#!/usr/bin/env bash

##--------------------------------------------------------------
##
##  msmtpq : queue funtions to both use & manage the msmtp queue,
##             as it was defined by Martin Lambers
##  Copyright (C) 2008 - 2015 Chris Gianniotis
##
##  This program is free software: you can redistribute it and/or modify
##  it under the terms of the GNU General Public License as published by
##  the Free Software Foundation, either version 3 of the License, or, at
##  your option, any later version.
##
##--------------------------------------------------------------
##
## msmtpq is meant to be used by an email client - in 'sendmail' mode
##   for this purpose, it is invoked directly as 'msmtpq'
## it is also meant to be used to maintain the msmtp queue
##   when it is evoked by the wrapper script 'msmtp-queue'
##   (which calls this script as msmtpq --q-mgmt)
##
## there is a queue log file, distinct from the msmtp log,
##   for all events & operations on the msmtp queue
##   that is defined below
##
## (mutt users, using msmtpq in 'sendmail' mode,
##  should make at least the following two settings in their .muttrc
##    set sendmail = /path/to/msmtpq
##    set sendmail_wait = -1
##
##  please see the msmtp man page and docs for further mutt settings
##    and optimisations
## )
##
## two essential patches by Philipp Hartwig
## 19 Oct 2011 & 27 Oct 2011
##
##--------------------------------------------------------------
## the msmtp queue contains unique filenames of the following form :
##   two files for each mail in the queue
##
## creates new unique filenames of the form :
##   MLF: ccyy-mm-dd-hh.mm.ss[-x].mail   -- mail file
##   MSF: ccyy-mm-dd-hh.mm.ss[-x].msmtp  -- msmtp commands file
## where x is a consecutive number only appended for uniqueness
##   if more than one mail per second is sent
##--------------------------------------------------------------


log_later() { LOG_LATER_ARGS=( "$@" ) ; }
dsp() { local L ; for L ; do [ -n "$L" ] && echo "  $L" || echo ; done ; }
err() { dsp '' "$@" '' ; exit 1 ; }

## ======================================================================================
##      !!!          please define or confirm the following three vars           !!!
##      !!!           before using the msmtpq or msmtp-queue scripts             !!!
## ======================================================================================
##
## only if necessary (in unusual circumstances - e.g. embedded systems),
##   export the location of the msmtp executable before running this script  (no quotes !!)
##   e.g. ( export MSMTP=/path/to/msmtp )
MSMTP="${MSMTP:-msmtp}"
"$MSMTP" --version >/dev/null 2>&1 || \
  log_later -e 1 "msmtpq : can't run the msmtp executable [ $MSMTP ]"   # if not found - complain ; quit
##
## set the queue var to the location of the msmtp queue directory
##   if the queue dir doesn't yet exist, create it (0700)
##     before using this script
##       e.g. ( mkdir msmtp.queue      )
##            ( chmod 0700 msmtp.queue )
##
## the queue dir - export this variable to reflect where you'd like it to be  (no quotes !!)
MSMTPQ_Q=${MSMTPQ_Q:-${Q:-~/.msmtp.queue}}
[ -d "$MSMTPQ_Q" ] || mkdir -m 0700 -p "$MSMTPQ_Q" || \
  err '' "msmtpq : can't find or create msmtp queue directory [ $MSMTPQ_Q ]" ''     # if not present - complain ; quit
##
## set the queue log file var to the location of the msmtp queue log file
##   where it is or where you'd like it to be
##     ( note that the MSMTPQ_LOG setting could be the same as the )
##     ( 'logfile' setting in .msmtprc - but there may be   )
##     ( some advantage in keeping the two logs separate    )
##   if you don't want the log at all set the var to an empty string
##     (doing so would be inadvisable under most conditions, however)
##
## the queue log file - export this variable to change where logs are stored  (but no quotes !!)
##                      Set it to "" (empty string) to disable logging.
if [ ! -v MSMTPQ_LOG ] ; then
  if [ -v LOG ] ; then
    MSMTPQ_LOG="$LOG"
  else
    MSMTPQ_LOG=~/log/msmtp.queue.log
  fi
fi
[ -d "$(dirname "$MSMTPQ_LOG")" ] || mkdir -p "$(dirname "$MSMTPQ_LOG")"
## ======================================================================================

