require "nokogiri"

module BibTeX
  class Bibliography
    attr_accessor :filepath

    class << self
      def trim_unnecessary_entries!(bib, citekeys)
        bib.entries.each do |k,v|
          if !citekeys.include? k 
            bib.delete(k)
          end
        end
      end

      def from_bcf(path)
        File.open(path, "r") do |f|
          @bcf = Nokogiri::XML(f).remove_namespaces!
        end
        filepath = File.dirname(path) + "/" + @bcf.at_xpath("//datasource").content
        citekeys = @bcf.xpath("//citekey", 'bcf'=>'URI').map(&:content)
        bib = open(filepath, :filter => 'latex')
        bib.filepath = filepath
        trim_unnecessary_entries!(bib, citekeys)
        bib.sort! { |a,b| a.author <=> b.author }
        bib.extend(BibtexMunge)
        bib.fix_everything!
        return bib
      end  
    end
  end
end