1 files changed, 199 insertions, 0 deletions
diff --git a/lib/reline/face.rb b/lib/reline/face.rb
new file mode 100644
index 0000000000..d07196e2e7
--- /dev/null
+++ b/lib/reline/face.rb
@@ -0,0 +1,199 @@
+# frozen_string_literal: true
+
+class Reline::Face
+  SGR_PARAMETERS = {
+    foreground: {
+      black: 30,
+      red: 31,
+      green: 32,
+      yellow: 33,
+      blue: 34,
+      magenta: 35,
+      cyan: 36,
+      white: 37,
+      bright_black: 90,
+      gray: 90,
+      bright_red: 91,
+      bright_green: 92,
+      bright_yellow: 93,
+      bright_blue: 94,
+      bright_magenta: 95,
+      bright_cyan: 96,
+      bright_white: 97
+    },
+    background: {
+      black: 40,
+      red: 41,
+      green: 42,
+      yellow: 43,
+      blue: 44,
+      magenta: 45,
+      cyan: 46,
+      white: 47,
+      bright_black: 100,
+      gray: 100,
+      bright_red: 101,
+      bright_green: 102,
+      bright_yellow: 103,
+      bright_blue: 104,
+      bright_magenta: 105,
+      bright_cyan: 106,
+      bright_white: 107,
+    },
+    style: {
+      reset: 0,
+      bold: 1,
+      faint: 2,
+      italicized: 3,
+      underlined: 4,
+      slowly_blinking: 5,
+      blinking: 5,
+      rapidly_blinking: 6,
+      negative: 7,
+      concealed: 8,
+      crossed_out: 9
+    }
+  }.freeze
+
+  class Config
+    ESSENTIAL_DEFINE_NAMES = %i(default enhanced scrollbar).freeze
+    RESET_SGR = "\e[0m".freeze
+
+    def initialize(name, &block)
+      @definition = {}
+      block.call(self)
+      ESSENTIAL_DEFINE_NAMES.each do |name|
+        @definition[name] ||= { style: :reset, escape_sequence: RESET_SGR }
+      end
+    end
+
+    attr_reader :definition
+
+    def define(name, **values)
+      values[:escape_sequence] = format_to_sgr(values.to_a).freeze
+      @definition[name] = values
+    end
+
+    def reconfigure
+      @definition.each_value do |values|
+        values.delete(:escape_sequence)
+        values[:escape_sequence] = format_to_sgr(values.to_a).freeze
+      end
+    end
+
+    def [](name)
+      @definition.dig(name, :escape_sequence) or raise ArgumentError, "unknown face: #{name}"
+    end
+
+    private
+
+    def sgr_rgb(key, value)
+      return nil unless rgb_expression?(value)
+      if Reline::Face.truecolor?
+        sgr_rgb_truecolor(key, value)
+      else
+        sgr_rgb_256color(key, value)
+      end
+    end
+
+    def sgr_rgb_truecolor(key, value)
+      case key
+      when :foreground
+        "38;2;"
+      when :background
+        "48;2;"
+      end + value[1, 6].scan(/../).map(&:hex).join(";")
+    end
+
+    def sgr_rgb_256color(key, value)
+      # 256 colors are
+      # 0..15: standard colors, hight intensity colors
+      # 16..232: 216 colors (R, G, B each 6 steps)
+      # 233..255: grayscale colors (24 steps)
+      # This methods converts rgb_expression to 216 colors
+      rgb = value[1, 6].scan(/../).map(&:hex)
+      # Color steps are [0, 95, 135, 175, 215, 255]
+      r, g, b = rgb.map { |v| v <= 95 ? v / 48 : (v - 35) / 40 }
+      color = (16 + 36 * r + 6 * g + b)
+      case key
+      when :foreground
+        "38;5;#{color}"
+      when :background
+        "48;5;#{color}"
+      end
+    end
+
+    def format_to_sgr(ordered_values)
+      sgr = "\e[" + ordered_values.map do |key_value|
+        key, value = key_value
+        case key
+        when :foreground, :background
+          case value
+          when Symbol
+            SGR_PARAMETERS[key][value]
+          when String
+            sgr_rgb(key, value)
+          end
+        when :style
+          [ value ].flatten.map do |style_name|
+            SGR_PARAMETERS[:style][style_name]
+          end.then do |sgr_parameters|
+            sgr_parameters.include?(nil) ? nil : sgr_parameters
+          end
+        end.then do |rendition_expression|
+          unless rendition_expression
+            raise ArgumentError, "invalid SGR parameter: #{value.inspect}"
+          end
+          rendition_expression
+        end
+      end.join(';') + "m"
+      sgr == RESET_SGR ? RESET_SGR : RESET_SGR + sgr
+    end
+
+    def rgb_expression?(color)
+      color.respond_to?(:match?) and color.match?(/\A#[0-9a-fA-F]{6}\z/)
+    end
+  end
+
+  private_constant :SGR_PARAMETERS, :Config
+
+  def self.truecolor?
+    @force_truecolor || %w[truecolor 24bit].include?(ENV['COLORTERM'])
+  end
+
+  def self.force_truecolor
+    @force_truecolor = true
+    @configs&.each_value(&:reconfigure)
+  end
+
+  def self.[](name)
+    @configs[name]
+  end
+
+  def self.config(name, &block)
+    @configs ||= {}
+    @configs[name] = Config.new(name, &block)
+  end
+
+  def self.configs
+    @configs.transform_values(&:definition)
+  end
+
+  def self.load_initial_configs
+    config(:default) do |conf|
+      conf.define :default, style: :reset
+      conf.define :enhanced, style: :reset
+      conf.define :scrollbar, style: :reset
+    end
+    config(:completion_dialog) do |conf|
+      conf.define :default, foreground: :bright_white, background: :gray
+      conf.define :enhanced, foreground: :black, background: :white
+      conf.define :scrollbar, foreground: :white, background: :gray
+    end
+  end
+
+  def self.reset_to_initial_configs
+    @configs = {}
+    load_initial_configs
+  end
+end