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require 'set'
require_relative 'keyword'
module RCM
# To track recource dependencies
module ResourceDependencies
def initialize(...)
super(...)
@depends_on = Set.new
@valid_resources = Set.new
ObjectSpace.each_object(Class).each do |klass|
@valid_resources << klass.to_s.sub('RCM::', '').downcase.to_sym if klass < Resource
end
end
class NoSuchResourceType < StandardError; end
def method_missing(method_name, *args)
raise NoSuchResourceType, "No such resource type: #{method_name}" unless @valid_resources.include?(method_name)
args.map { |arg| "#{method_name}('#{arg}')" }
end
def respond_to_missing? = true
def depends_on(*others)
return @depends_on if others.empty?
others.flatten.each do |other|
info "Registered dependency on #{other}"
@depends_on << other
end
end
def depends_on?(*others) = others.flatten.none? { |other| !@depends_on&.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
raise DependencyLoop, "Dependency loop detected for #{id}" if @loop_detection
@loop_detection = true
# Try to evaluate all dependencies recursively.
@depends_on.each.map { Resource.find(_1) }.each(&:evaluate!)
# Raise an exception when there are still unresolved dependencies.
unresolved = @depends_on.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 DependencyEvaluator
include ResourceDependencies
class NoSuchResourceObject < StandardError; end
def self.find(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
end
end
end
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