public static List <List <Papers> > GroupPapers(List <Papers> papers)
{
Random r = new Random();
papers.OrderBy(p => r.Next());
List <List <Papers> > timeGroups = new List <List <Papers> >();
TimeSpan timeZoneStart = TimeSpan.FromHours(-12);
TimeSpan timePeriod = TimeSpan.FromHours(24).Divide(timeZoneGroups);
for (int i = 0; i < timeZoneGroups; i++)
{
timeGroups.Add(new List <Papers>());
}
foreach (Papers p in papers)
{
TimeZoneInfo tzi = TimeZoneInfo.FindSystemTimeZoneById(p.TimeZone);
TimeSpan ts = tzi.BaseUtcOffset;
for (int i = 0; i < timeZoneGroups; i++)
{
if (ts.TotalMinutes <= timeZoneStart.Add(timePeriod.Multiply(i + 1)).TotalMinutes)
{
timeGroups[i].Add(p);
break;
}
}
}
List <Dictionary <int, List <Papers> > > topicGroups = new List <Dictionary <int, List <Papers> > >();
for (int i = 0; i < timeZoneGroups; i++)
{
topicGroups.Add(new Dictionary <int, List <Papers> >());
foreach (Papers p in timeGroups[i])
{
int key = PaperTopic.GetCategory(p.PaperTopic).ID;
if (!topicGroups[i].ContainsKey(key))
{
topicGroups[i].Add(key, new List <Papers>());
}
topicGroups[i][key].Add(p);
}
}
List <List <List <Papers> > > finalGroups = new List <List <List <Papers> > >();
for (int i = 0; i < timeZoneGroups; i++)
{
finalGroups.Add(new List <List <Papers> >());
int j = 0;
foreach (List <Papers> topicGroup in topicGroups[i].Values)
{
finalGroups[i].Add(new List <Papers>());
foreach (Papers p in topicGroup)
{
if (finalGroups[i][j].Count >= papersPerGroup)
{
j++;
finalGroups[i].Add(new List <Papers>());
}
finalGroups[i][j].Add(p);
}
List <List <Papers> > groupsToRemove = new List <List <Papers> >();
foreach (List <Papers> fg in finalGroups[i])
{
if (fg.Count < minPapersPerGroup)
{
groupsToRemove.Add(fg);
}
}
foreach (List <Papers> gtr in groupsToRemove)
{
finalGroups[i].Remove(gtr);
}
foreach (Papers p in finalGroups[i].SelectMany(p => p))
{
topicGroup.Remove(p);
}
}
if (finalGroups[i].Count == 0)
{
finalGroups[i].Add(new List <Papers>());
}
int k = 0;
foreach (Papers p in topicGroups[i].Values.SelectMany(l => l).OrderBy(p => r.Next()))
{
while (finalGroups[i][k].Count >= papersPerGroup)
{
k++;
finalGroups[i].Add(new List <Papers>());
}
finalGroups[i][k].Add(p);
}
}
return(finalGroups.SelectMany(fg => fg).Where(fg => fg.Count > 0).ToList());
}
// returns the parent, or the topic itself if it is null (is a parent)
public static PaperTopic GetCategory(int ID)
{
PaperTopic topic = Get(ID);
return(topic.ParentID == null ? topic : Get(topic.ParentID));
}