# Set parameters.
BACKUP_PATH=$HOME/backups
DRUPAL_PATH=/var/www/html

# Create the backup folder if necessary.
if [ ! -d $BACKUP_PATH ]; then
        mkdir -p $BACKUP_PATH
fi

# Discard old backups.
for FILE_DATE in $(ls $BACKUP_PATH | grep -E ^[0-9]{8}\.tar\.gz | cut -c-8)
do

        # Compute backup characteristics.
        DAYS_SINCE=$(( ($(date +%s) - $(date --date=$FILE_DATE +%s) )/(60*60*24) ))
        FILE_MONTH=$(echo $FILE_DATE | cut -c5-6)
        FILE_DAY=$(echo $FILE_DATE | cut -c7-8)

        # Discard backups more than a year old that are not the first of the year.
        if [ $DAYS_SINCE -gt 365 ] && [ $FILE_MONTH$FILE_DAY != '0101' ]; then
                rm $BACKUP_PATH/$FILE_DATE.tar.gz

        # Discard backups more than three months old that are not the first of the month.
        elif [ $DAYS_SINCE -gt 90 ] && [ $FILE_DAY != '01' ]; then
                rm $BACKUP_PATH/$FILE_DATE.tar.gz

        # Discard backups more than a week old that are not a Sunday or the first of the month.
        elif [ $DAYS_SINCE -gt 7 ] && [ $FILE_DAY != '01' ] && [ $(date --date=$FILE_DATE +%A) != 'Sunday' ]; then
                rm $BACKUP_PATH/$FILE_DATE.tar.gz
        fi
done

# Put the site into maintenance mode, perform updates, and generate today's backup.
CURRENT_PATH=$(pwd)
cd $DRUPAL_PATH
drush vset maintenance_mode 1
drush up -y
drush cc all
drush ard --destination=$BACKUP_PATH/$(date +%Y%m%d).tar.gz --overwrite
drush vset maintenance_mode 0
cd $CURRENT_PATH