# frozen_string_literal: true
require 'optparse'

require_relative '../../rdoc'

require_relative 'formatter' # For RubyGems backwards compatibility
# TODO: Fix weird documentation with `require_relative`

##
# The RI driver implements the command-line ri tool.
#
# The driver supports:
# * loading RI data from:
#   * Ruby's standard library
#   * RubyGems
#   * ~/.rdoc
#   * A user-supplied directory
# * Paging output (uses RI_PAGER environment variable, PAGER environment
#   variable or the less, more and pager programs)
# * Interactive mode with tab-completion
# * Abbreviated names (ri Zl shows Zlib documentation)
# * Colorized output
# * Merging output from multiple RI data sources

class RDoc::RI::Driver

  ##
  # Base Driver error class

  class Error < RDoc::RI::Error; end

  ##
  # Raised when a name isn't found in the ri data stores

  class NotFoundError < Error

    def initialize(klass, suggestion_proc = nil) # :nodoc:
      @klass = klass
      @suggestion_proc = suggestion_proc
    end

    ##
    # Name that wasn't found

    def name
      @klass
    end

    def message # :nodoc:
      str = "Nothing known about #{@klass}"
      suggestions = @suggestion_proc&.call
      if suggestions and !suggestions.empty?
        str += "\nDid you mean?  #{suggestions.join("\n               ")}"
      end
      str
    end
  end

  ##
  # Show all method documentation following a class or module

  attr_accessor :show_all

  ##
  # An RDoc::RI::Store for each entry in the RI path

  attr_accessor :stores

  ##
  # Controls the user of the pager vs $stdout

  attr_accessor :use_stdout

  ##
  # Default options for ri

  def self.default_options
    options = {}
    options[:interactive] = false
    options[:profile]     = false
    options[:show_all]    = false
    options[:expand_refs] = true
    options[:use_stdout]  = !$stdout.tty?
    options[:width]       = 72

    # By default all standard paths are used.
    options[:use_system]     = true
    options[:use_site]       = true
    options[:use_home]       = true
    options[:use_gems]       = true
    options[:extra_doc_dirs] = []

    return options
  end

  ##
  # Dump +data_path+ using pp

  def self.dump(data_path)
    require 'pp'

    File.open data_path, 'rb' do |io|
      pp Marshal.load(io.read)
    end
  end

  ##
  # Parses +argv+ and returns a Hash of options

  def self.process_args(argv)
    options = default_options

    opts = OptionParser.new do |opt|
      opt.program_name = File.basename $0
      opt.version = RDoc::VERSION
      opt.release = nil
      opt.summary_indent = ' ' * 4

      opt.banner = <<-EOT
Usage: #{opt.program_name} [options] [name ...]

Where name can be:

  Class | Module | Module::Class

  Class::method | Class#method | Class.method | method

  gem_name: | gem_name:README | gem_name:History

  ruby: | ruby:NEWS | ruby:globals

All class names may be abbreviated to their minimum unambiguous form.
If a name is ambiguous, all valid options will be listed.

A '.' matches either class or instance methods, while #method
matches only instance and ::method matches only class methods.

README and other files may be displayed by prefixing them with the gem name
they're contained in.  If the gem name is followed by a ':' all files in the
gem will be shown.  The file name extension may be omitted where it is
unambiguous.

'ruby' can be used as a pseudo gem name to display files from the Ruby
core documentation. Use 'ruby:' by itself to get a list of all available
core documentation files.

For example:

    #{opt.program_name} Fil
    #{opt.program_name} File
    #{opt.program_name} File.new
    #{opt.program_name} zip
    #{opt.program_name} rdoc:README
    #{opt.program_name} ruby:comments

Note that shell quoting or escaping may be required for method names
containing punctuation:

    #{opt.program_name} 'Array.[]'
    #{opt.program_name} compact\\!

To see the default directories #{opt.program_name} will search, run:

    #{opt.program_name} --list-doc-dirs

Specifying the --system, --site, --home, --gems, or --doc-dir options
will limit ri to searching only the specified directories.

ri options may be set in the RI environment variable.

