defmodule Minipeg.Input do
  use Minipeg.Types

  @moduledoc ~S"""
  An input wrapper
  """
  defstruct col: 1, context: %{}, input: "", lnb: 1

  @type t :: %__MODULE__{col: pos_integer(), context: map(), input: binary(), lnb: pos_integer()}
  @type take_and_rest_t :: {binary(), t()}

  @spec new(input_t(), pos_integer(), pos_integer()) :: t()
  def new(source, col \\ 1, lnb \\ 1, context \\ %{})
  def new(%__MODULE__{} = src, col, lnb, ctxt), do: %{src | col: col, lnb: lnb, context: ctxt}

  def new(source, col, lnb, ctxt) when is_binary(source),
    do: %__MODULE__{input: source, col: col, lnb: lnb, context: ctxt}

  @spec drop(t(), str_or_count_t()) :: t()
  def drop(inp, str_or_count \\ 1)

  def drop(%__MODULE__{} = inp, str) when is_binary(str) do
    _drop(inp, String.length(str))
  end

  def drop(%__MODULE__{} = inp, count) do
    _drop(inp, count)
  end

  @spec position(t()) :: position_t()
  def position(%__MODULE__{col: col, lnb: lnb}), do: {col, lnb}

  @spec report_position(t(), binary?()) :: binary()
  def report_position(input, name \\ nil)

  def report_position(%__MODULE__{col: col, lnb: lnb}, nil) do
    "#{lnb},#{col}"
  end

  def report_position(%__MODULE__{col: col, lnb: lnb}, name) do
    "#{lnb},#{col} in #{name}"
  end

  @spec _drop(t(), non_neg_integer()) :: t()
  defp _drop(inp, count)
  defp _drop(%__MODULE__{} = inp, 0), do: inp
  defp _drop(%__MODULE__{input: ""} = inp, _), do: inp

  defp _drop(%__MODULE__{input: input, col: col, lnb: lnb} = inp, 1) do
    <<first::utf8, rest::binary>> = input
    graph = List.to_string([first])
    {col1, lnb1} = if graph == "\n", do: {1, lnb + 1}, else: {col + 1, lnb}
    %{inp | input: rest, col: col1, lnb: lnb1}
  end

  defp _drop(%__MODULE__{input: input, col: col, lnb: lnb} = inp, count) do
    <<first::utf8, rest::binary>> = input
    graph = List.to_string([first])
    {col1, lnb1} = if graph == "\n", do: {1, lnb + 1}, else: {col + 1, lnb}
    _drop(%{inp | input: rest, col: col1, lnb: lnb1}, count - 1)
  end

  @spec take(t(), str_or_count_t()) :: take_and_rest_t()
  def take(input, str_or_count \\ 1)

  def take(%__MODULE__{} = inp, str) when is_binary(str) do
    take(inp, String.length(str))
  end

  def take(%__MODULE__{input: input} = inp, count) do
    {
      input |> String.slice(0, count),
      drop(inp, count)
    }
  end
end

# SPDX-License-Identifier: Apache-2.0