public IEnumerable <JGram.Entry> Lookup(string key)
{
int limit = 50;
var(start, end) = index.EqualRange(key, kvp => kvp.Key);
var outOfBoundLimit = (limit - (end - start)) / 2;
start = Math.Max(0, start - outOfBoundLimit);
end = Math.Min(entries.Count, end + outOfBoundLimit);
var mid = (start + end) / 2;
var resultEntries = EnumerableExt.Range(start, end - start)
.OrderBy(i => Math.Abs(i - mid))
.Select(i => index[i])
.Select(indexEntry =>
{
var indexKey = indexEntry.Key;
var entryKey = indexEntry.Value;
var(entry, id) = entries.BinarySearch(entryKey, e => e.Id);
return((indexKey, entry).SomeWhen(_ => id != -1));
})
.Values()
.OrderByDescending(r => CommonPrefixLength(r.indexKey, key))
.Where(r => CommonPrefixLength(r.indexKey, key) != 0)
.Select(r => r.entry);
return(EnumerableExt.DistinctBy(resultEntries, entry => entry.Id));
}