## msmtpq can use the following environment variables :
##   EMAIL_CONN_NOTEST   if set will suppress any testing for a connection
##                         (the above var is deprecated & will be removed ; use the var below)
##   EMAIL_CONN_TEST     if =x will suppress any testing for a connection
##                       if =p or unset will use a ping test (debian.org) for a connection
##                       if =P will use a fast ping test (8.8.8.8) for a connection
##                       if =n will use netcat (nc) to test for a connection
##                       if =s will use bash sockets to test for a connection
##   EMAIL_QUEUE_QUIET   if set will cause suppression of messages and 'chatter'
##                         (perhaps useful for some of the emacs mail clients)
##
## ======================================================================================
##      !!!      define or confirm the following vars if you wish to set         !!!
##      !!!      these properties here in the script - the same properties       !!!
##      !!!      may be set externally, by means of environment variables        !!!
##      !!!      note the internal variables, if set, will take precedence       !!!
##      !!!      over properties set via environment variables                   !!!
## ======================================================================================
##
#EMAIL_CONN_NOTEST=y                 # deprecated ; use below var
#EMAIL_CONN_TEST={x| |p|P|n|s}       # see settings above for EMAIL_CONN_TEST
#EMAIL_QUEUE_QUIET=t
## ======================================================================================

umask 077                            # set secure permissions on created directories and files

declare -i CNT                       # a count of mail(s) currently in the queue
declare -a Q_LST                     # queue list array ; used selecting a mail (to send or remove)

## do ; test this !
#for sig in INT TERM EXIT; do
#  trap "rm -f \"\$TMPFILE\"; [[ $sig == EXIT ]] || kill -$sig $$" $sig
#done
trap on_exit INT TERM EXIT           # run 'on_exit' on exit
on_exit() {                          # unlock the queue on exit if the lock was set here
  [ -n "$LKD" ] && lock_queue -u 2>/dev/null
}

#
## ----------------------------------- functions common to both modes
## ----------------------------------- (msmtpq & msmtp-queue)
#

## make an entry to the queue log file, possibly an error
##   (log queue changes only ; not interactive chatter)
## usage : log [ -e errcode ] msg [ msg ... ]
##  opts : -e <exit code>  an error ; log msg & terminate w/prejudice
## display msg to user, as well
##
log() {
  local ARG RC PFX
  PFX="$('date' +'%Y %d %b %H:%M:%S')"
                                     # time stamp prefix - "2008 13 Mar 03:59:45 "
  if [ "$1" = '-e' ] ; then          # there's an error exit code
    RC="$2"                          # take it
    shift 2                          # shift opt & its arg off
  fi

  [ -z "$EMAIL_QUEUE_QUIET" ] && dsp "$@"  # display msg to user, as well as logging it

  if [ -n "$MSMTPQ_LOG" ] ; then     # log is defined and in use
    for ARG ; do                     # each msg line out
      [ -n "$ARG" ] && \
        echo "$PFX : $ARG" >> "$MSMTPQ_LOG" # line has content ; send it to log
    done
  fi

  if [ -n "$RC" ] ; then             # an error ; leave w/error return
    [ -n "$LKD" ] && lock_queue -u   # unlock here (if locked)
    [ -n "$MSMTPQ_LOG" ] && \
      echo "    exit code = $RC" >> "$MSMTPQ_LOG" # logging ok ; send exit code to log
    exit "$RC"                       # exit w/return code
  fi
}

