#!/bin/bash

# autoreply.sh
#
# This script sends a canned email response to those who've errone-
# ously emailed me at <amcooper@gmail.com>. Once I've manually
# tagged those emails `misdirected`, it iterates over those emails and
# responds.

set -euo pipefail

if [[ -z "$(notmuch search tag:misdirected)" ]] ; then
    echo "[autoreply.sh] Currently no emails are tagged 'misdirected'. Exiting..."
    exit 1
fi

# Handle option(s)
dry_run=
while getopts n opt ; do
    printf "[debug] opt: %s\n\n" $opt
    case $opt in
    n)  dry_run=1;;
    ?)  echo "Usage: /path/to/autoreply.sh/ [ -n ]"
        exit 2;;
    esac
done

# This weird feed-find-output-into-while-loop comes from
# https://github.com/koalaman/shellcheck/wiki/SC2044#correct-code
while IFS= read -r -d '' thread ; do
    echo "[loop] Preparing the email..."

    # Make a temporary file
    temporary_file=$(mktemp /tmp/autoreply-XXXXX)
    echo "[debug] Temporary file: $temporary_file"

    # Parse out the thread-id
    thread_id=$(echo "$thread" | cut -f2 -d':')
    echo "[debug] thread_id: $thread_id"

    # Parse out the reply headers and original message body
    temporary_reply=$(mktemp /tmp/notmuch-reply-XXXXX)
    echo "[debug] Temporary reply: $temporary_reply"
    notmuch reply --reply-to=sender --format=json thread:$thread_id > $temporary_reply
    subject="$(jq -r '."reply-headers".Subject' $temporary_reply)"
    sender="$(jq -r '."reply-headers".From' $temporary_reply)"
    recipient="$(jq -r '."reply-headers".To' $temporary_reply)"
    in_reply_to="$(jq -r '."reply-headers"."In-reply-to"' $temporary_reply)"
    references="$(jq -r '."reply-headers".References' $temporary_reply)"
    orig_sender="$(jq -r '.original.headers.From' $temporary_reply)"
    date="$(jq -r '.original.headers.Date' $temporary_reply)"

    # We have to check for multipart messages.
    orig_body="$(jq -r '.original.body[] | select( ."content-type" == "text/plain" ) | .content' $temporary_reply)"
    if [[ -z $orig_body ]] ; then
        orig_body="$(jq -r '.original.body[] | select( ."content-type" == "multipart/alternative" ) | .content[] | select( ."content-type" == "text/plain" ) | .content' $temporary_reply)"
    fi

    # Copy canned message to temporary file
    printf "From: %s\nSubject: %s\nTo: %s\nCc: amcooper@gmail.com\nDate: $(date +'%a, %d %b %Y %R %z')\nIn-Reply-To: %s\nReferences: %s\n\n" "$sender" "$subject" "$recipient" "$in_reply_to" "$references" >> "$temporary_file"
    cat /home/adam/dotfiles/bin/autoreply/misdirected_email_autoreply.txt >> "$temporary_file"
    printf "\n\nOn %s, %s wrote:\n" "$date" "$orig_sender" >> "$temporary_file"

    # Append email body to temporary file (with prefixed quote marker `> `)
    echo "$orig_body" | sed 's/^/\> /g' >> "$temporary_file"

    # Send the email!
    printf "[debug] Outgoing mail:\n%s\n" "$(cat $temporary_file)"
    if [[ -z "$dry_run" ]] ; then
        echo "[loop] Sending reply to $recipient ... "
        msmtp --read-envelope-from --read-recipients <"$temporary_file"
        notmuch insert --folder=Sent -inbox -unread +sent +misdirected-reply <"$temporary_file"

        # Remove the misdirected tag
        notmuch tag -misdirected -- thread:"$thread_id"
    fi

    printf "%s\n\n" "[loop] Done."

done < <(notmuch search --output=threads --format=text0 tag:misdirected)

echo "[autoreply.sh] All done!"