module RainbowColors
  class Scheme
    def self.analogous(base_color)
      secondary = color_with_variance  30, base_color
      tertiary  = color_with_variance -30, base_color
      
      [base_color, secondary, tertiary]
    end
    
    def self.complementary(base_color)
      secondary = color_with_variance 180, base_color
      
      [base_color, secondary]
    end
    
    def self.complementary_split(base_color)
      secondary = color_with_variance 150, base_color
      tertiary  = color_with_variance 210, base_color
      
      [base_color, secondary, tertiary]
    end
    
    def self.triad(base_color)
      secondary = color_with_variance  120, base_color
      tertiary  = color_with_variance -120, base_color
      
      [base_color, secondary, tertiary]
    end
    
    def self.tints(base_color)
      shades_tints "#FFFFFF", base_color
    end
    
    def self.shades(base_color)
      shades_tints "#000000", base_color
    end
    
    def self.harmonious_grays(base_color)
      weight = 90
      colors = []
      colors << mix("#424242", base_color, weight)
      colors << mix("#FAFAFA", base_color, weight)
      colors
    end
    
    private
    
    private_class_method def self.color_with_variance(variance, base_color)
      rgb = RainbowColors::Convertor.rgb_from_hex base_color
      hsl = RainbowColors::Convertor.hsl_from_rgb rgb
      
      color = RainbowColors::Convertor.rgb_from_hsl({ hue: hsl[:hue] + variance, saturation: hsl[:saturation], luminance: hsl[:luminance] })
      RainbowColors::Convertor.hex_from_rgb color
    end    
    
    # Algorithm shamelessly stolen from SASS:
    # https://github.com/sass/sass/blob/stable/lib/sass/script/functions.rb#L1313
    private_class_method def self.mix(color1, color2, weight)
      color1 = RainbowColors::Convertor.rgb_from_hex color1
      color2 = RainbowColors::Convertor.rgb_from_hex color2
      
      p = weight / 100.0
      w = p * 2 - 1
      
      w1 = (w + 1) / 2
      w2 = 1 - w1
      
      r = (color1[:red]   * w1 + color2[:red]   * w2).round
      g = (color1[:green] * w1 + color2[:green] * w2).round
      b = (color1[:blue]  * w1 + color2[:blue]  * w2).round
      
      RainbowColors::Convertor.hex_from_rgb({ red: r, green: g, blue: b })
    end
    
    private_class_method def self.shades_tints(mix_color, base_color)
      colors = [base_color]
      
      weight = 0
      increment = 15
      
      5.times do
        weight = weight + increment
        colors.push mix(mix_color, base_color, weight)
      end
      
      colors
    end
  end
end