Database
[{"emblem":1,"name":"Z"},{"emblem":2,"name":"H"},{"emblem":3,"name":"T"},{"emblem":4,"name":"Q"},{"emblem":6,"name":"L"}]
Query
db.collection.aggregate([{"$addFields":{"lowerName":{"$toLower":"$name"}}},{"$setWindowFields":{"partitionBy":null,"sortBy":{"lowerName":1,"emblem":1},"output":{"before":{"$sum":1,"window":{"documents":["unbounded",-1]}},"after":{"$sum":1,"window":{"documents":[1,"unbounded"]}}}}}])