path: root/libical/src/libicalss/icalfileset.c

/* -*- Mode: C -*-
  ======================================================================
  FILE: icalfileset.c
  CREATOR: eric 23 December 1999
  
  $Id$
  $Locker$
    
 (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 eric. The Initial Developer of the Original
 Code is Eric Busboom


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


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

#include "icalfileset.h"
#include "icalgauge.h"
#include <errno.h>
#include <sys/stat.h> /* for stat */
#ifndef WIN32
#include <unistd.h> /* for stat, getpid */
#else
#include <io.h>
#include <share.h>
#endif
#include <stdlib.h>
#include <string.h>
#include <fcntl.h> /* for fcntl */
#include "icalfilesetimpl.h"
#include "icalclusterimpl.h"

#ifdef WIN32
#define snprintf    _snprintf
#define strcasecmp  stricmp

#define _S_ISTYPE(mode, mask)  (((mode) & _S_IFMT) == (mask))

#define S_ISDIR(mode)    _S_ISTYPE((mode), _S_IFDIR)
#define S_ISREG(mode)    _S_ISTYPE((mode), _S_IFREG)
#endif

extern int errno;

/** Default options used when NULL is passed to icalset_new() **/
icalfileset_options icalfileset_options_default = {O_RDWR|O_CREAT, 0644, 0};

int icalfileset_lock(icalfileset *set);
int icalfileset_unlock(icalfileset *set);
icalerrorenum icalfileset_read_file(icalfileset* set, mode_t mode);
int icalfileset_filesize(icalfileset* set);

icalerrorenum icalfileset_create_cluster(const char *path);

icalset* icalfileset_new(const char* path)
{
  return icalset_new(ICAL_FILE_SET, path, &icalfileset_options_default);
}

icalset* icalfileset_new_reader(const char* path)
{
  icalfileset_options reader_options = icalfileset_options_default;
  reader_options.flags = O_RDONLY;

  return icalset_new(ICAL_FILE_SET, path, &reader_options);
}

icalset* icalfileset_new_writer(const char* path)
{
  icalfileset_options writer_options = icalfileset_options_default;
  writer_options.flags = O_RDONLY;

  return icalset_new(ICAL_FILE_SET, path, &writer_options);
}

icalset* icalfileset_init(icalset *set, const char* path, void* options_in)
{
  icalfileset_options *options = (options_in) ? options_in : &icalfileset_options_default;
  icalfileset *fset = (icalfileset*) set;
  int flags;
  mode_t mode;
  off_t cluster_file_size;

  icalerror_clear_errno();
  icalerror_check_arg_rz( (path!=0), "path");
  icalerror_check_arg_rz( (fset!=0), "fset");

  fset->path = strdup(path);
  fset->options = *options;

  flags = options->flags;
  mode  = options->mode;

  cluster_file_size = icalfileset_filesize(fset);
  
  if(cluster_file_size < 0){
    icalfileset_free(set);
    return 0;
  }

#ifndef WIN32
  fset->fd = open(fset->path, flags, mode);
#else
  fset->fd = open(fset->path, flags, mode);
  /* fset->fd = sopen(fset->path,flags, _SH_DENYWR, _S_IREAD | _S_IWRITE); */
#endif
    
  if (fset->fd < 0){
    icalerror_set_errno(ICAL_FILE_ERROR);
    icalfileset_free(set);
    return 0;
  }

#ifndef WIN32
    icalfileset_lock(fset);
#endif
    
    if(cluster_file_size > 0 ){
    icalerrorenum error;
    if((error = icalfileset_read_file(fset,mode))!= ICAL_NO_ERROR){
      icalfileset_free(set);
      return 0;
    }
    }
 
    if (options->cluster) {
    fset->cluster = icalcomponent_new_clone(icalcluster_get_component(options->cluster));
    fset->changed = 1;
    }

    if (fset->cluster == 0) {
      fset->cluster = icalcomponent_new(ICAL_XROOT_COMPONENT);
    }

    return set;
}


icalcluster* icalfileset_produce_icalcluster(const char *path) {
  icalset *fileset;
  icalcluster *ret;

  int errstate = icalerror_errors_are_fatal;
  icalerror_errors_are_fatal = 0;
    
  fileset = icalfileset_new_reader(path);
  

  if (fileset == 0 && icalerrno == ICAL_FILE_ERROR) {
    /* file does not exist */
    ret = icalcluster_new(path, NULL);
  } else {
    ret = icalcluster_new(path, ((icalfileset*)fileset)->cluster);
    icalfileset_free(fileset);
  }
  
  icalerror_errors_are_fatal = errstate;
  icalerror_set_errno(ICAL_NO_ERROR);
  return ret;
}



char* icalfileset_read_from_file(char *s, size_t size, void *d)
{
    char* p = s;
    int fd = (int)d;

