module RDoc::RI::Paths

def self.each system = true, site = true, home = true, gems = :latest, *extra_dirs # :yields: directory, type
  return enum_for __method__, system, site, home, gems, *extra_dirs unless
    block_given?
  extra_dirs.each do |dir|
    yield dir, :extra
  end
  yield system_dir,  :system if system
  yield site_dir,    :site   if site
  yield home_dir,    :home   if home and HOMEDIR
  gemdirs(gems).each do |dir|
    yield dir, :gem
  end if gems
  nil
end

def self.gem_dir name, version
  req = Gem::Requirement.new "= #{version}"
  spec = Gem::Specification.find_by_name name, req
  File.join spec.doc_dir, 'ri'
end

def self.gemdirs filter = :latest
  require 'rubygems' unless defined?(Gem)
  ri_paths = {}
  all = Gem::Specification.map do |spec|
    [File.join(spec.doc_dir, 'ri'), spec.name, spec.version]
  end
  if filter == :all then
    gemdirs = []
    all.group_by do |_, name, _|
      name
    end.sort_by do |group, _|
      group
    end.map do |group, items|
      items.sort_by do |_, _, version|
        version
      end.reverse_each do |dir,|
        gemdirs << dir
      end
    end
    return gemdirs
  end
  all.each do |dir, name, ver|
    next unless File.exist? dir
    if ri_paths[name].nil? or ver > ri_paths[name].first then
      ri_paths[name] = [ver, name, dir]
    end
  end
  ri_paths.sort_by { |_, (_, name, _)| name }.map { |k, v| v.last }
rescue LoadError
  []
end

def self.home_dir
  HOMEDIR
end

def self.path(system = true, site = true, home = true, gems = :latest, *extra_dirs)
  path = raw_path system, site, home, gems, *extra_dirs
  path.select { |directory| File.directory? directory }
end

def self.raw_path(system, site, home, gems, *extra_dirs)
  path = []
  each(system, site, home, gems, *extra_dirs) do |dir, type|
    path << dir
  end
  path.compact
end

def self.site_dir
  File.join BASE, 'site'
end

def self.system_dir
  File.join BASE, 'system'
end