3 files changed, 192 insertions, 81 deletions

diff --git a/Makefile b/Makefile
index cda8018..472af80 100644
--- a/Makefile
+++ b/Makefile
@@ -10,7 +10,7 @@ ifeq (,$(socat))
 prereqs += socat
 endif
 .PHONY: install deps
-executables = read-tty write-tty read_chars.bash
+executables = read-tty write-tty read_chars.bash finally.bash
 executables_sources = $(addprefix src/,$(executables))
 install: deps
         $(install) -v -T -- src/twopane.bash /usr/local/bin/twopane
diff --git a/src/finally.bash b/src/finally.bash
new file mode 100755
index 0000000..7700c98
--- /dev/null
+++ b/src/finally.bash
@@ -0,0 +1,51 @@
+#!/bin/bash
+#
+# Usage:
+#
+#       finally <eval-string> <cmd> [args...]
+#
+# What it does:
+#
+#       (1) First, the <cmd> is executed with its arguments if any.
+#
+#       (2) Then <eval-string> is executed as it would be by eval in
+#           the most global scope of the shell.  (It is actually sent to
+#           the bash prompt's standard input as a list of quoted words.)
+#
+# Reason to exist:
+#
+#       If execution of <cmd> is interrupted by signal, the
+#       <eval-string> will still run.
+
+finally()
+{
+        exec \
+                {FINALLY_0}<&0 \
+                {FINALLY_1}>&1 \
+                {FINALLY_2}>&2 \
+                0< <(finally_unwind "$1") \
+                &> /dev/null # silence prompt
+                # note that finally_unwind still has un-redirected
+                # stdin/stderr
+        {
+                "${@:2}"
+        } <&$FINALLY_0 >&$FINALLY_1 2>&$FINALLY_2
+}
+
+finally_unwind()
+{
+        case $# in
+                0 )
+                        exec \
+                                0<&$FINALLY_0 \
+                                1>&$FINALLY_1 \
+                                2>&$FINALLY_2 \
+                                {FINALLY_0}<&- \
+                                {FINALLY_1}>&- \
+                                {FINALLY_2}>&-
+                ;;
+                1 )
+                        echo "history -d -1; finally_unwind; $1"
+                ;;
+        esac
+}
diff --git a/src/twopane.bash b/src/twopane.bash
index 327d246..c266828 100755
--- a/src/twopane.bash
+++ b/src/twopane.bash
@@ -6,7 +6,10 @@ set -f
 set -o pipefail
 shopt -s lastpipe
 
+PS4='+ \t$LINENO\t '
+
 . read_chars.bash
+. finally.bash
 
 kill_tty_forward()
 {
@@ -17,17 +20,39 @@ kill_tty_forward()
 BOT_SIZE=8
 BOT_TITLE=input
 
+DO_RESTART=y
+DO_RESTART=
+DO_START=
+DO_START=y
+
 if [ $# = 0 ]
 then
         TOP_CMD="$SHELL -i"
-        BOT_CMD=start
-        #TOP_EXIT=quit
-        #TOP_EXIT=prompt
-        TOP_EXIT=restart
+        if [ "$DO_RESTART" ]
+        then
+                SIG=INT
+                BOT_CMD=PROMPT_COMMAND=prompt_command
+                TOP_EXIT=restart
+        elif [ "$DO_START" ]
+        then
+                BOT_CMD=start
+                TOP_EXIT=quit
+        else
+                BOT_CMD=PROMPT_COMMAND=prompt_command
+                TOP_EXIT=prompt
+        fi
 elif [ "$TWOPANE" -a "$*" = detach ]
 then
         kill_tty_forward -TSTP
         exit
+elif [ "$TWOPANE" -a "$*" = focus ]
+then
+        screen -X focus
+        exit
+elif [ "$TWOPANE" -a "$*" = quit ]
+then
+        screen -X quit
+        exit
 else
         TOP_CMD=$*
         BOT_CMD=start
@@ -156,33 +181,42 @@ restart_top_pane()
         with_screen_pane 1 restart_pane "$@"
 }
 
