#!/usr/bin/env bash
#
# @license Apache-2.0
#
# Copyright (c) 2017 The Stdlib Authors.
#
# Licensed under the Apache License, Version 2.0 (the "License");
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
#    http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.

# Prints summary statistics for merged pull requests.
#
# <month> <day> <year> <num_files> <additions> <deletions>

# shellcheck disable=SC2034


# FUNCTIONS #

# Computes summary statistics.
sum() {
	local sadd=0
	local sdel=0
	local i=0
	while read -r add del file
	do
		i=$((i + 1))
		sadd=$((sadd + add))
		sdel=$((sdel + del))
	done
	echo "${i} ${sadd} ${sdel}"
}


# MAIN #

# * `git log --reverse --merges`
#   - Show commit logs in reverse order.
# * `grep 'Merge pull request #'`
#   - Filter for commit messages which explicitly state that a commit merges a pull request.
# * `while read`
#   - Read stdin line-by-line.
# * `git show --numstat`
#   - Given a commit hash, print each line along with the associated number of additions and deletions.
# * `sum`
#   - Compute summary statistics over the list of files.
# * `while read`
#   - Print summarized output.
git log --reverse --merges --format=format:"%ad %H %s" --date=format:"%b %d %Y" | grep 'Merge pull request #' | \
while IFS=" " read -r mon day year hash msg
do
	git show "${hash}" --format=tformat: --numstat | sum | \
	while read -r n add del
	do
		echo "${mon} ${day} ${year} ${n} ${add} ${del}"
	done
done
