require 'i18n'
require 'parliament/utils/helpers/translation_helper'

# attr [String] previous_path the path to redirect back to in the case of an error.
module Parliament
  module Utils
    module Helpers
      module PostcodeHelper
        include Parliament::Utils::Helpers::TranslationHelper

        attr_accessor :previous_path

        # Makes requests to the postcode_lookup endpoint.
        # @param [String] raw_input the data inputted by the user.
        # @return [Parliament::Response::NTripleResponse, Parliament::ClientError, Parliament::ServerError] if successful, a response is returned, otherwise an error is returned.
        def self.lookup(raw_input)
          postcode = clean_input(raw_input)

          begin
            Parliament::Utils::Helpers::ParliamentHelper.parliament_request.constituency_lookup_by_postcode.get(params: { postcode: postcode })
          rescue Parliament::ClientError
            raise(PostcodeError, I18n.t('error.postcode_invalid_html'))
          rescue Parliament::ServerError
            raise(PostcodeError, I18n.t('error.lookup_unavailable'))
          end
        end

        # Replaces whitespace with a hyphen.
        # @param [String] postcode the string to be hyphenated.
        # @return [String] a hyphenated string.
        def self.hyphenate(postcode)
          postcode.strip.gsub(/\s+/, '-')
        end

        # Replaces a hyphen with whitespace, restoring a postcode to its usual format.
        # @param [String] postcode the string to be processed.
        # @return [String] the restored postcode with hyphen replaced by whitespace.
        def self.unhyphenate(postcode)
          postcode.tr('-', ' ')
        end

        # Returns the previous path variable.
        # @return [String] previous_path the path to redirect back to in the case of an error.
        def self.previous_path
          @previous_path
        end

        # Sets the previous path variable.
        # @return [String] previous_path the path to redirect back to in the case of an error.
        def self.previous_path=(path)
          @previous_path = path
        end

        private_class_method

        # We decided to use a loose regex - this matches the different postcode formats, but doesn't validate against invalid letters and numbers, only their positions.
        def self.clean_input(raw_input)
          postcode = raw_input.gsub(/\s+/, '').upcase

          postcode.match(/[A-Z]{1,2}[0-9][0-9A-Z]?\s?[0-9][A-Z]{2}/).nil? ? raise(PostcodeError, I18n.t('error.postcode_invalid_html')) : postcode
        end

        class PostcodeError < StandardError
          def initialize(message)
            super(message)
          end
        end
      end
    end
  end
end