#!/bin/bash

FOLDER_FROM=''
FOLDER_TO=''
DAYS=20

print_help () {
    cat << EOF
Usage:
  $(basename "$0") <options>

Possible options:
    -f|--from <folder>  Folder where to look for mails
    -t|--to <folder>    Folder to put outdated mails
    -d|--days <days>    Number of days to keep the mails
EOF
}

while [ $# -gt 0 ]
do
    case "$1" in
        --from|-f)
            FOLDER_FROM="$2"
            shift
            ;;
        --to|-t)
            FOLDER_TO="$2"
            shift
            ;;
        --days|--day|-d)
            DAYS="$2"
            shift
            ;;
        --help|-h)
            print_help
            exit
            ;;
        *)
            echo "Unrecognized option: $1"
            print_help
            exit 1
            ;;
    esac
    shift
done

ensure_mail_folder () {
    local folder="$1"
    if ! echo "$folder" | grep '/cur/*$' > /dev/null; then
        folder="$folder/cur/"
    fi

    if [ ! -d "$folder" -o ! -w "$folder" -o ! -r "$folder" -o ! -x "$folder" ]; then
        echo "This is no valid folder: $folder"
        exit 1
    fi
    
    echo -n "$folder"
}

if [ -z "$FOLDER_FROM" ]; then
    echo "There is no folder given to read the mails from. Please provide it with --from"
    exit 1
fi

if [ -z "$FOLDER_TO" ]; then
    echo "There is no folder given to put the outdated mails. Please provide it with --to"
    exit 1
fi

FOLDER_FROM=$(ensure_mail_folder "$FOLDER_FROM")
FOLDER_TO=$(ensure_mail_folder "$FOLDER_TO")

if [ ! "$DAYS" -ge 0 ]; then
    echo 'No valid number of days given.'
    exit 1
fi

find "$FOLDER_FROM" -type f -mtime +$DAYS | while read l
do
    suffix=$(echo "$l" | grep -o ',[^,]*$')
    
    if ! echo "$suffix" | grep 'S' > /dev/null ; then
        # echo Unseen Mail $l
        continue
    fi
    
    if echo "$suffix" | grep 'F' > /dev/null ; then
        # echo Flagged Mail $l
        continue
    fi
    
    mv -n "$l" "$FOLDER_TO"
done