dl.rb

require 'io/console'
require 'net/http'
require 'digest'

class Loader
  def initialize(url, download_dir)
    @url = url
    uri = URI.parse url
    @file_name = File.basename(url).gsub(/[^a-zA-Z0-9_.]/, '').gsub(/^\./, 'file.')
    @file_path = "#{download_dir}/#{@file_name}"
    @loaded_size = File.exist?(@file_path) ? File.size(@file_path) : 0
    @content_length = Net::HTTP.new(uri.hostname, uri.port).head(uri.path).header['content-length'].to_i
    p @url
    p @content_length
    @missings = [[@loaded_size, @content_length]]
    @mutex = Mutex.new
    @partials = []
  end

  def take(size, &block)
    @mutex.synchronize do
      segment = @missings.shift
      return nil unless segment
      from, to = segment
      if to - from >= 2 * size
        @missings.unshift [from + size, to]
        [from, from + size]
      else
        [from, to]
      end
    end
  end

  def flush
    @partials.sort_by!(&:first)
    while true do
      from, to, data = @partials.first
      break unless from == @loaded_size
      File.open @file_path, 'a' do |f|
        f.write data
      end
      @partials.shift
      @loaded_size = to
    end
  end

  def loaded from, to, data
    @mutex.synchronize do
      @partials << [from, to, data]
      flush
      show_progress
    end
  end

  def failed from, to
    @mutex.synchronize do
      @missings.unshift [from, to]
    end
  end

  def show_progress
    @loaded_size
    @content_length
    width = [IO.console.winsize.last, 40].max
    progress = [' '] * width
    (width * @loaded_size / @content_length).times { |i| progress[i] = 'a' }
    @partials.map do |from, to|
      from_idx = width * from / @content_length
      to_idx = width * to / @content_length
      (from_idx...to_idx).each { |i| progress[i] = 'b' }
    end
    progress_text = progress.join
    {
      ' ' => ["\e[47m", ' '],
      'a' => ["\e[42;32m", '#'],
      'b' => ["\e[47;32m", '|']
    }.each do |c, (esc, c2)|
      progress_text.gsub!(/#{c}+/) { |s| esc + c2 * s.size + "\e[m" }
    end
    stat = "%#{@content_length.to_s.size}d / %d  %02.2f%%" % [
      @loaded_size,
      @content_length,
      100.0 * @loaded_size / @content_length
    ]
    message = "#{@file_name[0, width - stat.size - 2]}  #{stat}"
    STDOUT.write "\n" + progress_text + "\eM\r\e[K" + message
  end

  def partial from, to
    range = "#{from}-#{to - 1}"
    # data = HTTP::Client.get(@url, headers: { range: range }).response.body
    data = IO.popen ['curl', '-r', range, @url], err: File::NULL do |io|
      io.binmode.read
    end
    raise "wrong size #{data.size} #{to - from}" if data.size != to - from
    data
  end

  def run partial_size: 500_000, num: 16
    threads = num.times.map do
      Thread.new do
        loop do
          segment = take partial_size
          break unless segment
          begin
            data = partial(*segment)
            loaded(*segment, data)
          rescue => e
            p e
            puts e.backtrace
            failed(*segment)
            sleep 1
          end
        end
      end
    end
    threads.map(&:join)
  end
end

download_dir = 'downloads'
Dir.mkdir download_dir unless Dir.exist? download_dir
gitignore_file = '.gitignore'
File.write gitignore_file, "#{download_dir}/\n#{gitignore_file}\n" unless File.exist? gitignore_file

url = ARGV[0]
Loader.new(url, download_dir).run