Epub Generator

require 'zip'
require 'open-uri'

# EXAMPLE USE AT THE BOTTOM OF THIS FILE (after the __END__)

class EpubGenerator

  # When you add a chapter, naming the div_id according to the guide_roles allows
  # apple to treat the files differently
  # I have no idea how it does it, or what it does, but Apple likes it.
  # it is not required, and naming your div something else will tell apple it's "text"
  guide_roles = %w(cover
                  title-page
                  toc
                  index
                  glossary
                  acknowledgements
                  bibliography
                  colophon
                  copyright-page
                  dedication
                  epigraph
                  foreword
                  notes
                  preface)
  guide_roles << 'loi' #list of images
  guide_roles << 'lot' #list of tables

  def self.generate
    dir = "my_epub_#{Time.current}"
    Dir.mkdir(dir) unless Dir.exist?(dir)
    Dir.chdir(dir) {
      service = EpubGenerator.send(:new)
      yield service if block_given?
      service.send(:build_support_files)
      service.send(:zip_files)
    }
    File.join(Dir.pwd, dir, 'my.epub')
  end

  attr_accessor :author_name, :isbn, :book_title, :publisher,
                :publication_date, :subject_classification, :table_of_contents_title,
                :cover_file_name, :styles

  alias_method :style=, :styles=
  alias_method :style, :styles

  def add_chapter(div_id, title, body)
    Dir.mkdir('OEBPS') unless Dir.exist?('OEBPS')
    Dir.chdir("OEBPS") {
      Dir.mkdir('Text') unless Dir.exist?('Text')
      Dir.chdir("Text") {
        add_raw_content(div_id, title, body)
        @content[div_id] = title
      }
    }
  end

  def add_image(dest_name, sourc_url)
    Dir.mkdir('OEBPS') unless Dir.exist?('OEBPS')
    Dir.chdir("OEBPS") {
      Dir.mkdir('Images') unless Dir.exist?('Images')
      open("Images/#{dest_name}", 'wb') do |file|
        file << open(sourc_url).read
      end
    }
  end

  private

  def self.new
    super
  end

  def initialize
    @content = {}
    @author_name ='David Rawk'
    @isbn = SecureRandom.uuid
    @book_title = 'The ePub of wonders'
    @publisher = 'Bootstrap Dragon'
    @publication_date = Date.current.to_s
    @subject_classification = 'NON000000 NON-CLASSIFIABLE' # The list of options is here https://bisg.org/page/BISACEdition
    @table_of_contents_title = 'Table Of Contents'
    @cover_file_name = 'cover.jpeg'
    @styles = ""
  end

  def zip_files
    entries = list_dir Dir.pwd

    ::Zip::OutputStream.open('my.epub') do |stream|
      # This has to be done without compression, because that's required by the standard
      stream.put_next_entry('mimetype', nil, nil, ::Zip::Entry::STORED)
      stream.write 'application/epub+zip'
    end

    zip_file = Zip::File.open('my.epub')
    writeEntries(entries, "", zip_file)
    zip_file.close
  end

  def writeEntries(entries, path, io)
    entries.each { |e|
      zipFilePath = path == "" ? e : File.join(path, e)
      diskFilePath = File.join(Dir.pwd, zipFilePath)
      if  File.directory?(diskFilePath)
        io.mkdir(zipFilePath)
        subdir = list_dir(diskFilePath)
        writeEntries(subdir, zipFilePath, io)
      else
        io.get_output_stream(zipFilePath) { |f| f.puts(File.open(diskFilePath, "rb").read())}
      end
    }
  end

  def build_support_files
      Dir.mkdir('META-INF') unless Dir.exist?('META-INF')
      Dir.chdir("META-INF") {
        make_container
        make_apple_hack
      }