    /* Simulate fgets -- read single characters and stop at '\n' */

    for(p=s; p<s+size-1;p++){
    
    if(read(fd,p,1) != 1 || *p=='\n'){
        p++;
        break;
    } 
    }

    *p = '\0';
    
    if(*s == 0){
    return 0;
    } else {
    return s;
    }

}


icalerrorenum icalfileset_read_file(icalfileset* set,mode_t mode)
{
    icalparser *parser;
  
    parser = icalparser_new();

    icalparser_set_gen_data(parser,(void*)set->fd);
    set->cluster = icalparser_parse(parser,icalfileset_read_from_file);
    icalparser_free(parser);

    if (set->cluster == 0 || icalerrno != ICAL_NO_ERROR){
    icalerror_set_errno(ICAL_PARSE_ERROR);
    /*return ICAL_PARSE_ERROR;*/
    }
  
    if (icalcomponent_isa(set->cluster) != ICAL_XROOT_COMPONENT){
    /* The parser got a single component, so it did not put it in
       an XROOT. */
    icalcomponent *cl = set->cluster;
    set->cluster = icalcomponent_new(ICAL_XROOT_COMPONENT);
    icalcomponent_add_component(set->cluster,cl);
    }

    return ICAL_NO_ERROR;
}

int icalfileset_filesize(icalfileset* fset)
{
    int cluster_file_size;
    struct stat sbuf;
    
    if (stat(fset->path,&sbuf) != 0){
    
    /* A file by the given name does not exist, or there was
       another error */
    cluster_file_size = 0;
    if (errno == ENOENT) {
        /* It was because the file does not exist */
        return 0;
    } else {
        /* It was because of another error */
        icalerror_set_errno(ICAL_FILE_ERROR);
        return -1;
    }
    } else {
    /* A file by the given name exists, but is it a regular file? */
    
    if (!S_ISREG(sbuf.st_mode)){ 
        /* Nope, not a regular file */
        icalerror_set_errno(ICAL_FILE_ERROR);
        return -1;
    } else {
        /* Lets assume that it is a file of the right type */
        return sbuf.st_size;
    }   
    }

    /*return -1; not reached*/
}

void icalfileset_free(icalset* set)
{
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_rv((set!=0),"set");

    if (fset->cluster != 0){
    icalfileset_commit(set);
    icalcomponent_free(fset->cluster);
    fset->cluster=0;
    }

    if (fset->gauge != 0){
    icalgauge_free(fset->gauge);
    fset->gauge=0;
    }

    if(fset->fd > 0){
    icalfileset_unlock(fset);
    close(fset->fd);
    fset->fd = -1;
    }

    if(fset->path != 0){
    free(fset->path);
    fset->path = 0;
    }
}

const char* icalfileset_path(icalset* set) {
    icalerror_check_arg_rz((set!=0),"set");

    return ((icalfileset*)set)->path;
}


int icalfileset_lock(icalfileset *set)
{
#ifndef WIN32
    struct flock lock;
    int rtrn;

    icalerror_check_arg_rz((set->fd>0),"set->fd");
    errno = 0;
    lock.l_type = F_WRLCK;     /* F_RDLCK, F_WRLCK, F_UNLCK */
    lock.l_start = 0;  /* byte offset relative to l_whence */
    lock.l_whence = SEEK_SET; /* SEEK_SET, SEEK_CUR, SEEK_END */
    lock.l_len = 0;       /* #bytes (0 means to EOF) */

    rtrn = fcntl(set->fd, F_SETLKW, &lock);

    return rtrn;
#else
    return 0;
#endif
}

int icalfileset_unlock(icalfileset *set)
{
#ifndef WIN32
    struct flock lock;
    icalerror_check_arg_rz((set->fd>0),"set->fd");

