require 'sass/script/literal'

module Sass::Script
  # A SassScript object representing a CSS color.
  #
  # A color may be represented internally as RGBA, HSLA, or both.
  # It's originally represented as whatever its input is;
  # if it's created with RGB values, it's represented as RGBA,
  # and if it's created with HSL values, it's represented as HSLA.
  # Once a property is accessed that requires the other representation --
  # for example, \{#red} for an HSL color --
  # that component is calculated and cached.
  #
  # The alpha channel of a color is independent of its RGB or HSL representation.
  # It's always stored, as 1 if nothing else is specified.
  # If only the alpha channel is modified using \{#with},
  # the cached RGB and HSL values are retained.
  class Color < Literal
    class << self; include Sass::Util; end

    # A hash from color names to `[red, green, blue]` value arrays.
    HTML4_COLORS = map_vals({
        'black'   => 0x000000,
        'silver'  => 0xc0c0c0,
        'gray'    => 0x808080,
        'white'   => 0xffffff,
        'maroon'  => 0x800000,
        'red'     => 0xff0000,
        'purple'  => 0x800080,
        'fuchsia' => 0xff00ff,
        'green'   => 0x008000,
        'lime'    => 0x00ff00,
        'olive'   => 0x808000,
        'yellow'  => 0xffff00,
        'navy'    => 0x000080,
        'blue'    => 0x0000ff,
        'teal'    => 0x008080,
        'aqua'    => 0x00ffff
      }) {|color| (0..2).map {|n| color >> (n << 3) & 0xff}.reverse}
    # A hash from `[red, green, blue]` value arrays to color names.
    HTML4_COLORS_REVERSE = map_hash(HTML4_COLORS) {|k, v| [v, k]}

    # Constructs an RGB or HSL color object,
    # optionally with an alpha channel.
    # 
    # The RGB values must be between 0 and 255.
    # The saturation and lightness values must be between 0 and 100.
    # The alpha value must be between 0 and 1.
    #
    # @raise [Sass::SyntaxError] if any color value isn't in the specified range
    #
    # @overload initialize(attrs)
    #   The attributes are specified as a hash.
    #   This hash must contain either `:hue`, `:saturation`, and `:value` keys,
    #   or `:red`, `:green`, and `:blue` keys.
    #   It cannot contain both HSL and RGB keys.
    #   It may also optionally contain an `:alpha` key.
    #
    #   @param attrs [{Symbol => Numeric}] A hash of color attributes to values
    #   @raise [ArgumentError] if not enough attributes are specified,
    #     or both RGB and HSL attributes are specified
    #
    # @overload initialize(rgba)
    #   The attributes are specified as an array.
    #   This overload only supports RGB or RGBA colors.
    #
    #   @param rgba [Array<Numeric>] A three- or four-element array
    #     of the red, green, blue, and optionally alpha values (respectively)
    #     of the color
    #   @raise [ArgumentError] if not enough attributes are specified
    def initialize(attrs, allow_both_rgb_and_hsl = false)
      super(nil)

      if attrs.is_a?(Array)
        unless (3..4).include?(attrs.size)
          raise ArgumentError.new("Color.new(array) expects a three- or four-element array")
        end

        red, green, blue = attrs[0...3].map {|c| c.to_i}
        @attrs = {:red => red, :green => green, :blue => blue}
        @attrs[:alpha] = attrs[3] ? attrs[3].to_f : 1
      else
        attrs = attrs.reject {|k, v| v.nil?}
        hsl = [:hue, :saturation, :lightness] & attrs.keys
        rgb = [:red, :green, :blue] & attrs.keys
        if !allow_both_rgb_and_hsl && !hsl.empty? && !rgb.empty?
          raise ArgumentError.new("Color.new(hash) may not have both HSL and RGB keys specified")
        elsif hsl.empty? && rgb.empty?
          raise ArgumentError.new("Color.new(hash) must have either HSL or RGB keys specified")
        elsif !hsl.empty? && hsl.size != 3
          raise ArgumentError.new("Color.new(hash) must have all three HSL values specified")
        elsif !rgb.empty? && rgb.size != 3
          raise ArgumentError.new("Color.new(hash) must have all three RGB values specified")
        end

        @attrs = attrs
        @attrs[:hue] %= 360 if @attrs[:hue]
        @attrs[:alpha] ||= 1
      end

      [:red, :green, :blue].each do |k|
        next if @attrs[k].nil?
        @attrs[k] = @attrs[k].to_i
        Sass::Util.check_range("#{k.to_s.capitalize} value", 0..255, @attrs[k])
      end

      [:saturation, :lightness].each do |k|
        next if @attrs[k].nil?
        value = Number.new(@attrs[k], ['%']) # Get correct unit for error messages
        @attrs[k] = Sass::Util.check_range("#{k.to_s.capitalize}", 0..100, value, '%')
      end