The ri pager can be set with the RI_PAGER environment variable
or the PAGER environment variable.
      EOT

      opt.separator nil
      opt.separator "Options:"

      opt.separator nil

      opt.on("--[no-]interactive", "-i",
             "In interactive mode you can repeatedly",
             "look up methods with autocomplete.") do |interactive|
        options[:interactive] = interactive
      end

      opt.separator nil

      opt.on("--[no-]all", "-a",
             "Show all documentation for a class or",
             "module.") do |show_all|
        options[:show_all] = show_all
      end

      opt.separator nil

      opt.on("--[no-]list", "-l",
             "List classes ri knows about.") do |list|
        options[:list] = list
      end

      opt.separator nil

      opt.on("--[no-]pager",
             "Send output to a pager,",
             "rather than directly to stdout.") do |use_pager|
        options[:use_stdout] = !use_pager
      end

      opt.separator nil

      opt.on("-T",
             "Synonym for --no-pager.") do
        options[:use_stdout] = true
      end

      opt.separator nil

      opt.on("--width=WIDTH", "-w", OptionParser::DecimalInteger,
             "Set the width of the output.") do |width|
        options[:width] = width
      end

      opt.separator nil

      opt.on("--server[=PORT]", Integer,
             "Run RDoc server on the given port.",
             "The default port is 8214.") do |port|
        options[:server] = port || 8214
      end

      opt.separator nil

      formatters = RDoc::Markup.constants.grep(/^To[A-Z][a-z]+$/).sort
      formatters = formatters.sort.map do |formatter|
        formatter.to_s.sub('To', '').downcase
      end
      formatters -= %w[html label test] # remove useless output formats

      opt.on("--format=NAME", "-f",
             "Use the selected formatter.  The default",
             "formatter is bs for paged output and ansi",
             "otherwise.  Valid formatters are:",
             "#{formatters.join(', ')}.", formatters) do |value|
        options[:formatter] = RDoc::Markup.const_get "To#{value.capitalize}"
      end

      opt.separator nil

      opt.on("--[no-]expand-refs", "Expand rdoc-refs at the end of output") do |value|
        options[:expand_refs] = value
      end

      opt.separator nil

      opt.on("--help", "-h",
             "Show help and exit.") do
        puts opts
        exit
      end

      opt.separator nil

      opt.on("--version", "-v",
             "Output version information and exit.") do
        puts "#{opts.program_name} #{opts.version}"
        exit
      end

      opt.separator nil
      opt.separator "Data source options:"
      opt.separator nil

      opt.on("--[no-]list-doc-dirs",
             "List the directories from which ri will",
             "source documentation on stdout and exit.") do |list_doc_dirs|
        options[:list_doc_dirs] = list_doc_dirs
      end

      opt.separator nil

      opt.on("--doc-dir=DIRNAME", "-d", Array,
             "List of directories from which to source",
             "documentation in addition to the standard",
             "directories.  May be repeated.") do |value|
        value.each do |dir|
          unless File.directory? dir then
            raise OptionParser::InvalidArgument, "#{dir} is not a directory"
          end

          options[:extra_doc_dirs] << File.expand_path(dir)
        end
      end

      opt.separator nil

      opt.on("--no-standard-docs",
             "Do not include documentation from",
             "the Ruby standard library, site_lib,",
             "installed gems, or ~/.rdoc.",
             "Use with --doc-dir.") do
        options[:use_system] = false
        options[:use_site] = false
        options[:use_gems] = false
        options[:use_home] = false
      end

      opt.separator nil

      opt.on("--[no-]system",
             "Include documentation from Ruby's",
             "standard library.  Defaults to true.") do |value|
        options[:use_system] = value
      end

      opt.separator nil

      opt.on("--[no-]site",
             "Include documentation from libraries",
             "installed in site_lib.",
             "Defaults to true.") do |value|
        options[:use_site] = value
      end

      opt.separator nil

      opt.on("--[no-]gems",
             "Include documentation from RubyGems.",
             "Defaults to true.") do |value|
        options[:use_gems] = value
      end

      opt.separator nil

      opt.on("--[no-]home",
             "Include documentation stored in ~/.rdoc.",
             "Defaults to true.") do |value|
        options[:use_home] = value
      end

      opt.separator nil
      opt.separator "Debug options:"
      opt.separator nil

      opt.on("--[no-]profile",
             "Run with the ruby profiler.") do |value|
        options[:profile] = value
      end

      opt.separator nil

      opt.on("--dump=CACHE",
             "Dump data from an ri cache or data file.") do |value|
        unless File.readable?(value)
          abort "#{value.inspect} is not readable"
        end

        if File.directory?(value)
          abort "#{value.inspect} is a directory"
        end

        options[:dump_path] = File.new(value)
      end
    end

    argv = ENV['RI'].to_s.split(' ').concat argv

    opts.parse! argv

    options[:names] = argv

    options[:use_stdout] ||= !$stdout.tty?
    options[:use_stdout] ||= options[:interactive]
    options[:width] ||= 72

    options

  rescue OptionParser::InvalidArgument, OptionParser::InvalidOption => e
    puts opts
    puts
    puts e
    exit 1
  end