    lock.l_type = F_WRLCK;     /* F_RDLCK, F_WRLCK, F_UNLCK */
    lock.l_start = 0;  /* byte offset relative to l_whence */
    lock.l_whence = SEEK_SET; /* SEEK_SET, SEEK_CUR, SEEK_END */
    lock.l_len = 0;       /* #bytes (0 means to EOF) */

    return (fcntl(set->fd, F_UNLCK, &lock)); 
#else
    return 0;
#endif
}

icalerrorenum icalfileset_commit(icalset* set)
{
    char tmp[ICAL_PATH_MAX]; 
    char *str;
    icalcomponent *c;
    off_t write_size=0;
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_re((fset!=0),"set",ICAL_BADARG_ERROR);  
    
    icalerror_check_arg_re((fset->fd>0),"set->fd is invalid",
               ICAL_INTERNAL_ERROR) ;

    if (fset->changed == 0 ){
    return ICAL_NO_ERROR;
    }
    
    if(lseek(fset->fd, 0, SEEK_SET) < 0){
    icalerror_set_errno(ICAL_FILE_ERROR);
    return ICAL_FILE_ERROR;
    }
    
    for(c = icalcomponent_get_first_component(fset->cluster,ICAL_ANY_COMPONENT);
    c != 0;
    c = icalcomponent_get_next_component(fset->cluster,ICAL_ANY_COMPONENT)){
    int sz;

    str = icalcomponent_as_ical_string(c);
    
    sz=write(fset->fd,str,strlen(str));

    if ( sz != strlen(str)){
        perror("write");
        icalerror_set_errno(ICAL_FILE_ERROR);
        return ICAL_FILE_ERROR;
    }

    write_size += sz;
    }
    
    fset->changed = 0;    

#ifndef WIN32
    if(ftruncate(fset->fd,write_size) < 0){
    return ICAL_FILE_ERROR;
    }
#else
    chsize( fset->fd, tell( fset->fd ) );
#endif
    
    return ICAL_NO_ERROR;
} 

void icalfileset_mark(icalset* set) {
    icalerror_check_arg_rv((set!=0),"set");

    ((icalfileset*)set)->changed = 1;
}

icalcomponent* icalfileset_get_component(icalset* set){
    icalfileset *fset = (icalfileset*) set;
    icalerror_check_arg_rz((set!=0),"set");

    return fset->cluster;
}


/* manipulate the components in the set */

icalerrorenum icalfileset_add_component(icalset *set,
                    icalcomponent* child)
{
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_re((set!=0),"set", ICAL_BADARG_ERROR);
    icalerror_check_arg_re((child!=0),"child",ICAL_BADARG_ERROR);

    icalcomponent_add_component(fset->cluster,child);

    icalfileset_mark(set);

    return ICAL_NO_ERROR;
}

icalerrorenum icalfileset_remove_component(icalset *set,
                       icalcomponent* child)
{
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_re((set!=0),"set",ICAL_BADARG_ERROR);
    icalerror_check_arg_re((child!=0),"child",ICAL_BADARG_ERROR);

    icalcomponent_remove_component(fset->cluster,child);

    icalfileset_mark(set);

    return ICAL_NO_ERROR;
}

int icalfileset_count_components(icalset *set,
                 icalcomponent_kind kind)
{
    icalfileset *fset = (icalfileset*) set;

    if (set == 0){
    icalerror_set_errno(ICAL_BADARG_ERROR);
    return -1;
    }

    return icalcomponent_count_components(fset->cluster,kind);
}

icalerrorenum icalfileset_select(icalset* set, icalgauge* gauge)
{
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_re(gauge!=0,"gauge",ICAL_BADARG_ERROR);

    fset->gauge = gauge;

    return ICAL_NO_ERROR;
}

void icalfileset_clear(icalset* set)
{
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_rv(set!=0,"set");

    fset->gauge = 0;
}

icalcomponent* icalfileset_fetch(icalset* set,const char* uid)
{
    icalfileset *fset = (icalfileset*) set;
    icalcompiter i;    

    icalerror_check_arg_rz(set!=0,"set");
    
    for(i = icalcomponent_begin_component(fset->cluster,ICAL_ANY_COMPONENT);
    icalcompiter_deref(&i)!= 0; icalcompiter_next(&i)){
    
        icalcomponent *this = icalcompiter_deref(&i);
        icalcomponent *inner;
        icalproperty *p;
        const char *this_uid;

