1 files changed, 139 insertions, 0 deletions
diff --git a/lib/rubygems/resolver/api_set.rb b/lib/rubygems/resolver/api_set.rb
new file mode 100644
index 0000000000..3f443519d8
--- /dev/null
+++ b/lib/rubygems/resolver/api_set.rb
@@ -0,0 +1,139 @@
+# frozen_string_literal: true
+
+##
+# The global rubygems pool, available via the Compact Index API.
+# Returns instances of APISpecification.
+
+class Gem::Resolver::APISet < Gem::Resolver::Set
+  autoload :GemParser, File.expand_path("api_set/gem_parser", __dir__)
+
+  ##
+  # The URI for the Compact Index API this APISet uses.
+
+  attr_reader :dep_uri # :nodoc:
+
+  ##
+  # The Gem::Source that gems are fetched from
+
+  attr_reader :source
+
+  ##
+  # The corresponding place to fetch gems.
+
+  attr_reader :uri
+
+  ##
+  # Creates a new APISet that will retrieve gems from +uri+ using the Compact
+  # Index API URL +dep_uri+ which is described at
+  # https://guides.rubygems.org/rubygems-org-compact-index-api
+
+  def initialize(dep_uri = "https://index.rubygems.org/info/")
+    super()
+
+    dep_uri = Gem::URI dep_uri unless Gem::URI === dep_uri
+
+    @dep_uri = dep_uri
+    @uri     = dep_uri + ".."
+
+    @data   = Hash.new {|h,k| h[k] = [] }
+    @source = Gem::Source.new @uri
+
+    @to_fetch = []
+  end
+
+  ##
+  # Return an array of APISpecification objects matching
+  # DependencyRequest +req+.
+
+  def find_all(req)
+    res = []
+
+    return res unless @remote
+
+    if @to_fetch.include?(req.name)
+      prefetch_now
+    end
+
+    versions(req.name).each do |ver|
+      if req.dependency.match? req.name, ver[:number], @prerelease
+        res << Gem::Resolver::APISpecification.new(self, ver)
+      end
+    end
+
+    res
+  end
+
+  ##
+  # A hint run by the resolver to allow the Set to fetch
+  # data for DependencyRequests +reqs+.
+
+  def prefetch(reqs)
+    return unless @remote
+    names = reqs.map {|r| r.dependency.name }
+    needed = names - @data.keys - @to_fetch
+
+    @to_fetch += needed
+  end
+
+  def prefetch_now # :nodoc:
+    needed = @to_fetch
+    @to_fetch = []
+
+    needed.sort.each do |name|
+      versions(name)
+    end
+  end
+
+  def pretty_print(q) # :nodoc:
+    q.group 2, "[APISet", "]" do
+      q.breakable
+      q.text "URI: #{@dep_uri}"
+
+      q.breakable
+      q.text "gem names:"
+      q.pp @data.keys
+    end
+  end
+
+  ##
+  # Return data for all versions of the gem +name+.
+
+  def versions(name) # :nodoc:
+    if @data.key?(name)
+      return @data[name]
+    end
+
+    uri = @dep_uri + name
+
+    begin
+      str = Gem::RemoteFetcher.fetcher.fetch_path uri
+    rescue Gem::RemoteFetcher::FetchError
+      @data[name] = []
+    else
+      lines(str).each do |ver|
+        number, platform, dependencies, requirements = parse_gem(ver)
+
+        platform ||= "ruby"
+        dependencies = dependencies.map {|dep_name, reqs| [dep_name, reqs.join(", ")] }
+        requirements = requirements.map {|req_name, reqs| [req_name.to_sym, reqs] }.to_h
+
+        @data[name] << { name: name, number: number, platform: platform, dependencies: dependencies, requirements: requirements }
+      end
+    end
+
+    @data[name]
+  end
+
+  private
+
+  def lines(str)
+    lines = str.split("\n")
+    header = lines.index("---")
+    header ? lines[header + 1..-1] : lines
+  end
+
+  def parse_gem(string)
+    @gem_parser ||= GemParser.new
+    @gem_parser.parse(string)
+  end
+end