defmodule Yameru.Parser.Literal do
  @moduledoc """
  Scalar, Block, and Tuple parser
  """

  use Pelecanus, sigil_p: true

  alias Yameru.Parser.IndentLevel
  alias Yameru.Parser.Dictionary
  alias Yameru.Parser.Sequence
  alias Yameru.Parser.Text

  @doc """
  Parses scalar; inline value.
  """
  @spec scalar() :: Pelecanus.parser()
  def scalar do
    choice([
      special(),
      double_quoted(),
      single_quoted(),
      plain_string()
    ])
  end

  @doc """
  Parses string sandwitched with double quote sign.
  """
  @spec double_quoted() :: Pelecanus.parser()
  def double_quoted do
    seq =
      sequence([
        ignore(~p/"/),
        ~p/(\\"|[^\r\n"])*/,
        ignore(~p/"/),
        ignore_trailing_spaces()
      ])

    seq
    |> stlip()
    |> map(&Macro.unescape_string/1)
  end

  @doc """
  Parses string sandwitched with single quote sign.
  """
  @spec single_quoted() :: Pelecanus.parser()
  def single_quoted do
    seq =
      sequence([
        ignore(~p/'/),
        ~p/(''|[^\r\n'])*/,
        ignore(~p/'/),
        ignore_trailing_spaces()
      ])

    seq
    |> stlip()
    |> map(&String.replace(&1, "''", "'"))
  end

  @doc """
  Parses plain_string.

  This function don't check that head isn't quote sign or bracket sign.
  """
  @spec plain_string() :: Pelecanus.parser()
  def plain_string() do
    sequence([
      not_predicate(~p/- +|-$/ms),
      not_predicate(~p/\/ *$/Ums),
      ~p/[^\r\n]*[^:\r\n]((?=: |:$|$)| +(?=\/ *$))/Ums
    ])
    |> stlip()
    |> trim_trailing()
  end

  @doc """
  Parses special scalar; sandwitched with brackets.
  """
  @spec special() :: Pelecanus.parser()
  def special do
    # get string between brackets
    primary =
      sequence([
        ignore(~p/\[/),
        ~p/[^\r\n\]]*/,
        ignore(~p/\]/),
        ignore_trailing_spaces()
      ])
      |> stlip()

    # map it to non-string type
    secondary =
      choice([
        boolean(),
        number(),
        iso8601()
      ])

    fn state ->
      with {:ok, s, raw} <- primary.(state),
           {:ok, _, value} <- Pelecanus.parse(raw, secondary),
           do: {:ok, s, value}
    end
  end

  defp ignore_trailing_spaces do
    ignore(~p/ *(?=: |:$|$)| +(?=\/ *$)/Ums)
  end

  @doc """
  Parses number (in brackets).

  Note that number literal is expected to follow SI.
  Decimal separator is comma or period. Digit group separator is space.
  """
  @spec number() :: Pelecanus.parser()
  def number do
    formal =
      ~p/.*/
      |> map(&String.replace(&1, " ", ""))

    choice([
      formal |> try_convert(&String.to_integer/1),
      formal |> try_convert(&String.to_float/1)
    ])
  end

  @doc """
  Parses boolean value (yes / no)
  """
  @spec boolean() :: Pelecanus.parser()
  def boolean do
    ~p/ *(yes|no) */
    |> map(&String.trim/1)
    |> map(fn
      "yes" -> true
      "no" -> false
    end)
  end

  @doc """
  Parses extended iso 8601 (in Elixir can parse)
  """
  def iso8601 do
    formal =
      ~p/.*/
      |> map(&String.trim/1)

    choice([
      formal |> try_convert(&NaiveDateTime.from_iso8601!/1),
      formal |> try_convert(&Date.from_iso8601!/1),
      formal |> try_convert(&Time.from_iso8601!/1)
    ])
  end

  @spec try_convert(Pelecanus.parser(), (Pelecanus.value() -> Pelecanus.value())) ::
          Pelecanus.parser()
  defp try_convert(e, fun) do
    fn state ->
      try do
        map(e, fun).(state)
      rescue
        _error -> {:error, "fails to convertion"}
      end
    end
  end

  @doc """
  Parses any block in +1 indent level.
  """
  @spec block() :: Pelecanus.parser()
  def block do
    choice([
      dict_block(),
      sequence_block(),
      text_block()
    ])
  end

  @doc false
  @spec dict_block() :: Pelecanus.parser()
  def dict_block do
    x_block(~p//, {Dictionary, :dictionary, []})
  end

  @doc false
  @spec sequence_block() :: Pelecanus.parser()
  def sequence_block do
    x_block(~p//, {Sequence, :sequence, []})
  end

  @doc false
  @spec text_block() :: Pelecanus.parser()
  def text_block do
    x_block(~p/\/ */, {Text, :text, []})
  end

  defp x_block(delimiter, {mod, name, args}) do
    sequence([
      ignore(with_line_end(delimiter)),
      IndentLevel.block(mod, name, args)
    ])
    |> stlip()
  end

  @doc """
  Parses tuple and scalar or block.

  In this parser any value is tuple.
  Just scalar is mapped to `{scalar, nil}` and just block is mapped to `{nil, block}`.
  When both exist, its are mapped to `{scalar, nil}`

  Note that this function check that either scalar or block isn't nil.
  """
  @spec tuple() :: Pelecanus.parser()
  def tuple do
    sequence([
      choice([
        scalar(),
        ~p// |> map(fn _ -> nil end)
      ]),
      choice([
        block(),
        ~p// |> with_line_end() |> map(fn _ -> nil end)
      ])
    ])
    |> map(fn [s, b] -> {s, b} end)
    |> validate(&(&1 != {nil, nil}))
  end

  @doc """
  Discards line break on the heels of given parser consumed.
  """
  @spec with_line_end(Pelecanus.parser()) :: Pelecanus.parser()
  def with_line_end(e) do
    sequence([e, ignore(~p/(\R|\z)/)])
    |> stlip()
  end

  @doc """
  Consumes empty (only spaces) line and replace with empty string.
  """
  @spec empty_line() :: Pelecanus.parser()
  def empty_line do
    ~p/ *$/Ums
    |> with_line_end()
    |> map(fn _ -> "" end)
  end

  defp trim_trailing(e) do
    e |> map(&trim/1)
  end

  defp trim(string) do
    String.replace(string, ~r/ *$/, "")
  end
end