gistfile1.rb

#!/usr/bin/env ruby

# We require...
require "httpclient"
require "json"

# Startup variables
url = "http://archive.org/advancedsearch.php"
query = {"q" => 'collection:"harvardclassicsbound" AND (collection:harvardclassicsbound)',
        "output" => "json",
        "rows" => "60",
        "fl[]" => "identifier",
        "save" => "yes",
        "page" => "1"}
headers = {"Accept" => "application/json", "Content-Type" => "application/json"}

http = HTTPClient.new
http.ssl_config.verify_mode = OpenSSL::SSL::VERIFY_NONE

request = http.get(url, query)
json_response = JSON.parse(request.content)
doc_list = json_response["response"]["docs"]

doc_list.each do |doc|
  # Download URL format: https://archive.org/download/identifier/identifier.epub
  doc_id = doc["identifier"]
  new_url = "https://archive.org/download/#{doc_id}/#{doc_id}.epub"
  puts "Downloading #{new_url}"

  begin
    downloaded_file = File.new("#{doc_id}.epub", "wb")
    downloaded_file.write(http.get_content(new_url))
  rescue
    # Let's try a PDF is the EPUB doesn't exist
    begin
      File.delete("#{doc_id}.epub")
      puts "Failed to download EPUB. Trying the PDF version..."
      new_url = "https://archive.org/download/#{doc_id}/#{doc_id}.pdf"
      downloaded_file = File.new("#{doc_id}.pdf", "wb")
      downloaded_file.write(http.get_content(new_url))
    rescue
      begin
        # PDF failed, so TXT then
        File.delete("#{doc_id}.pdf")
        puts "Failed to download PDF. Trying the TXT version..."
        new_url = "https://archive.org/download/#{doc_id}/#{doc_id}.txt"
        downloaded_file = File.new("#{doc_id}.txt", "wb")
        downloaded_file.write(http.get_content(new_url))
      rescue
        # TXT failed? Try DJVu then
        File.delete("#{doc_id}.txt")
        puts "Failed to download TXT. Trying the DjVu version..."
        new_url = "https://archive.org/download/#{doc_id}/#{doc_id}.djvu"
        downloaded_file = File.new("#{doc_id}.djvu", "wb")
        downloaded_file.write(http.get_content(new_url))
      end
    end
  end
end