Convert a timestamp to MongoDB ObjectId to get fast (indexed) create_at queries for free.

mongo_id_from_date.rb

# USAGE:
# ------
#     mongo_id_from_date Date.parse('2020-12-24') # => "5fe3da000000000000000000" 
#     mongo_id_from_date(Time.now) # => "5fe471d90000000000000000"

def mongo_id_from_date(date)
  min_date = Time.at 0
  max_date = Time.at 0xffffffff
  raise "Error: date must be between #{min_date.to_date} and #{max_date.to_date}" if date < min_date || date > max_date

  hex_seconds = date.to_time.to_i.to_s(16)

  "#{hex_seconds.rjust(8, '0')}0000000000000000"
end


# LINKS:
# -----
# - [MongoDB ObjectID to Timestamp converter (and vice-versa)](https://github.com/SteveRidout/mongo-object-time)
# - [MongoDB ObjectId ↔ Timestamp Converter](http://steveridout.github.io/mongo-object-time/)