# The GC module provides an interface to Ruby's mark and sweep garbage
# collection mechanism.
#
# Some of the underlying methods are also available via the ObjectSpace module.
#
# You may obtain information about the operation of the GC through GC::Profiler.
#
module GC
  # The number of times GC occurred.
  #
  # It returns the number of times GC occurred since the process started.
  #
  def self.count: () -> Integer

  # Disables garbage collection, returning `true` if garbage collection was
  # already disabled.
  #
  #     GC.disable   #=> false
  #     GC.disable   #=> true
  #
  def self.disable: () -> bool

  # Enables garbage collection, returning `true` if garbage collection was
  # previously disabled.
  #
  #     GC.disable   #=> false
  #     GC.enable    #=> true
  #     GC.enable    #=> false
  #
  def self.enable: () -> bool

  # Initiates garbage collection, even if manually disabled.
  #
  # This method is defined with keyword arguments that default to true:
  #
  #     def GC.start(full_mark: true, immediate_sweep: true); end
  #
  # Use full_mark: false to perform a minor GC. Use immediate_sweep: false to
  # defer sweeping (use lazy sweep).
  #
  # Note: These keyword arguments are implementation and version dependent. They
  # are not guaranteed to be future-compatible, and may be ignored if the
  # underlying implementation does not support them.
  #
  def self.start: (?immediate_sweep: boolish immediate_sweep, ?immediate_mark: boolish immediate_mark, ?full_mark: boolish full_mark) -> nil

  # Returns a Hash containing information about the GC.
  #
  # The hash includes information about internal statistics about GC such as:
  #
  #     {
  #         :count=>0,
  #         :heap_allocated_pages=>24,
  #         :heap_sorted_length=>24,
  #         :heap_allocatable_pages=>0,
  #         :heap_available_slots=>9783,
  #         :heap_live_slots=>7713,
  #         :heap_free_slots=>2070,
  #         :heap_final_slots=>0,
  #         :heap_marked_slots=>0,
  #         :heap_eden_pages=>24,
  #         :heap_tomb_pages=>0,
  #         :total_allocated_pages=>24,
  #         :total_freed_pages=>0,
  #         :total_allocated_objects=>7796,
  #         :total_freed_objects=>83,
  #         :malloc_increase_bytes=>2389312,
  #         :malloc_increase_bytes_limit=>16777216,
  #         :minor_gc_count=>0,
  #         :major_gc_count=>0,
  #         :remembered_wb_unprotected_objects=>0,
  #         :remembered_wb_unprotected_objects_limit=>0,
  #         :old_objects=>0,
  #         :old_objects_limit=>0,
  #         :oldmalloc_increase_bytes=>2389760,
  #         :oldmalloc_increase_bytes_limit=>16777216
  #     }
  #
  # The contents of the hash are implementation specific and may be changed in the
  # future.
  #
  # This method is only expected to work on C Ruby.
  #
  def self.stat: (?::Hash[Symbol, Integer] arg0) -> ::Hash[Symbol, Integer]
               | (?Symbol arg0) -> Integer

  # Returns current status of GC stress mode.
  #
  def self.stress: () -> (Integer | TrueClass | FalseClass)

  # Updates the GC stress mode.
  #
  # When stress mode is enabled, the GC is invoked at every GC opportunity: all
  # memory and object allocations.
  #
  # Enabling stress mode will degrade performance, it is only for debugging.
  #
  # flag can be true, false, or an integer bit-ORed following flags.
  #     0x01:: no major GC
  #     0x02:: no immediate sweep
  #     0x04:: full mark after malloc/calloc/realloc
  #
  def self.stress=: (Integer | TrueClass | FalseClass flag) -> (Integer | TrueClass | FalseClass)

  def self.compact: () -> ::Hash[:considered | :moved, Hash[Symbol | Integer, Integer]]

  # Verify compaction reference consistency.
  #
  # This method is implementation specific.  During compaction, objects that were
  # moved are replaced with T_MOVED objects.  No object should have a reference to
  # a T_MOVED object after compaction.
  #
  # This function doubles the heap to ensure room to move all objects, compacts
  # the heap to make sure everything moves, updates all references, then performs
  # a full GC.  If any object contains a reference to a T_MOVED object, that
  # object should be pushed on the mark stack, and will make a SEGV.
  #
  def self.verify_compaction_references: () -> ::Hash[:considered | :moved, Hash[Symbol | Integer, Integer]]

