#!/bin/bash
# script to check for completed torrents and stop and move them

# lock dirs/files
LOCKDIR="/tmp/statsgen-lock"
PIDFILE="${LOCKDIR}/PID"

# exit codes and text for them - additional features nobody needs :-)
ENO_SUCCESS=0; ETXT[0]="ENO_SUCCESS"
ENO_GENERAL=1; ETXT[1]="ENO_GENERAL"
ENO_LOCKFAIL=2; ETXT[2]="ENO_LOCKFAIL"
ENO_RECVSIG=3; ETXT[3]="ENO_RECVSIG"

###
### start locking attempt
###

trap 'ECODE=$?; echo "[statsgen] Exit: ${ETXT[ECODE]}($ECODE)" >&2' 0
echo -n "[statsgen] Locking: " >&2

if mkdir "${LOCKDIR}" &>/dev/null; then
        # lock succeeded, install signal handlers before storing the PID just in case
        # storing the PID fails
        trap 'ECODE=$?;
                echo "[statsgen] Removing lock. Exit: ${ETXT[ECODE]}($ECODE)" >&2
                rm -rf "${LOCKDIR}"' 0
        echo "$$" >"${PIDFILE}"
        # the following handler will exit the script on receiving these signals
        # the trap on "0" (EXIT) from above will be triggered by this trap's "exit" command!
        trap 'echo "[statsgen] Killed by a signal." >&2
                exit ${ENO_RECVSIG}' 1 2 3 15
        echo "success, installed signal handlers"
else
        # lock failed, now check if the other PID is alive
        OTHERPID="$(cat "${PIDFILE}")"

        # if cat wasn't able to read the file anymore, another instance probably is
        # about to remove the lock -- exit, we're *still* locked
        #  Thanks to Grzegorz Wierzowiecki for pointing this race condition out on
        #  http://wiki.grzegorz.wierzowiecki.pl/code:mutex-in-bash
        if [ $? != 0 ]; then
                echo "lock failed, PID ${OTHERPID} is active" >&2
                exit ${ENO_LOCKFAIL}
        fi

        if ! kill -0 $OTHERPID &>/dev/null; then
                # lock is stale, remove it and restart
                echo "removing stale lock of nonexistant PID ${OTHERPID}" >&2
                rm -rf "${LOCKDIR}"
                echo "[statsgen] restarting myself" >&2
                exec "$0" "$@"
        else
                # lock is valid and OTHERPID is active - exit, we're locked!
                echo "lock failed, PID ${OTHERPID} is active" >&2
                exit ${ENO_LOCKFAIL}
        fi
fi
 
BLOCKLIST="/var/lib/transmission/.config/transmission-daemon/blocklists/blocklist.bin"
# Update blocklist if older than 1 day
if [[ $(find "$BLOCKLIST" -mtime +0 -print) ]]; then
        transmission-remote --blocklist-update
fi

TORRENTLIST=$(transmission-remote --list | sed -e '1d;$d;s/^ *//' | cut -f1 -d' ')
 
for TORRENTID in $TORRENTLIST
do
        TORRENTID=$(echo "$TORRENTID" | sed 's:*::')
 
        INFO=$(transmission-remote --torrent $TORRENTID --info)
 
        NAME=$(echo "$INFO" | grep "Name: *")
        DL_COMPLETED=$(echo "$INFO" | grep "Percent Done: 100%")
        STATE_STOPPED=$(echo "$INFO" | grep "State: Stopped\|Finished\|Idle")
 
        if [ "$DL_COMPLETED" != "" ] && [ "$STATE_STOPPED" != "" ]; then
                echo "Removing torrent from list"
                transmission-remote --torrent $TORRENTID --remove
        fi
done