Websafe Color Converter

websafe_color_converter.rb

class WebsafeColorConverter

  class InvalidHexError < StandardError; end;

  def call(hex_color)
    raise InvalidHexError unless valid_hex?(hex_color)

    return hex_color if valid_3_char_hex?(hex_color)
    return websafe_hex_color(hex_color) if valid_6_char_hex?(hex_color)


    # hex_values = hex_color.split('#').last

    # '#' + hex_values.chars.each_slice(2).flat_map do |value|
    #   second_hex_value = value.last
    #   round
    #   [value.first, value.first]
    # end.join
  end

private

  def valid_hex_color?(hex_color)
    hex_color =~ /\A#?(?:[0-9A-F]{3}){1,2}\z/i
  end

  def websafe_hex_color(hex_color)
    value_portion = hex_color.each_slice(2).flat_map do |hex_string|
      closest_websafe_number(hex_string)
    end

    "##{value_portion}"
  end

  # F4 => EE
  def closest_websafe_number(hex_string)
    # convert F4 to integer
    # absolute value trick to get closest integer
    # convert integer to hex
  end

end


# F0 => EE FF

# FFF

websafe_color_converter_spec.rb

require 'rspec'
require_relative '../websafe_color_converter'

RSpec.describe WebsafeColorConverter do

  let(:converter) { described_class.new }

  describe '#call' do

    it 'converts to a websafe color' do
      expect(converter.call('#ffbc40')).to eq '#ffbb44'
    end

    it 'returns same value if it is already websafe' do
      expect(converter.call('#FFFFFF')).to eq '#FFFFFF'
    end

    it 'raises exception when hex color that is too long is passed in' do
      expect { converter.call('#12Af567') }.to raise_error(WebsafeColorConverter::InvalidHexError)
    end

    it 'raises exception when hex color that is too short is passed in' do
      expect { converter.call('#12Af5') }.to raise_error(WebsafeColorConverter::InvalidHexError)
    end

    it 'works when no # provided' do
      expect(converter.call('12Af51')).to eq '#11AA55'
    end

    it 'works when hex value provided is only 3 digits' do
      expect(converter.call('12A')).to eq '#1122AA'
    end

  end

end