module QueryDam

# File lib/query_dam.rb, line 54
def expiration
  @expiration || DEFAULT_EXPIRATION
end

# File lib/query_dam.rb, line 50
def expiration=(value)
  @expiration = value
end

# File lib/query_dam.rb, line 23
def get_updates(tracking_key)
  query_hash = Redis::HashKey.new(tracking_key)
  return nil unless query_hash.exists?
  query_hash.expire(expiration)

  model = query_hash[:model].constantize
  additions_set, updates_set, removals_set = query_sets(tracking_key)

  updated_ids = (additions_set.members + updates_set.members).uniq
  removed_ids = removals_set.members

  result = {
    model: model,
    updates: model.where(id: updated_ids),
    exclusions: removed_ids.map(&:to_i) }

  [additions_set, updates_set, removals_set].each(&:clear)

  result
end

# File lib/query_dam.rb, line 44
def query_sets(tracking_key)
  %w[additions updates removals].map do |set_type|
    Redis::Set.new("#{tracking_key} #{set_type}")
  end
end

# File lib/query_dam.rb, line 13
def watch_relation(relation)
  tracking_key = SecureRandom.uuid
  query = relation.select("`#{relation.model.table_name}`.`id`").to_sql
  query_hash = Redis::HashKey.new(tracking_key)
  query_hash.bulk_set(model: relation.model.name, query: query)
  query_hash.expire(expiration)
  Redis::Set.new(relation.model.name) << tracking_key
  tracking_key
end