module Vedeu

  # Provides escape sequence strings for setting the cursor position and various
  # display related functions.
  #
  # @api private
  module Esc

    extend self

    # @return [Hash]
    def codes
      {
        black:   30,
        red:     31,
        green:   32,
        yellow:  33,
        blue:    34,
        magenta: 35,
        cyan:    36,
        white:   37,
        default: 39,
      }
    end

    # Dynamically creates methods for each terminal named colour. When a block
    # is given, then the colour is reset to 'default' once the block is called.
    #
    # @example
    #   Esc.red                     # => "\e[31m"
    #
    #   Esc.red { 'some text' }     # => "\e[31msome text\e[39m"
    #
    #   Esc.on_blue                 # => "\e[44m"
    #
    #   Esc.on_blue { 'some text' } # => "\e[44msome text\e[49m"
    #
    # @return [String]
    codes.each do |key, code|
      define_method(key) do |&blk|
        "\e[#{code}m" + (blk ? blk.call + "\e[39m" : '')
      end
      define_method('on_' + key.to_s) do |&blk|
        "\e[#{code + 10}m" + (blk ? blk.call + "\e[49m" : '')
      end
    end

    # Return the escape sequence required to position the cursor at a particular
    # point on the screen. When passed a block, will do the aforementioned,
    # call the block and then reposition to this location.
    #
    # @param y     [Fixnum] The row/line position.
    # @param x     [Fixnum] The column/character position.
    # @param block [Proc]
    # @return      [String]
    def set_position(y = 1, x = 1, &block)
      Position.new(y, x).to_s(&block)
    end

    # Return the escape sequence string from the list of recognised sequence
    # 'commands', or an empty string if the 'command' cannot be found.
    #
    # @param value [String|Symbol]
    # @return [String]
    def string(value = '')
      return '' if value.to_sym.empty?

      sequences.fetch(value.to_sym, proc { '' }).call
    end

    private

    # @return [Hash]
    def sequences
      {
        bg_reset:        proc { bg_reset },
        blink:           proc { blink },
        blink_off:       proc { blink_off },
        bold:            proc { bold },
        bold_off:        proc { bold_off },
        clear:           proc { clear },
        clear_line:      proc { clear_line },
        clear_last_line: proc { clear_last_line },
        colour_reset:    proc { colour_reset },
        dim:             proc { dim },
        fg_reset:        proc { fg_reset },
        hide_cursor:     proc { hide_cursor },
        negative:        proc { negative },
        normal:          proc { normal },
        positive:        proc { positive },
        reset:           proc { reset },
        screen_init:     proc { screen_init },
        screen_exit:     proc { screen_exit },
        show_cursor:     proc { show_cursor },
        underline:       proc { underline },
        underline_off:   proc { underline_off },
      }
    end

    # @return [String]
    def bg_reset
      "\e[48;2;49m"
    end

    # @return [String]
    def blink
      "\e[5m"
    end

    # @return [String]
    def blink_off
      "\e[25m"
    end

    # @return [String]
    def bold
      "\e[1m"
    end

    # @return [String]
    def bold_off
      "\e[22m"
    end

    # @return [String]
    def clear
      [ colour_reset,
        "\e[2J" ].join
    end

    # @return [String]
    def clear_line
      [ colour_reset,
        "\e[2K" ].join
    end

    # @return [String]
    def clear_last_line
      [set_position((Terminal.height - 1), 1), clear_line].join
    end

    # @return [String]
    def colour_reset
      [fg_reset, bg_reset].join
    end

    # @return [String]
    def dim
      "\e[2m"
    end

    # @return [String]
    def fg_reset
      "\e[38;2;39m"
    end

    # @return [String]
    def hide_cursor
      "\e[?25l"
    end

    # @return [String]
    def negative
      "\e[7m"
    end

    # @return [String]
    def normal
      [underline_off, bold_off, positive].join
    end

    # @return [String]
    def positive
      "\e[27m"
    end

    # @return [String]
    def reset
      "\e[0m"
    end

    # @return [String]
    def screen_init
      [reset, clear, hide_cursor].join
    end

    # @return [String]
    def screen_exit
      [show_cursor, colour_reset, reset].join
    end

    # @return [String]
    def show_cursor
      "\e[?25h"
    end

    # @return [String]
    def underline
      "\e[4m"
    end

    # @return [String]
    def underline_off
      "\e[24m"
    end

  end # Esc

end # Vedeu