Main2.ex

defmodule Main2 do

    @spec main :: {:ok, BookShop.Order.t} | {:error, term}
    def main do
        data = BookShop.test_data
        handle_create_order data, %{}
    end


    @spec handle_create_order(map, map) :: {:ok, BookShop.Order.t} | {:error, term}
    def handle_create_order data0, state do
        case BookShop.validate_incoming_data data0 do
            {:error, reason} -> {:error, reason}
            {:ok, data} -> validate_cat data, state
        end
    end


    @spec validate_cat(map, map) :: {:ok, BookShop.Order.t} | {:error, term}
    def validate_cat %{"cat" => cat0} = data, state0 do
        case BookShop.validate_cat cat0 do
            {:error, reason} -> {:error, reason}
            {:ok, cat} ->
                state = Map.put state0, :cat, cat
                validate_address data, state
        end
    end


    @spec validate_address(map, map) :: {:ok, BookShop.Order.t} | {:error, term}
    def validate_address %{"address" => address0} = data, state0 do
        case BookShop.validate_address address0 do
            {:error, reason} -> {:error, reason}
            {:ok, address} ->
                state = Map.put state0, :address, address
                validate_books data, state
        end
    end


    @spec validate_books(map, map) :: {:ok, BookShop.Order.t} | {:error, term}
    def validate_books %{"books" => books0}, state0 do
        books = Enum.map books0,
            fn %{"title" => title, "author" => author} ->
                BookShop.get_book title, author
            end
        invalid_books = Enum.filter books, fn {res, _} -> res == :error end
        case invalid_books do
            [{:error, reason} | _] -> {:error, reason}
            [] ->
                state = Map.put state0, :books, books
                create_order state
        end
    end


    @spec create_order(map) :: {:ok, BookShop.Order.t}
    def create_order %{:cat => cat, :address => address, :books => books0} do
        books = Enum.map books0, fn {:ok, book} -> book end
        order = BookShop.create_order cat, address, books
        {:ok, order}
    end

end