ICAL_TZID_PROPERTY);
  if (!tzid_prop)
    return;

  tzid = icalproperty_get_tzid (tzid_prop);
  if (!tzid)
    return;

  /* See if there is already a VTIMEZONE in comp with the same TZID. */
  existing_vtimezone = icalcomponent_get_timezone (comp, tzid);

  /* If there is no existing VTIMEZONE with the same TZID, we can just move
     the VTIMEZONE to comp and return. */
  if (!existing_vtimezone) {
    icalcomponent_remove_component (icalcomponent_get_parent (vtimezone),
				    vtimezone);
    icalcomponent_add_component (comp, vtimezone);
    return;
  }

  /* If the TZID has a '/' prefix, then we don't have to worry about the
     clashing TZIDs, as they are supposed to be exactly the same VTIMEZONE. */
  if (tzid[0] == '/')
    return;

  /* Now we have two VTIMEZONEs with the same TZID (which isn't a globally
     unique one), so we compare the VTIMEZONE components to see if they are
     the same. If they are, we don't need to do anything. We make a copy of
     the tzid, since the parameter may get modified in these calls. */
  tzid_copy = strdup (tzid);
  if (!tzid_copy) {
    icalerror_set_errno(ICAL_NEWFAILED_ERROR);
    return;
  }

  if (!icalcomponent_compare_vtimezones (comp, vtimezone)) {
    /* FIXME: Handle possible NEWFAILED error. */

    /* Now we have two different VTIMEZONEs with the same TZID. */
    icalcomponent_handle_conflicting_vtimezones (comp, vtimezone, tzid_prop,
						 tzid_copy, tzids_to_rename);
  }
  free (tzid_copy);
}


static void
icalcomponent_handle_conflicting_vtimezones (icalcomponent *comp,
					     icalcomponent *vtimezone,
					     icalproperty *tzid_prop,
					     const char *tzid,
					     icalarray *tzids_to_rename)
{
  int i, suffix, max_suffix = 0, num_elements;
  unsigned int tzid_len;
  char *tzid_copy, *new_tzid, suffix_buf[32];
  (void)tzid_prop; /* hack to stop unused variable warning */

  /* Find the length of the TZID without any trailing digits. */
  tzid_len = icalcomponent_get_tzid_prefix_len (tzid);

  /* Step through each of the VTIMEZONEs in comp. We may already have the
     clashing VTIMEZONE in the calendar, but it may have been renamed
     (i.e. a unique number added on the end of the TZID, e.g. 'London2').
     So we compare the new VTIMEZONE with any VTIMEZONEs that have the
     same prefix (e.g. 'London'). If it matches any of those, we have to
     rename the TZIDs to that TZID, else we rename to a new TZID, using
     the biggest numeric suffix found + 1. */
  num_elements = comp->timezones ? comp->timezones->num_elements : 0;
  for (i = 0; i < num_elements; i++) {
    icaltimezone *zone;
    const char *existing_tzid;
    const char *existing_tzid_copy;
    unsigned int existing_tzid_len;

    zone = icalarray_element_at (comp->timezones, i);
    existing_tzid = icaltimezone_get_tzid (zone);

    /* Find the length of the TZID without any trailing digits. */
    existing_tzid_len = icalcomponent_get_tzid_prefix_len (existing_tzid);

    /* Check if we have the same prefix. */
    if (tzid_len == existing_tzid_len
	&& !strncmp (tzid, existing_tzid, tzid_len)) {
      /* Compare the VTIMEZONEs. */
      if (icalcomponent_compare_vtimezones (icaltimezone_get_component (zone),
					    vtimezone)) {
	/* The VTIMEZONEs match, so we can use the existing VTIMEZONE. But
	   we have to rename TZIDs to this TZID. */
	tzid_copy = strdup (tzid);
        if(!tzid_copy) {
          icalerror_set_errno(ICAL_NEWFAILED_ERROR);
          return;
        }
	existing_tzid_copy = strdup (existing_tzid);
        if (!existing_tzid_copy) {
	  icalerror_set_errno(ICAL_NEWFAILED_ERROR);
          free(tzid_copy);
	} else {
	  icalarray_append (tzids_to_rename, tzid_copy);
	  free(tzid_copy);
	  icalarray_append (tzids_to_rename, existing_tzid_copy);
	}
	return;
      } else {
	/* FIXME: Handle possible NEWFAILED error. */