        for(inner = icalcomponent_get_first_component(this,ICAL_ANY_COMPONENT);
            inner != 0;
            inner = icalcomponent_get_next_component(this,ICAL_ANY_COMPONENT)){

            p = icalcomponent_get_first_property(inner,ICAL_UID_PROPERTY);
            if ( p )
            {
                this_uid = icalproperty_get_uid(p);

                if(this_uid==0){
                icalerror_warn("icalfileset_fetch found a component with no UID");
                continue;
                }

                if (strcmp(uid,this_uid)==0){
                    return this;
                }
            }
        }
    }

    return 0;
}

int icalfileset_has_uid(icalset* set,const char* uid)
{
    assert(0); /* HACK, not implemented */
    return 0;
}

/******* support routines for icalfileset_fetch_match *********/

struct icalfileset_id{
    char* uid;
    char* recurrence_id;
    int sequence;
};

void icalfileset_id_free(struct icalfileset_id *id)
{
    if(id->recurrence_id != 0){
    free(id->recurrence_id);
    }

    if(id->uid != 0){
    free(id->uid);
    }
}


struct icalfileset_id icalfileset_get_id(icalcomponent* comp)
{
    icalcomponent *inner;
    struct icalfileset_id id;
    icalproperty *p;

    inner = icalcomponent_get_first_real_component(comp);
    
    p = icalcomponent_get_first_property(inner, ICAL_UID_PROPERTY);

    assert(p!= 0);

    id.uid = strdup(icalproperty_get_uid(p));

    p = icalcomponent_get_first_property(inner, ICAL_SEQUENCE_PROPERTY);

    if(p == 0) {
    id.sequence = 0;
    } else { 
    id.sequence = icalproperty_get_sequence(p);
    }

    p = icalcomponent_get_first_property(inner, ICAL_RECURRENCEID_PROPERTY);

    if (p == 0){
    id.recurrence_id = 0;
    } else {
    icalvalue *v;
    v = icalproperty_get_value(p);
    id.recurrence_id = strdup(icalvalue_as_ical_string(v));

    assert(id.recurrence_id != 0);
    }

    return id;
}


/* Find the component that is related to the given
   component. Currently, it just matches based on UID and
   RECURRENCE-ID */
icalcomponent* icalfileset_fetch_match(icalset* set, icalcomponent *comp)
{
    icalfileset *fset = (icalfileset*) set;
    icalcompiter i;    

    struct icalfileset_id comp_id, match_id;
    
    comp_id = icalfileset_get_id(comp);

    for(i = icalcomponent_begin_component(fset->cluster,ICAL_ANY_COMPONENT);
    icalcompiter_deref(&i)!= 0; icalcompiter_next(&i)){
    
    icalcomponent *match = icalcompiter_deref(&i);

    match_id = icalfileset_get_id(match);

    if(strcmp(comp_id.uid, match_id.uid) == 0 &&
       ( comp_id.recurrence_id ==0 || 
         strcmp(comp_id.recurrence_id, match_id.recurrence_id) ==0 )){

        /* HACK. What to do with SEQUENCE? */

        icalfileset_id_free(&match_id);
        icalfileset_id_free(&comp_id);
        return match;
        
    }
    
    icalfileset_id_free(&match_id);
    }

    icalfileset_id_free(&comp_id);
    return 0;

}


icalerrorenum icalfileset_modify(icalset* set, icalcomponent *old,
                 icalcomponent *new)
{
    icalfileset *fset = (icalfileset*) set;

    assert(0); /* HACK, not implemented */
    return ICAL_NO_ERROR;
}


/* Iterate through components */
icalcomponent* icalfileset_get_current_component (icalset* set)
{
    icalfileset *fset = (icalfileset*) set;

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

    return icalcomponent_get_current_component(fset->cluster);
}


icalcomponent* icalfileset_get_first_component(icalset* set)
{
    icalcomponent *c=0;
    icalfileset *fset = (icalfileset*) set;

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

    do {
    if (c == 0){
        c = icalcomponent_get_first_component(fset->cluster,
                          ICAL_ANY_COMPONENT);
    } else {
        c = icalcomponent_get_next_component(fset->cluster,
                         ICAL_ANY_COMPONENT);
    }

    if(c != 0 && (fset->gauge == 0 ||
              icalgauge_compare(fset->gauge, c) == 1)){
        return c;
    }

