require 'pry/module_candidate'

class Pry
  class << self
    # If the given object is a `Pry::WrappedModule`, return it unaltered. If it's
    # anything else, return it wrapped in a `Pry::WrappedModule` instance.
    def WrappedModule(obj)
      if obj.is_a? Pry::WrappedModule
        obj
      else
        Pry::WrappedModule.new(obj)
      end
    end
  end

  class WrappedModule
    include Helpers::BaseHelpers
    include CodeObject::Helpers

    attr_reader :wrapped

    # Convert a string to a module.
    #
    # @param [String] mod_name
    # @param [Binding] target The binding where the lookup takes place.
    # @return [Module, nil] The module or `nil` (if conversion failed).
    # @example
    #   Pry::WrappedModule.from_str("Pry::Code")
    def self.from_str(mod_name, target=TOPLEVEL_BINDING)
      if safe_to_evaluate?(mod_name, target)
        Pry::WrappedModule.new(target.eval(mod_name))
      else
        nil
      end
    rescue RescuableException
      nil
    end

    class << self
      private

      # We use this method to decide whether code is safe to eval. Method's are
      # generally not, but everything else is.
      # TODO: is just checking != "method" enough??
      # TODO: see duplication of this method in Pry::CodeObject
      # @param [String] str The string to lookup.
      # @param [Binding] target Where the lookup takes place.
      # @return [Boolean]
      def safe_to_evaluate?(str, target)
        return true if str.strip == "self"
        kind = target.eval("defined?(#{str})")
        kind =~ /variable|constant/
      end
    end

    # @raise [ArgumentError] if the argument is not a `Module`
    # @param [Module] mod
    def initialize(mod)
      raise ArgumentError, "Tried to initialize a WrappedModule with a non-module #{mod.inspect}" unless ::Module === mod
      @wrapped = mod
      @memoized_candidates = []
      @host_file_lines = nil
      @source = nil
      @source_location = nil
      @doc = nil
    end

    # Returns an array of the names of the constants accessible in the wrapped
    # module. This avoids the problem of accidentally calling the singleton
    # method `Module.constants`.
    # @param [Boolean] inherit Include the names of constants from included
    #   modules?
    def constants(inherit = true)
      Module.instance_method(:constants).bind(@wrapped).call(inherit)
    end

    # The prefix that would appear before methods defined on this class.
    #
    # i.e. the "String." or "String#" in String.new and String#initialize.
    #
    # @return String
    def method_prefix
      if singleton_class?
        if Module === singleton_instance
          "#{WrappedModule.new(singleton_instance).nonblank_name}."
        else
          "self."
        end
      else
        "#{nonblank_name}#"
      end
    end

    # The name of the Module if it has one, otherwise #<Class:0xf00>.
    #
    # @return [String]
    def nonblank_name
      if name.to_s == ""
        wrapped.inspect
      else
        name
      end
    end

    # Is this a singleton class?
    # @return [Boolean]
    def singleton_class?
      if Pry::Method.safe_send(wrapped, :respond_to?, :singleton_class?)
        Pry::Method.safe_send(wrapped, :singleton_class?)
      else
        wrapped != Pry::Method.safe_send(wrapped, :ancestors).first
      end
    end

    # Is this strictly a module? (does not match classes)
    # @return [Boolean]
    def module?
      wrapped.instance_of?(Module)
    end

    # Is this strictly a class?
    # @return [Boolean]
    def class?
      wrapped.instance_of?(Class)
    end

    # Get the instance associated with this singleton class.
    #
    # @raise ArgumentError: tried to get instance of non singleton class
    #
    # @return [Object]
    def singleton_instance
      raise ArgumentError, "tried to get instance of non singleton class" unless singleton_class?

      if Helpers::BaseHelpers.jruby?
        wrapped.to_java.attached
      else
        @singleton_instance ||= ObjectSpace.each_object(wrapped).detect{ |x| (class << x; self; end) == wrapped }
      end
    end

