defmodule SimpleForm do
  @moduledoc false

  @type tag_name() :: String.t()
  @type content() :: [String.t() | element()]
  @type attribute() :: {key :: String.t(), value :: String.t()}
  @type element() :: {tag_name(), [attribute()], content()}

  @doc """
  Checks if value is an element.

  ## Examples

      iex> SimpleForm.element?(true)
      false
      iex> SimpleForm.element?({"p", [{"class", "intro"}], [{"strong", [], ["Hello"]}, " world!"]})
      true
      iex> SimpleForm.element?({"class", "strong"})
      false
      iex> SimpleForm.element?("Hello World!")
      false
  """
  @spec element?(term()) :: boolean()
  def element?({tag_name, attributes, content})
      when is_binary(tag_name) and is_list(attributes) and is_list(content) do
    Enum.all?(attributes, &attribute?/1) and Enum.all?(content, &content?/1)
  end

  def element?(_),
    do: false

  @doc """
  Checks if value is an attribute.

  ## Examples

      iex> SimpleForm.attribute?(true)
      false
      iex> SimpleForm.attribute?({"p", [{"class", "intro"}], [{"strong", [], ["Hello"]}, " world!"]})
      false
      iex> SimpleForm.attribute?({"class", "strong"})
      true
      iex> SimpleForm.attribute?("Hello World!")
      false
  """
  @spec attribute?(term()) :: boolean()
  def attribute?({name, value}) when is_binary(name) and is_binary(value),
    do: true

  def attribute?(_),
    do: false

  @doc """
  Checks if value is content.

  ## Examples

      iex> SimpleForm.content?(true)
      false
      iex> SimpleForm.content?({"p", [{"class", "intro"}], [{"strong", [], ["Hello"]}, " world!"]})
      true
      iex> SimpleForm.content?({"class", "strong"})
      false
      iex> SimpleForm.content?("Hello World!")
      true
  """
  @spec content?(term()) :: boolean()
  def content?(content) when is_binary(content),
    do: true

  def content?(value),
    do: element?(value)
end