#! @shell@

set -e
export PATH=/empty
for i in @path@; do PATH=$PATH:$i/bin:$i/sbin; done
action="$1"

if ! test -e /etc/NIXOS; then
    echo "This is not a NixOS installation (/etc/NIXOS) is missing!"
    exit 1
fi

if test -z "$action"; then
    cat <<EOF
Usage: $0 [switch|boot|test]

switch: make the configuration the boot default and activate now
boot:   make the configuration the boot default
test:   activate the configuration, but don't make it the boot default
EOF
    exit 1
fi

# Install or update the bootloader.
if [ "$action" = "switch" -o "$action" = "boot" ]; then
    @installBootLoader@ @out@
fi

# Activate the new configuration.
if [ "$action" != switch -a "$action" != test ]; then exit 0; fi

oldVersion=$(cat /run/current-system/upstart-interface-version 2> /dev/null || echo 0)
newVersion=$(cat @out@/upstart-interface-version 2> /dev/null || echo 0)

if test "$oldVersion" -ne "$newVersion"; then
        cat <<EOF
Warning: the new NixOS configuration has an Upstart version that is
incompatible with the current version.  The new configuration won't
take effect until you reboot the system.
EOF
        exit 1
fi

# Ignore SIGHUP so that we're not killed if we're running on (say)
# virtual console 1 and we restart the "tty1" job.
trap "" SIGHUP

jobsDir=$(readlink -f @out@/etc/init)

# Stop all currently running jobs that are not in the new Upstart
# configuration.  (Here "running" means all jobs that are not in the
# stop/waiting state.)
for job in $(initctl list | sed -e '/ stop\/waiting/ d; /^[^a-z]/ d; s/^\([^ ]\+\).*/\1/' | sort); do
    if ! [ -e "$jobsDir/$job.conf" ] ; then
        echo "stopping obsolete job ‘$job’..."
        stop --quiet "$job" || true
    fi
done

# Activate the new configuration (i.e., update /etc, make accounts,
# and so on).
echo "activating the configuration..."
@out@/activate @out@

# Make Upstart reload its jobs.
initctl reload-configuration

# Allow Upstart jobs to react intelligently to a config change.
initctl emit config-changed

declare -A tasks=(@tasks@)
declare -A noRestartIfChanged=(@noRestartIfChanged@)

start_() {
    local job="$1"
    if start --quiet "$job"; then
        # Handle services that cancel themselves.
        if ! [ -n "${tasks[$job]}" ]; then
            local status=$(status "$job")
            [[ "$status" =~ start/running ]] || echo "job ‘$job’ failed to start!"
        fi
    fi
}

log() {
    echo "$@" >&2 || true
}

# Restart all running jobs that have changed.  (Here "running" means
# all jobs that don't have a "stop" goal.)  We use the symlinks in
# /var/run/upstart-jobs (created by each job's pre-start script) to
# determine if a job has changed.
for job in @jobs@; do
    status=$(status "$job")
    if ! [[ "$status" =~ start/ ]]; then continue; fi
    if [ "$(readlink -f "$jobsDir/$job.conf")" = "$(readlink -f "/var/run/upstart-jobs/$job")" ]; then continue; fi
    if [ -n "${noRestartIfChanged[$job]}" ]; then
        log "not restarting changed service ‘$job’"
        continue
    fi
    log "restarting changed service ‘$job’..."
    # Note: can't use "restart" here, since that only restarts the
    # job's main process.
    stop --quiet "$job" || true
    start_ "$job" || true
done

# Start all jobs that are not running but should be.  The "should be"
# criterion is tricky: the intended semantics is that we end up with
# the same jobs as after a reboot.  If it's a task, start it if it
# differs from the previous instance of the same task; if it wasn't
# previously run, don't run it.  If it's a service, only start it if
# it has a "start on" condition.
for job in @jobs@; do
    status=$(status "$job")
    if ! [[ "$status" =~ stop/ ]]; then continue; fi

    if [ -n "${tasks[$job]}" ]; then
        if [ ! -e "/var/run/upstart-jobs/$job" -o \
            "$(readlink -f "$jobsDir/$job.conf")" = "$(readlink -f "/var/run/upstart-jobs/$job")" ];
        then continue; fi
        if [ -n "${noRestartIfChanged[$job]}" ]; then continue; fi
        log "starting task ‘$job’..."
        start --quiet "$job" || true
    else
        if ! grep -q "^start on" "$jobsDir/$job.conf"; then continue; fi
        log "starting service ‘$job’..."
        start_ "$job" || true
    fi
    
done

# Signal dbus to reload its configuration.
dbusPid=$(initctl status dbus 2> /dev/null | sed -e 's/.*process \([0-9]\+\)/\1/;t;d')
[ -n "$dbusPid" ] && kill -HUP "$dbusPid"