defmodule MapBot do
  @moduledoc """
  `MapBot` builds and creates Elixir Maps/Structs based on factory definitions and attributes.

  If you want to check how `MapBot` should be installed, configured and used please [check this out](https://hexdocs.pm/map_bot/).

  In summary you should create your own Factory module such as this:

  ```elixir
  defmodule YourApp.Factory do
    use MapBot

    @impl MapBot
    def repo(), do: Repo

    @impl MapBot
    def new(YouyApp.Car), do: %YouyApp.Car{model: "SUV", color: :black}
    def new(:greenish), do: %{color: :green}
    def new(:tomato), do: %{name: "Tomato", color: :red}
    def new(:with_code_and_ref), do: %{code: &"CODE-\#{&1}", reference: &"REF-\#{&1}"}
  end
  ```

  For building your own maps and structs take a look on the functions `MapBot.build/4`, `MapBot.create/4` and `MapBot.create!/4`.
  """

  @type factory :: module()
  @type name :: module() | atom()
  @type traits :: map() | keyword()
  @type attributes :: map() | keyword()
  @type result :: struct() | map()
  @type repo :: module()

  @callback new(name) :: result
  @callback repo :: repo

  @doc """
  Builds an Elixir Map or Struct.

  ## Examples

      iex> YourApp.Factory.build(:tomato)
      %{name: "Tomato", color: :red}

      iex> YourApp.Factory.build(YourApp.Car)
      %YourApp.Car{model: "SUV", color: :black}

      iex> YourApp.Factory.build(:tomato, color: :green)
      %{name: "Tomato", color: :green}

      iex> YourApp.Factory.build(:tomato, %{color: :green})
      %{name: "Tomato", color: :green}

      iex> YourApp.Factory.build(YourApp.Car, color: :yellow)
      %YourApp.Car{model: "SUV", color: :yellow}

      iex> YourApp.Factory.build(YourApp.Car, %{color: :yellow})
      %YourApp.Car{model: "SUV", color: :yellow}

      iex> YourApp.Factory.build(YourApp.Car, [:greenish])
      %YourApp.Car{model: "SUV", color: :green}

      iex> YourApp.Factory.build(YourApp.Car, [:greenish], model: "Sport")
      %YourApp.Car{model: "Sport", color: :green}

      iex> YourApp.Factory.build(YourApp.Car, [:greenish, model: "Sport"])
      %YourApp.Car{model: "Sport", color: :green}
  """
  @spec build(factory, name, traits, attributes) :: result
  def build(factory, name, traits \\ [], attrs \\ [])

  def build(factory, name, %{} = traits, attrs) do
    build(factory, name, Map.to_list(traits), attrs)
  end

  def build(factory, name, traits, %{} = attrs) do
    build(factory, name, traits, Map.to_list(attrs))
  end

  def build(factory, name, traits, attrs) do
    ([name] ++ traits ++ attrs)
    |> Enum.reduce(%{}, &apply_attr(factory, &1, &2))
    |> apply_sequence()
  end

  @doc """
  Creates an Elixir Map or Struct using your Repo.insert/1

  ## Examples

      iex> YourApp.Factory.create(YourApp.Car, color: :yellow)
      {:ok, %YourApp.Car{id: "123", model: "SUV", color: :yellow}}
  """
  @spec create(factory, name, traits, attributes) :: {:ok, result}
  def create(factory, name, traits \\ [], attrs \\ []) do
    factory |> build(name, traits, attrs) |> factory.repo().insert()
  end

  @doc """
  Creates an Elixir Map or Struct using your Repo.insert!/1

  ## Examples

      iex> YourApp.Factory.create!(YourApp.Car, color: :yellow)
      %YourApp.Car{id: "123", model: "SUV", color: :yellow}
  """
  @spec create!(factory, name, traits, attributes) :: result
  def create!(factory, name, traits \\ [], attrs \\ []) do
    factory |> build(name, traits, attrs) |> factory.repo().insert!()
  end

  defp apply_attr(_factory, {key, value}, map), do: Map.put(map, key, value)
  defp apply_attr(factory, name, map), do: Map.merge(map, factory.new(name))

  defp apply_sequence(map) do
    next_int = MapBot.Sequence.next_int()
    map |> Map.to_list() |> Enum.reduce(map, &sequence(&1, &2, next_int))
  end

  defp sequence({_key, val}, map, _i) when not is_function(val), do: map
  defp sequence({key, func}, map, i), do: Map.put(map, key, func.(i))

  defmacro __using__(_opts) do
    quote do
      @behaviour MapBot

      def build(name, traits \\ [], attrs \\ []) do
        MapBot.build(__MODULE__, name, traits, attrs)
      end

      def create(name, traits \\ [], attrs \\ []) do
        MapBot.create(__MODULE__, name, traits, attrs)
      end

      def create!(name, traits \\ [], attrs \\ []) do
        MapBot.create!(__MODULE__, name, traits, attrs)
      end
    end
  end
end