package xmpp

// Manages the stack of filters that can read and modify stanzas on

// their way from the remote to the application.

// Receive new filters on filterAdd; those new filters get added to

// the top of the stack. Receive stanzas at the bottom of the stack on

// input. Send stanzas out the top of the stack on output.

func filterMgr(filterAdd <-chan Filter, input <-chan Stanza, output chan<- Stanza) {

	botFiltIn := output

	topFiltOut := input

loop:

	for {

		select {

		case stan, ok := <-input:

			if !ok {

				break loop

			}

			botFiltIn <- stan

		case stan, ok := <-topFiltOut:

			if !ok {

				break loop

			}

			output <- stan

		case filt := <-filterAdd:

			newTop := make(chan Stanza)

			go filt(topFiltOut, newTop)

			topFiltOut = newTop

		}

	}

	close(botFiltIn)

}

// Starts the filter chain. Filters will all interpose themselves

// between srvIn and cliOut.

func (cl *Client) startFilters(srvIn, cliIn <-chan Stanza) (<-chan Stanza, <-chan Stanza) {

	cliOut := make(chan Stanza)

	srvOut := make(chan Stanza)

	go filterMgr(cl.sendFilterAdd, srvIn, cliOut)

	go filterMgr(cl.recvFilterAdd, cliIn, srvOut)

	return cliOut, srvOut

}

// AddRecvFilter adds a new filter to the top of the stack through which

// incoming stanzas travel on their way up to the client.

func (cl *Client) AddRecvFilter(filt Filter) {

	if filt == nil {

		return

	}

	cl.recvFilterAdd <- filt

}

// AddSendFilter adds a new filter to the top of the stack through

// which outgoing stanzas travel on their way down from the client to

// the network.

func (cl *Client) AddSendFilter(filt Filter) {

	if filt == nil {

		return

	}

	cl.sendFilterAdd <- filt

}