      Dir.mkdir('OEBPS') unless Dir.exist?('OEBPS')
      Dir.chdir("OEBPS") {
        Dir.mkdir('Styles') unless Dir.exist?('Styles')
        Dir.chdir("Styles") {
          add_style(@styles)
        }
        Dir.mkdir('Text') unless Dir.exist?('Text')
        Dir.chdir("Text") {
          add_cover
          create_toc_html
        }
        create_toc_ncx
        create_content_opf
      }
  end

  def add_cover
    add_raw_content('cover', 'Cover', "<div id=\"cover-image\">
    <img alt=\"#{@book_title}\" src=\"../Images/#{@cover_file_name}\" />
    </div>")
  end

  def add_style(string = "")
    File.open("style.css", 'w') do |file|
      text = []
      text << "body { line-height: 1.5em;} "
      text << 'p.first {text-indent: 0;} '
      text << '@media amzn-mobi {p.first {text-indent: 0;}} '
      text << 'img { max-width: 100%; } #cover-image { text-align: center; }'
      text << string
      file.write(text.join("\n"))
    end
  end

  def add_raw_content(div_id, title, body)
    File.open("#{div_id}.xhtml", 'w') do |file|
      text = []
      text << '<?xml version="1.0" encoding="utf-8" standalone="no"?>'
      text << '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN" "http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">'
      text << '<html xmlns="http://www.w3.org/1999/xhtml">'
      text << "<head><title>#{title}</title>"
      text << '<link href="../Styles/style.css" rel="stylesheet" type="text/css" />'
      text << '</head><body>'
      text << "<div id=\"#{div_id}\" xml:lang=\"en-US\"> #{body} </div>"
      text << "</body></html>"
      file.write(text.join("\n"))
    end
  end


  def make_container
    File.open('container.xml', 'w') do |file|
      text =  []
      text << '<?xml version="1.0" encoding="UTF-8"?>'
      text << '<container version="1.0" xmlns="urn:oasis:names:tc:opendocument:xmlns:container">'
      text << '  <rootfiles>'
      text << '    <rootfile full-path="OEBPS/content.opf" media-type="application/oebps-package+xml"/>'
      text << '  </rootfiles>'
      text << '</container>'
      file.write(text.join("\n"))
    end
  end

  def make_apple_hack
    File.open('com.apple.ibooks.display-options.xml', 'w') do |file|
      text = <<-FOO
        <?xml version="1.0" encoding="UTF-8"?>
        <display_options>
        <platform name="*">
        <option name="specified-fonts">false</option>
        </platform>
        </display_options>
        FOO
      file.write(text)
    end
  end

  def list_dir(dir)
    entries = Dir.entries(dir)
    entries.delete(".")
    entries.delete("..")
    entries.delete(".DS_Store")
    entries
  end

  def manifest_text # MUST CONTAIN ALL THE FILES.
    text = []
    # <!-- MANIFEST (mandatory)'
    # List of all the resources of the book (XHTML, CSS, images,…).'
    # The order of item elements in the manifest is NOT significant.'
    # http://idpf.org/epub/20/spec/OPF_2.0.1_draft.htm#Section2.3 '
    # -->'

    text << '  <item href="toc.ncx" id="ncx" media-type="application/x-dtbncx+xml" />'
    text << '  <item href="Styles/style.css" id="css" media-type="text/css" />'

    list_dir("Images").each do |entry|
      type = entry.split('.').last
      type = 'jpeg' if type == 'jpg'
      text << "   <item href=\"Images/#{entry}\" id=\"#{entry}\" media-type=\"image/#{type}\" />"
    end
    list_dir("Text").each do |entry|
      text << "   <item href=\"Text/#{entry}\" id=\"#{entry.split('.').first}\" media-type=\"application/xhtml+xml\" />"
    end

