class Term::ANSIColor::Attribute

def self.[](name, true_coloring: false)
  true_coloring ||= Term::ANSIColor.true_coloring?
  if true_coloring
    case
    when self === name                              then name
    when Array === name                             then true_color name
    when name.respond_to?(:to_rgb_triple)           then true_color(name.to_rgb_triple.to_a)
    when name.to_s =~ /\A(on_)?(\d+)\z/             then get "#$1color#$2"
    when name.to_s =~ /\A#([0-9a-f]{3}){1,2}\z/i    then true_color name
    when name.to_s =~ /\Aon_#([0-9a-f]{3}){1,2}\z/i then on_true_color name
    else                                            get name
    end
  else
    case
    when self === name                              then name
    when Array === name                             then nearest_rgb_color name
    when name.respond_to?(:to_rgb_triple)           then nearest_rgb_color(name.to_rgb_triple.to_a)
    when name.to_s =~ /\A(on_)?(\d+)\z/             then get "#$1color#$2"
    when name.to_s =~ /\A#([0-9a-f]{3}){1,2}\z/i    then nearest_rgb_color name
    when name.to_s =~ /\Aon_#([0-9a-f]{3}){1,2}\z/i then nearest_rgb_on_color name
    else                                            get name
    end
  end
end

def self.attributes(&block)
  @__store__.each_value(&block)
end

def self.get(name)
  @__store__[name.to_sym]
end

def self.named_attributes(&block)
  @named_attributes ||= attributes.reject(&:rgb_color?).each(&block)
end

def self.nearest_rgb_color(color, options = {})
  rgb = RGBTriple[color]
  rgb_foreground_colors(options).min_by { |c| c.distance_to(rgb, options) }
end

def self.nearest_rgb_on_color(color, options = {})
  rgb = RGBTriple[color]
  rgb_background_colors(options).min_by { |c| c.distance_to(rgb, options) }
end

def self.on_true_color(color, options = {})
  rgb = RGBTriple[color]
  new(:on_true, "", { true_color: rgb, background: true })
end

def self.set(name, code, **options)
  name = name.to_sym
  result = @__store__[name] = new(name, code, options)
  unless options[:skip_definition]
    ::Term::ANSIColor.class_eval do
      define_method(name) do |string = nil, &block|
        apply_attribute(name, string, &block)
      end
    end
  end
  result
end

def self.true_color(color, options = {})
  rgb = RGBTriple[color]
  new(:true, "", { true_color: rgb, background: false })
end

def apply(string = nil, &block)
  ::Term::ANSIColor.apply_attribute(self, string, &block)
end

def background?
  !!@background
end

def code
  if true_color?
    background? ? "48;2;#{@rgb.to_a * ?;}" : "38;2;#{@rgb.to_a * ?;}"
  elsif rgb_color?
    background? ? "48;5;#{@code}" : "38;5;#{@code}"
  elsif direct?
    background? ? (@code.to_i + 10).to_s : @code
  else
    @code
  end
end

def direct?
  !!@direct
end

def distance_to(other, options = {})
  if our_rgb = to_rgb_triple and
    other.respond_to?(:to_rgb_triple) and
    other_rgb = other.to_rgb_triple
  then
    our_rgb.distance_to(other_rgb, options)
  else
    1 / 0.0
  end
end

def gradient_to(other, options = {})
  if our_rgb = to_rgb_triple and
      other.respond_to?(:to_rgb_triple) and
      other_rgb = other.to_rgb_triple
    then
    true_coloring = options[:true_coloring] || Term::ANSIColor.true_coloring?
    our_rgb.gradient_to(other_rgb, options).map do |rgb_triple|
      if true_coloring
        self.class.true_color(rgb_triple, options)
      else
        self.class.nearest_rgb_color(rgb_triple, options)
      end
    end
  else
    []
  end
end

def gray?
  rgb_color? && to_rgb_triple.gray?
end

def initialize(name, code, options = {})
  @name       = name.to_sym
  @background = !!options[:background]
  @code       = code.to_s
  @direct     = false
  @true_color = false
  if rgb = options[:true_color]
    @true_color = true
    @rgb = rgb
  elsif rgb = options[:direct]
    @direct = true
    @rgb = RGBTriple.from_html(rgb)
  elsif html = options[:html]
    @rgb = RGBTriple.from_html(html)
  elsif options.slice(:red, :green, :blue).size == 3
    @rgb = RGBTriple.from_hash(options)
  else
    @rgb = nil # prevent instance variable not initialized warnings
  end
end

def rgb_background_colors(options = {}, &block)
  rgb_colors(options).select(&:background?).each(&block)
end

def rgb_color?
  !!@rgb && !@true_color && !@direct
end

def rgb_colors(options = {}, &block)
  colors = attributes.select(&:rgb_color?)
  if options.key?(:gray) && !options[:gray]
    colors = colors.reject(&:gray?)
  end
  colors.each(&block)
end

def rgb_foreground_colors(options = {}, &block)
  rgb_colors(options).reject(&:background?).each(&block)
end

def to_rgb_triple
  @rgb
end

def true_color?
  !!(@rgb && @true_color)
end