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require 'set'
require_relative 'keyword'
module RCM
# Concern that wraps side-effecting blocks so they are skipped (and
# logged as dry-run) when the --dry option is active. Kept separate
# from dependency tracking so each module has a single responsibility.
module DryRun
# Log the action and yield the block, unless --dry is active.
# In dry-run mode only logs the message (with " - dry run!" appended)
# and returns without executing the block.
def do?(message)
if option :dry
info("#{message} - dry run!")
return
end
info(message)
yield
end
end
# To track resource dependencies
module ResourceDependencies
def initialize(...)
super(...)
@requires = Set.new
# Use the class-level registry (populated via Resource.inherited) rather
# than scanning ObjectSpace — deterministic, load-order-safe, and O(1).
@valid_resources = Resource.subclass_names
end
def method_missing(method_name, *args)
super(method_name, *args) unless @valid_resources.include?(method_name)
args.map { |arg| "#{method_name}('#{arg}')" }
end
def respond_to_missing? = true
def requires(*others)
return @requires if others.empty?
others.flatten.each do |other|
unless other.include?('(')
# Convert "notify foo" to "notify('foo')"
resource, rest = other.split(' ', 2)
other = "#{resource}('#{rest}')"
end
info "Registered dependency on #{other}"
@requires << other
end
end
def requires?(*others) = others.flatten.none? { |other| !@requires&.include?(other) }
end
# To resolve dependencies
module DependencyEvaluator
attr_reader :evaluated
class DependencyLoop < StandardError; end
class UnresolvedDependency < StandardError; end
def evaluate!
return false if @evaluated
info 'Evaluating...'
raise DependencyLoop, "Dependency loop detected for #{id}" if @loop_detection
@loop_detection = true
# Try to evaluate all dependencies recursively.
@requires.each.map { Resource.find(_1) }.each(&:evaluate!)
# Raise an exception when there are still unresolved dependencies.
unresolved = @requires.each.map { Resource.find(_1) }.reject(&:evaluated)
raise UnresolvedDependency, "Unresolved dependencies: #{unresolved.map(&:id)}" if unresolved.count.positive?
@loop_detection = false
@evaluated = true
end
end
# A resource is something concrete to be managed, e.g. a file, or a CRON job.
class Resource < Keyword
include DryRun
include DependencyEvaluator
include ResourceDependencies
class NoSuchResourceObject < StandardError; end
@@resource_find_cache = {}
# Class-level registry: every subclass is registered here when it is
# first loaded (via the inherited hook), so ResourceDependencies can
# look up valid keyword names without scanning ObjectSpace.
@@subclass_names = Set.new
def self.inherited(subclass)
super
@@subclass_names << subclass.to_s.sub('RCM::', '').downcase.to_sym
end
# Return a frozen snapshot so callers cannot accidentally mutate the
# shared registry through the @valid_resources instance variable.
def self.subclass_names = @@subclass_names.freeze
def self.find(id)
return @@resource_find_cache[id] if @@resource_find_cache.key?(id)
klass = Object.const_get("RCM::#{id.split(/[( ]/).first.capitalize}")
resource = ObjectSpace.each_object(klass).find { _1.id == id }
raise NoSuchResourceObject, "Unable to find resource #{id}" if resource.nil?
@@resource_find_cache[id] = resource
end
end
end
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