require "optparse"
require "uri"
require "epub/parser"

def main(argv)
  option_parser = OptionParser.new {|opt|
    opt.banner = <<EOB
Extract cover image.
Image is put to current directory with the same name in EPUB.
It is put to specified directory when `--output' option is given.

Usage: #{opt.program_name} [options] EPUBFILE

EOB
    opt.separator "Options:"
    opt.on "-o", "--output=DIR", "Directory to put image file"
  }
  options = option_parser.getopts(argv)
  path = argv.shift
  error "EPUBFILE not given" unless path
  unless File.file? path
    if File.directory? path
      EPUB::OCF::PhysicalContainer.adapter = :UnpackedDirectory
    else
      path = URI.parse(path) rescue nil
      if path
        EPUB::OCF::PhysicalContainer.adapter = :UnpackedURI
      else
        error "EPUBFILE not a file"
      end
    end
  end
  error "output not a directory" if options["output"] && !File.directory?(options["output"])
  cover_image = EPUB::Parser.parse(path).cover_image
  error "cover image not found", option_parser.program_name, option_parser.help unless cover_image
  path = File.basename(cover_image.href.to_s)
  path = File.join(options["output"], path) if options["output"]
  File.write path, cover_image.read
  $stderr.print "Cover image output to "
  print path
  $stderr.puts ""
end

def error(message, program_name, help)
  $stderr.puts "Error: #{message}"
  $stderr.puts ""
  $stderr.puts program_name
  $stderr.puts "=" * program_name.length
  $stderr.puts help
  abort
end

main(ARGV)