class Gem::Source::Local

def download(spec, cache_dir=nil)
  load_specs :complete
  @specs.each do |name, data|
    return data[0] if data[1].spec == spec
  end
  raise Gem::Exception, "Unable to find file for '#{spec.full_name}'"
end

def fetch_spec(name)
  load_specs :complete
  if data = @specs[name]
    data.last.spec
  else
    raise Gem::Exception, "Unable to find spec for '#{name}'"
  end
end

def find_gem(gem_name, version=Gem::Requirement.default,
             prerelease=false)
  load_specs :complete
  found = []
  @specs.each do |n, data|
    if n.name == gem_name
      s = data[1].spec
      if version.satisfied_by?(s.version)
        if prerelease
          found << s
        elsif !s.version.prerelease?
          found << s
        end
      end
    end
  end
  found.sort_by { |s| s.version }.last
end

def initialize
  @uri = nil
end

def load_specs(type)
  names = []
  @specs = {}
  Dir["*.gem"].each do |file|
    begin
      pkg = Gem::Package.new(file)
    rescue SystemCallError, Gem::Package::FormatError
      # ignore
    else
      tup = pkg.spec.name_tuple
      @specs[tup] = [File.expand_path(file), pkg]
      case type
      when :released
        unless pkg.spec.version.prerelease?
          names << pkg.spec.name_tuple
        end
      when :prerelease
        if pkg.spec.version.prerelease?
          names << pkg.spec.name_tuple
        end
      when :latest
        tup = pkg.spec.name_tuple
        cur = names.find { |x| x.name == tup.name }
        if !cur
          names << tup
        elsif cur.version < tup.version
          names.delete cur
          names << tup
        end
      else
        names << pkg.spec.name_tuple
      end
    end
  end
  names
end