#!/usr/bin/env bash
#
# Runs mbsync, with pre-hooks and post-hooks
# by default, the pre-hook first runs imapfilter
# and afterwards the post-hook indexes with notmuch.
#
# At the very least, you will have to set up a gpg
# encrypted file containing the password for your
# remote mailbox. It can be set directly below or
# through the environment variable
# `MBSYNC_PASSWORD_FILE` and should point to any
# gpg decryptable file.
#
# To run without invoking any hooks or retry attempts,
# run `checkmail raw`.
# this will simply invoke a single isync run on all
# boxes with the correct config file set.
#
# To invoke mbsync for a specific group or channel,
# simply run it with `checkmail <channelname>` and
# it will only sync the correspondingly named.
#
# To run your own commands as hooks overwrite the
# environment variables `MBSYNC_PRE` and
# `MBSYNC_POST`. If you want to not have anything run
# for either of them the easiest way is to set the
# corresponding environment variable to true.
# Be careful which commands you put here since they
# will be evaluated without any special precautions.
#
# for more advanced, per-account/channel hooks, see
# https://sourceforge.net/p/isync/feature-requests/8/

# available env vars:
# MBSYNC_MAX_TRIES=3
# MBSYNC_PRE="/bin/usr/cmd-to-run"
# MBSYNC_POST="/bin/usr/cmd-to-run"
# MBSYNC_NOTIFY=1
# MBSYNC_PASSWORD_FILE="/path/to/gpg/file.gpg"

# What to run before and after decrypting the password file.
PASSWORD_CMD="pass open -t 1min"
# POST_PASSWORD_CMD=""

prehook() {
    if [ -n "$MBSYNC_PRE" ]; then
        eval "$MBSYNC_PRE"
        return 0
    fi
    imapfilter -c "${XDG_CONFIG_HOME:-$HOME/.config}/imapfilter/config.lua"
}

posthook() {
    if [ -n "$MBSYNC_POST" ]; then
        eval "$MBSYNC_POST"
        return 0
    fi

    notmuch new 2>/dev/null
    countnew
}

# use notmuch to index incoming mail and set the
# correct number of mails if new ones arrived for notifications
countnew() {
    num=$(notmuch count tag:unread and tag:inbox)
    HASMAIL="${num:-0}"
}

# fail the routine and optionally send a message why
fail() {
    [ -n "$1" ] && echo "$1"
    exit 1
}

checkmail() {
    mbsync -c "${XDG_CONFIG_HOME:-$HOME/.config}/isync/mbsyncrc" "${1:--a}"
}

checkonline() {
    # Ping 1.1.1.1 to confirm that we are on the internet
    ping -c 1 "1.1.1.1" >/dev/null 2>/dev/null || fail "checkmail can not access the internet."
}

# warn user that he has to enter his password in a moment
# to stop catching him offguard or entering something by accident
checkwarnuser() {
    enablegpgagent
    if echo "$agt" | grep -qE 'No secret key'; then
        notify "Mail" "Password phrase needed!"
        sleep 2.5
    fi
}

enablegpgagent() {
    [ -n "$agt" ] && return

    if [ -n "$PASSWORD_CMD" ]; then
        IFS=" " read -r -a PASSWORD_CMD <<<"$PASSWORD_CMD"
        # shellcheck disable=SC2068
        agt=$(${PASSWORD_CMD[@]})
    fi

    if [ -n "$POST_PASSWORD_CMD" ]; then
        IFS=" " read -r -a POST_PASSWORD_CMD <<<"$POST_PASSWORD_CMD"
        "${POST_PASSWORD_CMD[@]}"
    fi

    ## exit program after first failed attempt
    if echo "$agt" | grep -qE 'decryption failed' ||
        echo "$agt" | grep -qE 'No such file'; then
        notify "Mail" "Process aborted."
        exit 1
    fi
}

# send out a notification on new mail, to libnotify and stdout
notify_on_new_mail() {
    [ "${MBSYNC_NOTIFY:-1}" -eq 0 ] && return

    if [ "${HASMAIL:-0}" -gt 0 ]; then
        notify "Mail" "New Mail ($HASMAIL)"
    fi
}

notify() {
    command -v notify-send >/dev/null && notify-send "$@"
    echo "$@"
}

# Routine start

# check

# skip any retries and pre/post hooks, just run mbsync
if [ "$1" = "raw" ]; then
    checkmail
    exit
# any other argument passed through selects mbsync targets
elif [ -n "$1" ]; then
    selected_mailbox="$1"
fi

main() {
    checkwarnuser
    enablegpgagent
    prehook

    tries=0
    while true; do
        if checkmail "$selected_mailbox"; then
            break
        fi

        tries=$((tries + 1))
        if [ $tries -gt "${MBSYNC_MAX_TRIES:-3}" ]; then
            fail "maximum retries reached without success."
        fi
    done
    unset tries

    posthook
    notify_on_new_mail
}

main