## write/remove queue lockfile for a queue op
##
lock_queue() {        # <-- '-u' to remove lockfile
  local LOK="${MSMTPQ_Q}/.lock"      # lock file name
  local -i MAX=240 SEC=0             # max seconds to gain a lock ; seconds waiting

  if [ -z "$1" ] ; then              # lock queue
    ## Philipp Hartwig patch #2
    'mkdir' "$LOK" 2>/dev/null && LKD='t'
    while [ -z "$LKD" ] && [ "$SEC" -lt "$MAX" ]; do # lock file present
      sleep 1                                        # wait a second
      SEC=$((SEC + 1))                               # accumulate seconds
      'mkdir' "$LOK" 2>/dev/null && LKD='t'          # make lockdir ; lock queue ; set flag
    done                                             # try again while locked for MAX secs
    [ -z "$LKD" ] && \
	    err '' "cannot use queue $MSMTPQ_Q : waited $MAX seconds for"\
	           "  lockdir [ $LOK ] to vanish ; giving up"\
	           'if you are certain that no other instance of this script'\
	           "  is running, then 'rmdir' the lock dir manually" '' # lock file still there, give up

  elif [ "$1" = '-u' ] ; then        # unlock queue
    'rmdir' "$LOK"                   # remove the lock
    unset LKD                        # unset flag
  fi
}

## test whether system is connected
## returns t/f (0/1)
##
connect_test() {
  if [ -z "$EMAIL_CONN_TEST" ] || \
     [ "$EMAIL_CONN_TEST" = 'p' ] ; then                       # use ping test (default)
    # verify net connection - ping ip address of debian.org
    # would ping -qnc2 -w4 be better ?
    # would ping -qnc1 -w10 or -w20 be better ?
    #ping -qnc1 -w4 debian.org >/dev/null 2>&1 || return 1
    ping -qnc2 -w10 debian.org >/dev/null 2>&1 || return 1

  elif [ "$EMAIL_CONN_TEST" = 'P' ] ; then                     # use quicker ping test
    # I personally think that including a DNS lookup
    # is a better connection test but some
    # have found the above test too slow
    ping -qnc1 -w4 8.8.8.8 >/dev/null 2>&1 || return 1

  elif [ "$EMAIL_CONN_TEST" = 'n' ] ; then                     # use netcat (nc) test
    # must, of course, have netcat (nc) installed
    which nc >/dev/null 2>&1 || \
      log -e 1 "msmtpq : can't find netcat executable [ nc ]"  # if not found - complain ; quit
    'nc' -vz www.debian.org 80 >/dev/null 2>&1 || return 1

  elif [ "$EMAIL_CONN_TEST" = 's' ] ; then                     # use sh sockets test
    # note that this does not work on debian systems
    #   where bash opened sockets are suppressed for security
    #   reasons on multiuser systems - however, this should be
    #   ok for single user systems (including embedded systems)
    # test whether this is supported on your system before using...
    # thank you to Brian Goose, on the list, for encouraging this
    exec 3<>/dev/udp/debian.org/80 || return 1                 # open socket on site ; use dns
    exec 3<&- ; exec 3>&-                                      # close socket
  fi
  return 0
}

#
## ----------------------------------- functions for queue management
## ----------------------------------- queue maintenance mode - (msmtp-queue)
#

## show queue maintenance functions
##
usage() {        # <-- error msg
  dsp ''\
      'usage : msmtp-queue functions' ''\
      '        msmtp-queue < op >'\
      '        ops : -r   run (flush) mail queue - all mail in queue'\
      '              -R   send selected individual mail(s) in queue'\
      '              -d   display (list) queue contents   (<-- default)'\
      '              -p   purge individual mail(s) from queue'\
      '              -a   purge all mail in queue'\
      '              -h   this helpful blurt' ''\
      '        ( one op only ; any others ignored )' ''
  if [ -z "$1" ]; then
    exit 0;
  else
    dsp "$@" '';
    exit 1;
  fi
}

## get user [y/n] acknowledgement
##
ok() {
  local R YN='Y/n'                   # default to yes

  [ "$1" = '-n' ] && \
    { YN='y/N' ; shift ; }           # default to no ; change prompt ; shift off spec

  dsp "$@"
  while true ; do
    echo -n "  ok [${YN}] ..: "
    read -r R
    case $R in
      y|Y) return 0 ;;
      n|N) return 1 ;;
      '')  [ "$YN" = 'Y/n' ] && return 0 || return 1 ;;
      *)   echo 'yYnN<cr> only please' ;;
    esac
  done
}

