require 'set'


module Orchestrator
    module Core
        class SystemProxy
            def initialize(thread, sys_id, origin = nil)
                @system = sys_id.to_sym
                @thread = thread
                @origin = origin    # This is the module that requested the proxy
            end

            # Alias for get
            def [](mod)
                get mod
            end

            # Provides a proxy to a module for a safe way to communicate across threads
            #
            # @param module [String, Symbol] the name of the module in the system
            # @param index [Integer] the index of the desired module (starting at 1)
            # @return [::Orchestrator::Core::RequestsProxy] proxies requests to a single module
            def get(mod, index = 1)
                index -= 1  # Get the real index
                name = mod.to_sym

                RequestProxy.new(@thread, system.get(name, index))
            end

            # Checks for the existence of a particular module
            #
            # @param module [String, Symbol] the name of the module in the system
            # @param index [Integer] the index of the desired module (starting at 1)
            # @return [true, false] does the module exist?
            def exists?(mod, index = 1)
                index -= 1  # Get the real index
                name = mod.to_sym

                !system.get(name, index).nil?
            end

            # Provides a proxy to multiple modules. A simple way to send commands to multiple devices
            #
            # @param module [String, Symbol] the name of the module in the system
            # @return [::Orchestrator::Core::RequestsProxy] proxies requests to multiple modules
            def all(mod)
                name = mod.to_sym
                RequestsProxy.new(@thread, system.all(name))
            end

            # Iterates over the modules in the system. Can also specify module types.
            # 
            # @param mod_name [String, Symbol] the optional names of modules to iterate over
            # @yield [Module Instance, Symbol, Integer] yields the modules with their name and index
            def each(*args)
                mods = args.empty? ? modules : args
                mods.each do |mod|
                    number = count(mod)
                    (1..number).each do |index|
                        yield(get(mod, index), mod, index)
                    end
                end
            end

            # Grabs the number of a particular device type
            #
            # @param module [String, Symbol] the name of the module in the system
            # @return [Integer] the number of modules with a shared name
            def count(mod)
                name = mod.to_sym
                system.count(name)
            end

            # Returns a list of all the module names in the system
            #
            # @return [Array] a list of all the module names
            def modules
                system.modules
            end

            # Returns the system name as defined in the database
            #
            # @return [String] the name of the system 
            def name
                system.config.name
            end

            # Used to be notified when an update to a status value occurs
            #
            # @param module [String, Symbol] the name of the module in the system
            # @param index [Integer] the index of the module as there may be more than one
            # @param status [String, Symbol] the name of the status variable
            # @param callback [Proc] method, block, proc or lambda to be called when a change occurs
            # @return [Object] a reference to the subscription for un-subscribing
            def subscribe(mod_name, index, status = nil, callback = nil, &block)
                # Allow index to be optional
                if not index.is_a?(Integer)
                    callback = status || block
                    status = index.to_sym
                    index = 1
                else
                    callback ||= block
                end
                mod_name = mod_name.to_sym

                raise 'callback required' unless callback.respond_to? :call

                # We need to get the system to schedule threads
                sys = system
                options = {
                    sys_id: @system,
                    sys_name: sys.config.name,
                    mod_name: mod_name,
                    index: index,
                    status: status,
                    callback: callback,
                    on_thread: @thread
                }

                # if the module exists, subscribe on the correct thread
                # use a bit of promise magic as required
                mod_man = sys.get(mod_name, index - 1)
                sub = if mod_man
                    defer = @thread.defer

                    options[:mod_id] = mod_man.settings.id.to_sym
                    options[:mod] = mod_man
                    thread = mod_man.thread
                    thread.schedule do
                        defer.resolve (
                            thread.observer.subscribe(options)
                        )
                    end

                    defer.promise
                else
                    @thread.observer.subscribe(options)
                end

                @origin.add_subscription sub if @origin
                sub
            end


            protected


            def system
                ::Orchestrator::System.get(@system)
            end
        end
    end
end