    # Forward method invocations to the wrapped module
    def method_missing(method_name, *args, &block)
      wrapped.send(method_name, *args, &block)
    end

    def respond_to?(method_name)
      super || wrapped.respond_to?(method_name)
    end

    # Retrieve the source location of a module. Return value is in same
    # format as Method#source_location. If the source location
    # cannot be found this method returns `nil`.
    #
    # @param [Module] mod The module (or class).
    # @return [Array<String, Fixnum>, nil] The source location of the
    #   module (or class), or `nil` if no source location found.
    def source_location
      @source_location ||= primary_candidate.source_location
    rescue Pry::RescuableException
      nil
    end

    # @return [String, nil] The associated file for the module (i.e
    #   the primary candidate: highest ranked monkeypatch).
    def file
      Array(source_location).first
    end
    alias_method :source_file, :file

    # @return [Fixnum, nil] The associated line for the module (i.e
    #   the primary candidate: highest ranked monkeypatch).
    def line
      Array(source_location).last
    end
    alias_method :source_line, :line

    # Returns documentation for the module.
    # This documentation is for the primary candidate, if
    # you would like documentation for other candidates use
    # `WrappedModule#candidate` to select the candidate you're
    # interested in.
    # @raise [Pry::CommandError] If documentation cannot be found.
    # @return [String] The documentation for the module.
    def doc
      @doc ||= primary_candidate.doc
    end

    # Returns the source for the module.
    # This source is for the primary candidate, if
    # you would like source for other candidates use
    # `WrappedModule#candidate` to select the candidate you're
    # interested in.
    # @raise [Pry::CommandError] If source cannot be found.
    # @return [String] The source for the module.
    def source
      @source ||= primary_candidate.source
    end

    # @return [String] Return the associated file for the
    #   module from YARD, if one exists.
    def yard_file
      YARD::Registry.at(name).file if yard_docs?
    end

    # @return [Fixnum] Return the associated line for the
    #   module from YARD, if one exists.
    def yard_line
      YARD::Registry.at(name).line if yard_docs?
    end

    # @return [String] Return the YARD docs for this module.
    def yard_doc
      YARD::Registry.at(name).docstring.to_s if yard_docs?
    end

    # Return a candidate for this module of specified rank. A `rank`
    # of 0 is equivalent to the 'primary candidate', which is the
    # module definition with the highest number of methods. A `rank`
    # of 1 is the module definition with the second highest number of
    # methods, and so on. Module candidates are necessary as modules
    # can be reopened multiple times and in multiple places in Ruby,
    # the candidate API gives you access to the module definition
    # representing each of those reopenings.
    # @raise [Pry::CommandError] If the `rank` is out of range. That
    #   is greater than `number_of_candidates - 1`.
    # @param [Fixnum] rank
    # @return [Pry::WrappedModule::Candidate]
    def candidate(rank)
      @memoized_candidates[rank] ||= Candidate.new(self, rank)
    end

    # @return [Fixnum] The number of candidate definitions for the
    #   current module.
    def number_of_candidates
      method_candidates.count
    end

    # @note On JRuby 1.9 and higher, in certain conditions, this method chucks
    #   away its ability to be quick (when there are lots of monkey patches,
    #   like in Rails). However, it should be efficient enough on other rubies.
    # @see https://github.com/jruby/jruby/issues/525
    # @return [Enumerator, Array] on JRuby 1.9 and higher returns Array, on
    #  other rubies returns Enumerator
    def candidates
      enum = Enumerator.new do |y|
               (0...number_of_candidates).each do |num|
                 y.yield candidate(num)
               end
             end
      Pry::Helpers::BaseHelpers.jruby_19? ? enum.to_a : enum
    end

    # @return [Boolean] Whether YARD docs are available for this module.
    def yard_docs?
      !!(defined?(YARD) && YARD::Registry.at(name))
    end

