class ActiveRecord::ConnectionAdapters::PoolManager

def each_pool_config(role = nil, &block)
  if role
    @role_to_shard_mapping[role].each_value(&block)
  else
    @role_to_shard_mapping.each_value do |shard_map|
      shard_map.each_value(&block)
    end
  end
end

def get_pool_config(role, shard)
  @role_to_shard_mapping[role][shard]
end

def initialize
  @role_to_shard_mapping = Hash.new { |h, k| h[k] = {} }
end

def pool_configs(role = nil)
  if role
    @role_to_shard_mapping[role].values
  else
    @role_to_shard_mapping.flat_map { |_, shard_map| shard_map.values }
  end
end

def remove_pool_config(role, shard)
  @role_to_shard_mapping[role].delete(shard)
end

def remove_role(role)
  @role_to_shard_mapping.delete(role)
end

def role_names
  @role_to_shard_mapping.keys
end

def set_pool_config(role, shard, pool_config)
  if pool_config
    @role_to_shard_mapping[role][shard] = pool_config
  else
    raise ArgumentError, "The `pool_config` for the :#{role} role and :#{shard} shard was `nil`. Please check your configuration. If you want your writing role to be something other than `:writing` set `config.active_record.writing_role` in your application configuration. The same setting should be applied for the `reading_role` if applicable."
  end
end

def shard_names
  @role_to_shard_mapping.values.flat_map { |shard_map| shard_map.keys }.uniq
end