  ##
  # Runs the ri command line executable using +argv+

  def self.run(argv = ARGV)
    options = process_args argv

    if options[:dump_path] then
      dump options[:dump_path]
      return
    end

    ri = new options
    ri.run
  end

  ##
  # Creates a new driver using +initial_options+ from ::process_args

  def initialize(initial_options = {})
    @paging = false
    @classes = nil

    options = self.class.default_options.update(initial_options)

    @formatter_klass = options[:formatter]

    require 'profile' if options[:profile]

    @names = options[:names]
    @list = options[:list]

    @doc_dirs = []
    @stores   = []

    RDoc::RI::Paths.each(options[:use_system], options[:use_site],
                         options[:use_home], options[:use_gems],
                         *options[:extra_doc_dirs]) do |path, type|
      @doc_dirs << path

      store = RDoc::RI::Store.new(RDoc::Options.new, path: path, type: type)
      store.load_cache
      @stores << store
    end

    @list_doc_dirs = options[:list_doc_dirs]

    @interactive = options[:interactive]
    @server      = options[:server]
    @use_stdout  = options[:use_stdout]
    @show_all    = options[:show_all]
    @width       = options[:width]
    @expand_refs = options[:expand_refs]
  end

  ##
  # Adds paths for undocumented classes +also_in+ to +out+

  def add_also_in(out, also_in)
    return if also_in.empty?

    out << RDoc::Markup::Rule.new(1)
    out << RDoc::Markup::Paragraph.new("Also found in:")

    paths = RDoc::Markup::Verbatim.new
    also_in.each do |store|
      paths.parts.push store.friendly_path, "\n"
    end
    out << paths
  end

  ##
  # Adds a class header to +out+ for class +name+ which is described in
  # +classes+.

  def add_class(out, name, classes)
    heading = if classes.all? { |klass| klass.module? } then
                name
              else
                superclass = classes.map do |klass|
                  klass.superclass unless klass.module?
                end.compact.shift || 'Object'

                superclass = superclass.full_name unless String === superclass

                "#{name} < #{superclass}"
              end

    out << RDoc::Markup::Heading.new(1, heading)
    out << RDoc::Markup::BlankLine.new
  end

  ##
  # Adds "(from ...)" to +out+ for +store+

  def add_from(out, store)
    out << RDoc::Markup::Paragraph.new("(from #{store.friendly_path})")
  end

  ##
  # Adds +extends+ to +out+

  def add_extends(out, extends)
    add_extension_modules out, 'Extended by', extends
  end

  ##
  # Adds a list of +extensions+ to this module of the given +type+ to +out+.
  # add_includes and add_extends call this, so you should use those directly.

  def add_extension_modules(out, type, extensions)
    return if extensions.empty?

    out << RDoc::Markup::Rule.new(1)
    out << RDoc::Markup::Heading.new(1, "#{type}:")

    extensions.each do |modules, store|
      if modules.length == 1 then
        add_extension_modules_single out, store, modules.first
      else
        add_extension_modules_multiple out, store, modules
      end
    end
  end

  ##
  # Renders multiple included +modules+ from +store+ to +out+.

  def add_extension_modules_multiple(out, store, modules) # :nodoc:
    out << RDoc::Markup::Paragraph.new("(from #{store.friendly_path})")

    wout, with = modules.partition { |incl| incl.comment.empty? }

    out << RDoc::Markup::BlankLine.new unless with.empty?

    with.each do |incl|
      out << RDoc::Markup::Paragraph.new(incl.name)
      out << RDoc::Markup::BlankLine.new
      out << incl.comment.parse
    end

    unless wout.empty? then
      verb = RDoc::Markup::Verbatim.new

      wout.each do |incl|
        verb.push incl.name, "\n"
      end

      out << verb
    end
  end

  ##
  # Adds a single extension module +include+ from +store+ to +out+

  def add_extension_modules_single(out, store, include) # :nodoc:
    name = include.name
    path = store.friendly_path
    out << RDoc::Markup::Paragraph.new("#{name} (from #{path})")

    if include.comment then
      out << RDoc::Markup::BlankLine.new
      out << include.comment.parse
    end
  end

  ##
  # Adds +includes+ to +out+

  def add_includes(out, includes)
    add_extension_modules out, 'Includes', includes
  end

  ##
  # Looks up the method +name+ and adds it to +out+

  def add_method(out, name)
    filtered = lookup_method name
    method_document out, name, filtered
  end

  ##
  # Adds documentation for all methods in +klass+ to +out+

  def add_method_documentation(out, klass)
    klass.method_list.each do |method|
      begin
        add_method out, method.full_name
      rescue NotFoundError
        next
      end
    end
  end

