# frozen_string_literal: true

require 'zip'

require_relative 'bookspec_generator'
require_relative 'opf_file'
require_relative 'nav_file'
require_relative 'encryption_handler'

module Epuber
  class FromFileExecutor
    MIMETYPE_PATH = 'mimetype'

    ENCRYPTION_PATH = 'META-INF/encryption.xml'
    CONTAINER_PATH = 'META-INF/container.xml'

    # @param [String] filepath path to EPUB file
    #
    def initialize(filepath)
      @filepath = filepath
    end

    def run
      UI.info "📖 Loading EPUB file #{@filepath}"

      Zip::File.open(@filepath) do |zip_file|
        @zip_file = zip_file

        validate_mimetype

        @opf_path = content_opf_path
        UI.info "  Parsing OPF file at #{@opf_path}"
        @opf = OpfFile.new(zip_file.read(@opf_path))

        if zip_file.find_entry(ENCRYPTION_PATH)
          UI.info '  Parsing encryption.xml file'
          @encryption_handler = EncryptionHandler.new(zip_file.read(ENCRYPTION_PATH), @opf)
        end

        UI.info '  Generating bookspec file'
        basename = File.basename(@filepath, File.extname(@filepath))
        File.write("#{basename}.bookspec", generate_bookspec)

        export_files

        UI.info '' # empty line
        UI.info <<~TEXT.rstrip.ansi.green
          🎉 Project initialized.
          Please review generated #{basename}.bookspec file and start using Epuber.

          For more information about Epuber, please visit https://github.com/epuber-io/epuber/tree/master/docs.
        TEXT
      end
    end

    # @param [Zip::File] zip_file
    #
    # @return [void]
    #
    def validate_mimetype
      entry = @zip_file.find_entry(MIMETYPE_PATH)
      UI.error! "This is not valid EPUB file (#{MIMETYPE_PATH} file is missing)" if entry.nil?

      mimetype = @zip_file.read(entry)

      return if mimetype == 'application/epub+zip'

      UI.error! <<~MSG
        This is not valid EPUB file (#{MIMETYPE_PATH} file does not contain required application/epub+zip, it is #{mimetype} instead)
      MSG
    end

    # @param [Zip::File] zip_file
    #
    # @return [String]
    def content_opf_path
      entry = @zip_file.find_entry(CONTAINER_PATH)
      UI.error! "This is not valid EPUB file (#{CONTAINER_PATH} file is missing)" if entry.nil?

      doc = Nokogiri::XML(@zip_file.read(entry))
      doc.remove_namespaces!

      rootfile = doc.at_xpath('//rootfile')
      if rootfile.nil?
        UI.error! "This is not valid EPUB file (#{CONTAINER_PATH} file does not contain any <rootfile> element)"
      end

      rootfile['full-path']
    end

    # @param [Nokogiri::XML::Document] opf
    # @param [Zip::File] zip_file
    #
    # @return [String]
    def generate_bookspec
      nav_node, nav_mode = @opf.find_nav
      if nav_node
        nav_path = Pathname.new(@opf_path)
                           .dirname
                           .join(nav_node.href)
                           .to_s
        nav = NavFile.new(@zip_file.read(nav_path), nav_mode)
      end

      BookspecGenerator.new(@opf, nav).generate_bookspec
    end

    def export_files
      @opf.manifest_items.each_value do |item|
        # ignore text files which are not in spine
        text_file_extensions = %w[.xhtml .html]
        extension = File.extname(item.href).downcase
        if text_file_extensions.include?(extension) &&
           @opf.spine_items.none? { |spine_item| spine_item.idref == item.id }
          UI.info "  Skipping #{item.href} (not in spine)"
          next
        end

        # ignore ncx file
        if item.media_type == 'application/x-dtbncx+xml'
          UI.info "  Skipping #{item.href} (ncx file)"
          next
        end

        full_path = Pathname.new(@opf_path)
                            .dirname
                            .join(item.href)
                            .to_s

        UI.info "  Exporting #{item.href} (from #{full_path})"

        contents = @zip_file.read(full_path)
        contents = @encryption_handler.process_file(full_path, contents) if @encryption_handler

        FileUtils.mkdir_p(File.dirname(item.href))
        File.write(item.href, contents)
      end
    end
  end
end