# encoding: utf-8
# This file is distributed under New Relic's license terms.
# See https://github.com/newrelic/rpm/blob/master/LICENSE for complete details.

require 'dependency_detection/version'
module DependencyDetection

  module_function
  @@items = []
  def defer(&block)
    item = Dependent.new
    item.instance_eval(&block)
    @@items << item
  end

  def detect!
    @@items.each do |item|
      if item.dependencies_satisfied?
        item.execute
      end
    end
  end

  def dependency_by_name(name)
    @@items.find {|i| i.name == name }
  end

  def installed?(name)
    item = dependency_by_name(name)
    item && item.executed
  end

  class Dependent
    attr_reader :executed
    attr_reader :name
    def executed!
      @executed = true
    end

    attr_reader :dependencies

    def initialize
      @dependencies = []
      @executes = []
    end

    def dependencies_satisfied?
      !executed and check_dependencies
    end

    def execute
      @executes.each do |x|
        x.call
      end
    ensure
      executed!
    end

    def check_dependencies
      dependencies && dependencies.all? { |d| d.call }
    end

    def depends_on
      @dependencies << Proc.new
    end

    def executes
      @executes << Proc.new
    end
  end
end