module Gem::BUNDLED_GEMS
  SINCE = {
    "rexml" => "3.0.0",
    "rss" => "3.0.0",
    "webrick" => "3.0.0",
    "matrix" => "3.1.0",
    "net-ftp" => "3.1.0",
    "net-imap" => "3.1.0",
    "net-pop" => "3.1.0",
    "net-smtp" => "3.1.0",
    "prime" => "3.1.0",
    "abbrev" => "3.4.0",
    "base64" => "3.4.0",
    "bigdecimal" => "3.4.0",
    "csv" => "3.4.0",
    "drb" => "3.4.0",
    "getoptlong" => "3.4.0",
    "mutex_m" => "3.4.0",
    "nkf" => "3.4.0",
    "observer" => "3.4.0",
    "racc" => "3.4.0",
    "resolv-replace" => "3.4.0",
    "rinda" => "3.4.0",
    "syslog" => "3.4.0",
  }.freeze

  EXACT = {
    "abbrev" => true,
    "base64" => true,
    "bigdecimal" => true,
    "csv" => true,
    "drb" => true,
    "getoptlong" => true,
    "mutex_m" => true,
    "nkf" => true, "kconv" => "nkf",
    "observer" => true,
    "resolv-replace" => true,
    "rinda" => true,
    "syslog" => true,
  }.freeze

  PREFIXED = {
    "bigdecimal" => true,
    "csv" => true,
    "drb" => true,
    "rinda" => true,
    "syslog" => true,
  }.freeze

  WARNED = {}                   # unfrozen

  conf = ::RbConfig::CONFIG
  LIBDIR = (conf["rubylibdir"] + "/").freeze
  ARCHDIR = (conf["rubyarchdir"] + "/").freeze
  dlext = [conf["DLEXT"], "so"].uniq
  DLEXT = /\.#{Regexp.union(dlext)}\z/
  LIBEXT = /\.#{Regexp.union("rb", *dlext)}\z/

  def self.replace_require(specs)
    return if [::Kernel.singleton_class, ::Kernel].any? {|klass| klass.respond_to?(:no_warning_require) }

    [::Kernel.singleton_class, ::Kernel].each do |kernel_class|
      kernel_class.send(:alias_method, :no_warning_require, :require)
      kernel_class.send(:define_method, :require) do |name|
        if message = ::Gem::BUNDLED_GEMS.warning?(name, specs: specs) # rubocop:disable Style/HashSyntax
          warn message, :uplevel => 1
        end
        kernel_class.send(:no_warning_require, name)
      end
      if kernel_class == ::Kernel
        kernel_class.send(:private, :require)
      else
        kernel_class.send(:public, :require)
      end
    end
  end

  def self.find_gem(path)
    if !path
      return
    elsif path.start_with?(ARCHDIR)
      n = path.delete_prefix(ARCHDIR).sub(DLEXT, "")
    elsif path.start_with?(LIBDIR)
      n = path.delete_prefix(LIBDIR).chomp(".rb")
    else
      return
    end
    EXACT[n] or PREFIXED[n = n[%r[\A[^/]+(?=/)]]] && n
  end

  def self.warning?(name, specs: nil)
    feature = File.path(name) # name can be a feature name or a file path with String or Pathname
    return if specs.to_a.map(&:name).include?(feature.sub(LIBEXT, ""))
    _t, path = $:.resolve_feature_path(feature)
    name = feature.tr("/", "-")
    if gem = find_gem(path)
      caller = caller_locations(3, 3).find {|c| c&.absolute_path}
      return if find_gem(caller&.absolute_path)
      name = name.sub(LIBEXT, "") # assume "foo.rb"/"foo.so" belongs to "foo" gem
    elsif SINCE[name]
      gem = true
    else
      return
    end
    return if WARNED[name]
    WARNED[name] = true
    if gem == true
      gem = name
      "#{feature} was loaded from the standard library, but"
    elsif gem
      return if WARNED[gem]
      WARNED[gem] = true
      "#{feature} is found in #{gem}, which"
    else
      return
    end + build_message(gem)
  end

  def self.build_message(gem)
    msg = " #{RUBY_VERSION < SINCE[gem] ? "will no longer be" : "is not"} part of the default gems since Ruby #{SINCE[gem]}."

    if defined?(Bundler)
      msg += " Add #{gem} to your Gemfile or gemspec."
      # We detect the gem name from caller_locations. We need to skip 2 frames like:
      # lib/ruby/3.3.0+0/bundled_gems.rb:90:in `warning?'",
      # lib/ruby/3.3.0+0/bundler/rubygems_integration.rb:247:in `block (2 levels) in replace_require'",
      location = caller_locations(3,3)[0]&.path
      if File.file?(location) && !location.start_with?(Gem::BUNDLED_GEMS::LIBDIR)
        caller_gem = nil
        Gem.path.each do |path|
          if location =~ %r{#{path}/gems/([\w\-\.]+)}
            caller_gem = $1
            break
          end
        end
        if caller_gem
          msg += " Also contact author of #{caller_gem} to add #{gem} into its gemspec."
        end
      end
    else
      msg += " Install #{gem} from RubyGems."
    end

    msg
  end

  freeze
end

# for RubyGems without Bundler environment.
# If loading library is not part of the default gems and the bundled gems, warn it.
class LoadError
  def message
    return super unless path

    name = path.tr("/", "-")
    if !defined?(Bundler) && Gem::BUNDLED_GEMS::SINCE[name] && !Gem::BUNDLED_GEMS::WARNED[name]
      warn name + Gem::BUNDLED_GEMS.build_message(name)
    end
    super
  end
end