## send a queued mail out via msmtp
##
send_queued_mail() {   # <-- mail id
  local FQP="${MSMTPQ_Q}/${1}"       # fully qualified path name
  local -i RC=0                      # for msmtp exit code

  if [ -f "${FQP}.msmtp" ] ; then    # corresponding .msmtp file found
    [ "$EMAIL_CONN_TEST" != 'x' ] && \
    [ -z "$EMAIL_CONN_NOTEST" ] && { # do connection test
      connect_test || {
        log "mail [ $2 ] [ $1 ] from queue ; couldn't be sent - host not connected"
        return
      }
    }

    if "$MSMTP" $(< "${FQP}.msmtp") < "${FQP}.mail" ; then     # this mail goes out the door
      log "mail [ $2 ] [ $1 ] from queue ; send was successful ; purged from queue"  # good news to user
      'rm' -f "${FQP}".*                                       # nuke both queue mail files
      ALT='t'                        # set queue changed flag
    else                             # send was unsuccessful
      RC=$?                          # take msmtp exit code
      log "mail [ $2 ] [ $1 ] from queue ; send failed ; msmtp rc = $RC" # bad news ...
    fi
    return $RC                       # func returns exit code
  else                               # corresponding MSF file not found
    log "preparing to send .mail file [ $1 ] [ ${FQP}.mail ] but"\
        "  corresponding .msmtp file [ ${FQP}.msmtp ] was not found in queue"\
        '  skipping this mail ; this is worth looking into'    # give user the bad news
  fi                                                           # (but allow continuation)
}

## run (flush) queue
##
run_queue() {    # <- 'sm' mode      # run queue
  # This will reset nullglob to its original value once the function
  # ends. I could potentially enable nullglob for the entire script,
  # but I have a feeling that doing so would break things.
  #
  # Credit goes to Robin A. Meade (https://stackoverflow.com/users/1157557/robin-a-meade)
  # for the idea of using a trap to do this:
  # <https://stackoverflow.com/a/50808490>
  trap "$(shopt -p nullglob)" RETURN
  # This will prevent the for loop from running if there’s no .mail
  # files in the queue directory.
  shopt -s nullglob

  local M LST
  local -i NDX=0

  for M in "$MSMTPQ_Q"/*.mail ; do        # process all mails
    NDX=$((NDX + 1))
    send_queued_mail "$(basename "$M" .mail)" "$NDX"     # send mail - pass {id} only
  done
  if [ "$NDX" = 0 ] && [ -z "$1" ]; then  # queue is empty. inform user (if not running in sendmail mode)
    dsp '' 'mail queue is empty (nothing to send)' ''
  fi
}

## display queue contents
##
display_queue() {      # <-- { 'purge' | 'send' } (op label) ; { 'rec' } (record array of mail ids)
  # See the comments about the trap and shopt lines in run_queue().
  trap "$(shopt -p nullglob)" RETURN
  shopt -s nullglob

  local M ID

  for M in "$MSMTPQ_Q"/*.mail ; do   # cycle through each
    ID="$(basename "$M" .mail)"      # take mail id from filename
    CNT="$((CNT + 1))"
    dsp '' "mail  num=[ $CNT ]  id=[ $ID ]"                  # show mail id ## patch in
    'grep' -E -s --colour -h -m 3 '(^From:|^To:|^Subject:)' "$M" # show mail info
    [ -n "$2" ] && Q_LST["$CNT"]="$ID" # bang mail id into array (note 1-based array indexing)
  done
  echo
  if [ "$CNT" = 0 ]; then            # no mails ; no contents
    if [ -z "$1" ]; then
      dsp '' 'no mail in queue' ''
    else
      dsp '' "mail queue is empty (nothing to $1)" ''    # inform user
    fi
    exit 0
  fi
}