    # @param [Fixnum] times How far to travel up the ancestor chain.
    # @return [Pry::WrappedModule, nil] The wrapped module that is the
    #   superclass.
    #   When `self` is a `Module` then return the
    #   nth ancestor, otherwise (in the case of classes) return the
    #   nth ancestor that is a class.
    def super(times=1)
      return self if times.zero?

      if wrapped.is_a?(Class)
        sup = ancestors.select { |v| v.is_a?(Class) }[times]
      else
        sup = ancestors[times]
      end

      Pry::WrappedModule(sup) if sup
    end

    private

    # @return [Pry::WrappedModule::Candidate] The candidate with the
    #   highest rank, that is the 'monkey patch' of this module with the
    #   highest number of methods, which contains a source code line that
    #   defines the module. It is considered the 'canonical' definition
    #   for the module. In the absense of a suitable candidate, the
    #   candidate of rank 0 will be returned, or a CommandError raised if
    #   there are no candidates at all.
    def primary_candidate
      @primary_candidate ||= candidates.find { |c| c.file } ||
        # This will raise an exception if there is no candidate at all.
        candidate(0)
    end

    # @return [Array<Array<Pry::Method>>] The array of `Pry::Method` objects,
    #   there are two associated with each candidate. The first is the 'base
    #   method' for a candidate and it serves as the start point for
    #   the search in  uncovering the module definition. The second is
    #   the last method defined for that candidate and it is used to
    #   speed up source code extraction.
    def method_candidates
      @method_candidates ||= all_source_locations_by_popularity.map do |group|
        methods_sorted_by_source_line  = group.last.sort_by(&:source_line)
        [methods_sorted_by_source_line.first, methods_sorted_by_source_line.last]
      end
    end

    # A helper method.
    def all_source_locations_by_popularity
      return @all_source_locations_by_popularity if @all_source_locations_by_popularity

      ims = all_relevant_methods_for(wrapped)
      @all_source_locations_by_popularity = ims.group_by { |v| Array(v.source_location).first }.
        sort_by do |path, methods|
          expanded = File.expand_path(path)
          load_order = $LOADED_FEATURES.index{ |file| expanded.end_with?(file) }

          [-methods.size, load_order || (1.0 / 0.0)]
        end
    end

    # We only want methods that have a non-nil `source_location`. We also
    # skip some spooky internal methods.
    # (i.e we skip `__class_init__` because it's an odd rbx specific thing that causes tests to fail.)
    # @return [Array<Pry::Method>]
    def all_relevant_methods_for(mod)
      methods = all_methods_for(mod).select(&:source_location).
        reject{ |x| x.name == '__class_init__' || method_defined_by_forwardable_module?(x) }

      return methods unless methods.empty?

      safe_send(mod, :constants).map do |const_name|
        if const = nested_module?(mod, const_name)
          all_relevant_methods_for(const)
        else
          []
        end
      end.flatten
    end

    # Return all methods (instance methods and class methods) for a
    # given module.
    # @return [Array<Pry::Method>]
    def all_methods_for(mod)
      Pry::Method.all_from_obj(mod, false) + Pry::Method.all_from_class(mod, false)
    end

    def nested_module?(parent, name)
      return if safe_send(parent, :autoload?, name)
      child = safe_send(parent, :const_get, name)
      return unless Module === child
      return unless safe_send(child, :name) == "#{safe_send(parent, :name)}::#{name}"
      child
    end

    # Detect methods that are defined with `def_delegator` from the Forwardable
    # module. We want to reject these methods as they screw up module
    # extraction since the `source_location` for such methods points at forwardable.rb
    # TODO: make this more robust as valid user-defined files called
    # forwardable.rb are also skipped.
    def method_defined_by_forwardable_module?(method)
      method.source_location.first =~ /forwardable\.rb/
    end

    # memoized lines for file
    def lines_for_file(file)
      @lines_for_file ||= {}

      if file == Pry.eval_path
        @lines_for_file[file] ||= Pry.line_buffer.drop(1)
      else
        @lines_for_file[file] ||= File.readlines(file)
      end
    end
  end
end