#!/usr/bin/ksh93

# poll(1) builtin test

typeset -T circus_t=(
	typeset fifo_name
	integer in_fd
	integer out_fd

	function cinit
	{
		integer pid
		# fixme: we can't assign fd directly because ast-ksh.2012-08-13 has a bug
		# with "redirect"
		integer fd
		_.fifo_name="$1"
		rm -f "${_.fifo_name}"
		mkfifo "${_.fifo_name}"

		# little "trick" with fifos - "redirect" would block if
		# there is no reader... so we create one in a
		# sub-process and kill it below after we opened the fd
		{ redirect {dummy}<"${_.fifo_name}" ; for (( ;; )) ; do sleep 3600 ; done ; } &
		(( pid=$! ))

		redirect {fd}>"${_.fifo_name}"
		(( _.out_fd=fd ))
		#printf '%s: outfd=%d\n' "${_.fifo_name}" _.out_fd

		kill $pid ; wait

		redirect {fd}<"${_.fifo_name}"
		(( _.in_fd=fd ))
		#printf '%s: infd=%d\n' "${_.fifo_name}" _.in_fd
	}

	function cleanup
	{
		rm "${_.fifo_name}"
	}
)

function main
{
	integer i
	typeset name subname
	typeset -M toupper up

	#set -x

	circus_t -A ar

	for name in 'a' 'b' 'c' 'd' ; do
		ar[${name}].cinit "fifo_${name}"
	done

	compound -A pollfd
	for name in "${!ar[@]}" ; do
		subname="fifo_${name}_in"
		pollfd[${subname}]=(  fd=${ar[${name}].in_fd} events=( pollin='true'  pollerr='false' pollhup='false' ) revents=() )
		subname="fifo_${name}_out"
		pollfd[${subname}]=( fd=${ar[${name}].out_fd} events=( pollout='true' pollerr='false' pollhup='false' ) revents=() )
	done

	print -v pollfd

	for (( i=0 ; i < 120 ; i++ )) ; do
		poll -t5 pollfd || true

		# print results table
		printf '|'
		for name in "${!ar[@]}" ; do
			up="$name"

			subname="fifo_${name}_in"
			if ${pollfd[${subname}].revents.pollin}    ; then printf '%sI+' "${up}" ; else printf '...' ; fi
			if ${pollfd[${subname}].revents.pollhup}   ; then printf '%sIH' "${up}" ; else printf '...' ; fi
			if ${pollfd[${subname}].revents.pollerr}   ; then printf '%sIE' "${up}" ; else printf '...' ; fi
			subname="fifo_${name}_out"
			if ${pollfd[${subname}].revents.pollout}   ; then printf '%sO+' "${up}" ; else printf '...' ; fi
			if ${pollfd[${subname}].revents.pollhup}   ; then printf '%sOH' "${up}" ; else printf '...' ; fi
			if ${pollfd[${subname}].revents.pollerr}   ; then printf '%sOE' "${up}" ; else printf '...' ; fi
			printf '|'
		done
		printf '\n'

		# pass token around
		if ${pollfd[fifo_a_in].revents.pollin} && ${pollfd[fifo_b_out].revents.pollout}; then
			if read -u${pollfd[fifo_a_in].fd} -N1 x ; then
				print -u${pollfd[fifo_b_out].fd} -f "%s" "$x"
			fi
		fi
		if ${pollfd[fifo_b_in].revents.pollin} && ${pollfd[fifo_c_out].revents.pollout}; then
			if read -u${pollfd[fifo_b_in].fd} -N1 x ; then
				print -u${pollfd[fifo_c_out].fd} -f "%s" "$x"
			fi
		fi
		if ${pollfd[fifo_c_in].revents.pollin} && ${pollfd[fifo_d_out].revents.pollout}; then
			if read -u${pollfd[fifo_c_in].fd} -N1 x ; then
				print -u${pollfd[fifo_d_out].fd} -f "%s" "$x"
			fi
		fi
		if ${pollfd[fifo_d_in].revents.pollin} && ${pollfd[fifo_a_out].revents.pollout}; then
			if read -u${pollfd[fifo_d_in].fd} -N1 x ; then
				print -u${pollfd[fifo_a_out].fd} -f "%s" "$x"
			fi
		fi

		# fixme: send HUP around

		# send start token
		(( i==0 )) && print -u${pollfd[fifo_a_out].fd} -f '\u[20ac]'
	done
	return 0
}

set -o nounset
set -o errexit

builtin mkfifo
builtin poll
builtin rm

main