# calendar database is e.g. /redirectedFolders/Users/mark/.thunderbird/28ngbwvw.default/calendar-data/local.sqlite

if [ -z "$1" ]
then
  echo syntax: `basename $0` databaseFile
  exit
fi

DATABASE="$1"

# Time formats and timezone info. I know I'm -5 hours GMT, so I'm just hard-coding that
FMT="Y%m%dT%H%M%SZ"
FMT2="%Y%m%dT%H%M%S"
TZADJ=18000

# The original published .ics file seems to not have lines longer than 70 character.
# This function chop lines into 70 characters or less. The tilde (~) character is
# assumed to be a newline substitute and is replaced by a litteral "\n" after splitting.

function emit70
{
    t=`echo "$1"`
    while [ ${#t} -gt 0 ]
    do
        if [ ${#1} -ne ${#t} ]; then echo -n " "; fi
        echo "$t" | cut -c1-70 | sed 's/~/\\n/g'
        t=`echo "$t" | cut -c71-`
    done
}

# The following "boilderplate" is copied directly from the originally published .ics file.

cat <<EOF
BEGIN:VCALENDAR
PRODID:-//Mozilla.org/NONSGML Mozilla Calendar V1.1//EN
VERSION:2.0
METHOD:PUBLISH
BEGIN:VTIMEZONE
TZID:America/New_York
BEGIN:DAYLIGHT
TZOFFSETFROM:-0500
TZOFFSETTO:-0400
TZNAME:EDT
DTSTART:19700308T020000
RRULE:FREQ=YEARLY;BYDAY=2SU;BYMONTH=3
END:DAYLIGHT
BEGIN:STANDARD
TZOFFSETFROM:-0400
TZOFFSETTO:-0500
TZNAME:EST
DTSTART:19701101T020000
RRULE:FREQ=YEARLY;BYDAY=1SU;BYMONTH=11
END:STANDARD
END:VTIMEZONE
EOF

# GET EVENTS
# Note that this query does not take into account the possibility of multiple
# calendars stored in the local.sqlite database. Possibly need to first
# 'select distinct cal_id' then loop through those. A "todo" for the future.

sqlite3 "$DATABASE"  \
"select cal_id, id, time_created, last_modified, title, priority, privacy, event_start, event_end,
  event_stamp, event_start_tz, event_end_tz
  from cal_events" | \
while read event
do
    x=`echo $event`
    if [ -z "$x" ]; then continue; fi

    # icalString is multi-line. Get separately to make parsing easier

    cal_id=`echo "$event" | cut "-d|" -f1`
    id=`echo "$event" | cut "-d|" -f2`

    icalString=`sqlite3 "$DATABASE" \
    "select icalString from cal_alarms where cal_id = '$cal_id' and item_id = '$id';"`

    time_created=`echo $event | cut "-d|" -f3 | cut -c1-10`
    time_created=$[ $time_created + $TZADJ ]
    time_created=`date -d@$time_created +$FMT`

    last_modified=`echo "$event" | cut "-d|" -f4 | cut -c1-10`
    last_modified=$[ $last_modified + $TZADJ ]
    last_modified=`date -d@$last_modified +$FMT`

    title=`echo "$event" | cut "-d|" -f5`
    priority=`echo "$event" | cut "-d|" -f6`
    privacy=`echo "$event" | cut "-d|" -f7`
    event_start=`echo "$event" | cut "-d|" -f8 | cut -c1-10`
    event_start=`date -d@$event_start +$FMT2`
    event_end=`echo "$event" | cut "-d|" -f9 | cut -c1-10`
    event_end=`date -d@$event_end +$FMT2`

    event_stamp=`echo "$event" | cut "-d|" -f10 | cut -c1-10`
    event_stamp=$[ $event_stamp + $TZADJ ]
    event_stamp=`date -d@$event_stamp +$FMT`

    event_start_tz=`echo "$event" | cut "-d|" -f11`
    event_end_tz=`echo "$event" | cut "-d|" -f12`

    cat << EOF
BEGIN:VEVENT
CREATED:$time_created
LAST_MODIFIED:$last_modified
DTSTAMP:$event_stamp
EOF

    # Split up UIDs longer than 70 characters (could have used emit70() function)

    echo UID:`echo $id | cut -c1-70`
    if [ ${#id} -gt 70 ]; then echo " "`echo $id | cut -c71-`; fi

    echo "SUMMARY:$title"

    if [ -n "$priority" ]; then echo "PRIORITY:$priority"; fi
    echo "DTSTART;TZID=$event_start_tz:$event_start"
    echo "DTEND;TZID=$event_end_tz:$event_end"

    # Get additional calendar properties (LOCATION, PRIVACY, etc.)
    # Some have multi-line entries such as X-ALT-DESC. Substitute
    # tilde (~) for newline (char(10)) to get everything on one
    # line. emit70() will put litteral "\n" (not newline) back in.

    sqlite3 "$DATABASE" "select key, value from cal_properties where cal_id = '$cal_id' and item_id = '$id';" | \
    while read xtra
    do
        k=`echo $xtra | cut "-d|" -f1`
        v=`echo $xtra | cut "-d|" -f2-`
        x=`echo $v`

        if [ -n "$x" ]; then emit70 "$k:$v"; fi
    done

    x=`echo $icalString`
    if [ -n "$x" ]; then echo "$icalString"; fi

    echo END:VEVENT
done

echo END:VCALENDAR

exit