class Thor
  Correctable =
    begin
      require 'did_you_mean'

      # In order to support versions of Ruby that don't have keyword
      # arguments, we need our own spell checker class that doesn't take key
      # words. Even though this code wouldn't be hit because of the check
      # above, it's still necessary because the interpreter would otherwise be
      # unable to parse the file.
      class NoKwargSpellChecker < DidYouMean::SpellChecker # :nodoc:
        def initialize(dictionary)
          @dictionary = dictionary
        end
      end

      DidYouMean::Correctable
    rescue LoadError, NameError
    end

  # Thor::Error is raised when it's caused by wrong usage of thor classes. Those
  # errors have their backtrace suppressed and are nicely shown to the user.
  #
  # Errors that are caused by the developer, like declaring a method which
  # overwrites a thor keyword, SHOULD NOT raise a Thor::Error. This way, we
  # ensure that developer errors are shown with full backtrace.
  class Error < StandardError
  end

  # Raised when a command was not found.
  class UndefinedCommandError < Error
    class SpellChecker
      attr_reader :error

      def initialize(error)
        @error = error
      end

      def corrections
        @corrections ||= spell_checker.correct(error.command).map(&:inspect)
      end

      def spell_checker
        NoKwargSpellChecker.new(error.all_commands)
      end
    end

    attr_reader :command, :all_commands

    def initialize(command, all_commands, namespace)
      @command = command
      @all_commands = all_commands

      message = "Could not find command #{command.inspect}"
      message = namespace ? "#{message} in #{namespace.inspect} namespace." : "#{message}."

      super(message)
    end

    prepend Correctable if Correctable
  end
  UndefinedTaskError = UndefinedCommandError

  class AmbiguousCommandError < Error
  end
  AmbiguousTaskError = AmbiguousCommandError

  # Raised when a command was found, but not invoked properly.
  class InvocationError < Error
  end

  class UnknownArgumentError < Error
    class SpellChecker
      attr_reader :error

      def initialize(error)
        @error = error
      end

      def corrections
        @corrections ||=
          error.unknown.flat_map { |unknown| spell_checker.correct(unknown) }.uniq.map(&:inspect)
      end

      def spell_checker
        @spell_checker ||= NoKwargSpellChecker.new(error.switches)
      end
    end

    attr_reader :switches, :unknown

    def initialize(switches, unknown)
      @switches = switches
      @unknown = unknown

      super("Unknown switches #{unknown.map(&:inspect).join(', ')}")
    end

    prepend Correctable if Correctable
  end

  class RequiredArgumentMissingError < InvocationError
  end

  class MalformattedArgumentError < InvocationError
  end

  if Correctable
    DidYouMean::SPELL_CHECKERS.merge!(
      'Thor::UndefinedCommandError' => UndefinedCommandError::SpellChecker,
      'Thor::UnknownArgumentError' => UnknownArgumentError::SpellChecker
    )
  end
end