# Copyright (c) 2021 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true

require 'fiber'
require 'monitor'
require 'contrast/agent/scope'

# This is the Scope component.
#
# It tracks /Contrast/ scope.  That is, "are we currently doing assess or protect stuff within a patched method?" --
# this is how we avoid doing Contrast stuff on Contrast code or creating infinite loops -- or "are we in some other
# execution context for which we need to special case?".
module Contrast
  module Components
    module Scope # :nodoc:
      MONITOR = Monitor.new
      EXECUTION_CONTEXT = {} # rubocop:disable Style/MutableConstant

      class Interface # :nodoc:
        def initialize
          # This is probably redundant with #scope_for_current_ec's nil check.
          EXECUTION_CONTEXT[Fiber.current] = Contrast::Agent::Scope.new
        end

        # This returns the scope governing the current execution context. Use this sparingly, preferring the instance
        # & class methods to access and query scope, rather than interacting with the scope object directly.
        def scope_for_current_ec
          MONITOR.synchronize do
            return EXECUTION_CONTEXT[Fiber.current] ||= Contrast::Agent::Scope.new
          end
        end
      end

      module InstanceMethods # :nodoc:
        # For each instance method on a scope, define a forwarder to the scope on the current execution context's scope.
        def scope_for_current_ec
          MONITOR.synchronize do
            return EXECUTION_CONTEXT[Fiber.current] ||= Contrast::Agent::Scope.new
          end
        end

        def enter_contrast_scope!
          scope_for_current_ec.enter_contrast_scope!
        end

        def enter_deserialization_scope!
          scope_for_current_ec.enter_deserialization_scope!
        end

        def enter_split_scope!
          scope_for_current_ec.enter_split_scope!
        end

        def enter_scope! name
          scope_for_current_ec.enter_scope! name
        end

        def exit_contrast_scope!
          scope_for_current_ec.exit_contrast_scope!
        end

        def exit_deserialization_scope!
          scope_for_current_ec.exit_deserialization_scope!
        end

        def exit_split_scope!
          scope_for_current_ec.exit_split_scope!
        end

        def exit_scope! name
          scope_for_current_ec.exit_scope! name
        end

        def in_contrast_scope?
          scope_for_current_ec.in_contrast_scope?
        end

        def in_deserialization_scope?
          scope_for_current_ec.in_deserialization_scope?
        end

        def in_split_scope?
          scope_for_current_ec.in_split_scope?
        end

        def split_scope_depth
          scope_for_current_ec.split_scope_depth
        end

        def in_scope? name
          scope_for_current_ec.in_scope? name
        end

        def with_contrast_scope
          scope_for_current_ec.enter_contrast_scope!
          yield
        ensure
          scope_for_current_ec.exit_contrast_scope!
        end

        def with_deserialization_scope
          scope_for_current_ec.enter_deserialization_scope!
          yield
        ensure
          scope_for_current_ec.exit_deserialization_scope!
        end

        def with_split_scope
          scope_for_current_ec.enter_split_scope!
          yield
        ensure
          scope_for_current_ec.exit_split_scope!
        end
      end

      def self.sweep_dead_ecs
        # TODO: RUBY-534, #sweep_dead_ecs compensates for a lack of weak tables. when we can use WeakRef, we should
        #   investigate removing this call and instead use the WeakRef for the Execution Context's Keys or using our
        #   Finalizers Hash for Fibers
        MONITOR.synchronize do
          EXECUTION_CONTEXT.delete_if do |ec, _scope|
            !ec.alive?
          end
        end
      end

      ClassMethods = InstanceMethods
    end
  end
end