      @attrs[:alpha] = Sass::Util.check_range("Alpha channel", 0..1, @attrs[:alpha])
    end

    # The red component of the color.
    #
    # @return [Fixnum]
    def red
      hsl_to_rgb!
      @attrs[:red]
    end

    # The green component of the color.
    #
    # @return [Fixnum]
    def green
      hsl_to_rgb!
      @attrs[:green]
    end

    # The blue component of the color.
    #
    # @return [Fixnum]
    def blue
      hsl_to_rgb!
      @attrs[:blue]
    end

    # The hue component of the color.
    #
    # @return [Numeric]
    def hue
      rgb_to_hsl!
      @attrs[:hue]
    end

    # The saturation component of the color.
    #
    # @return [Numeric]
    def saturation
      rgb_to_hsl!
      @attrs[:saturation]
    end

    # The lightness component of the color.
    #
    # @return [Numeric]
    def lightness
      rgb_to_hsl!
      @attrs[:lightness]
    end

    # The alpha channel (opacity) of the color.
    # This is 1 unless otherwise defined.
    #
    # @return [Fixnum]
    def alpha
      @attrs[:alpha]
    end

    # Returns whether this color object is translucent;
    # that is, whether the alpha channel is non-1.
    #
    # @return [Boolean]
    def alpha?
      alpha < 1
    end

    # Returns the red, green, and blue components of the color.
    #
    # @return [Array<Fixnum>] A frozen three-element array of the red, green, and blue
    #   values (respectively) of the color
    def rgb
      [red, green, blue].freeze
    end

    # Returns the hue, saturation, and lightness components of the color.
    #
    # @return [Array<Fixnum>] A frozen three-element array of the
    #   hue, saturation, and lightness values (respectively) of the color
    def hsl
      [hue, saturation, lightness].freeze
    end

    # The SassScript `==` operation.
    # **Note that this returns a {Sass::Script::Bool} object,
    # not a Ruby boolean**.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Bool] True if this literal is the same as the other,
    #   false otherwise
    def eq(other)
      Sass::Script::Bool.new(
        other.is_a?(Color) && rgb == other.rgb && alpha == other.alpha)
    end

    # Returns a copy of this color with one or more channels changed.
    # RGB or HSL colors may be changed, but not both at once.
    #
    # For example:
    #
    #     Color.new([10, 20, 30]).with(:blue => 40)
    #       #=> rgb(10, 40, 30)
    #     Color.new([126, 126, 126]).with(:red => 0, :green => 255)
    #       #=> rgb(0, 255, 126)
    #     Color.new([255, 0, 127]).with(:saturation => 60)
    #       #=> rgb(204, 51, 127)
    #     Color.new([1, 2, 3]).with(:alpha => 0.4)
    #       #=> rgba(1, 2, 3, 0.4)
    #
    # @param attrs [{Symbol => Numeric}]
    #   A map of channel names (`:red`, `:green`, `:blue`,
    #   `:hue`, `:saturation`, `:lightness`, or `:alpha`) to values
    # @return [Color] The new Color object
    # @raise [ArgumentError] if both RGB and HSL keys are specified
    def with(attrs)
      attrs = attrs.reject {|k, v| v.nil?}
      hsl = !([:hue, :saturation, :lightness] & attrs.keys).empty?
      rgb = !([:red, :green, :blue] & attrs.keys).empty?
      if hsl && rgb
        raise ArgumentError.new("Cannot specify HSL and RGB values for a color at the same time")
      end

      if hsl
        [:hue, :saturation, :lightness].each {|k| attrs[k] ||= send(k)}
      elsif rgb
        [:red, :green, :blue].each {|k| attrs[k] ||= send(k)}
      else
        # If we're just changing the alpha channel,
        # keep all the HSL/RGB stuff we've calculated
        attrs = @attrs.merge(attrs)
      end
      attrs[:alpha] ||= alpha

      Color.new(attrs, :allow_both_rgb_and_hsl)
    end

    # The SassScript `+` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Adds the number to each of the RGB color channels.
    #
    # {Color}
    # : Adds each of the RGB color channels together.
    #
    # {Literal}
    # : See {Literal#plus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def plus(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :+)
      else
        super
      end
    end

    # The SassScript `-` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Subtracts the number from each of the RGB color channels.
    #
    # {Color}
    # : Subtracts each of the other color's RGB color channels from this color's.
    #
    # {Literal}
    # : See {Literal#minus}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def minus(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :-)
      else
        super
      end
    end

    # The SassScript `*` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Multiplies the number by each of the RGB color channels.
    #
    # {Color}
    # : Multiplies each of the RGB color channels together.
    #
    # @param other [Number, Color] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def times(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :*)
      else
        raise NoMethodError.new(nil, :times)
      end
    end