  ##
  # Adds a list of +methods+ to +out+ with a heading of +name+

  def add_method_list(out, methods, name)
    return if methods.empty?

    out << RDoc::Markup::Heading.new(1, "#{name}:")
    out << RDoc::Markup::BlankLine.new

    if @use_stdout and !@interactive then
      out.concat methods.map { |method|
        RDoc::Markup::Verbatim.new method
      }
    else
      out << RDoc::Markup::IndentedParagraph.new(2, methods.join(', '))
    end

    out << RDoc::Markup::BlankLine.new
  end

  ##
  # Returns ancestor classes of +klass+

  def ancestors_of(klass)
    ancestors = []

    unexamined = [klass]
    seen = []

    loop do
      break if unexamined.empty?
      current = unexamined.shift
      seen << current

      stores = classes[current]

      next unless stores and not stores.empty?

      klasses = stores.flat_map do |store|
        store.ancestors[current] || []
      end.uniq

      klasses = klasses - seen

      ancestors.concat klasses
      unexamined.concat klasses
    end

    ancestors.reverse
  end

  ##
  # For RubyGems backwards compatibility

  def class_cache # :nodoc:
  end

  ##
  # Builds a RDoc::Markup::Document from +found+, +klasess+ and +includes+

  def class_document(name, found, klasses, includes, extends)
    also_in = []

    out = RDoc::Markup::Document.new

    add_class out, name, klasses

    add_includes out, includes
    add_extends  out, extends

    found.each do |store, klass|
      render_class out, store, klass, also_in
    end

    add_also_in out, also_in

    expand_rdoc_refs_at_the_bottom(out)
    out
  end

  ##
  # Adds the class +comment+ to +out+.

  def class_document_comment(out, document) # :nodoc:
    unless document.empty? then
      out << RDoc::Markup::Rule.new(1)

      if document.merged? then
        parts = document.parts
        parts = parts.zip [RDoc::Markup::BlankLine.new] * parts.length
        parts.flatten!
        parts.pop

        out.concat parts
      else
        out << comment
      end
    end
  end

  ##
  # Adds the constants from +klass+ to the Document +out+.

  def class_document_constants(out, klass) # :nodoc:
    return if klass.constants.empty?

    out << RDoc::Markup::Heading.new(1, "Constants:")
    out << RDoc::Markup::BlankLine.new
    list = RDoc::Markup::List.new :NOTE

    constants = klass.constants.sort_by { |constant| constant.name }

    list.items.concat constants.map { |constant|
      parts = constant.comment.parse.parts
      parts << RDoc::Markup::Paragraph.new('[not documented]') if
        parts.empty?

      RDoc::Markup::ListItem.new(constant.name, *parts)
    }

    out << list
    out << RDoc::Markup::BlankLine.new
  end

  ##
  # Hash mapping a known class or module to the stores it can be loaded from

  def classes
    return @classes if @classes

    @classes = {}

    @stores.each do |store|
      store.cache[:modules].each do |mod|
        # using default block causes searched-for modules to be added
        @classes[mod] ||= []
        @classes[mod] << store
      end
    end

    @classes
  end

  ##
  # Returns the stores wherein +name+ is found along with the classes,
  # extends and includes that match it

  def classes_and_includes_and_extends_for(name)
    klasses = []
    extends = []
    includes = []

    found = @stores.map do |store|
      begin
        klass = store.load_class name
        klasses  << klass
        extends  << [klass.extends,  store] if klass.extends
        includes << [klass.includes, store] if klass.includes
        [store, klass]
      rescue RDoc::Store::MissingFileError
      end
    end.compact

    extends.reject!  do |modules,| modules.empty? end
    includes.reject! do |modules,| modules.empty? end

    [found, klasses, includes, extends]
  end

  ##
  # Completes +name+ based on the caches.  For Readline

  def complete(name)
    completions = []

    klass, selector, method = parse_name name

    complete_klass  name, klass, selector, method, completions
    complete_method name, klass, selector,         completions

    completions.uniq.select {|s| s.start_with? name }.sort
  end

  def complete_klass(name, klass, selector, method, completions) # :nodoc:
    klasses = classes.keys

