# Copyright, 2017, by Samuel G. D. Williams. <http://www.codeotaku.com>
# 
# Permission is hereby granted, free of charge, to any person obtaining a copy
# of this software and associated documentation files (the "Software"), to deal
# in the Software without restriction, including without limitation the rights
# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
# copies of the Software, and to permit persons to whom the Software is
# furnished to do so, subject to the following conditions:
# 
# The above copyright notice and this permission notice shall be included in
# all copies or substantial portions of the Software.
# 
# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
# THE SOFTWARE.

require 'objspace'

module Async
	module RSpec
		module Memory
			Allocation = Struct.new(:count, :size) do
				SLOT_SIZE = 40
				
				def << object
					self.count += 1
					
					# We don't want to force specs to take the slot size into account.
					self.size += ObjectSpace.memsize_of(object) - SLOT_SIZE
				end
				
				def self.default_hash
					Hash.new{|h,k| h[k] = Allocation.new(0, 0)}
				end
			end
			
			class Trace
				def self.supported?
					# There are issues on truffleruby-1.0.0rc9
					return false if RUBY_ENGINE == "truffleruby"
					
					ObjectSpace.respond_to?(:trace_object_allocations)
				end
				
				if supported?
					def self.capture(*args, &block)
						self.new(*args).tap do |trace|
							trace.capture(&block)
						end
					end
				else
					def self.capture(*args, &block)
						yield
						
						return nil
					end
				end
				
				def initialize(klasses)
					@klasses = klasses
					
					@allocated = Allocation.default_hash
					@retained = Allocation.default_hash
					
					@ignored = Allocation.default_hash
					
					@total = Allocation.new(0, 0)
				end
				
				attr :allocated
				attr :retained
				
				attr :ignored
				
				attr :total
				
				def current_objects(generation)
					allocations = []
					
					ObjectSpace.each_object do |object|
						if ObjectSpace.allocation_generation(object) == generation
							allocations << object
						end
					end
					
					return allocations
				end
				
				def find_base(object)
					@klasses.find{|klass| object.is_a? klass}
				end
				
				def capture(&block)
					GC.start
					
					begin
						GC.disable
						
						generation = GC.count
						ObjectSpace.trace_object_allocations(&block)
						
						allocated = current_objects(generation)
					ensure
						GC.enable
					end
					
					GC.start
					retained = current_objects(generation)
					
					# All allocated objects, including those freed in the last GC:
					allocated.each do |object|
						if klass = find_base(object)
							@allocated[klass] << object
						else
							# If the user specified classes, but we can't pin this allocation to a specific class, we issue a warning.
							if @klasses.any?
								warn "Ignoring allocation of #{object.class} at #{ObjectSpace.allocation_sourcefile(object)}:#{ObjectSpace.allocation_sourceline(object)}"
							end
							
							@ignored[object.class] << object
						end
						
						@total << object
					end
					
					# Retained objects are still alive after a final GC:
					retained.each do |object|
						if klass = find_base(object)
							@retained[klass] << object
						end
					end
				end
			end
		end
	end
end