class Bundler::SelfManager

def autoswitching_applies?
  ENV["BUNDLER_VERSION"].nil? &&
    Bundler.rubygems.supports_bundler_trampolining? &&
    SharedHelpers.in_bundle? &&
    lockfile_version
end

def current_version
  @current_version ||= Gem::Version.new(Bundler::VERSION)
end

def find_latest_matching_spec(requirement)
  local_result = find_latest_matching_spec_from_collection(local_specs, requirement)
  return local_result if local_result && requirement.specific?
  remote_result = find_latest_matching_spec_from_collection(remote_specs, requirement)
  return remote_result if local_result.nil?
  [local_result, remote_result].max
end

def find_latest_matching_spec_from_collection(specs, requirement)
  specs.sort.reverse_each.find {|spec| requirement.satisfied_by?(spec.version) }
end

def install(spec)
  spec.source.install(spec)
end

def install_and_restart_with(version)
  requirement = Gem::Requirement.new(version)
  spec = find_latest_matching_spec(requirement)
  if spec.nil?
    Bundler.ui.warn "Your lockfile is locked to a version of bundler (#{lockfile_version}) that doesn't exist at https://rubygems.org/. Going on using #{current_version}"
    return
  end
  install(spec)
rescue StandardError => e
  Bundler.ui.trace e
  Bundler.ui.warn "There was an error installing the locked bundler version (#{lockfile_version}), rerun with the `--verbose` flag for more details. Going on using bundler #{current_version}."
else
  restart_with(version)
end

def install_locked_bundler_and_restart_with_it_if_needed
  return unless needs_switching?
  Bundler.ui.info \
    "Bundler #{current_version} is running, but your lockfile was generated with #{lockfile_version}. " \
    "Installing Bundler #{lockfile_version} and restarting using that version."
  install_and_restart_with(lockfile_version)
end

def installed?
  Bundler.configure
  Bundler.rubygems.find_bundler(lockfile_version.to_s)
end

def local_specs
  @local_specs ||= Bundler::Source::Rubygems.new("allow_local" => true).specs.select {|spec| spec.name == "bundler" }
end

def lockfile_version
  return @lockfile_version if defined?(@lockfile_version)
  parsed_version = Bundler::LockfileParser.bundled_with
  @lockfile_version = parsed_version ? Gem::Version.new(parsed_version) : nil
end

def needs_switching?
  autoswitching_applies? &&
    released?(lockfile_version) &&
    !running?(lockfile_version) &&
    !updating?
end

def released?(version)
  !version.to_s.end_with?(".dev")
end

def remote_specs
  @remote_specs ||= begin
    source = Bundler::Source::Rubygems.new("remotes" => "https://rubygems.org")
    source.remote!
    source.add_dependency_names("bundler")
    source.specs
  end
end

def resolve_update_version_from(target)
  requirement = Gem::Requirement.new(target)
  update_candidate = find_latest_matching_spec(requirement)
  if update_candidate.nil?
    raise InvalidOption, "The `bundle update --bundler` target version (#{target}) does not exist"
  end
  resolved_version = update_candidate.version
  needs_update = requirement.specific? ? !running?(resolved_version) : running_older_than?(resolved_version)
  return unless needs_update
  update_candidate
end

def restart_with(version)
  configured_gem_home = ENV["GEM_HOME"]
  configured_gem_path = ENV["GEM_PATH"]
  cmd = [$PROGRAM_NAME, *ARGV]
  cmd.unshift(Gem.ruby) unless File.executable?($PROGRAM_NAME)
  Bundler.with_original_env do
    Kernel.exec(
      { "GEM_HOME" => configured_gem_home, "GEM_PATH" => configured_gem_path, "BUNDLER_VERSION" => version.to_s },
      *cmd
    )
  end
end

def restart_with_locked_bundler_if_needed
  return unless needs_switching? && installed?
  restart_with(lockfile_version)
end

def running?(version)
  version == current_version
end

def running_older_than?(version)
  current_version < version
end

def update_bundler_and_restart_with_it_if_needed(target)
  return unless autoswitching_applies?
  spec = resolve_update_version_from(target)
  return unless spec
  version = spec.version
  Bundler.ui.info "Updating bundler to #{version}."
  install(spec)
  restart_with(version)
end

def updating?
  "update".start_with?(ARGV.first || " ") && ARGV[1..-1].any? {|a| a.start_with?("--bundler") }
end