#!/usr/bin/env ruby-2.3

unless `which kindlerb` 
  abort "Please gem install kindlerb"
end

require 'nokogiri'
require 'fileutils'
require 'yaml'
require 'date'

module Kindle
  extend self

  def generate(output_dir, mobi_outfile, logfile)
    output_dir = File.absolute_path(output_dir)
    Dir.chdir output_dir do 
      puts "=> Using output dir: #{output_dir}"
      puts "=> Arranging html pages in document order"
      toc = File.read("toc.ncx")
      doc = Nokogiri::XML(toc).xpath("//ncx:content", 'ncx' => "http://www.daisy.org/z3986/2005/ncx/")
      html_pages = doc.select {|c| c[:src]}.map {|c| c[:src]}.uniq
     
      generate_front_matter(html_pages)

      generate_sections(html_pages)

      generate_document_metadata(mobi_outfile)

      puts "Creating MOBI document with kindlegen. This make take a while."
      cmd = "kindlerb . > #{File.absolute_path logfile} 2>&1"
      puts cmd
      system(cmd)
      puts "MOBI document generated at #{File.expand_path(mobi_outfile, output_dir)}"
    end
  end

  def generate_front_matter(html_pages)
    frontmatter = []
    html_pages.delete_if {|x| 
      if x =~ /(toc|welcome|credits|copyright).html/
        frontmatter << x unless x =~ /toc/
        true
      end
    }
    html = frontmatter.map {|x|
      Nokogiri::HTML(File.open(x)).at("body").inner_html
    }.join("\n")

    fdoc = Nokogiri::HTML(html)
    fdoc.search("h3").each do |h3|
      h3.name = 'h4'
    end
    fdoc.search("h2").each do |h2| 
      h2.name = 'h3'
      h2['id'] = h2.inner_text.gsub(/\s/, '-')
    end
    add_head_section fdoc, "Front Matter"
    File.open("frontmatter.html",'w') {|f| f.puts fdoc.to_html}
    html_pages.unshift "frontmatter.html"
  end

  def generate_sections(html_pages)
    FileUtils::rm_rf("sections/")
    html_pages.each_with_index do |page, section_idx|
      FileUtils::mkdir_p("sections/%03d" % section_idx)
      doc = Nokogiri::HTML(File.open(page))
      title = doc.at("title").inner_text.gsub("Ruby on Rails Guides: ", '')
      title = page.capitalize.gsub('.html', '') if title.strip == ''
      File.open("sections/%03d/_section.txt" % section_idx, 'w') {|f| f.puts title}
      doc.xpath("//h3[@id]").each_with_index do |h3,item_idx|
        subsection = h3.inner_text
        content = h3.xpath("./following-sibling::*").take_while {|x| x.name != "h3"}.map {|x| x.to_html}
        item = Nokogiri::HTML(h3.to_html + content.join("\n"))
        item_path = "sections/%03d/%03d.html" % [section_idx, item_idx] 
        add_head_section(item, subsection)
        item.search("img").each do |img|
          img['src'] = "#{Dir.pwd}/#{img['src']}"
        end
        item.xpath("//li/p").each {|p| p.swap(p.children); p.remove}
        File.open(item_path, 'w') {|f| f.puts item.to_html}
      end
    end
  end

  def generate_document_metadata(mobi_outfile)
    puts "=> Generating _document.yml"
    x = Nokogiri::XML(File.open("rails_guides.opf")).remove_namespaces!
    cover_jpg = "#{Dir.pwd}/images/rails_guides_kindle_cover.jpg"
    cover_gif = cover_jpg.sub(/jpg$/, 'gif')
    puts `convert #{cover_jpg} #{cover_gif}`
    document = {
      'doc_uuid' => x.at("package")['unique-identifier'],
      'title' => x.at("title").inner_text.gsub(/\(.*$/, " v2"),
      'publisher' => x.at("publisher").inner_text,
      'author' => x.at("creator").inner_text,
      'subject' => x.at("subject").inner_text,
      'date' => x.at("date").inner_text,
      'cover' => cover_gif,
      'masthead' => nil,
      'mobi_outfile' => mobi_outfile
    }
    puts document.to_yaml
    File.open("_document.yml", 'w'){|f| f.puts document.to_yaml}
  end

  def add_head_section(doc, title)
    head = Nokogiri::XML::Node.new "head", doc
    title_node = Nokogiri::XML::Node.new "title", doc
    title_node.content = title
    title_node.parent = head
    css = Nokogiri::XML::Node.new "link", doc
    css['rel'] = 'stylesheet'
    css['type'] = 'text/css'
    css['href'] = "#{Dir.pwd}/stylesheets/kindle.css"
    css.parent = head
    doc.at("body").before head
  end
end