    } while(c != 0);


    return 0;
}

icalcomponent* icalfileset_get_next_component(icalset* set)
{
    icalfileset *fset = (icalfileset*) set;
    icalcomponent *c;

    icalerror_check_arg_rz((set!=0),"set");
    
    do {
    c = icalcomponent_get_next_component(fset->cluster,
                         ICAL_ANY_COMPONENT);

    if(c != 0 && (fset->gauge == 0 ||
              icalgauge_compare(fset->gauge,c) == 1)){
        return c;
    }
    
    } while(c != 0);
    
    
    return 0;
}
/*
icalsetiter icalfileset_begin_component(icalset* set, icalcomponent_kind kind, icalgauge* gauge)
{
    icalsetiter itr = icalsetiter_null;
    icalcomponent* comp = NULL;
    icalcompiter citr;
    icalfileset *fset = (icalfileset*) set;

    icalerror_check_arg_re((set!=0), "set", icalsetiter_null);

    itr.gauge = gauge;

    citr = icalcomponent_begin_component(fset->cluster, kind);
    comp = icalcompiter_deref(&citr);

    while (comp != 0) {
    comp = icalcompiter_deref(&citr);
    if (gauge == 0 || icalgauge_compare(itr.gauge, comp) == 1) {
        itr.iter = citr;
        return itr;
    }
    comp =  icalcompiter_next(&citr);
    }

    return icalsetiter_null;
}
*/

icalsetiter icalfileset_begin_component(icalset* set, icalcomponent_kind kind, icalgauge* gauge)
{
    icalsetiter itr = icalsetiter_null;
    icalcomponent* comp = NULL;
    icalcompiter citr;
    icalfileset *fset = (icalfileset*) set;
    struct icaltimetype start, next;
    icalproperty *dtstart, *rrule, *prop, *due;
    struct icalrecurrencetype recur;
    int g = 0;

    icalerror_check_arg_re((set!=0), "set", icalsetiter_null);

    itr.gauge = gauge;

    citr = icalcomponent_begin_component(fset->cluster, kind);
    comp = icalcompiter_deref(&citr);

    if (gauge == 0) {
        itr.iter = citr;
        return itr;
    }

    while (comp != 0) {

        /* check if it is a recurring component and with guage expand, if so
           we need to add recurrence-id property to the given component */
        rrule = icalcomponent_get_first_property(comp, ICAL_RRULE_PROPERTY);
        g = icalgauge_get_expand(gauge);

        if (rrule != 0
            && g == 1) {

            recur = icalproperty_get_rrule(rrule);
            if (icalcomponent_isa(comp) == ICAL_VEVENT_COMPONENT) {
                dtstart = icalcomponent_get_first_property(comp, ICAL_DTSTART_PROPERTY);
                if (dtstart)
                    start = icalproperty_get_dtstart(dtstart);
            } else if (icalcomponent_isa(comp) == ICAL_VTODO_COMPONENT) {
                    due = icalcomponent_get_first_property(comp, ICAL_DUE_PROPERTY);
                    if (due)
                        start = icalproperty_get_due(due);
            }

            if (itr.last_component == NULL) {
                itr.ritr = icalrecur_iterator_new(recur, start);
                next = icalrecur_iterator_next(itr.ritr);
                itr.last_component = comp;
            }
            else {
                next = icalrecur_iterator_next(itr.ritr);
                if (icaltime_is_null_time(next)){
                    itr.last_component = NULL;
                    icalrecur_iterator_free(itr.ritr);
                    itr.ritr = NULL;
                    return icalsetiter_null;
                } else {
                    itr.last_component = comp;
                }
            }

            /* add recurrence-id to the component
               if there is a recurrence-id already, remove it, then add the new one */
            if (prop = icalcomponent_get_first_property(comp, ICAL_RECURRENCEID_PROPERTY))
                icalcomponent_remove_property(comp, prop);
            icalcomponent_add_property(comp, icalproperty_new_recurrenceid(next));

        }

        if (gauge == 0 || icalgauge_compare(itr.gauge, comp) == 1) {
            /* matches and returns */
            itr.iter = citr;
            return itr;
        }

