#!/bin/bash

# Copyright (C) 2022  Sean Whitton
#
# This program is free software: you can redistribute it and/or modify
# it under the terms of the GNU General Public License as published by
# the Free Software Foundation, either version 3 of the License, or (at
# your option) any later version.
#
# This program is distributed in the hope that it will be useful, but
# WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program.  If not, see <http://www.gnu.org/licenses/>.



# emacsclient(1) wrapper to handle updating the environment of existing
# daemons and choosing between installed and in-tree builds of Emacs.

min_arg=0
command -v ss >/dev/null || exit 1
socket_dir="/run/user/$(id -u)/emacs/"
get_listener () {
    local socket="$1"
    local listener=$(ss -Hplx src "$socket" \
			 | perl -wne'/pid=(\d+)/ and print $1')
    if [ -z "$listener" -a -e "$socket" ]; then
	# Nothing is listening: remove dangling socket.
	rm "$socket"
    else
	echo "$listener"
    fi
}

for arg do
    shift
    case "$arg" in
	'--spw/installed') mode=--spw/installed ;;
	'--spw/no-start') start=false ;;
	'--spw/update-environment') update=true ;;
	'-s'|'--socket-name') min_arg=2; daemon_name="$1"        ;;&
	'-s'?*)               min_arg=1; daemon_name="${arg:2}"  ;;&
	'--socket-name='?*)   min_arg=1; daemon_name="${arg:14}" ;;&
	*) set -- "$@" "$arg" ;;
    esac
done

socket="$socket_dir${daemon_name:-server}"
listener="$(get_listener $socket)"
if [ -n "$listener" ]; then
    case "$(ps h -o exe $listener | sed -e 's/ (deleted)$//')" in
	"$HOME/src/emacs/src/emacs")       devel_running=true     ;;
	"$(realpath $(command -v emacs))") installed_running=true ;;
	*) echo >&2 "Unknown Emacs listening on $socket"; exit 1  ;;
    esac
fi

if [ "$devel_running" = true -a "$mode" = --spw/installed ]; then
    kill "$listener"

    # Detach gdb so that Emacs can handle the SIGTERM.
    # We also have to quit gdb so that `gdb-inferior-status' is reset from
    # "signal-received"; see `spw/gdbmacs-attach' command.
    [ -n "$(get_listener ${socket_dir}gdbmacs)" ] \
	&& emacsclient -sgdbmacs --eval '(gud-basic-call "detach")' \
		       --eval '(gud-basic-call "quit")'

    [ -e "$socket" ] && inotifywait -qqt 2 -e delete "$socket"
    devel_running=false
fi

[ "$start" = false -a -z "$listener" ] && exit 0

# We check whether there is something which looks like the installed Emacs
# running because we do not want the in-tree emacsclient to try to connect to
# that, and we check whether there is a build in progress and no running
# daemon, as we don't want to start a new daemon until the build is finished.
# The idea is that I can always hit C-i e without worrying about builds.
if [ "$mode" != --spw/installed -a "$installed_running" != true \
	     -a -e "$HOME/src/emacs/admin/flagfile.melete" \
	     -a -x "$HOME/src/emacs/lib-src/emacsclient" \
	     -a -d "/usr/share/emacs-snapshot/site-lisp/elpa" ] \
       && ! ( [ "$devel_running" != true ] && ps h -o pid -C make \
		      | xargs pwdx | grep -q "$HOME/src/emacs" ); then
    emacs="$HOME/src/emacs/src/emacs"
    emacsclient="$HOME/src/emacs/lib-src/emacsclient"
else
    emacs=$(command -v emacs)
    emacsclient=$(PATH=$(echo "$PATH" | sed -e "s#$HOME/src/dotfiles/bin:##") \
		      command -v emacsclient)
fi

# Update Emacs daemon environment vars for a new interactive session.  This
# allows us to have the Emacs daemon survive restarts of the graphical desktop
# environment, and to update Emacs on a remote host when there is a new
# forwarded SSH agent socket.  See 'upenv' in .bash_defns.
if [ "$update" = true -a -n "$listener" ]; then
    for var in DISPLAY WAYLAND_DISPLAY \
		       XAUTHORITY WINDOWID \
		       XDG_SESSION_TYPE XDG_CURRENT_DESKTOP \
		       SWAYSOCK I3SOCK \
		       SSH_ASKPASS SSH_CONNECTION \
		       SSH_AUTH_SOCK SSH_AGENT_PID; do
	eval isset=\${$var+x}
	if [ "$isset" = "x" ]; then
	    eval val=\$$var
	    args="$args"' "'$var'" "'$val'"'
	fi
    done
    [ -n "$args" ] \
	&& "$emacsclient" -s"${daemon_name:-server}" \
			  --eval "(spw/update-environment$args))"
fi

# emacsclient(1) requires an argument.  As a special case, if there are no
# arguments except -s/--socket-name, and no daemon is running, just start one.
# And if there were no arguments but we were requested just to update env
# vars, exit peacefully.
if [ "$#" -eq "$min_arg" -a -z "$listener" ]; then
    exec "$emacs" --daemon"${daemon_name:+=$daemon_name}"
elif ! [ "$#" -eq "$min_arg" -a "$update" = true ]; then
    exec "$emacsclient" -a "" "$@"
fi