defmodule Syntactic do
  @moduledoc """
  Provides some syntactic sugars
  """

  @doc """
  Expands to a keyword list with keys as atoms of given vars.
  For example `keys([name, age])` expands to `[name: name, age: age]`

  Useful in matches:

      def full_name(keys(first_name, last_name)) do
        first_name <> " " <> last_name
      end

      full_name(first_name: "Alan", last_name: "Parsons")
      # => "Alan Parsons"
  """
  defmacro keys(keys) when is_list(keys), do: keywords(keys)

  defmacro keys(a), do: keywords([a])
  defmacro keys(a,b), do: keywords([a,b])
  defmacro keys(a,b,c), do: keywords([a,b,c])
  defmacro keys(a,b,c,d), do: keywords([a,b,c,d])
  defmacro keys(a,b,c,d,e), do: keywords([a,b,c,d,e])

  defp keywords(keys) do
    Enum.into keys, [], fn var = {name,_,_} -> {name, var} end
  end

  @doc """
  Expands to a `Map` with keys as atoms of given vars.
  For example `map([name, age])` expands to `%{name: name, age: age}`

  Useful in matches:

      map(a, b) = %{a: 10, b: "Some Value"}
  """
  defmacro map(keys) when is_list(keys), do: map_of(keys)

  defmacro map(a), do: map_of([a])
  defmacro map(a,b), do: map_of([a,b])
  defmacro map(a,b,c), do: map_of([a,b,c])
  defmacro map(a,b,c,d), do: map_of([a,b,c,d])
  defmacro map(a,b,c,d,e), do: map_of([a,b,c,d,e])

  defp map_of(keys) do
    names = Enum.into keys, [], fn var = {name,_,_} -> {name, var} end
    quote do: %{unquote_splicing(names)}
  end

  @doc """
  Expands to a `Map` with keys as strings of given vars.
  For example `maps([name, age])` expands to `%{"name" => name, "age" => age}`
  """
  defmacro maps(keys) when is_list(keys), do: maps_of(keys)
  defmacro maps(a), do: maps_of([a])
  defmacro maps(a,b), do: maps_of([a,b])
  defmacro maps(a,b,c), do: maps_of([a,b,c])
  defmacro maps(a,b,c,d), do: maps_of([a,b,c,d])
  defmacro maps(a,b,c,d,e), do: maps_of([a,b,c,d,e])

  defp maps_of(keys) do
    names = Enum.into keys, [], fn var = {name,_,_} -> {Atom.to_string(name), var} end
    quote do: %{unquote_splicing(names)}
  end
end