	/* Convert the suffix to an integer and remember the maximum numeric
	   suffix found. */
	suffix = atoi (existing_tzid + existing_tzid_len);
	if (max_suffix < suffix)
	  max_suffix = suffix;
      }
    }
  }

  /* We didn't find a VTIMEZONE that matched, so we have to rename the TZID,
     using the maximum numerical suffix found + 1. */
  tzid_copy = strdup (tzid);
  if(!tzid_copy) {
    icalerror_set_errno(ICAL_NEWFAILED_ERROR);
    return;
  }

  snprintf (suffix_buf, sizeof(suffix_buf), "%i", max_suffix + 1);
  new_tzid = malloc (tzid_len + strlen (suffix_buf) + 1);
  if (!new_tzid) {
    icalerror_set_errno(ICAL_NEWFAILED_ERROR);
    free(tzid_copy);
    return;
  }

  strncpy (new_tzid, tzid, tzid_len);
  strcpy (new_tzid + tzid_len, suffix_buf);
  icalarray_append (tzids_to_rename, tzid_copy);
  icalarray_append (tzids_to_rename, new_tzid);
  free(tzid_copy);
  free(new_tzid);
}


/* Returns the length of the TZID, without any trailing digits. */
static unsigned int icalcomponent_get_tzid_prefix_len (const char *tzid)
{
  int len;
  const char *p;

  len = strlen (tzid);
  p = tzid + len - 1;
  while (len > 0 && *p >= '0' && *p <= '9') {
    p--;
    len--;
  }

  return len;
}


/**
 * Renames all references to the given TZIDs to a new name. rename_table
 * contains pairs of strings - a current TZID, and the new TZID to rename it
 * to.
 */
static void icalcomponent_rename_tzids(icalcomponent* comp,
				       icalarray* rename_table)
{
    icalcomponent_foreach_tzid (comp, icalcomponent_rename_tzids_callback,
				rename_table);
}


static void icalcomponent_rename_tzids_callback(icalparameter *param, void *data)
{
    icalarray *rename_table = data;
    const char *tzid;
    int i;

    tzid = icalparameter_get_tzid (param);
    if (!tzid)
        return;

    /* Step through the rename table to see if the current TZID matches
       any of the ones we want to rename. */
    for (i = 0; (unsigned int)i < rename_table->num_elements - 1; i += 2) {
        if (!strcmp (tzid, icalarray_element_at (rename_table, i))) {
	    icalparameter_set_tzid (param, icalarray_element_at (rename_table, i + 1));
	    break;
	}
    }
}


/**
 * Calls the given function for each TZID parameter found in the component.
 */
void icalcomponent_foreach_tzid(icalcomponent* comp,
				void (*callback)(icalparameter *param, void *data),
				void *callback_data)
{
    icalproperty *prop;
    icalproperty_kind kind;
    icalparameter *param;
    icalcomponent *subcomp;

    /* First look for any TZID parameters used in this component itself. */
    prop = icalcomponent_get_first_property (comp, ICAL_ANY_PROPERTY);
    while (prop) {
      kind = icalproperty_isa (prop);

