class Gem::Resolver::Strategy

# File lib/rubygems/resolver/strategy.rb, line 8
def initialize(source)
  @source = source
  @package_priority_cache = Hash.new {|h, pkg| h[pkg] = {} }

  @version_indexes = Hash.new do |h, k|
    if Gem::PubGrub::Package.root?(k)
      h[k] = { Gem::PubGrub::Package.root_version => 0 }
    else
      h[k] = @source.all_versions_for(k).each.with_index.to_h
    end
  end
end

# File lib/rubygems/resolver/strategy.rb, line 21
def next_package_and_version(unsatisfied)
  package, range = next_term_to_try_from(unsatisfied)
  [package, most_preferred_version_of(package, range)]
end

# File lib/rubygems/resolver/strategy.rb, line 28
def most_preferred_version_of(package, range)
  versions = @source.versions_for(package, range)
  indexes = @version_indexes[package]
  versions.min_by {|version| indexes[version] || Float::INFINITY }
end

# File lib/rubygems/resolver/strategy.rb, line 34
def next_term_to_try_from(unsatisfied)
  unsatisfied.min_by do |package, range|
    @package_priority_cache[package][range] ||= begin
      matching_versions = @source.versions_for(package, range)
      higher_versions = @source.versions_for(package, range.upper_invert)

      [matching_versions.count <= 1 ? 0 : 1, higher_versions.count]
    end
  end
end