#!/bin/bash

set -o errexit
set -o nounset
set -o pipefail
shopt -s lastpipe

function join_by {
	local d=${1-} f=${2-}
	if shift 2; then
		printf %s "$f" "${@/#/$d}"
	fi
}

results=$(mktemp)
cleanup() {
	rm "$results"
}
trap cleanup SIGINT SIGHUP SIGABRT EXIT

declare -a addresses
while read -r key _; do
	addresses+=("${key%:*}")
done </etc/exim4/otrs_emails

grep -E '=> ('"$(join_by '|' "${addresses[@]}")"')' < <(zcat /var/log/exim4/mainlog.*.gz) >"$results"

declare -Ai domain_names
declare -Ai local_names
for email in "${addresses[@]}"; do
	count=$(grep -c '=> '"$email" <"$results") || true
	IFS='@' read -r local_name domain_name <<<"$email"
	local_names[$local_name]+=$count
	domain_names[$domain_name]+=$count
done

printf '\nTop Local Names:\n'
for local_name in "${!local_names[@]}"; do
	printf '%d\t%s\n' "${local_names[$local_name]}" "$local_name"
done | sort -n | tail -n 20

printf '\nTop Domain Names:\n'
for domain_name in "${!domain_names[@]}"; do
	printf '%d\t%s\n' "${domain_names[$domain_name]}" "$domain_name"
done | sort -n | tail -n 20