defmodule CQL.QueryParams do
  import CQL.DataTypes.Encoder

  require Bitwise

  defstruct [
    consistency: :one,
    values: nil,
    skip_metadata: false,
    page_size: nil,
    paging_state: nil,
    serial_consistency: nil,
    timestamp: nil,
  ]

  @flags %{
    :values                  => 0x01,
    :skip_metadata           => 0x02,
    :page_size               => 0x04,
    :with_paging_state       => 0x08,
    :with_serial_consistency => 0x10,
    :with_default_timestamp  => 0x20,
    :with_names              => 0x40,
  }

  def flags(flags) do
    flags
    |> Enum.map(&Map.fetch!(@flags, &1))
    |> Enum.reduce(0, &Bitwise.bor(&1, &2))
  end

  def encode(q = %__MODULE__{values: values}) when is_nil(values) do
    encode(q, false, false, nil)
  end

  def encode(q = %__MODULE__{values: values}) when is_list(values) or is_map(values) do
    if Enum.empty?(values) do
      encode(q, false, false, nil)
    else
      case values(values) do
        :error -> :error
        encoded -> encode(q, true, is_map(values), encoded)
      end
    end
  end

  def encode(_), do: :error

  defp encode(q, has_values, has_names, values) do
    has_timestamp = is_integer(q.timestamp) and q.timestamp > 0

    flags =
      []
      |> prepend(:values, has_values)
      |> prepend(:skip_metadata, q.skip_metadata)
      |> prepend(:page_size, q.page_size)
      |> prepend(:with_paging_state, q.paging_state)
      |> prepend(:with_serial_consistency, q.serial_consistency)
      |> prepend(:with_default_timestamp, has_timestamp)
      |> prepend(:with_names, has_names)
      |> flags
      |> byte

    q.consistency
    |> consistency
    |> List.wrap
    |> prepend(flags)
    |> prepend(values, has_values)
    |> prepend_not_nil(q.page_size, :int)
    |> prepend_not_nil(q.paging_state, :bytes)
    |> prepend_not_nil(q.serial_consistency, :consistency)
    |> prepend(q.timestamp, has_timestamp)
    |> Enum.reverse
    |> Enum.join
  end

  defp values(list) when is_list(list) do
    parts = Enum.map(list, &CQL.DataTypes.encode/1)

    if Enum.any?(parts, &(&1 == :error)) do
      :error
    else
      n = Enum.count(list)
      Enum.join([short(n) | parts])
    end
  end

  defp values(map) when is_map(map) do
    parts = Enum.flat_map map, fn {k, v} ->
      [string(to_string(k)), CQL.DataTypes.encode(v)]
    end

    if Enum.any?(parts, &(&1 == :error)) do
      :error
    else
      n = Enum.count(map)
      Enum.join([short(n) | parts])
    end
  end

  defp values(_), do: :error
end