## delete all mail in queue, after confirmation
##
purge_queue() {
  display_queue 'purge'              # show queue contents
  if ok -n 'remove (purge) all mail from the queue' ; then
    lock_queue                       # lock here
    'rm' -f "$MSMTPQ_Q"/*.*
    log 'msmtp queue purged (all mail)'
    lock_queue -u                    # unlock here
  else
    dsp '' 'nothing done ; queue is untouched' ''
  fi
}

## select a single mail from queue ; delete it or send it
## select by mail index (position in queue) or mail id
##
select_mail() {  # <-- < 'purge' | 'send' >
  local OK ID                                        # mail id
  local -i I NDX                                     # mail index (position in queue)

  while true ; do                                    # purge an individual mail from queue
    display_queue "$1" 'rec'                         # show queue contents ; make mail ids array

    ## allow selection also by mail index
    if [ $CNT -eq 1 ] ; then                         # only one mail in queue ; take its id
      NDX=1
      ID="${Q_LST[1]}"
    else                                             # more than one mail ; select its id
      while true ; do                                # get mail id
        OK='t'                                       # optimistic to a fault
        dsp "enter mail number or id to $1"          # <-- num or file name (only, no suff)
        echo -n '    ( <cr> alone to exit ) ..: '
        read -r ID
        [ -n "$ID" ] || return                       # entry made - or say good bye

        if [ "${ID:4:1}" != '-' ] ; then             # mail id *not* entered ; test index num
          I=0
          while [ "$I" -lt ${#ID} ]; do              # test index number
            if [ "${ID:${I}:1}" -lt '0' ] || \
                  [ "${ID:${I}:1}" -gt '9' ] ; then
              dsp '' "[ $ID ] is neither a valid mail id"\
                     'nor a valid mail number' ''
              unset OK
            fi
          I=$((I + 1))
          done
          [ -z "$OK" ] && continue                   # format not ok (not all nums)

          NDX=$ID
          if [ "$NDX" -lt 1 ] || [ "$NDX" -gt "$CNT" ] ; then  # test number range (1 - $CNT)
            dsp '' "[ $NDX ] is out of range as a mail number"\
                   "validity is from 1 to $CNT"
            continue                                 # try again
          fi

          ID="${Q_LST[$NDX]}"                        # format & range were ok ; use it
          break                                      # valid mail selection
        else                                         # mail id entered
          NDX=1
          while [ "$NDX" -le ${#Q_LST[*]} ]; do                 # find entered id in queue list
            [ "$ID" = "${Q_LST[$NDX]}" ] && break
            NDX=$((NDX + 1))
          done
          if [ "$NDX" -le ${#Q_LST[*]} ]; then
            break
          else
            dsp '' "mail [ $ID ] not found ; invalid id" # mail selection valid (found) or
          fi
        fi                                               # fell through (not found) complain
      done                                               # and ask again
    fi

    if ok '' "$1 :"\
          "  mail num=[ $NDX ]"\
          "        id=[ $ID ]" '' ; then             # confirm mail op
      if [ "$1" = 'purge' ] ; then                   # purging
        lock_queue                                   # lock here
        'rm' -f "$MSMTPQ_Q"/"$ID".*                  # msmtp - nukes single mail (both files) in queue
        log "mail [ $ID ] purged from queue"         # log op
        lock_queue -u                                # unlock here
        ALT='t'                                      # mark that a queue alteration has taken place
      else                                           # sending
        lock_queue                                   # lock here
        send_queued_mail "$ID" "$NDX"                # send out the mail
        lock_queue -u                                # unlock here
      fi
    else                                             # user opts out
      dsp '' 'nothing done to this queued email'     # soothe user
      [ $CNT -eq 1 ] && break                        # single mail ; user opted out
    fi
    dsp '' "--------------------------------------------------"
  done

  if [ -n "$ALT" ] ; then            # queue was changed
    dsp '' 'done' ''
  else                               # queue is untouched
    dsp '' 'nothing done ; queue is untouched' ''
  fi
}

#
## ----------------------------------- functions for directly sending mail
## ----------------------------------- 'sendmail' mode - (msmtpq)
#

## ('sendmail' mode only)
## make base filename id for queue
##
make_id() {
  local -i INC                       # increment counter for (possible) base fqp name collision

