pathex

defmodule Pathex do

  @moduledoc """
  This module contains macroses to be used by user
  """

  @type struct_type :: :map | :keyword | :list | :tuple
  @type key_type :: :integer | :atom | :binary

  @type path :: [{struct_type(), any()}]

  @type el_structure :: map() | list() | Keyword.t() | tuple()

  @type result :: {:ok, any()} | {:error, any()} | :error
  @type t :: (
    :get | :set | :update,
    {el_structure()} | {el_structure(), any()} | {el_structure(), (any() -> any())}
  -> result())

  defp detect_mod('json'), do: 'json'
  defp detect_mod(_), do: 'naive'

  @doc """
  Sigil for paths. Has only two modes:
  `naive` (default) and `json`.
  Naive paths should look like `~P["string"/:atom/1]`
  Json paths should look like `~P[string/this_one_is_too/1/0]`
  """
  defmacro sigil_P({_, _, [string]}, mod) do
    mod = detect_mod(mod)
    string
    |> Pathex.Parser.parse(mod)
    |> Pathex.Combination.from_suggested_path()
    |> Pathex.Builder.build(mod)
  end

  @doc """
  Macro of three arguments which applies given function
  for item in the given path of given structure
  """
  defmacro over(path, struct, function) do
    quote generated: true do
      unquote(path).(:update, {unquote(struct), unquote(function)})
    end
  end

  @doc """
  Macro of three arguments which sets the given value
  in the given path of given structure
  """
  defmacro set(path, struct, value) do
    quote generated: true do
      unquote(path).(:set, {unquote(struct), unquote(value)})
    end
  end

  @doc """
  Macro gets the value in the given path of the given structure
  """
  defmacro view(path, struct) do
    quote generated: true do
      unquote(path).(:get, {unquote(struct)})
    end
  end

  @doc """
  Creates path for given structure

  Example:
      iex> x = 1
      iex> mypath = path 1 / :atom / "string" / {"tuple?"} / x
  """
  defmacro path(quoted, mod \\ 'naive') do
    mod = detect_mod(mod)
    quoted
    |> Pathex.QuotedParser.parse(__ENV__)
    |> Pathex.Builder.build(mod)
  end

  @doc """
  Creates composition of two paths
  """
  defmacro a ~> b do
    quote generated: true do
      fn
        :get, arg ->
          with {:ok, res} <- unquote(a).(:get, arg) do
            unquote(b).(:get, {res})
          end

        cmd, {target, arg} ->
          with(
            {:ok, inner} <- unquote(a).(:get, {target}),
            {:ok, inner} <- unquote(b).(cmd, {inner, arg})
          ) do
            unquote(a).(:set, {target, inner})
          end
      end
    end
  end

end