+# connect_coproc() -- start a coprocess and connect it to copied file
+# descriptors named {NAME}_IN and {NAME}_OUT where {NAME} is the
+# supplied first argument or default "COPROC".  {NAME} is the name of
+# the created bash coprocess.
+
+# The copied file descriptors (unlike the original coprocess
+# file descriptors, in ${NAME[0]} and ${NAME[1]}) can be
+# passed to external processes (e.g.: socat(1) instances) and
+# used in subshells.
+
+# The created coprocess is silently disowned from job control before
+# bash can make noise about it.
 connect_coproc()
 {
         [ $# -gt 0 ] || set -- COPROC
         declare -n coproc="$1"
         shift
         [ $# -gt 0 ] || set -- "${!coproc}"
-        declare -n std1="${!coproc}_STDOUT"
-        declare -n std0="${!coproc}_STDIN"
-        declare -n opid="${!coproc}_PID"
-        if ! [ "$opid" ]
+        declare -n std0="${!coproc}_IN"
+        declare -n std1="${!coproc}_OUT"
+        declare -n std2="${!coproc}_ERR"
+        declare -n pid="${!coproc}_PID"
+        if ! [ "$pid" ]
         then
                 i "coproc starting: ${!coproc}"
-                local STDERR
                 {
                         coproc "${!coproc}" \
                         {
                                 "$@"
-                        } 2>&$STDERR {STDERR}>&-
+                        } 2>&$std2 {std2}>&-
+                        unset std2
                         disown "%coproc ${!coproc} "
-                } {STDERR}>&2 2>/dev/null
+                } {std2}>&2 2>/dev/null
         else
                 i "coproc already running: ${!coproc}"
         fi
-        # The copied file descriptors (unlike the original coprocess
-        # file descriptors, in ${coproc[0]} and ${coproc[1]}) can be
-        # passed to external processes (e.g.: socat(1) instances) and
-        # used in subshells.
         {
                 exec {std0}<&0 {std1}>&1
         } <&${coproc[0]} >&${coproc[1]}
@@ -192,8 +226,8 @@ disconnect_coproc()
 {
         [ $# -gt 0 ] || set -- COPROC
         declare -n coproc="$1"
-        declare -n std0="${!coproc}_STDIN"
-        declare -n std1="${!coproc}_STDOUT"
+        declare -n std0="${!coproc}_IN"
+        declare -n std1="${!coproc}_OUT"
         declare -n  pid="${!coproc}_PID"
         if [ "$std0" -o "$std1" ]
         then
@@ -209,12 +243,17 @@ disconnect_coproc()
 
 connect()
 {
-        connect_coproc TOP_PANE
+        if ! [ "$TOP_PANE_PID" ]
+        then
+                disconnect_sink ECHOSEND
+                connect_coproc TOP_PANE
+        fi
+        connect_sink ECHOSEND echo_sender
 }
 
 disconnect()
 {
-        : "${TOP_PANE_STDIN@A} ${TOP_PANE_STDOUT@A} ${TOP_PANE_PID@A} ${TOP_PANE[@]@A}"
+        : "${TOP_PANE_IN@A} ${TOP_PANE_OUT@A} ${TOP_PANE_PID@A} ${TOP_PANE[@]@A}"
         disconnect_coproc TOP_PANE
         : "${ECHOSEND@A} ${ECHOSEND_PID@A}"
         disconnect_sink ECHOSEND
@@ -223,23 +262,13 @@ disconnect()
 sendc()
 {
         [ "${TOP_PANE[0]}" ] || connect
-        printf '%s' "$*" >&${TOP_PANE[1]}
+        printf '%s' "$*" >&${TOP_PANE_OUT?Internal error}
 }
 
 send()
 {
         [ "${TOP_PANE[0]}" ] || connect
-        printf '%s\n' "$*" >&${TOP_PANE[1]}
-}
-
-restart()
-{
-        start "$@"
-}
-
-start()
-{
-        foreground "$@"
+        printf '%s\n' "$*" >&${TOP_PANE_OUT?Internal error}
 }
 
 tty_forward()
@@ -252,18 +281,16 @@ tty_forward()
 TOP_PANE()
 {
         (exec -a bottom-pane-tty-forward socat - UNIX-CONNECT:"$TWOPANE"/socket,forever)
-        x kill_tty_forward -STOP
         case "$TOP_EXIT" in
                 restart )
-                        # x kill -USR1 $$
+                        x kill_tty_forward -STOP
                         x kill -INT $$
-                        # with_screen_pane 1 start_screen_pane "$@"
                 ;;
                 quit )
-                        kill -INT $$
                         quit
                 ;;
                 prompt | * )
+                        x kill_tty_forward -STOP
                         focus bottom
                 ;;
         esac
@@ -271,10 +298,14 @@ TOP_PANE()
 
 connect_sink()
 {
-        [ "$1" ] || return
+        (( $# > 0 )) || set -- SINK
         declare -n fd="$1"
         declare -n pid="${!fd}_PID"
-        disconnect_sink "$fd"
+        if [ "$pid" ]
+        then
+                i "sink already running: ${!fd}"
+                return
+        fi
         i "sink starting: ${!fd}"
         exec {fd}> >("${@:2}")
         pid=$!
@@ -282,7 +313,7 @@ connect_sink()
 
 disconnect_sink()
 {
-        [ "$1" ] || return
+        (( $# > 0 )) || set -- SINK
         declare -n fd="$1"
         [ "$fd" ] || return
         declare -n pid="${!fd}_PID"
@@ -300,51 +331,66 @@ quiet_bg()
         } {STDERR}>&2 2>/dev/null
 }
 