    # may need to include Foo when given Foo::
    klass_name = method ? name : klass

    if name !~ /#|\./ then
      completions.replace klasses.grep(/^#{Regexp.escape klass_name}[^:]*$/)
      completions.concat klasses.grep(/^#{Regexp.escape name}[^:]*$/) if
        name =~ /::$/

      completions << klass if classes.key? klass # to complete a method name
    elsif selector then
      completions << klass if classes.key? klass
    elsif classes.key? klass_name then
      completions << klass_name
    end
  end

  def complete_method(name, klass, selector, completions) # :nodoc:
    if completions.include? klass and name =~ /#|\.|::/ then
      methods = list_methods_matching name

      if not methods.empty? then
        # remove Foo if given Foo:: and a method was found
        completions.delete klass
      elsif selector then
        # replace Foo with Foo:: as given
        completions.delete klass
        completions << "#{klass}#{selector}"
      end

      methods.each do |klass_sel_method|
        match = klass_sel_method.match(/^(.+)(#|\.|::)([^#.:]+)$/)
        # match[2] is `::` for class method and `#` for instance method.
        # To be consistent with old completion that completes `['Foo#i', 'Foo::c']` for `Foo.`,
        # `.` should be a wildcard for both `#` and `::` here.
        if match && match[2] == selector || selector == '.'
          completions << match[1] + selector + match[3]
        end
      end
    end
  end

  ##
  # Converts +document+ to text and writes it to the pager

  def display(document)
    page do |io|
      f = formatter(io)
      f.width = @width if @width and f.respond_to?(:width)
      text = document.accept f

      io.write text
    end
  end

  ##
  # Outputs formatted RI data for class +name+.  Groups undocumented classes

  def display_class(name)
    return if name =~ /#|\./

    found, klasses, includes, extends =
      classes_and_includes_and_extends_for name

    return if found.empty?

    out = class_document name, found, klasses, includes, extends

    display out
  end

  ##
  # Outputs formatted RI data for method +name+

  def display_method(name)
    out = RDoc::Markup::Document.new

    add_method out, name

    expand_rdoc_refs_at_the_bottom(out)

    display out
  end

  ##
  # Outputs formatted RI data for the class or method +name+.
  #
  # Returns true if +name+ was found, false if it was not an alternative could
  # be guessed, raises an error if +name+ couldn't be guessed.

  def display_name(name)
    if name =~ /\w:(\w|$)/ then
      display_page name
      return true
    end

    return true if display_class name

    display_method name if name =~ /::|#|\./

    true
  rescue NotFoundError
    matches = list_methods_matching name if name =~ /::|#|\./
    matches = classes.keys.grep(/^#{Regexp.escape name}/) if matches.empty?

    raise if matches.empty?

    page do |io|
      io.puts "#{name} not found, maybe you meant:"
      io.puts
      io.puts matches.sort.join("\n")
    end

    false
  end

  ##
  # Displays each name in +name+

  def display_names(names)
    names.each do |name|
      name = expand_name name

      display_name name
    end
  end

  ##
  # Outputs formatted RI data for page +name+.

  def display_page(name)
    store_name, page_name = name.split ':', 2

    store = @stores.find { |s| s.source == store_name }

    return display_page_list store if page_name.empty?

    pages = store.cache[:pages]

    unless pages.include? page_name then
      found_names = pages.select do |n|
        n =~ /#{Regexp.escape page_name}\.[^.]+$/
      end

      if found_names.length.zero? then
        return display_page_list store, pages
      elsif found_names.length > 1 then
        return display_page_list store, found_names, page_name
      end

      page_name = found_names.first
    end

    page = store.load_page page_name

    display page.comment.parse
  end

  ##
  # Outputs a formatted RI page list for the pages in +store+.

  def display_page_list(store, pages = store.cache[:pages], search = nil)
    out = RDoc::Markup::Document.new

    title = if search then
              "#{search} pages"
            else
              'Pages'
            end

    out << RDoc::Markup::Heading.new(1, "#{title} in #{store.friendly_path}")
    out << RDoc::Markup::BlankLine.new

    list = RDoc::Markup::List.new(:BULLET)

    pages.each do |page|
      list << RDoc::Markup::Paragraph.new(page)
    end

    out << list

    display out
  end

  def check_did_you_mean # :nodoc:
    if defined? DidYouMean::SpellChecker
      true
    else
      begin
        require 'did_you_mean'
        if defined? DidYouMean::SpellChecker
          true
        else
          false
        end
      rescue LoadError
        false
      end
    end
  end

  ##
  # Expands abbreviated klass +klass+ into a fully-qualified class.  "Zl::Da"
  # will be expanded to Zlib::DataError.

  def expand_class(klass)
    class_names = classes.keys
    ary = class_names.grep(Regexp.new("\\A#{klass.gsub(/(?=::|\z)/, '[^:]*')}\\z"))
    if ary.length != 1 && ary.first != klass
      if check_did_you_mean
        suggestion_proc = -> { DidYouMean::SpellChecker.new(dictionary: class_names).correct(klass) }
        raise NotFoundError.new(klass, suggestion_proc)
      else
        raise NotFoundError, klass
      end
    end
    ary.first
  end

