module Blueprints
  # Defines a root namespace that is used when no other namespace is. Apart from functionality in namespace it also allows
  # building blueprints/namespaces by name. Is also used for copying instance variables between blueprints/contexts/global
  # context.
  class RootNamespace < Namespace
    # Lists of executed blueprints (to prevent executing twice). Cleared before each test.
    attr_reader :executed_blueprints
    # Context that blueprints/namespaces are built against. Reset before each test.
    attr_writer :eval_context

    # Initialized new root context.
    def initialize
      @executed_blueprints = @global_executed_blueprints = []
      @auto_iv_list = Set.new

      super '', Context.new
    end

    # Loads all instance variables from global context to current one. Creates new eval context.
    def setup
      @eval_context = EvalContext.new
      (@executed_blueprints - @global_executed_blueprints).each(&:undo!)
      @executed_blueprints = @global_executed_blueprints.clone

      if Blueprints.config.transactions
        Marshal.load(@global_variables).each { |name, value| eval_context.instance_variable_set(name, value) }
      else
        build(Blueprints.config.prebuild)
      end
    end

    # Sets up global context and executes prebuilt blueprints against it.
    # @param [Array<Symbol, String>] blueprints Names of blueprints that are prebuilt.
    def prebuild(blueprints)
      build(blueprints) if blueprints

      @global_executed_blueprints = @executed_blueprints
      @global_variables = Marshal.dump(eval_context.instance_variables.each_with_object({}) { |iv, hash| hash[iv] = eval_context.instance_variable_get(iv) })
    end

    # Builds blueprints that are passed against current context. Copies instance variables to context given if one is given.
    # @param [Array<Symbol, String>] names List of blueprints/namespaces to build.
    # @param current_context Object to copy instance variables from eval context after building to.
    # @param build_once (see Buildable.build)
    # @return Result of last blueprint/namespace.
    def build(names, current_context = nil, build_once = true)
      names = [names] unless names.is_a?(Array)
      result = names.inject(nil) do |result, member|
        if member.is_a?(Hash)
          member.map { |name, options| self[name].build(eval_context, build_once, options) }.last
        else
          self[member].build(eval_context, build_once)
        end
      end

      eval_context.copy_instance_variables(current_context) if current_context
      result
    end

    # Return current eval context or creates a new one.
    # @return [Blueprints::EvalContext] Eval context to be used to build blueprints.
    def eval_context
      @eval_context ||= EvalContext.new
    end

    @@root = RootNamespace.new
  end
end