        /* if there is no previous component pending, then get the next component */
        if (itr.last_component == NULL)
            comp =  icalcompiter_next(&citr);
    }

    return icalsetiter_null;
}
icalcomponent* icalfileset_form_a_matched_recurrence_component(icalsetiter* itr)
{
    icalcomponent* comp = NULL;
    struct icaltimetype start, next;
    icalproperty *dtstart, *rrule, *prop, *due;
    struct icalrecurrencetype recur;

    comp = itr->last_component;

    if (comp == NULL || itr->gauge == NULL) {
        return NULL;
    }

    rrule = icalcomponent_get_first_property(comp, ICAL_RRULE_PROPERTY);

    recur = icalproperty_get_rrule(rrule);

    if (icalcomponent_isa(comp) == ICAL_VEVENT_COMPONENT) {
        dtstart = icalcomponent_get_first_property(comp, ICAL_DTSTART_PROPERTY);
        if (dtstart)
            start = icalproperty_get_dtstart(dtstart);
    } else if (icalcomponent_isa(comp) == ICAL_VTODO_COMPONENT) {
        due = icalcomponent_get_first_property(comp, ICAL_DUE_PROPERTY);
        if (due)
            start = icalproperty_get_due(due);
    }

    if (itr->ritr == NULL) {
        itr->ritr = icalrecur_iterator_new(recur, start);
        next = icalrecur_iterator_next(itr->ritr);
        itr->last_component = comp;
    } else {
        next = icalrecur_iterator_next(itr->ritr);
        if (icaltime_is_null_time(next)){
            /* no more recurrence, returns */
            itr->last_component = NULL;
            icalrecur_iterator_free(itr->ritr);
            itr->ritr = NULL;
            return NULL;
        } else {
            itr->last_component = comp;
        }
    }

    /* add recurrence-id to the component
     * if there is a recurrence-id already, remove it, then add the new one */
    if (prop = icalcomponent_get_first_property(comp, ICAL_RECURRENCEID_PROPERTY))
        icalcomponent_remove_property(comp, prop);
        icalcomponent_add_property(comp, icalproperty_new_recurrenceid(next));

     if (itr->gauge == 0 || icalgauge_compare(itr->gauge, comp) == 1) {
         /* matches and returns */
         return comp;
     }
     /* not matched */
     return NULL;

}
icalcomponent* icalfilesetiter_to_next(icalset* set, icalsetiter* i)
{

    icalcomponent* c = NULL;
    icalfileset *fset = (icalfileset*) set;
    struct icaltimetype start, next;
    icalproperty *dtstart, *rrule, *prop, *due;
    struct icalrecurrencetype recur;
    int g = 0;


    do {
        c = icalcompiter_next(&(i->iter));

        if (c == 0) continue;
        if (i->gauge == 0) return c;


        rrule = icalcomponent_get_first_property(c, ICAL_RRULE_PROPERTY);
        g = icalgauge_get_expand(i->gauge);

        /* a recurring component with expand query */
        if (rrule != 0
            && g == 1) {

            recur = icalproperty_get_rrule(rrule);

            if (icalcomponent_isa(c) == ICAL_VEVENT_COMPONENT) {
                dtstart = icalcomponent_get_first_property(c, ICAL_DTSTART_PROPERTY);
                if (dtstart)
                    start = icalproperty_get_dtstart(dtstart);
            } else if (icalcomponent_isa(c) == ICAL_VTODO_COMPONENT) {
                due = icalcomponent_get_first_property(c, ICAL_DUE_PROPERTY);
                if (due)
                    start = icalproperty_get_due(due);
            }

            if (i->ritr == NULL) {
                i->ritr = icalrecur_iterator_new(recur, start);
                next = icalrecur_iterator_next(i->ritr);
                i->last_component = c;
            } else {
                next = icalrecur_iterator_next(i->ritr);
                if (icaltime_is_null_time(next)) {
                    /* no more recurrence, returns */
                    i->last_component = NULL;
                    icalrecur_iterator_free(i->ritr);
                    i->ritr = NULL;
                    return NULL;
                } else {
                    i->last_component = c;
                }
            }
        }

        /* add recurrence-id to the component
         * if there is a recurrence-id already, remove it, then add the new one */
        if (prop = icalcomponent_get_first_property(c, ICAL_RECURRENCEID_PROPERTY))
            icalcomponent_remove_property(c, prop);
        icalcomponent_add_property(c, icalproperty_new_recurrenceid(next));

        if(c != 0 && (i->gauge == 0 ||
                        icalgauge_compare(i->gauge, c) == 1)){
            return c;
        }
    } while (c != 0);

    return 0;

}