  ##
  # Expands the class portion of +name+ into a fully-qualified class.  See
  # #expand_class.

  def expand_name(name)
    klass, selector, method = parse_name name

    return [selector, method].join if klass.empty?

    case selector
    when ':' then
      [find_store(klass),   selector, method]
    else
      [expand_class(klass), selector, method]
    end.join
  end

  ##
  # Filters the methods in +found+ trying to find a match for +name+.

  def filter_methods(found, name)
    regexp = name_regexp name

    filtered = found.find_all do |store, methods|
      methods.any? { |method| method.full_name =~ regexp }
    end

    return filtered unless filtered.empty?

    found
  end

  ##
  # Yields items matching +name+ including the store they were found in, the
  # class being searched for, the class they were found in (an ancestor) the
  # types of methods to look up (from #method_type), and the method name being
  # searched for

  def find_methods(name)
    klass, selector, method = parse_name name

    types = method_type selector

    klasses = nil
    ambiguous = klass.empty?

    if ambiguous then
      klasses = classes.keys
    else
      klasses = ancestors_of klass
      klasses.unshift klass
    end

    methods = []

    klasses.each do |ancestor|
      ancestors = classes[ancestor]

      next unless ancestors

      klass = ancestor if ambiguous

      ancestors.each do |store|
        methods << [store, klass, ancestor, types, method]
      end
    end

    methods = methods.sort_by do |_, k, a, _, m|
      [k, a, m].compact
    end

    methods.each do |item|
      yield(*item) # :yields: store, klass, ancestor, types, method
    end

    self
  end

  ##
  # Finds a store that matches +name+ which can be the name of a gem, "ruby",
  # "home" or "site".
  #
  # See also RDoc::Store#source

  def find_store(name)
    @stores.each do |store|
      source = store.source

      return source if source == name

      return source if
        store.type == :gem and source =~ /^#{Regexp.escape name}-\d/
    end

    raise RDoc::RI::Driver::NotFoundError, name
  end

  ##
  # Creates a new RDoc::Markup::Formatter.  If a formatter is given with -f,
  # use it.  If we're outputting to a pager, use bs, otherwise ansi.

  def formatter(io)
    if @formatter_klass then
      @formatter_klass.new
    elsif paging? or !io.tty? then
      RDoc::Markup::ToBs.new
    else
      RDoc::Markup::ToAnsi.new
    end
  end

  ##
  # Runs ri interactively using Readline if it is available.

  def interactive
    puts "\nEnter the method name you want to look up."

    begin
      require 'readline'
    rescue LoadError
    end
    if defined? Readline then
      Readline.completion_proc = method :complete
      puts "You can use tab to autocomplete."
    end

    puts "Enter a blank line to exit.\n\n"

    loop do
      name = if defined? Readline then
               Readline.readline ">> ", true
             else
               print ">> "
               $stdin.gets
             end

      return if name.nil? or name.empty?

      begin
        display_name expand_name(name.strip)
      rescue NotFoundError => e
        puts e.message
      end
    end

  rescue Interrupt
    exit
  end

  ##
  # Lists classes known to ri starting with +names+.  If +names+ is empty all
  # known classes are shown.

  def list_known_classes(names = [])
    classes = []

    stores.each do |store|
      classes << store.module_names
    end

    classes = classes.flatten.uniq.sort

    unless names.empty? then
      filter = Regexp.union names.map { |name| /^#{name}/ }

      classes = classes.grep filter
    end

    page do |io|
      if paging? or io.tty? then
        if names.empty? then
          io.puts "Classes and Modules known to ri:"
        else
          io.puts "Classes and Modules starting with #{names.join ', '}:"
        end
        io.puts
      end

      io.puts classes.join("\n")
    end
  end

  ##
  # Returns an Array of methods matching +name+

  def list_methods_matching(name)
    found = []

    find_methods name do |store, klass, ancestor, types, method|
      if types == :instance or types == :both then
        methods = store.instance_methods[ancestor]

        if methods then
          matches = methods.grep(/^#{Regexp.escape method.to_s}/)

          matches = matches.map do |match|
            "#{klass}##{match}"
          end

          found.concat matches
        end
      end

      if types == :class or types == :both then
        methods = store.class_methods[ancestor]

        next unless methods
        matches = methods.grep(/^#{Regexp.escape method.to_s}/)

        matches = matches.map do |match|
          "#{klass}::#{match}"
        end

        found.concat matches
      end
    end

    found.uniq
  end

  ##
  # Loads RI data for method +name+ on +klass+ from +store+.  +type+ and
  # +cache+ indicate if it is a class or instance method.