      /* These are the only properties that can have a TZID. Note that
	 COMPLETED, CREATED, DTSTAMP & LASTMODIFIED must be in UTC. */
      if (kind == ICAL_DTSTART_PROPERTY || kind == ICAL_DTEND_PROPERTY
	  || kind == ICAL_DUE_PROPERTY || kind == ICAL_EXDATE_PROPERTY
	  || kind == ICAL_RDATE_PROPERTY) {
	param = icalproperty_get_first_parameter (prop, ICAL_TZID_PARAMETER);
	if (param)
	    (*callback) (param, callback_data);
      }

      prop = icalcomponent_get_next_property (comp, ICAL_ANY_PROPERTY);
    }

    /* Now recursively check child components. */
    subcomp = icalcomponent_get_first_component (comp, ICAL_ANY_COMPONENT);
    while (subcomp) {
        icalcomponent_foreach_tzid (subcomp, callback, callback_data);
        subcomp = icalcomponent_get_next_component (comp, ICAL_ANY_COMPONENT);
    }
}



/**
 *  Returns the icaltimezone from the component corresponding to the given
 *  TZID, or NULL if the component does not have a corresponding VTIMEZONE.
 */
icaltimezone* icalcomponent_get_timezone(icalcomponent* comp, const char *tzid)
{
    icaltimezone *zone;
    int lower, upper, middle, cmp;
    const char *zone_tzid;

    if (!comp->timezones)
	return NULL;

    /* Sort the array if necessary (by the TZID string). */
    if (!comp->timezones_sorted) {
	icalarray_sort (comp->timezones, icalcomponent_compare_timezone_fn);
	comp->timezones_sorted = 1;
    }

    /* Do a simple binary search. */
    lower = middle = 0;
    upper = comp->timezones->num_elements;

    while (lower < upper) {
	middle = (lower + upper) >> 1;
	zone = icalarray_element_at (comp->timezones, middle);
	zone_tzid = icaltimezone_get_tzid (zone);
	if (zone_tzid != NULL) {
		cmp = strcmp (tzid, zone_tzid);
		if (cmp == 0)
			return zone;
		else if (cmp < 0)
			upper = middle;
		else
			lower = middle + 1;
	}
    }

    return NULL;
}


/**
 * A function to compare 2 icaltimezone elements, used for qsort().
 */
static int icalcomponent_compare_timezone_fn	(const void	*elem1,
						 const void	*elem2)
{
    icaltimezone *zone1, *zone2;
    const char *zone1_tzid, *zone2_tzid;

    zone1 = (icaltimezone*) elem1;
    zone2 = (icaltimezone*) elem2;

    zone1_tzid = icaltimezone_get_tzid (zone1);
    zone2_tzid = icaltimezone_get_tzid (zone2);

    return strcmp (zone1_tzid, zone2_tzid);
}


/**
 * Compares 2 VTIMEZONE components to see if they match, ignoring their TZIDs.
 * It returns 1 if they match, 0 if they don't, or -1 on error.
 */
static int icalcomponent_compare_vtimezones (icalcomponent	*vtimezone1,
					     icalcomponent	*vtimezone2)
{
    icalproperty *prop1, *prop2;
    const char *tzid1, *tzid2;
    char *tzid2_copy, *string1, *string2;
    int cmp;

    /* Get the TZID property of the first VTIMEZONE. */
    prop1 = icalcomponent_get_first_property (vtimezone1, ICAL_TZID_PROPERTY);
    if (!prop1)
	return -1;

    tzid1 = icalproperty_get_tzid (prop1);
    if (!tzid1)
	return -1;

    /* Get the TZID property of the second VTIMEZONE. */
    prop2 = icalcomponent_get_first_property (vtimezone2, ICAL_TZID_PROPERTY);
    if (!prop2)
	return -1;

    tzid2 = icalproperty_get_tzid (prop2);
    if (!tzid2)
	return -1;

    /* Copy the second TZID, and set the property to the same as the first
       TZID, since we don't care if these match of not. */
    tzid2_copy = strdup (tzid2);
    if (!tzid2_copy) {
      icalerror_set_errno (ICAL_NEWFAILED_ERROR);
      return 0;
    }

    icalproperty_set_tzid (prop2, tzid1);

