support fetch builds from repo

lib/one_gadget/gadget.rb

@@ -45,11 +45,14 @@ module OneGadget
         require_all if BUILDS.empty?
         return BUILDS[build_id] if BUILDS.key?(build_id)
         # fetch remote builds
-        # table = OneGadget::Helper.remote_builds.find { |c| c.include?(build_id) }
+        table = OneGadget::Helper.remote_builds.find { |c| c.include?(build_id) }
-        # return [] if table.nil? # remote doesn't have this one.
+        return [] if table.nil? # remote doesn't have this one either.
         # builds found in remote! Ask update gem and download remote gadgets.
-        # TODO: fetch remote builds information.
+        OneGadget::Helper.ask_update(msg: 'The desired one-gadget can be found in lastest version!')
-        []
+        tmp_file = OneGadget::Helper.download_build(table)
+        require tmp_file.path
+        tmp_file.unlink
+        BUILDS[build_id]
       end
 
       # Add a gadget, for scripts in builds/ to use.

lib/one_gadget/helper.rb

@@ -1,5 +1,8 @@
 require 'pathname'
 require 'shellwords'
+require 'net/http'
+require 'openssl'
+require 'tempfile'
 
 module OneGadget
   # Define some helpful methods here.
@@ -60,6 +63,65 @@ module OneGadget
         color = cc.key?(sev) ? cc[sev] : ''
         "#{color}#{str.sub(cc[:esc_m], color)}#{cc[:esc_m]}"
       end
+
+      # Fetch the latest release version's tag name.
+      # @return [String] The tag name, in form +vx.x.x+.
+      def latest_tag
+        latest = url_request('https://github.com/david942j/one_gadget/releases').scan(%r{/tree/v([\d.]+)"}).map do |tag|
+          Gem::Version.new(tag.first)
+        end.max.to_s
+        'v' + latest
+      end
+
+      # Get the url which can fetch +filename+ from remote repo.
+      # @param [String] filename
+      # @return [String] The url.
+      def url_of_file(filename)
+        raw_file_url = 'https://raw.githubusercontent.com/david942j/one_gadget/@tag/@file'
+        raw_file_url.gsub('@tag', latest_tag).gsub('@file', filename)
+      end
+
+      # Download the latest version of +file+ in +lib/one_gadget/builds/+ from remote repo.
+      #
+      # @param [String] file The filename desired.
+      # @return [Tempfile] The temp file be created.
+      def download_build(file)
+        temp = Tempfile.new(['gadgets', file + '.rb'])
+        url_request(url_of_file(File.join('lib', 'one_gadget', 'builds', file + '.rb')))
+        temp.write url_request(url_of_file(File.join('lib', 'one_gadget', 'builds', file + '.rb')))
+        temp.close
+        temp
+      end
+
+      # Get the latest builds list from repo.
+      # @return [Array<String>] List of build ids.
+      def remote_builds
+        url_request(url_of_file('builds_list')).lines.map(&:strip)
+      end
+
+      # Get request.
+      # @param [String] url The url.
+      # @return [String] The request response body.
+      def url_request(url)
+        # TODO: add timeout to handle github crashed or in no network environment.
+        uri = URI.parse(url)
+        http = Net::HTTP.new(uri.host, uri.port)
+        http.use_ssl = true
+        http.verify_mode = ::OpenSSL::SSL::VERIFY_NONE
+
+        request = Net::HTTP::Get.new(uri.request_uri)
+
+        response = http.request(request)
+        response.body
+      end
+
+      # Show the message of ask user to update gem.
+      # @return [void]
+      def ask_update(msg: '')
+        name = 'one_gadget'
+        cmd = colorize("gem update #{name}")
+        STDERR.puts msg + "\n" + "Update with: $ #{cmd}"
+      end
     end
     extend ClassMethods
   end

spec/gadget_spec.rb

@@ -7,6 +7,10 @@ describe OneGadget::Gadget do
     OneGadget::Gadget.add(@build_id, 0x1234, constraints: ['[rsp+0x30] == NULL', 'rax == 0'])
   end
 
+  after(:all) do
+    OneGadget::Gadget::ClassMethods::BUILDS.delete @build_id
+  end
+
   it 'inspect' do
     expect(OneGadget::Gadget.builds(@build_id).map(&:inspect).join).to eq <<-EOS
 offset: 0x1234

spec/one_gadget_spec.rb

@@ -1,9 +1,7 @@
 require 'one_gadget'
 
 describe 'one_gadget' do
-  before(:all) do
+  before(:each) do
-    # To force require all again.
-    OneGadget::Gadget::ClassMethods::BUILDS.clear
     @build_id = '60131540dadc6796cab33388349e6e4e68692053'
     @libcpath = File.join(File.dirname(__FILE__), 'data', 'libc-2.19.so')
   end
@@ -21,5 +19,13 @@ describe 'one_gadget' do
     it 'invalid' do
       expect { OneGadget.gadgets(build_id: '^_^') }.to raise_error(ArgumentError, 'invalid BuildID format: "^_^"')
     end
+
+    it 'fetch from remote' do
+      entry = OneGadget::Gadget::ClassMethods::BUILDS.delete(@build_id)
+      OneGadget::Gadget::ClassMethods::BUILDS[:a] = 1
+      expect(OneGadget.gadgets(build_id: @build_id)).not_to be_empty
+      OneGadget::Gadget::ClassMethods::BUILDS.delete(:a)
+      OneGadget::Gadget::ClassMethods::BUILDS[@build_id] = entry unless entry.nil?
+    end
   end
 end