require 'rubygems/command'
require 'rubygems/package'
require 'rubygems/installer'
require 'rubygems/version_option'

class Gem::Commands::PristineCommand < Gem::Command

  include Gem::VersionOption

  def initialize
    super 'pristine',
          'Restores installed gems to pristine condition from files located in the gem cache',
          :version => Gem::Requirement.default,
          :extensions => true,
          :extensions_set => false,
          :all => false

    add_option('--all',
               'Restore all installed gems to pristine',
               'condition') do |value, options|
      options[:all] = value
    end

    add_option('--[no-]extensions',
               'Restore gems with extensions',
               'in addition to regular gems') do |value, options|
      options[:extensions_set] = true
      options[:extensions]     = value
    end

    add_option('--only-executables',
               'Only restore executables') do |value, options|
      options[:only_executables] = value
    end

    add_option('-E', '--[no-]env-shebang',
               'Rewrite executables with a shebang',
               'of /usr/bin/env') do |value, options|
      options[:env_shebang] = value
    end

    add_version_option('restore to', 'pristine condition')
  end

  def arguments # :nodoc:
    "GEMNAME       gem to restore to pristine condition (unless --all)"
  end

  def defaults_str # :nodoc:
    '--extensions'
  end

  def description # :nodoc:
    <<-EOF
The pristine command compares an installed gem with the contents of its
cached .gem file and restores any files that don't match the cached .gem's
copy.

If you have made modifications to an installed gem, the pristine command
will revert them.  All extensions are rebuilt and all bin stubs for the gem
are regenerated after checking for modifications.

If the cached gem cannot be found it will be downloaded.

If --no-extensions is provided pristine will not attempt to restore a gem
with an extension.

If --extensions is given (but not --all or gem names) only gems with
extensions will be restored.
    EOF
  end

  def usage # :nodoc:
    "#{program_name} [GEMNAME ...]"
  end

  def execute
    specs = if options[:all] then
              Gem::Specification.map

            # `--extensions` must be explicitly given to pristine only gems
            # with extensions.
            elsif options[:extensions_set] and
                  options[:extensions] and options[:args].empty? then
              Gem::Specification.select do |spec|
                spec.extensions and not spec.extensions.empty?
              end
            else
              get_all_gem_names.map do |gem_name|
                Gem::Specification.find_all_by_name gem_name, options[:version]
              end.flatten
            end

    if specs.to_a.empty? then
      raise Gem::Exception,
            "Failed to find gems #{options[:args]} #{options[:version]}"
    end

    install_dir = Gem.dir # TODO use installer option

    raise Gem::FilePermissionError.new(install_dir) unless
      File.writable?(install_dir)

    say "Restoring gems to pristine condition..."

    specs.each do |spec|
      if spec.default_gem?
        say "Skipped #{spec.full_name}, it is a default gem"
        next
      end

      if spec.bundled_gem_in_old_ruby?
        say "Skipped #{spec.full_name}, it is bundled with old Ruby"
        next
      end

      unless spec.extensions.empty? or options[:extensions] then
        say "Skipped #{spec.full_name}, it needs to compile an extension"
        next
      end

      gem = spec.cache_file

      unless File.exist? gem then
        require 'rubygems/remote_fetcher'

        say "Cached gem for #{spec.full_name} not found, attempting to fetch..."

        dep = Gem::Dependency.new spec.name, spec.version
        found, _ = Gem::SpecFetcher.fetcher.spec_for_dependency dep

        if found.empty?
          say "Skipped #{spec.full_name}, it was not found from cache and remote sources"
          next
        end

        spec_candidate, source = found.first
        Gem::RemoteFetcher.fetcher.download spec_candidate, source.uri.to_s, spec.base_dir
      end

      env_shebang =
        if options.include? :env_shebang then
          options[:env_shebang]
        else
          install_defaults = Gem::ConfigFile::PLATFORM_DEFAULTS['install']
          install_defaults.to_s['--env-shebang']
        end

      installer = Gem::Installer.new(gem,
                                     :wrappers => true,
                                     :force => true,
                                     :install_dir => spec.base_dir,
                                     :env_shebang => env_shebang,
                                     :build_args => spec.build_args)

      if options[:only_executables] then
        installer.generate_bin
      else
        installer.install
      end

      say "Restored #{spec.full_name}"
    end
  end
end