    /* Now convert both VTIMEZONEs to strings and compare them. */
    string1 = icalcomponent_as_ical_string_r (vtimezone1);
    if (!string1) {
	free (tzid2_copy);
	return -1;
    }

    string2 = icalcomponent_as_ical_string_r (vtimezone2);
    if (!string2) {
	free (string1);
	free (tzid2_copy);
	return -1;
    }

    cmp = strcmp (string1, string2);

    free (string1);
    free (string2);

    /* Now reset the second TZID. */
    icalproperty_set_tzid (prop2, tzid2_copy);
    free (tzid2_copy);

    return (cmp == 0) ? 1 : 0;
}






/** 
 * @brief set the RELCALID property of a component.
 *
 * @param comp    Valid calendar component.
 * @param v       Relcalid URL value
 */

void icalcomponent_set_relcalid(icalcomponent* comp, const char* v)
{
  ICALSETUPSET(ICAL_RELCALID_PROPERTY);

  if (prop == 0){
    prop = icalproperty_new_relcalid(v);
    icalcomponent_add_property(inner, prop);
  }

  icalproperty_set_relcalid(prop,v);

}


/** 
 * @brief get the RELCALID property of a component.
 *
 * @param comp    Valid calendar component.
 */

const char* icalcomponent_get_relcalid(icalcomponent* comp){
    icalcomponent *inner;
    icalproperty *prop;
    icalerror_check_arg_rz(comp!=0,"comp");

    inner = icalcomponent_get_inner(comp);

    if(inner == 0){
        return 0;
    }

    prop= icalcomponent_get_first_property(inner,ICAL_RELCALID_PROPERTY);

    if (prop == 0){
        return 0;
    }

    return icalproperty_get_relcalid(prop);
}


/** @brief Return the time a TODO task is DUE.
 *
 *  @param comp Valid calendar component.
 *
 *  Uses the DUE: property if it exists, otherwise we calculate the DUE
 *  value by adding the task's duration to the DTSTART time
 */

struct icaltimetype icalcomponent_get_due(icalcomponent* comp)
{
    icalcomponent *inner = icalcomponent_get_inner(comp);

    icalproperty *due_prop
        = icalcomponent_get_first_property(inner,ICAL_DUE_PROPERTY);

    icalproperty *dur_prop
        = icalcomponent_get_first_property(inner, ICAL_DURATION_PROPERTY);

    if ( due_prop != 0) {
        return icalproperty_get_due(due_prop);
    } else if ( dur_prop != 0) {

        struct icaltimetype start =
            icalcomponent_get_dtstart(inner);
        struct icaldurationtype duration =
            icalproperty_get_duration(dur_prop);

        struct icaltimetype due = icaltime_add(start,duration);

        return due;

    }
    return icaltime_null_time();
}

/** @brief Set the due date of a VTODO task.
 *
 *  @param comp Valid VTODO component.
 *  @param v    Valid due date time.
 *
 *  - If no duration or due properties then set the DUE property.
 *  - If a DUE property is already set, then reset it to the value v.
 *  - If a DURATION property is already set, then calculate the new
 *    duration based on the supplied value of v.
 */

void icalcomponent_set_due(icalcomponent* comp, struct icaltimetype v)
{
    icalcomponent *inner = icalcomponent_get_inner(comp);

    icalproperty *due_prop
        = icalcomponent_get_first_property(inner,ICAL_DUE_PROPERTY);

    icalproperty *dur_prop
        = icalcomponent_get_first_property(inner,ICAL_DURATION_PROPERTY);


    if( due_prop == 0 && dur_prop == 0){
        due_prop = icalproperty_new_due(v);
        icalcomponent_add_property(inner,due_prop);
    } else if ( due_prop != 0) {
        icalproperty_set_due(due_prop,v);
    } else if ( dur_prop != 0) {
        struct icaltimetype start =
            icalcomponent_get_dtstart(inner);

        struct icaltimetype due =
            icalcomponent_get_due(inner);

        struct icaldurationtype dur
            = icaltime_subtract(due,start);

        icalproperty_set_duration(dur_prop,dur);

    }
}
