class Gem::CommandManager

def self.instance
  @command_manager ||= new
end

def self.reset
  @command_manager = nil
end

def [](command_name)
  command_name = command_name.intern
  return nil if @commands[command_name].nil?
  @commands[command_name] ||= load_and_instantiate(command_name)
end

def command_names
  @commands.keys.collect {|key| key.to_s }.sort
end

def find_alias_command(cmd_name)
  alias_name = ALIAS_COMMANDS[cmd_name]
  alias_name ? alias_name : cmd_name
end

def find_command(cmd_name)
  cmd_name = find_alias_command cmd_name
  possibilities = find_command_possibilities cmd_name
  if possibilities.size > 1
    raise Gem::CommandLineError,
          "Ambiguous command #{cmd_name} matches [#{possibilities.join(', ')}]"
  elsif possibilities.empty?
    raise Gem::CommandLineError, "Unknown command #{cmd_name}"
  end
  self[possibilities.first]
end

def find_command_possibilities(cmd_name)
  len = cmd_name.length
  found = command_names.select {|name| cmd_name == name[0, len] }
  exact = found.find {|name| name == cmd_name }
  exact ? [exact] : found
end

def initialize
  require 'timeout'
  @commands = {}
  BUILTIN_COMMANDS.each do |name|
    register_command name
  end
end

def instance
  self
end

def load_and_instantiate(command_name)
  command_name = command_name.to_s
  const_name = command_name.capitalize.gsub(/_(.)/) { $1.upcase } << "Command"
  load_error = nil
  begin
    begin
      require "rubygems/commands/#{command_name}_command"
    rescue LoadError => e
      load_error = e
    end
    Gem::Commands.const_get(const_name).new
  rescue Exception => e
    e = load_error if load_error
    alert_error clean_text("Loading command: #{command_name} (#{e.class})\n\t#{e}")
    ui.backtrace e
  end
end

def process_args(args, build_args=nil)
  if args.empty?
    say Gem::Command::HELP
    terminate_interaction 1
  end
  case args.first
  when '-h', '--help' then
    say Gem::Command::HELP
    terminate_interaction 0
  when '-v', '--version' then
    say Gem::VERSION
    terminate_interaction 0
  when /^-/ then
    alert_error clean_text("Invalid option: #{args.first}. See 'gem --help'.")
    terminate_interaction 1
  else
    cmd_name = args.shift.downcase
    cmd = find_command cmd_name
    cmd.deprecation_warning if cmd.deprecated?
    cmd.invoke_with_build_args args, build_args
  end
end

def register_command(command, obj=false)
  @commands[command] = obj
end

def run(args, build_args=nil)
  process_args(args, build_args)
rescue StandardError, Timeout::Error => ex
  alert_error clean_text("While executing gem ... (#{ex.class})\n    #{ex}")
  ui.backtrace ex
  terminate_interaction(1)
rescue Interrupt
  alert_error clean_text("Interrupted")
  terminate_interaction(1)
end

def unregister_command(command)
  @commands.delete command
end