# encoding: utf-8

require 'thread'
require 'one_apm/support/vm/snapshot'

module OneApm
  module Support
    module VM
      class MriVM
        def snapshot
          snap = Snapshot.new
          gather_stats(snap)
          snap
        end

        def gather_stats(snap)
          gather_gc_stats(snap)
          gather_ruby_vm_stats(snap)
          gather_thread_stats(snap)
          gather_gc_time(snap)
        end

        def gather_gc_stats(snap)
          if supports?(:gc_runs)
            snap.gc_runs = GC.count
          end

          if GC.respond_to?(:stat)
            gc_stats = GC.stat
            snap.total_allocated_object = gc_stats[:total_allocated_objects] || gc_stats[:total_allocated_object]
            snap.major_gc_count = gc_stats[:major_gc_count]
            snap.minor_gc_count = gc_stats[:minor_gc_count]
            snap.heap_live = gc_stats[:heap_live_slots] || gc_stats[:heap_live_slot] || gc_stats[:heap_live_num]
            snap.heap_free = gc_stats[:heap_free_slots] || gc_stats[:heap_free_slot] || gc_stats[:heap_free_num]
          end
        end

        def gather_gc_time(snap)
          if supports?(:gc_total_time)
            snap.gc_total_time = OneApm::Manager.agent.monotonic_gc_profiler.total_time_s
          end
        end

        def gather_ruby_vm_stats(snap)
          if supports?(:method_cache_invalidations)
            vm_stats = RubyVM.stat
            snap.method_cache_invalidations = vm_stats[:global_method_state]
            snap.constant_cache_invalidations = vm_stats[:global_constant_state]
          end
        end

        def gather_thread_stats(snap)
          snap.thread_count = Thread.list.size
        end

        def supports?(key)
          case key
          when :gc_runs
            RUBY_VERSION >= '1.9.2'
          when :gc_total_time
            OneApm::LanguageSupport.gc_profiler_enabled?
          when :total_allocated_object
            RUBY_VERSION >= '2.0.0'
          when :major_gc_count
            RUBY_VERSION >= '2.1.0'
          when :minor_gc_count
            RUBY_VERSION >= '2.1.0'
          when :heap_live
            RUBY_VERSION >= '1.9.3'
          when :heap_free
            RUBY_VERSION >= '1.9.3'
          when :method_cache_invalidations
            RUBY_VERSION >= '2.1.0'
          when :constant_cache_invalidations
            RUBY_VERSION >= '2.1.0'
          when :thread_count
            true
          else
            false
          end
        end
      end
    end
  end
end