  def load_method(store, cache, klass, type, name)
    methods = store.public_send(cache)[klass]

    return unless methods

    method = methods.find do |method_name|
      method_name == name
    end

    return unless method

    store.load_method klass, "#{type}#{method}"
  rescue RDoc::Store::MissingFileError => e
    comment = RDoc::Comment.new("missing documentation at #{e.file}")
    comment.parse

    method = RDoc::AnyMethod.new nil, name
    method.comment = comment
    method
  end

  ##
  # Returns an Array of RI data for methods matching +name+

  def load_methods_matching(name)
    found = []

    find_methods name do |store, klass, ancestor, types, method|
      methods = []

      methods << load_method(store, :class_methods, ancestor, '::',  method) if
        [:class, :both].include? types

      methods << load_method(store, :instance_methods, ancestor, '#',  method) if
        [:instance, :both].include? types

      found << [store, methods.compact]
    end

    found.reject do |path, methods| methods.empty? end
  end

  ##
  # Returns a filtered list of methods matching +name+

  def lookup_method(name)
    found = load_methods_matching name

    if found.empty?
      if check_did_you_mean
        methods = []
        _, _, method_name = parse_name name
        find_methods name do |store, klass, ancestor, types, method|
          methods.push(*store.class_methods[klass]) if [:class, :both].include? types
          methods.push(*store.instance_methods[klass]) if [:instance, :both].include? types
        end
        methods = methods.uniq
        suggestion_proc = -> { DidYouMean::SpellChecker.new(dictionary: methods).correct(method_name) }
        raise NotFoundError.new(name, suggestion_proc)
      else
        raise NotFoundError, name
      end
    end

    filter_methods found, name
  end

  ##
  # Builds a RDoc::Markup::Document from +found+, +klasses+ and +includes+

  def method_document(out, name, filtered)
    out << RDoc::Markup::Heading.new(1, name)
    out << RDoc::Markup::BlankLine.new

    filtered.each do |store, methods|
      methods.each do |method|
        render_method out, store, method, name
      end
    end

    out
  end

  ##
  # Returns the type of method (:both, :instance, :class) for +selector+

  def method_type(selector)
    case selector
    when '.', nil then :both
    when '#'      then :instance
    else               :class
    end
  end

  ##
  # Returns a regular expression for +name+ that will match an
  # RDoc::AnyMethod's name.

  def name_regexp(name)
    klass, type, name = parse_name name

    case type
    when '#', '::' then
      /^#{klass}#{type}#{Regexp.escape name}$/
    else
      /^#{klass}(#|::)#{Regexp.escape name}$/
    end
  end

  ##
  # Paginates output through a pager program.

  def page
    if pager = setup_pager then
      begin
        yield pager
      ensure
        pager.close
      end
    else
      yield $stdout
    end
  rescue Errno::EPIPE
  ensure
    @paging = false
  end

  ##
  # Are we using a pager?

  def paging?
    @paging
  end

  ##
  # Extracts the class, selector and method name parts from +name+ like
  # Foo::Bar#baz.
  #
  # NOTE: Given Foo::Bar, Bar is considered a class even though it may be a
  # method

  def parse_name(name)
    parts = name.split(/(::?|#|\.)/)

    if parts.length == 1 then
      if parts.first =~ /^[a-z]|^([%&*+\/<>^`|~-]|\+@|-@|<<|<=>?|===?|=>|=~|>>|\[\]=?|~@)$/ then
        type = '.'
        meth = parts.pop
      else
        type = nil
        meth = nil
      end
    elsif parts.length == 2 or parts.last =~ /::|#|\./ then
      type = parts.pop
      meth = nil
    elsif parts[1] == ':' then
      klass = parts.shift
      type  = parts.shift
      meth  = parts.join
    elsif parts[-2] != '::' or parts.last !~ /^[A-Z]/ then
      meth = parts.pop
      type = parts.pop
    end

    klass ||= parts.join

    [klass, type, meth]
  end

  ##
  # Renders the +klass+ from +store+ to +out+.  If the klass has no
  # documentable items the class is added to +also_in+ instead.

