Method: Gembuild::GemScraper#gem

Defined in:
lib/gembuild/gem_scraper.rb,
lib/gembuild/gem_scraper.rb

#gem ⇒ String (readonly)

Returns the rubygems URL for the frontend.

Returns:

  • (String) —

    the rubygems URL for the frontend



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# File 'lib/gembuild/gem_scraper.rb', line 35

class GemScraper
  attr_reader :agent, :deps, :gem, :gemname, :url

  # Creates a new GemScraper instance
  #
  # @raise [Gembuild::UndefinedGemName] if the gemname is nil or empty
  #
  # @example Create a new GemScraper object
  #   Gembuild::GemScraper.new('mina')
  #   # => #<Gembuild::GemScraper:0x00000002f8a500
  #   #  @agent=
  #   #   #<Mechanize
  #   #    #<Mechanize::CookieJar:0x00000002f8a410
  #   #     @store=
  #   #      #<HTTP::CookieJar::HashStore:0x00000002f8a370
  #   #       @gc_index=0,
  #   #       @gc_threshold=150,
  #   #       @jar={},
  #   #       @logger=nil,
  #   #       @mon_count=0,
  #   #       @mon_mutex=#<Mutex:0x00000002f8a320>,
  #   #       @mon_owner=nil>>
  #   #    nil>,
  #   #  @deps="https://rubygems.org/api/v1/dependencies?gems=mina",
  #   #  @gem="https://rubygems.org/gems/mina",
  #   #  @gemname="mina",
  #   #  @url="https://rubygems.org/api/v1/versions/mina.json">
  #
  # @param gemname [String] The gem about which to query.
  # @return [Gembuild::GemScraper] a new GemScraper instance
  def initialize(gemname)
    fail Gembuild::UndefinedGemNameError if gemname.nil? || gemname.empty?

    @gemname = gemname
    @agent = Mechanize.new

    @url = "https://rubygems.org/api/v1/versions/#{gemname}.json"
    @deps = "https://rubygems.org/api/v1/dependencies?gems=#{gemname}"
    @gem = "https://rubygems.org/gems/#{gemname}"
  end

  # Query the rubygems version api for the latest version.
  #
  # @raise [Gembuild::GemNotFoundError] if the page returns a 404 (not
  #   found) error.
  #
  # @example Query rubygems.org for version information
  #   s = Gembuild::GemScraper.new('mina')
  #   s.query_latest_version
  #   # => {:authors=>"Rico Sta. Cruz, Michael Galero",
  #   #  :built_at=>"2015-07-08T00:00:00.000Z",
  #   #  :created_at=>"2015-07-08T13:13:33.292Z",
  #   #  :description=>"Really fast deployer and server automation tool.",
  #   #  :downloads_count=>18709,
  #   #  :metadata=>{},
  #   #  :number=>"0.3.7",
  #   #  :summary=>"Really fast deployer and server automation tool.",
  #   #  :platform=>"ruby",
  #   #  :ruby_version=>">= 0",
  #   #  :prerelease=>false,
  #   #  :licenses=>[],
  #   #  :requirements=>[],
  #   #  :sha=>
  #   #   "bd1fa2b56ed1aded882a12f6365a04496f5cf8a14c07f8c4f1f3cfc944ef34f6"
  #   # }
  #
  # @return [Hash] the information about the latest version of the gem
  def query_latest_version
    response = JSON.parse(agent.get(url).body, symbolize_names: true)

    # Skip any release marked as a "prerelease"
    response.shift while response.first[:prerelease]

    response.first
  rescue Mechanize::ResponseCodeError, Net::HTTPNotFound
    raise Gembuild::GemNotFoundError
  end

  # Gets the version number from the parsed response.
  #
  # @param response [Hash] The JSON parsed results from rubygems.org.
  # @return [Gem::Version] the current version of the gem
  def get_version_from_response(response)
    Gem::Version.new(response.fetch(:number))
  end

  # Gets a well-formed gem description from the parsed response.
  #
  # @param response [Hash] The JSON parsed results from rubygems.org.
  # @return [String] the gem description or summary ending in a full-stop
  def format_description_from_response(response)
    description = response.fetch(:description)
    description = response.fetch(:summary) if description.empty?

    # Replace any newlines or tabs (which would mess up a PKGBUILD) with
    # spaces. Then, make sure there is no
    description = description.gsub(/[[:space:]]+/, ' ').strip

    # Ensure that the description ends in a full-stop.
    description += '.' unless description[-1, 1] == '.'

    description
  end

  # Gets the sha256 checksum returned from the rubygems.org API.
  #
  # @param response [Hash] The JSON parsed results from rubygems.org.
  # @return [String] the sha256 sum of the gem file
  def get_checksum_from_response(response)
    response.fetch(:sha)
  end

  # Get the array of licenses under which the gem is licensed.
  #
  # @param response [Hash] The JSON parsed results from rubygems.org.
  # @return [Array] the licenses for the gem
  def get_licenses_from_response(response)
    response.fetch(:licenses)
  end

  # Get all other gem dependencies for the given version.
  #
  # @param version [String|Gem::Version] The version for which to get the
  #   dependencies.
  # @return [Array] list of other gems upon which the gem depends
  def get_dependencies_for_version(version)
    version = Gem::Version.new(version) if version.is_a?(String)

    payload = Marshal.load(agent.get(deps).body)

    dependencies = payload.find do |v|
      Gem::Version.new(v[:number]) == version
    end

    dependencies[:dependencies].map(&:first)
  end

  # Scrape the rubygems.org frontend for the gem's homepage URL.
  #
  # @return [String] the homepage URL of the gem
  def scrape_frontend_for_homepage_url
    html = agent.get(gem).body
    links = Nokogiri::HTML(html).css('a')

    homepage_link = links.find do |a|
      a.text.strip == 'Homepage'
    end

    homepage_link[:href]
  end

  # Quick method to get all important information in a single hash for
  # later processing.
  #
  # @return [Hash] hash containing all the information available from the
  #   rubygems.org APIs and website
  def scrape!
    response = query_latest_version
    version = get_version_from_response(response)

    {
      version: version,
      description: format_description_from_response(response),
      checksum: get_checksum_from_response(response),
      license: get_licenses_from_response(response),
      dependencies: get_dependencies_for_version(version),
      homepage: scrape_frontend_for_homepage_url
    }
  end
end