#!/bin/sh
#
# reportfollowers.sh
#
# Send a diff of the follower dumps stored under ./followers per mail,
# designed to be run daily from cron.
#
# The optional argument overrides the timestamp to compare against, which
# defaults to "yesterday"
#
# Copyright © 2017–2019 by martin f. krafft <madduck@madduck.net>
# Released under the Artistic Licence 2.0
#

set -eu

MYDIR="${0%/*}"
cd "$MYDIR"/followers

export LC_ALL=$(locale -a | grep utf8 | head -1)

REVSPEC="${1:-master@{yesterday\}}"
DATESTAMP="$(git show --pretty=format:'%ai (%ar)' --no-patch $REVSPEC)"
COUNT=$(wc -l dump | cut -d' ' -f1)
STATS="$(git diff --numstat $REVSPEC | \
  sed -re 's,([[:digit:]]+)[[:space:]]+([[:digit:]]+).*,+\1/-\2,')"

SENDMAIL="/usr/sbin/sendmail madduck@madduck.net"
[ ! -t 0 ] || SENDMAIL=cat

$SENDMAIL <<_eof
From: Twitter follower report <madduck@madduck.net>
Subject: $(wc -l dump | cut -d' ' -f1) followers ($STATS)

Changes since $DATESTAMP:

$(git diff $REVSPEC | grep '^[-+][^-+]' | sort -k1.1,1.1)

=Total followers: $COUNT
_eof