#! /bin/sh
##
 # rmmproc.messageid -- tries to back up a message/file to a file that's
 #                      named based on Message ID
 #
 # This code is Copyright (c) 2013, by the authors of nmh.
 # See the COPYRIGHT file in the root directory of the nmh
 # distribution for complete copyright information.
 #
 # If called on a message, the current directory is the
 # message folder and $1 is the message filename.
 # If called on a file, $1 is the full path to the file.
 #
 # The backup directory will be:
 #   1) If input is a message, the folder of the message.
 #   2) If input is a file, the directory of the file.
 #   3) If input is standard input (-), the user's MHPATH directory.
 #
 # The backup filename will be:
 #   1) Message-ID with all / and \ converted to periods.
 #      Message-IDs should not contain \, but some
 #      filesystems can't handle them.  Message-IDs should
 #      be unique, so there should be no need to backup a
 #      file with the same name, especially if the result of
 #      malicious action.  If the backup file already
 #      exists, use 2).
 #      NOTE: conversion of some characters in the filename
 #      could result in an unintended name collision.  If
 #      that is a concern, a program that uses mktemp(3) to
 #      create a temporary file might be the basis for a
 #      remedy.
 #
 #   2) Concatenation of BACKUP_PREFIX and input filename.
 #      NOTE: if a file of that name already exists in the
 #      destination directory, it will be overwritten by the
 #      mv below.
 #
##

if [ "$1" = - ]; then
    #### Input is stdin; put backup in user's MHPATH directory.
    dir=`mhparam path`
    #### If Path is relative, prepend home directory.
    [ `dirname "$dir"` = . ]  &&  dir="$HOME/$dir"
else
    dir=`dirname "$1"`
fi

#### Extract first Message-Id, remove <>, substitute / and \.
messageid=`sed -n '
    /^$/q; /^[Mm][Ee][Ss][Ss][Aa][Gg][Ee]-[Ii][Dd]:/!d
    s/>.*//; s/.*<//; y#/\\\#..#; p
    ' "$1"`

if [ "$messageid"  -a  ! -f "$dir/$messageid" ]; then
    filename="$dir/$messageid"
else
    filename="$dir"/`mhparam sbackup``basename "$1"`
fi

#### If unable to backup the message, exit with status 1.
mv "$1" "$filename"