# Copyright 2018 Faraz Haider. All Rights Reserved.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#     http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

defmodule Storage do
  @moduledoc """
  Defines a general key-value storage for persisting and retrieval of the Compact Sparse Merkle Tree Nodes `t:CSMT.Types.tree_node/0`.
  We define callbacks that can be implemented by a number of potential backends.
  """

  @callback init_backend(term) :: term
  @callback set_node(term, term, term) :: term
  @callback get_node(term, term) :: term
  @callback delete_node(term, term) :: term

  @doc """
  Persists a node with the specified key, value in the given backend.
  """
  def set_node(backend, key, value) do
    backend_module = CSMT.Utils.get_backend_module(backend)
    backend_module.set_node(backend, key, value)
  end

  @doc """
  Retrieves a node with the specified key from the given backend.
  """
  def get_node(backend, key) do
    backend_module = CSMT.Utils.get_backend_module(backend)
    backend_module.get_node(backend, key)
  end

  @doc """
  Deletes a node with the specified key from the given backend.
  """
  def delete_node(backend, key) do
    backend_module = CSMT.Utils.get_backend_module(backend)
    backend_module.delete_node(backend, key)
  end
end