require 'rubygems'
require 'rubygems/dependency_list'
require 'rubygems/installer'
require 'rubygems/source_info_cache'
require 'rubygems/user_interaction'

class Gem::DependencyInstaller

  include Gem::UserInteraction

  attr_reader :gems_to_install
  attr_reader :installed_gems

  DEFAULT_OPTIONS = {
    :env_shebang => false,
    :domain => :both, # HACK dup
    :force => false,
    :ignore_dependencies => false,
    :security_policy => Gem::Security::NoSecurity, # HACK AlmostNo? Low?
    :wrappers => true
  }

  ##
  # Creates a new installer instance that will install +gem_name+ using
  # version requirement +version+ and +options+.
  #
  # Options are:
  # :env_shebang:: See Gem::Installer::new.
  # :domain:: :local, :remote, or :both.  :local only searches gems in the
  #           current directory.  :remote searches only gems in Gem::sources.
  #           :both searches both.
  # :force:: See Gem::Installer#install.
  # :ignore_dependencies: Don't install any dependencies.
  # :install_dir: See Gem::Installer#install.
  # :security_policy: See Gem::Installer::new and Gem::Security.
  # :wrappers: See Gem::Installer::new
  def initialize(gem_name, version = nil, options = {})
    options = DEFAULT_OPTIONS.merge options
    @env_shebang = options[:env_shebang]
    @domain = options[:domain]
    @force = options[:force]
    @ignore_dependencies = options[:ignore_dependencies]
    @install_dir = options[:install_dir] || Gem.dir
    @security_policy = options[:security_policy]
    @wrappers = options[:wrappers]

    @installed_gems = []

    spec_and_source = nil

    local_gems = Dir["#{gem_name}*"].sort.reverse
    unless local_gems.empty? then
      local_gems.each do |gem_file|
        next unless gem_file =~ /gem$/
        begin
          spec = Gem::Format.from_file_by_path(gem_file).spec
          spec_and_source = [spec, gem_file]
          break
        rescue SystemCallError, Gem::Package::FormatError
        end
      end
    end

    if spec_and_source.nil? then
      version ||= Gem::Requirement.default
      @dep = Gem::Dependency.new gem_name, version
      spec_and_sources = find_gems_with_sources(@dep).reverse

      spec_and_source = spec_and_sources.find do |spec, source|
        Gem::Platform.match spec.platform
      end
    end

    if spec_and_source.nil? then
      raise Gem::GemNotFoundException,
        "could not find #{gem_name} locally or in a repository"
    end

    @specs_and_sources = [spec_and_source]

    gather_dependencies
  end

  ##
  # Returns a list of pairs of gemspecs and source_uris that match
  # Gem::Dependency +dep+ from both local (Dir.pwd) and remote (Gem.sources)
  # sources.  Gems are sorted with newer gems prefered over older gems, and
  # local gems prefered over remote gems.
  def find_gems_with_sources(dep)
    gems_and_sources = []

    if @domain == :both or @domain == :local then
      Dir[File.join(Dir.pwd, "#{dep.name}-[0-9]*.gem")].each do |gem_file|
        spec = Gem::Format.from_file_by_path(gem_file).spec
        gems_and_sources << [spec, gem_file] if spec.name == dep.name
      end
    end

    if @domain == :both or @domain == :remote then
      gems_and_sources.push(*Gem::SourceInfoCache.search_with_source(dep, true))
    end

    gems_and_sources.sort_by do |gem, source|
      [gem, source !~ /^http:\/\// ? 1 : 0] # local gems win
    end
  end

  ##
  # Moves the gem +spec+ from +source_uri+ to the cache dir unless it is
  # already there.  If the source_uri is local the gem cache dir copy is
  # always replaced.
  def download(spec, source_uri)
    gem_file_name = "#{spec.full_name}.gem"
    local_gem_path = File.join @install_dir, 'cache', gem_file_name

    Gem.ensure_gem_subdirectories @install_dir

    source_uri = URI.parse source_uri unless URI::Generic === source_uri
    scheme = source_uri.scheme

    # URI.parse gets confused by MS Windows paths with forward slashes.
    scheme = nil if scheme =~ /^[a-z]$/i

    case scheme
    when 'http' then
      unless File.exist? local_gem_path then
        begin
          say "Downloading gem #{gem_file_name}" if
            Gem.configuration.really_verbose

          remote_gem_path = source_uri + "gems/#{gem_file_name}"

          gem = Gem::RemoteFetcher.fetcher.fetch_path remote_gem_path
        rescue Gem::RemoteFetcher::FetchError
          raise if spec.original_platform == spec.platform

          alternate_name = "#{spec.name}-#{spec.version}-#{spec.original_platform}.gem"

          say "Failed, downloading gem #{alternate_name}" if
            Gem.configuration.really_verbose

          remote_gem_path = source_uri + "gems/#{alternate_name}"

          gem = Gem::RemoteFetcher.fetcher.fetch_path remote_gem_path
        end

        File.open local_gem_path, 'wb' do |fp|
          fp.write gem
        end
      end
    when nil, 'file' then # TODO test for local overriding cache
      begin
        FileUtils.cp source_uri.to_s, local_gem_path
      rescue Errno::EACCES
        local_gem_path = source_uri.to_s
      end

      say "Using local gem #{local_gem_path}" if
        Gem.configuration.really_verbose
    else
      raise Gem::InstallError, "unsupported URI scheme #{source_uri.scheme}"
    end

    local_gem_path
  end

  ##
  # Gathers all dependencies necessary for the installation from local and
  # remote sources unless the ignore_dependencies was given.
  def gather_dependencies
    specs = @specs_and_sources.map { |spec,_| spec }

    dependency_list = Gem::DependencyList.new
    dependency_list.add(*specs)

    unless @ignore_dependencies then
      to_do = specs.dup
      seen = {}

      until to_do.empty? do
        spec = to_do.shift
        next if spec.nil? or seen[spec.name]
        seen[spec.name] = true

        spec.dependencies.each do |dep|
          results = find_gems_with_sources(dep).reverse # local gems first

          results.each do |dep_spec, source_uri|
            next if seen[dep_spec.name]
            @specs_and_sources << [dep_spec, source_uri]
            dependency_list.add dep_spec
            to_do.push dep_spec
          end
        end
      end
    end

    @gems_to_install = dependency_list.dependency_order.reverse
  end

  ##
  # Installs the gem and all its dependencies.
  def install
    spec_dir = File.join @install_dir, 'specifications'
    source_index = Gem::SourceIndex.from_gems_in spec_dir

    @gems_to_install.each do |spec|
      last = spec == @gems_to_install.last
      # HACK is this test for full_name acceptable?
      next if source_index.any? { |n,_| n == spec.full_name } and not last

      say "Installing gem #{spec.full_name}" if Gem.configuration.really_verbose

      _, source_uri = @specs_and_sources.assoc spec
      local_gem_path = download spec, source_uri

      inst = Gem::Installer.new local_gem_path,
                                :env_shebang => @env_shebang,
                                :force => @force,
                                :ignore_dependencies => @ignore_dependencies,
                                :install_dir => @install_dir,
                                :security_policy => @security_policy,
                                :wrappers => @wrappers

      spec = inst.install

      @installed_gems << spec
    end
  end

end