+# echo_sender() reads from two inputs and writes to two outputs.
+#
+# Read from both:
+#       read from stdin
+#       read from $TOP_PANE_IN
+# Write to both:
+#       write to stdout
+#       write to $TOP_PANE_OUT
+# I.e.:
+#       read from /dev/tty
+#       read from the socat-coproc-forwarded /dev/tty in the top pane.
+#       write to /dev/tty
+#       write to the socat-coproc-forwarded /dev/tty in the top pane.
 echo_sender()
 {
-        (exec -a echo_sender socat - fd:${TOP_PANE_STDIN?$0: Internal error}!!-) |
-        tee >(write-tty) >&${TOP_PANE_STDOUT?$0: Internal error}
+        (exec -a echo_sender socat - fd:${TOP_PANE_IN?$0: Internal error}!!-) |
+        tee >(write-tty) >&${TOP_PANE_OUT?$0: Internal error}
 }
 
-background()
+restart_tty_forward()
 {
+        {
+                kill -INT %tty_forward
+                disown %tty_forward
+        } &>/dev/null
+
         with_screen_pane 1 start_screen_pane "$@"
         focus bottom
-
-        disconnect_sink ECHOSEND
         connect
-        connect_sink ECHOSEND echo_sender
-        kill %tty_forward 2>/dev/null
-        %tty_forward &
-        disown %tty_forward
         i 'starting tty_forward'
         quiet_bg tty_forward >&$ECHOSEND
         echo $! > "$TWOPANE"/tty_forward.pid
 }
 
-foreground()
+attach()
 {
-        while true
-        do
-                background "$@"
-                focus top
-                set -x
-                %tty_forward >/dev/null 2>&1
-                if [ "$TOP_EXIT" != restart ] || jobs %tty_forward >/dev/null 2>&1
-                then
-                        focus bottom
-                        set +x
-                        break
-                fi
-                set +x
-        done
+        if ! jobs %tty_forward &>/dev/null
+        then
+                restart_tty_forward "$@"
+        fi
+        focus top
+        { %tty_forward; } &>/dev/null
+        focus bottom
 }
 
-twopane()
+detach()
 {
-        start "$@"
+        {
+                kill -INT %tty_forward
+                disown %tty_forward
+        } &>/dev/null
+        focus bottom
 }
 
+restart() { attach "$@"; }
+start() { attach "$@"; }
+foreground() { attach "$@"; }
+
+twopane() { attach "$@"; }
+
 quit()
 {
         screen -X quit
@@ -360,16 +406,6 @@ resize()
         screen -X resize "$@"
 }
 
-attach()
-{
-        if jobs %tty_forward >/dev/null 2>&1
-        then
-                %tty_forward
-        else
-                foreground
-        fi
-}
-
 SIGUSR1()
 {
         i "SIGUSR1: ${BASH_COMMAND@A}"
@@ -382,21 +418,45 @@ SIGCHLD()
 
 prompt_command()
 {
-        set -- 'unset PROMPT_COMMAND; restart'
+        [ "$TOP_EXIT" = 'restart' ] || return 0
+
+        if [ "$SIG" = INT ]
+        then
+                finally 'unset SIG; start' detach
+                return
+        fi
+
+        local job jobnew
+        if      job=$(jobs -n %tty_forward 2>/dev/null)
+        then
+                jobnew=y
+        else
+                job=$(jobs %tty_forward 2>/dev/null)
+                jobnew=
+        fi
+
+        if [ ! "$job" ]
+        then
+                finally 'start' :
+                return
+        fi
 
-        exec {FINALLY_0}<&0 {FINALLY_1}>&1 {FINALLY_2}>&2
-        if ! [ "$DEBUG" ]
+        if [ "$jobnew" ]
         then
-                exec &>/dev/null
+                read _ jobstatus _ <<< "$job"
+                if [ "$jobstatus" = 'Running' ]
+                then
+                        jobs -x finally 'attach' kill -CONT %tty_forward
+                fi
+                return
         fi
-        cmd="history -d -1; exec <&$FINALLY_0 >&$FINALLY_1 >&$FINALLY_2; $*"
-        exec <<< "$cmd"
 }
 
 SIGINT()
 {
         i INT "${BASH_COMMAND@A}"
         kill $TOP_PANE_PID $ECHOSEND_PID 2>/dev/null
+        SIG=INT
         PROMPT_COMMAND=prompt_command
 }