  # Verify internal consistency.
  #
  # This method is implementation specific. Now this method checks generational
  # consistency if RGenGC is supported.
  #
  def self.verify_internal_consistency: () -> nil

  def self.verify_transient_heap_internal_consistency: () -> nil

  # Returns information about the most recent garbage collection.
  #
  def self.latest_gc_info: () -> ::Hash[::Symbol, untyped]
                         | [K] (?Hash[K, untyped] hash) -> ::Hash[::Symbol | K, untyped]
                         | (Symbol key) -> untyped

  def garbage_collect: (?immediate_sweep: boolish immediate_sweep, ?immediate_mark: boolish immediate_mark, ?full_mark: boolish full_mark) -> nil
end

# internal constants
#
#
GC::INTERNAL_CONSTANTS: Hash[Symbol, Integer]

# GC build options
#
#
GC::OPTS: Array[String]

# The GC profiler provides access to information on GC runs including time,
# length and object space size.
#
# Example:
#
#     GC::Profiler.enable
#
#     require 'rdoc/rdoc'
#
#     GC::Profiler.report
#
#     GC::Profiler.disable
#
# See also GC.count, GC.malloc_allocated_size and GC.malloc_allocations
#
module GC::Profiler
  # Clears the GC profiler data.
  #
  def self.clear: () -> void

  # Stops the GC profiler.
  #
  def self.disable: () -> void

  # Starts the GC profiler.
  #
  def self.enable: () -> void

  # The current status of GC profile mode.
  #
  def self.enabled?: () -> bool

  # Returns an Array of individual raw profile data Hashes ordered from earliest
  # to latest by `:GC_INVOKE_TIME`.
  #
  # For example:
  #
  #     [
  #       {
  #          :GC_TIME=>1.3000000000000858e-05,
  #          :GC_INVOKE_TIME=>0.010634999999999999,
  #          :HEAP_USE_SIZE=>289640,
  #          :HEAP_TOTAL_SIZE=>588960,
  #          :HEAP_TOTAL_OBJECTS=>14724,
  #          :GC_IS_MARKED=>false
  #       },
  #       # ...
  #     ]
  #
  # The keys mean:
  #
  # `:GC_TIME`
  # :   Time elapsed in seconds for this GC run
  # `:GC_INVOKE_TIME`
  # :   Time elapsed in seconds from startup to when the GC was invoked
  # `:HEAP_USE_SIZE`
  # :   Total bytes of heap used
  # `:HEAP_TOTAL_SIZE`
  # :   Total size of heap in bytes
  # `:HEAP_TOTAL_OBJECTS`
  # :   Total number of objects
  # `:GC_IS_MARKED`
  # :   Returns `true` if the GC is in mark phase
  #
  #
  # If ruby was built with `GC_PROFILE_MORE_DETAIL`, you will also have access to
  # the following hash keys:
  #
  # `:GC_MARK_TIME`
  # `:GC_SWEEP_TIME`
  # `:ALLOCATE_INCREASE`
  # `:ALLOCATE_LIMIT`
  # `:HEAP_USE_PAGES`
  # `:HEAP_LIVE_OBJECTS`
  # `:HEAP_FREE_OBJECTS`
  # `:HAVE_FINALIZE`
  # :
  #
  def self.raw_data: () -> ::Array[::Hash[Symbol, untyped]]

  # Writes the GC::Profiler.result to `$stdout` or the given IO object.
  #
  def self.report: (?IO io) -> void

  # Returns a profile data report such as:
  #
  #     GC 1 invokes.
  #     Index    Invoke Time(sec)       Use Size(byte)     Total Size(byte)         Total Object                    GC time(ms)
  #         1               0.012               159240               212940                10647         0.00000000000001530000
  #
  def self.result: () -> String

  # The total time used for garbage collection in seconds
  #
  def self.total_time: () -> Float
end