# pry-stack_explorer.rb
# (C) John Mair (banisterfiend); MIT license

require "pry-stack_explorer/version"
require "pry"
require "binding_of_caller"

module PryStackExplorer

  def self.add_frame_manager(bindings, _pry_)
    Thread.current[:__pry_frame_managers__] ||= {}
    Thread.current[:__pry_frame_managers__][_pry_] = FrameManager.new(bindings, _pry_)
  end

  def self.delete_frame_manager(_pry_)
    Thread.current[:__pry_frame_managers__].delete(_pry_)
  end

  def self.frame_manager(_pry_)
    Thread.current[:__pry_frame_managers__][_pry_]
  end

  def self.bindings_equal?(b1, b2)
    (b1.eval('self') == b2.eval('self')) &&
      (b1.eval('__method__') == b2.eval('__method__')) &&
      (b1.eval('local_variables').map { |v| b1.eval("#{v}") } ==
       b2.eval('local_variables').map { |v| b2.eval("#{v}") })
  end

  class FrameManager
    attr_reader   :binding_index
    attr_accessor :bindings

    def initialize(bindings, _pry_)
      @bindings      = bindings
      @binding_index = 0
      @pry           = _pry_
    end

    def convert_from_one_index(n)
      if n >= 0
        n - 1
      else
        n
      end
    end
    private :convert_from_one_index

    def signature(b)
      if b.eval('__method__')
        "#{closure_type} in #{b.eval('self').class}##{b.eval('__method__')}"
      else
        if b.eval('self').is_a?(Module)
          "#{closure_type} in <class:#{b.eval('self')}>"
        end
      end
    end

    def binding_info_for(b)
      b_self = b.eval('self')
      b_method = b.eval('__method__')

      if b_method && b_method != :__binding__ && b_method != :__binding_impl__
        b_method.to_s
      elsif b_self.instance_of?(Module)
        "<module:#{b_self}>"
      elsif b_self.instance_of?(Class)
        "<class:#{b_self}>"
      else
        "<main>"
      end
    end

    def change_binding_to(index)
      index = convert_from_one_index(index)

      if index > bindings.size - 1
        @pry.output.puts "Warning: At top of stack, cannot go further!"
      elsif index < 0
        @pry.output.puts "Warning: At bottom of stack, cannot go further!"
      else
        @binding_index = index
        @pry.binding_stack[-1] = bindings[binding_index]

        @pry.run_command "whereami"
      end
    end
  end

  StackCommands = Pry::CommandSet.new do
    command "up", "Go up to the caller's context" do |inc_str|
      inc = inc_str.nil? ? 1 : inc_str.to_i

      if !PryStackExplorer.frame_manager(_pry_)
        output.puts "Nowhere to go!"
      else
        binding_index = PryStackExplorer.frame_manager(_pry_).binding_index
        PryStackExplorer.frame_manager(_pry_).change_binding_to binding_index + inc + 1
      end
    end

    command "down", "Go down to the callee's context." do |inc_str|
      inc = inc_str.nil? ? 1 : inc_str.to_i

      if !PryStackExplorer.frame_manager(_pry_)
        output.puts "Nowhere to go!"
      else
        binding_index = PryStackExplorer.frame_manager(_pry_).binding_index
        PryStackExplorer.frame_manager(_pry_).change_binding_to binding_index - inc + 1
      end
    end

    command "show-stack", "Show all frames" do |*args|
      opts = parse_options!(args) do |opt|
        opt.banner unindent <<-USAGE
            Usage: show-stack [OPTIONS]
            Show all accessible stack frames.
            e.g: show-stack -v
          USAGE

        opt.on :v, :verbose, "Include extra information."
      end

      if !PryStackExplorer.frame_manager(_pry_)
        output.puts "No caller stack available!"
      else
        output.puts "\n#{text.bold('Showing all accessible frames in stack:')}\n--\n"

        PryStackExplorer.frame_manager(_pry_).bindings.each_with_index do |b, i|
          meth = b.eval('__method__')
          b_self = b.eval('self')

          desc = b.frame_description ? "#{text.bold('Description:')} #{b.frame_description}".ljust(40) :
            "#{text.bold('Description:')} #{PryStackExplorer.frame_manager(_pry_).binding_info_for(b)}".ljust(40)
          sig = meth ? "#{text.bold('Signature:')} #{Pry::Method.new(b_self.method(meth)).signature}".ljust(40) : "".ljust(32)
          type = b.frame_type ? "#{text.bold('Type:')} #{b.frame_type}".ljust(20) : "".ljust(20)
          slf = "#{text.bold('Self:')} #{b_self}".ljust(20)
          path = "#{text.bold("@ File:")} #{b.eval('__FILE__')}:#{b.eval('__LINE__')}"

          info = "##{i + 1} #{desc} #{sig} #{slf if opts[:v]} #{type \
                  if opts[:v]} #{path if opts[:v]}"
          if i == PryStackExplorer.frame_manager(_pry_).binding_index

            output.puts "=> #{info}"
          else
            output.puts "   #{info}"
          end
        end
      end
    end

    command "frame", "Switch to a particular frame." do |frame_num|
      if !PryStackExplorer.frame_manager(_pry_)
        output.puts "nowhere to go!"
      else
        PryStackExplorer.frame_manager(_pry_).change_binding_to frame_num.to_i
      end
    end

    command "frame-type", "Display current frame type." do
      output.puts _pry_.binding_stack.last.frame_type
    end
  end
end

Pry.config.hooks.add_hook(:after_session, :delete_frame_manager) do |_, _, _pry_|
  PryStackExplorer.delete_frame_manager(_pry_)
end

Pry.config.hooks.add_hook(:when_started, :save_caller_bindings) do |binding_stack, _pry_|
  target = binding_stack.last

  if binding.of_caller(6).eval('__method__') == :pry
    drop_number = 7
  else
    drop_number = 6
  end

  bindings = binding.callers.drop(drop_number)

  # Use the binding returned by #of_caller if possible (as we get
  # access to frame_type).
  # Otherwise stick to the given binding (target).
  if !PryStackExplorer.bindings_equal?(target, bindings.first)
    bindings.shift
    bindings.unshift(target)
  end

  binding_stack.replace([bindings.first])
  PryStackExplorer.add_frame_manager(bindings, _pry_)
end

Pry.config.commands.import PryStackExplorer::StackCommands

# monkey-patch the whereami command to show some frame information,
# useful for navigating stack.
Pry.config.commands.before_command("whereami") do |num|
  if PryStackExplorer.frame_manager(_pry_)
    bindings      = PryStackExplorer.frame_manager(_pry_).bindings
    binding_index = PryStackExplorer.frame_manager(_pry_).binding_index

    output.puts "\n"
    output.puts "#{Pry::Helpers::Text.bold('Frame number:')} #{binding_index + 1}/#{bindings.size}"
    output.puts "#{Pry::Helpers::Text.bold('Frame type:')} #{bindings[binding_index].frame_type}" if bindings[binding_index].frame_type
  end
end