    # The SassScript `/` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Divides each of the RGB color channels by the number.
    #
    # {Color}
    # : Divides each of this color's RGB color channels by the other color's.
    #
    # {Literal}
    # : See {Literal#div}.
    #
    # @param other [Literal] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def div(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :/)
      else
        super
      end
    end

    # The SassScript `%` operation.
    # Its functionality depends on the type of its argument:
    #
    # {Number}
    # : Takes each of the RGB color channels module the number.
    #
    # {Color}
    # : Takes each of this color's RGB color channels modulo the other color's.
    #
    # @param other [Number, Color] The right-hand side of the operator
    # @return [Color] The resulting color
    # @raise [Sass::SyntaxError] if `other` is a number with units
    def mod(other)
      if other.is_a?(Sass::Script::Number) || other.is_a?(Sass::Script::Color)
        piecewise(other, :%)
      else
        raise NoMethodError.new(nil, :mod)
      end
    end

    # Returns a string representation of the color.
    # This is usually the color's hex value,
    # but if the color has a name that's used instead.
    #
    # @return [String] The string representation
    def to_s(opts = {})
      return rgba_str if alpha?
      return smallest if options[:style] == :compressed
      return HTML4_COLORS_REVERSE[rgb] if HTML4_COLORS_REVERSE[rgb]
      hex_str
    end
    alias_method :to_sass, :to_s

    # Returns a string representation of the color.
    #
    # @return [String] The hex value
    def inspect
      alpha? ? rgba_str : hex_str
    end

    private

    def smallest
      small_hex_str = hex_str.gsub(/^#(.)\1(.)\2(.)\3$/, '#\1\2\3')
      return small_hex_str unless (color = HTML4_COLORS_REVERSE[rgb]) &&
        color.size <= small_hex_str.size
      return color
    end

    def rgba_str
      split = options[:style] == :compressed ? ',' : ', '
      "rgba(#{rgb.join(split)}#{split}#{Number.round(alpha)})"
    end

    def hex_str
      red, green, blue = rgb.map { |num| num.to_s(16).rjust(2, '0') }
      "##{red}#{green}#{blue}"
    end

    def piecewise(other, operation)
      other_num = other.is_a? Number
      if other_num && !other.unitless?
        raise Sass::SyntaxError.new("Cannot add a number with units (#{other}) to a color (#{self}).") 
      end

      result = []
      for i in (0...3)
        res = rgb[i].send(operation, other_num ? other.value : other.rgb[i])
        result[i] = [ [res, 255].min, 0 ].max
      end

      if !other_num && other.alpha != alpha
        raise Sass::SyntaxError.new("Alpha channels must be equal: #{self} #{operation} #{other}")
      end

      with(:red => result[0], :green => result[1], :blue => result[2])
    end

    def hsl_to_rgb!
      return if @attrs[:red] && @attrs[:blue] && @attrs[:green]

      h = @attrs[:hue] / 360.0
      s = @attrs[:saturation] / 100.0
      l = @attrs[:lightness] / 100.0

      # Algorithm from the CSS3 spec: http://www.w3.org/TR/css3-color/#hsl-color.
      m2 = l <= 0.5 ? l * (s + 1) : l + s - l * s
      m1 = l * 2 - m2
      @attrs[:red], @attrs[:green], @attrs[:blue] = [
        hue_to_rgb(m1, m2, h + 1.0/3),
        hue_to_rgb(m1, m2, h),
        hue_to_rgb(m1, m2, h - 1.0/3)
      ].map {|c| (c * 0xff).round}
    end

    def hue_to_rgb(m1, m2, h)
      h += 1 if h < 0
      h -= 1 if h > 1
      return m1 + (m2 - m1) * h * 6 if h * 6 < 1
      return m2 if h * 2 < 1
      return m1 + (m2 - m1) * (2.0/3 - h) * 6 if h * 3 < 2
      return m1
    end

    def rgb_to_hsl!
      return if @attrs[:hue] && @attrs[:saturation] && @attrs[:lightness]
      r, g, b = [:red, :green, :blue].map {|k| @attrs[k] / 255.0}

      # Algorithm from http://en.wikipedia.org/wiki/HSL_and_HSV#Conversion_from_RGB_to_HSL_or_HSV
      max = [r, g, b].max
      min = [r, g, b].min
      d = max - min

      h =
        case max
        when min; 0
        when r; 60 * (g-b)/d
        when g; 60 * (b-r)/d + 120
        when b; 60 * (r-g)/d + 240
        end

      l = (max + min)/2.0

      s =
        if max == min
          0
        elsif l < 0.5
          d/(2*l)
        else
          d/(2 - 2*l)
        end

      @attrs[:hue] = h % 360
      @attrs[:saturation] = s * 100
      @attrs[:lightness] = l * 100
    end
  end
end