  def render_class(out, store, klass, also_in) # :nodoc:
    document = klass.comment.parse
    # TODO the store's cache should always return an empty Array
    class_methods    = store.class_methods[klass.full_name]    || []
    instance_methods = store.instance_methods[klass.full_name] || []
    attributes       = store.attributes[klass.full_name]       || []

    if document.empty? and
       instance_methods.empty? and class_methods.empty? then
      also_in << store
      return
    end

    add_from out, store

    class_document_comment out, document

    if class_methods or instance_methods or not klass.constants.empty? then
      out << RDoc::Markup::Rule.new(1)
    end

    class_document_constants out, klass

    add_method_list out, class_methods,    'Class methods'
    add_method_list out, instance_methods, 'Instance methods'
    add_method_list out, attributes,       'Attributes'

    add_method_documentation out, klass if @show_all
  end

  def render_method(out, store, method, name) # :nodoc:
    out << RDoc::Markup::Paragraph.new("(from #{store.friendly_path})")

    unless name =~ /^#{Regexp.escape method.parent_name}/ then
      out << RDoc::Markup::Heading.new(3, "Implementation from #{method.parent_name}")
    end

    out << RDoc::Markup::Rule.new(1)

    render_method_arguments out, method.arglists
    render_method_superclass out, method
    if method.is_alias_for
      al = method.is_alias_for
      alias_for = store.load_method al.parent_name, "#{al.name_prefix}#{al.name}"
      render_method_comment out, method, alias_for
    else
      render_method_comment out, method
    end
  end

  def render_method_arguments(out, arglists) # :nodoc:
    return unless arglists

    arglists = arglists.chomp.split "\n"
    arglists = arglists.map { |line| line + "\n" }
    out << RDoc::Markup::Verbatim.new(*arglists)
    out << RDoc::Markup::Rule.new(1)
  end

  def render_method_comment(out, method, alias_for = nil)# :nodoc:
    if alias_for
      unless method.comment.nil? or method.comment.empty?
        out << RDoc::Markup::BlankLine.new
        out << method.comment.parse
      end
      out << RDoc::Markup::BlankLine.new
      out << RDoc::Markup::Paragraph.new("(This method is an alias for #{alias_for.full_name}.)")
      out << RDoc::Markup::BlankLine.new
      out << alias_for.comment.parse
      out << RDoc::Markup::BlankLine.new
    else
      out << RDoc::Markup::BlankLine.new
      out << method.comment.parse
      out << RDoc::Markup::BlankLine.new
    end
  end

  def render_method_superclass(out, method) # :nodoc:
    return unless
      method.respond_to?(:superclass_method) and method.superclass_method

    out << RDoc::Markup::BlankLine.new
    out << RDoc::Markup::Heading.new(4, "(Uses superclass method #{method.superclass_method})")
    out << RDoc::Markup::Rule.new(1)
  end

  ##
  # Looks up and displays ri data according to the options given.

  def run
    if @list_doc_dirs then
      puts @doc_dirs
    elsif @list then
      list_known_classes @names
    elsif @server then
      start_server
    elsif @interactive or @names.empty? then
      interactive
    else
      display_names @names
    end
  rescue NotFoundError => e
    abort e.message
  end

  ##
  # Sets up a pager program to pass output through.  Tries the RI_PAGER and
  # PAGER environment variables followed by pager, less then more.

  def setup_pager
    return if @use_stdout

    pagers = [ENV['RI_PAGER'], ENV['PAGER'], 'pager', 'less', 'more']

    require 'shellwords'
    pagers.compact.uniq.each do |pager|
      pager = Shellwords.split(pager)
      next if pager.empty?

      io = IO.popen(pager, 'w') rescue next
      next if $? and $?.pid == io.pid and $?.exited? # pager didn't work

      @paging = true

      return io
    end

    @use_stdout = true

    nil
  end

  ##
  # Starts a WEBrick server for ri.

  def start_server
    begin
      require 'webrick'
    rescue LoadError
      abort "webrick is not found. You may need to `gem install webrick` to install webrick."
    end

    server = WEBrick::HTTPServer.new :Port => @server

    extra_doc_dirs = @stores.map {|s| s.type == :extra ? s.path : nil}.compact

    server.mount '/', RDoc::Servlet, nil, extra_doc_dirs

    trap 'INT'  do server.shutdown end
    trap 'TERM' do server.shutdown end

    server.start
  end

  RDOC_REFS_REGEXP = /\[rdoc-ref:([\w.]+)(@.*)?\]/

  def expand_rdoc_refs_at_the_bottom(out)
    return unless @expand_refs

    extracted_rdoc_refs = []

    out.each do |part|
      content = if part.respond_to?(:text)
        part.text
      else
        next
      end

      rdoc_refs = content.scan(RDOC_REFS_REGEXP).uniq.map do |file_name, _anchor|
        file_name
      end

      extracted_rdoc_refs.concat(rdoc_refs)
    end

    found_pages = extracted_rdoc_refs.map do |ref|
      begin
        @stores.first.load_page(ref)
      rescue RDoc::Store::MissingFileError
      end
    end.compact

    found_pages.each do |page|
      out << RDoc::Markup::Heading.new(4, "Expanded from #{page.full_name}")
      out << RDoc::Markup::BlankLine.new
      out << page.comment.parse
    end
  end
end