  ID="$(date +%Y-%m-%d-%H.%M.%S)"    # make filename id for queue    (global
  FQP="${MSMTPQ_Q}/$ID"              # make fully qualified pathname  vars)
  ## Philipp Hartwig patch #1
  if [ -f "${FQP}.mail" ] || [ -f "${FQP}.msmtp" ] ; then    # ensure fqp name is unique
    INC=1                            # initial increment
      while [ -f "${FQP}-${INC}.mail" ] || [ -f "${FQP}-${INC}.msmtp" ] ; do # fqp name w/incr exists
        INC=$((INC + 1))             # bump increment
      done
      ID="${ID}-${INC}"              # unique ; set id
      FQP="${FQP}-${INC}"            # unique ; set fqp name
  fi
}

## ('sendmail' mode only)
## enqueue a mail
##
enqueue_mail() { # <-- all mail args ; mail text via TMP
  if echo "$@" > "${FQP}.msmtp" ; then     # write msmtp command line to queue .msmtp file
    log "enqueued mail as : [ $ID ] ( $* ) : successful" # (queue .mail file is already there)
  else                                     # write failed ; bomb
    log -e "$?" "queueing - writing msmtp cmd line { $* }"\
                "           to [ ${ID}.msmtp ] : failed"
  fi
}

## ('sendmail' mode only)
## send a mail (if possible, otherwise enqueue it)
## if send is successful, msmtp will also log it (if logging enabled in ~/.msmtprc)
##
send_mail() {    # <-- all mail args ; mail text via TMP
  [ "$EMAIL_CONN_TEST" != 'x' ] && \
  [ -z "$EMAIL_CONN_NOTEST" ] && {   # do connection test
    connect_test || {
      log "mail for [ $* ] : couldn't be sent - host not connected"
      enqueue_mail "$@"              # enqueue the mail
      return
    }
  }

  if "$MSMTP" "$@" < "${FQP}.mail" > /dev/null ; then      # send mail using queue .mail fil
    log "mail for [ $* ] : send was successful"          # log it
    'rm' -f "${FQP}".*               # remove all queue mail files .mail & .msmtp file
    run_queue 'sm'                   # run/flush any other mails in queue
  else                               # send failed - the mail stays in the queue
    log "mail for [ $* ] : send was unsuccessful ; msmtp exit code was $?"\
        "enqueued mail as : [ $ID ] ( $* )"    # (queue .mail file is already there)
  fi
}

#
## -- entry point
#

[ -v LOG_LATER_ARGS ] && log "${LOG_LATER_ARGS[@]}"
if [ ! "$1" = '--q-mgmt' ] ; then    # msmtpq - sendmail mode
  lock_queue                         # lock here
  make_id                            # make base queue filename id for this mail
  # write mail body text to queue .mail file
  cat > "${FQP}.mail" || \
    log -e "$?" "creating mail body file [ ${FQP}.mail ] : failed" # test for error
  # write msmtp command line to queue .msmtp file
  echo "$@" > "${FQP}.msmtp" || \
    log -e "$?" "creating msmtp cmd line file { $* }"\
                "           to [ ${ID}.msmtp ] : failed" # test for error
  send_mail "$@"                     # send the mail if possible, queue it if not
  lock_queue -u                      # unlock here
else                                 # msmtp-queue - queue management mode
  shift                              # trim off first (--q-mgmt) arg
  OP=${1:1}                          # trim off first char of OP arg
  case "$OP" in                      # sort ops ; run according to spec
    r)    lock_queue
          run_queue
          lock_queue -u       ;;     # run (flush) the queue
    R)    select_mail send    ;;     # send individual mail(s) in queue
    d|'') display_queue       ;;     # display (list) all mail in queue (default)
    p)    select_mail purge   ;;     # purge individual mail(s) from queue
    a)    purge_queue         ;;     # purge all mail in queue
    h)    usage               ;;     # show help
    *)    usage "[ -$OP ] is an unknown msmtp-queue option" ;;
  esac
fi

exit 0
