defmodule Countries do
	alias Countries.Country, as: Country
	
	@doc """
	Returns all countries.
	"""
	def all do
		countries
	end
	
	@doc """
	Filters countries by given attribute.
	Returns a List of %Country{}
	
	## Examples
		iex> Countries.filter_by(:region, "Europe")
		[%Countries.Country{address_format: nil, alpha2: 'VA' ...
	"""
	def filter_by(attribute, value) do
		Enum.filter(countries, fn(country) -> 
			value_as_char_list = to_char_list(value)
			country[attribute] == value_as_char_list
		end)
	end

	defp countries do 
		# Lets load all country data from our yaml files
		codes = List.first(:yamerl.decode_file("lib/data/countries.yaml"))
		country_data = 
			Enum.reduce(codes, [], fn (code, countries) -> 
				countries ++ :yamerl.decode_file("lib/data/countries/#{code}.yaml") 
			end)
			
		# :yamerl returns a really terrible data structure 
		#		[[{'name', 'Germany'}, {'code', 'DE'}], [{'nam:e', 'Austria'}, {'code', 'AT'}]]
		# We need to transform that to maps:
		#		[%{name: 'Germany', code: "DE"}, %{name: 'Austria', code: "AT"}]
		countries = 
			Enum.reduce(country_data, [], fn (country_data, countries) ->
				country = 
					Enum.reduce(country_data, %Country{}, fn({key, value}, country) ->
						key_as_atom = String.to_atom(to_string key)
						Map.put(country, key_as_atom, value)
					end)
					
				List.insert_at(countries, 0, country)
			end)
	end
end