exiffer

defmodule Exiffer.OffsetBuffer do
  @moduledoc """
  Documentation for `Exiffer.OffsetBuffer`.

  Wraps Exiffer.Buffer while appending an offset amount to positions
  """

  alias Exiffer.Buffer

  require Logger

  @enforce_keys ~w(buffer offset)a
  defstruct ~w(buffer offset)a

  def new(%{} = buffer, offset \\ 0) do
    %__MODULE__{buffer: buffer, offset: offset}
  end

  def seek(%__MODULE__{buffer: buffer, offset: offset} = offset_buffer, position) do
    new_position = offset + position
    buffer = Buffer.seek(buffer, new_position)
    struct!(offset_buffer, buffer: buffer)
  end

  def consume(%__MODULE__{buffer: buffer} = offset_buffer, amount) do
    {result, buffer} = Buffer.consume(buffer, amount)
    {result, struct!(offset_buffer, buffer: buffer)}
  end

  def push(%__MODULE__{buffer: buffer} = offset_buffer, chunk) do
    buffer = Buffer.push(buffer, chunk)
    %{offset_buffer | buffer: buffer}
  end

  def skip(%__MODULE__{buffer: buffer} = offset_buffer, amount) do
    buffer = Buffer.skip(buffer, amount)
    struct!(offset_buffer, buffer: buffer)
  end

  def random(%__MODULE__{buffer: buffer, offset: offset}, position, count) do
    Buffer.random(buffer, offset + position, count)
  end

  def tell(%__MODULE__{buffer: buffer, offset: offset}) do
    buffer.position - offset
  end

  def read_eof(%__MODULE__{buffer: buffer} = offset_buffer) do
    {chunk, buffer} = Buffer.read_eof(buffer)
    {chunk, %{offset_buffer | buffer: buffer}}
  end

  defimpl Exiffer.Buffer do
    alias Exiffer.OffsetBuffer

    def offset_buffer(buffer, offset) do
      OffsetBuffer.new(buffer.buffer, offset)
    end

    def consume(buffer, count) do
      OffsetBuffer.consume(buffer, count)
    end

    def push(buffer, chunk) do
      OffsetBuffer.push(buffer, chunk)
    end

    def seek(buffer, position) do
      OffsetBuffer.seek(buffer, position)
    end

    def skip(buffer, count) do
      OffsetBuffer.skip(buffer, count)
    end

    def random(buffer, read_position, count) do
      OffsetBuffer.random(buffer, read_position, count)
    end

    def tell(buffer) do
      OffsetBuffer.tell(buffer)
    end

    def read_eof(buffer) do
      OffsetBuffer.read_eof(buffer)
    end
  end
end