require 'io/console'
require_relative 'color'
require_relative 'convert_size'

class ProgressBar
  attr_accessor :progress_bar_showing

  def initialize (total_size)
    # character used to fill the progress bar, one of the box-drawing character in unicode
    @bar_char = "\u2501"

    # color scheme of progress bar, can be changed
    # see color.rb for more available colors
    @bar_front_color = :lightcyan
    @bar_bg_color = :gray

    # all info blocks with space taken
    @info_before_bar = { downloaded_size_in_str: 20 }
    @info_after_bar = { percentage_in_str: 4, elapsed_time_in_str: 8 }

    @percentage = @downloaded = 0
    @total_size = total_size.to_f

    @total_size_in_str = human_size(@total_size)

    trap('WINCH') do
      # reset width settings after terminal resized
      # get terminal size, calculate the width of progress bar based on it
      @terminal_h, @terminal_w = IO.console.winsize

      @bar_width = @terminal_w -
                   @info_before_bar.merge(@info_after_bar).values.sum - # space that all info blocks takes
                   ( @info_before_bar.merge(@info_after_bar).length * 2 ) # space for separator (whitespaces) between each info

    rescue NoMethodError => e
      # fallback for non-interactive terminals
      unless $non_interactive_term_warned
        warn 'Non-interactive terminals may not be able to be queried for size.'
        $non_interactive_term_warned = true
      end

      @terminal_h, @terminal_w = [ 25, 80 ]
    end

    Process.kill('WINCH', 0) # trigger the trap above
  end

  def set_downloaded_size (downloaded_size)
    if @start_time
      @elapsed_time = (Time.now - @start_time).to_i
    else
      # record start time, used for calculating elapsed time
      @start_time = Time.now
      @elapsed_time = 0
    end

    @elapsed_time_in_str = Time.at(@elapsed_time).utc.strftime('%H:%M:%S')

    # calculate progress percentage, round to nearest 0.1
    @percentage = ( ( downloaded_size / @total_size ) * 100 ).round(1)
    @percentage_in_str = "#{@percentage.to_i}%"

    # {downloaded size}/{total size}
    @downloaded_size_in_str = "#{human_size(downloaded_size)}/#{@total_size_in_str}"
  end

  def show
    return Thread.new do
      @progress_bar_showing = true

      print "\e[?25l" # hide cursor to prevent cursor flickering

      while @progress_bar_showing
        sleep 0.15 # update progress bar after each 0.15 seconds

        completed_length = ( @bar_width * (@percentage / 100) ).to_i
        uncompleted_length = @bar_width - completed_length

        # print info and progress bar
        @info_before_bar.each_pair do |varName, width|
          printf "%*.*s  ", width, width, instance_variable_get("@#{varName}")
        end

        # print progress bar with color code
        print ( @bar_char * completed_length ).send(@bar_front_color),
              ( @bar_char * uncompleted_length ).send(@bar_bg_color)

        @info_after_bar.each_pair do |varName, width|
          printf "  %*.*s", width, width, instance_variable_get("@#{varName}")
        end

        # stop when 100%
        if @percentage >= 100
          print "\e[2K\r" # clear previous line (progress bar)
          break
        else
          print "\r"
        end
      end
    ensure
      print "\e[?25h" # restore cursor mode since we hide it before
    end
  end
end