    return "<manifest>\n"+ text.join("\n") + "\n</manifest>"
  end

  def contributers_text
    text = []
    text << '<!-- List of contributors'
    text << 'See: MARC Code List for Relators: http://www.loc.gov/marc/relators/relaterm.html'
    text << 'Examples: '
    text << '* Editor [edt]'
    text << 'Use for a person or organization who prepares for publication a work not primarily his/her own,'
    text << 'such as by elucidating text, adding introductory or other critical matter, or technically directing'
    text << 'an editorial staff.'
    text << '* Cover designer [cov]'
    text << 'Use for a person or organization responsible for the graphic design of a book cover,'
    text << 'album cover, slipcase, box, container, etc. For a person or organization responsible '
    text << 'for the graphic design of an entire book, use Book designer; for book jackets, use Bookjacket designer.'
    text << '* Translator [trl]'
    text << 'Use for a person or organization who renders a text from one language into another, or from an older '
    text << 'form of a language into the modern form.'
    text << '-->'
    text << '<!--'
    text << '<dc:contributor opf:file-as="[LASTNAME, NAME]" opf:role="edt">[NAME LASTNAME]</dc:contributor>'
    text << '<dc:contributor opf:file-as="[LASTNAME, NAME]" opf:role="cov">[NAME LASTNAME]</dc:contributor>'
    text << '-->'
    text.join("\n")
  end

  def spine_text
    text = []
    # <!-- SPINE (mandatory)'
    # The spine element defines the default reading order of the content. '
    # It does not list every file in the manifest, just the reading order.'
    # The value of the idref tag in the spine has to match the ID tag for that entry in the manifest.'
    # For example, if you have the following reference in your manifest:'
    # <item id="chapter-1" href="chapter01.xhtml" media-type="application/xhtml+xml" />'
    # your spine entry would be:'
    # <itemref idref="chapter-1" />'
    # http://idpf.org/epub/20/spec/OPF_2.0.1_draft.htm#Section2.4'
    # -->'
    text << '<spine toc="ncx">'
    text << '  <itemref idref="cover" />'
    text << '  <itemref idref="toc" />'
    @content.keys.each do |div_id|
      text << "  <itemref idref=\"#{div_id}\" />"
    end
    text << '</spine>'
    text.join("\n")
  end

  GUIDE_ROLES_MAP = Hash[guide_roles.zip(guide_roles)]
  def guide_text

    # <!-- GUIDE (optional, recommended by Apple)
    # The guide lets you specify the role of the book's files.
    # Available tags: cover, title-page, toc, index, glossary, acknowledgements, bibliography,
    # colophon, copyright-page, dedication, epigraph, foreword, loi (list of illustrations),
    # lot (list of tables), notes, preface, and text.
    # http://idpf.org/epub/20/spec/OPF_2.0.1_draft.htm#Section2.6
    #  -->

    text = []
    text << '<guide>'

    list_dir("Text").each do |entry|
      name = entry.split('.').first
      type = GUIDE_ROLES_MAP.fetch(name, 'text')
      text << "  <reference href=\"Text/#{entry}\" title=\"#{name.titlecase}\" type=\"#{type}\" />"
    end

    text << '</guide>'
    text.join("\n")
  end

  def create_content_opf
    text = []
    text << '<?xml version="1.0" encoding="utf-8" standalone="yes"?>'
    text << '<package xmlns="http://www.idpf.org/2007/opf" unique-identifier="bookid" version="2.0" xmlns:dc="http://purl.org/dc/elements/1.1/">'
      text << '<metadata xmlns:opf="http://www.idpf.org/2007/opf" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">'
        text << "  <dc:identifier id=\"bookid\" opf:scheme=\"ISBN\">urn:isbn:#{@isbn}</dc:identifier>"
        text << "  <dc:title>#{@book_title}</dc:title>"
        text << "  <dc:rights>Copyright © #{Date.current.year} #{@author_name}. All rights reserved.</dc:rights>"
        text << "  <dc:subject>#{@subject_classification}</dc:subject>"
        text << "  <dc:creator opf:file-as=\"#{@author_name}\" opf:role=\"aut\">#{@author_name}</dc:creator>"
        text << '  <dc:source>https://calypso.net</dc:source>'
        # text << contributers_text
        text << "  <dc:publisher>#{ @publisher }</dc:publisher>"
        text << "  <dc:date opf:event=\"publication\">#{ Date.current }</dc:date>"
        text << '  <dc:language>en</dc:language>' #http://en.wikipedia.org/wiki/List_of_ISO_639-2_codes
        text << "  <dc:identifier opf:scheme=\"UUID\">urn:uuid:#{ SecureRandom.uuid }</dc:identifier>"
        text << "  <meta name=\"cover\" content=\"#{@cover_file_name}\" />"
      text << '</metadata>'
      text << manifest_text
      text << spine_text
      text << guide_text
    text << '</package>'

