#!/bin/ksh

set -e # fail on error

# mail permission
UID=sdk
GID=sdk
MODE=600
BACKUP=0 # if 1, bak directory will be created within maildir

[[ -z $1 ]] && \
    print "$0 <maildir>" && exit 2

# conditions:
#  - filename as size S=
#  - filename does not end in Z (already compressed)
#  - file must not return gzip compressed data (already compressed)
# filename is cut from the file(1) output
FILES=$(cd "$1/cur/" \
        && find . -iname '*,S=*[^Z]' -exec file {} \; \
            | grep -v 'gzip compressed data' \
            | sed 's/: /!/' \
            | cut -d '!' -f 1)

[[ $BACKUP != 0 ]] && mkdir "$1/bak"

# loop through mail and compress appending Z
# sync mtime with original file
# set used,group,permissions
# remove original mail (or backup)
for MAIL in $FILES; do
    print "gzipping $1/cur/$MAIL to $1/cur/${MAIL}Z"
    gzip -8 -S Z "$1/cur/$MAIL" -c > "$1/cur/${MAIL}Z"
    touch -r "$1/cur/$MAIL" "$1/cur/${MAIL}Z"
    chown $UID:$GID "$1/cur/${MAIL}Z"
    chmod $MODE "$1/cur/${MAIL}Z"
    if [[ $BACKUP != 0 ]]; then
        mv "$1/cur/$MAIL" "$1/bak/$MAIL"
    else
        rm -f "$1/cur/$MAIL"
    fi
done