1 files changed, 96 insertions, 0 deletions
diff --git a/lib/bundler/compact_index_client/cache.rb b/lib/bundler/compact_index_client/cache.rb
new file mode 100644
index 0000000000..3bae6c9efd
--- /dev/null
+++ b/lib/bundler/compact_index_client/cache.rb
@@ -0,0 +1,96 @@
+# frozen_string_literal: true
+
+require "rubygems/resolver/api_set/gem_parser"
+
+module Bundler
+  class CompactIndexClient
+    class Cache
+      attr_reader :directory
+
+      def initialize(directory, fetcher = nil)
+        @directory = Pathname.new(directory).expand_path
+        @updater = Updater.new(fetcher) if fetcher
+        @mutex = Thread::Mutex.new
+        @endpoints = Set.new
+
+        @info_root = mkdir("info")
+        @special_characters_info_root = mkdir("info-special-characters")
+        @info_etag_root = mkdir("info-etags")
+      end
+
+      def names
+        fetch("names", names_path, names_etag_path)
+      end
+
+      def versions
+        fetch("versions", versions_path, versions_etag_path)
+      end
+
+      def info(name, remote_checksum = nil)
+        path = info_path(name)
+
+        if remote_checksum && remote_checksum != SharedHelpers.checksum_for_file(path, :MD5)
+          fetch("info/#{name}", path, info_etag_path(name))
+        else
+          Bundler::CompactIndexClient.debug { "update skipped info/#{name} (#{remote_checksum ? "versions index checksum is nil" : "versions index checksum matches local"})" }
+          read(path)
+        end
+      end
+
+      def reset!
+        @mutex.synchronize { @endpoints.clear }
+      end
+
+      private
+
+      def names_path = directory.join("names")
+      def names_etag_path = directory.join("names.etag")
+      def versions_path = directory.join("versions")
+      def versions_etag_path = directory.join("versions.etag")
+
+      def info_path(name)
+        name = name.to_s
+        # TODO: converge this into the info_root by hashing all filenames like info_etag_path
+        if /[^a-z0-9_-]/.match?(name)
+          name += "-#{SharedHelpers.digest(:MD5).hexdigest(name).downcase}"
+          @special_characters_info_root.join(name)
+        else
+          @info_root.join(name)
+        end
+      end
+
+      def info_etag_path(name)
+        name = name.to_s
+        @info_etag_root.join("#{name}-#{SharedHelpers.digest(:MD5).hexdigest(name).downcase}")
+      end
+
+      def mkdir(name)
+        directory.join(name).tap do |dir|
+          SharedHelpers.filesystem_access(dir) do
+            FileUtils.mkdir_p(dir)
+          end
+        end
+      end
+
+      def fetch(remote_path, path, etag_path)
+        if already_fetched?(remote_path)
+          Bundler::CompactIndexClient.debug { "already fetched #{remote_path}" }
+        else
+          Bundler::CompactIndexClient.debug { "fetching #{remote_path}" }
+          @updater&.update(remote_path, path, etag_path)
+        end
+
+        read(path)
+      end
+
+      def already_fetched?(remote_path)
+        @mutex.synchronize { !@endpoints.add?(remote_path) }
+      end
+
+      def read(path)
+        return unless path.file?
+        SharedHelpers.filesystem_access(path, :read, &:read)
+      end
+    end
+  end
+end