    File.open('content.opf', 'w') { |file| file.write(text.join("\n")) }
  end

  def create_toc_ncx
    text = []
    text << '<?xml version="1.0" encoding="UTF-8" standalone="no" ?>'
    text << '<!DOCTYPE ncx PUBLIC "-//NISO//DTD ncx 2005-1//EN" "http://www.daisy.org/z3986/2005/ncx-2005-1.dtd">'
    text << '<ncx xmlns="http://www.daisy.org/z3986/2005/ncx/" version="2005-1">'
    text << '<head>'
    text << "<meta content=\"urn:isbn:#{@isbn}\" name=\"dtb:uid\"/>"
    text << '<meta content="1" name="dtb:depth"/>'
    text << '<meta content="0" name="dtb:totalPageCount"/>'
    text << '<meta content="0" name="dtb:maxPageNumber"/>'
    text << '</head>'
    text << "<docTitle><text>#{@book_title}</text></docTitle>"
    text << '<navMap>'

    text << '<navPoint id="navpoint-cover"><navLabel><text>Cover</text></navLabel><content src="Text/cover.xhtml" /></navPoint>'

    @content.each do |div_id, title|
      text << "<navPoint id=\"#{div_id}\"><navLabel><text>#{title}</text></navLabel><content src=\"Text/#{div_id}.xhtml\" /></navPoint>"
    end

    text << '</navMap>'
    text << '</ncx>'

    File.open('toc.ncx', 'w') { |file| file.write(text.join("\n")) }
  end

  def create_toc_html
    text = []
    text << '<?xml version="1.0" encoding="utf-8" standalone="no"?>'
    text << '<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.1//EN"'
    text << '"http://www.w3.org/TR/xhtml11/DTD/xhtml11.dtd">'
    text << '<html xmlns="http://www.w3.org/1999/xhtml">'
    text << '<head>'
    text << " <title>#{@table_of_contents_title}</title>"
    text << ' <link href="../Styles/style.css" rel="stylesheet" type="text/css" />'
    text << '</head>'
    text << '<body>'
    text << ' <div id="toc" xml:lang="en-US">'
    text << " <h1>#{@table_of_contents_title}</h1>"
    text << ' <ul>'

    @content.each do |div_id, title|
      text << "  <li><a href=\"../Text/#{div_id}.xhtml\"><span>#{title}</span></a></li>"
    end

    text << ' </ul>'
    text << '</div></body></html>'

    File.open('toc.xhtml', 'w') { |file| file.write(text.join("\n")) }
  end
end

__END__

def example_use
  Dir.chdir("TMP") do
    EpubGenerator.generate { |service|
      service.book_title = "Daves Grand Adventure"
      service.table_of_contents_title = "Steps into the future"
      service.style = "h2{color: red}"
      service.style << "h2{background-color: blue}"
      service.add_chapter('chap_1', "Chapter 1", "<h2>Hello</h2>From the <i>overworld</i>.")
      service.add_image('cover.jpeg', 'https://images.unsplash.com/photo-1546146477-15a587cd3fcb?ixlib=rb-1.2.1&ixid=eyJhcHBfaWQiOjEyMDd9&auto=format&fit=crop&w=564&q=80' )
      service.cover_file_name = 'cover.jpeg'
    }
  end
end

example_use