#!/bin/bash
# Collect a log of candidate commits for consideration of commit authors as
# active developers according to https://www.wesnoth.org/constitution/
#   ("tangible output [...] at least once every three months within the last 12 calendar months"
#   for project manager: "increased to 18 calendar months")
#
# Note: Devs not committing their work themselves or devs performing
#       housekeeping are naturally not considered here!
#
# First optional argument is the stable release date in ISO 8601 format.
#   Default: 2021-10-24 (1.16 release date)
# Second optional argument is the path to a wesnoth repo checkout.
#   Default: . (current dir)
# The repo checkout must contain local tracking branches of all relevant stable
# branches or they won't be considered.
#
# Output is written to a new dir: wesnoth-election-<year>
# - There will be a complete commit log (commits-by-author.log) of the 18
#   months before the stable release.
# - A subdir "dev_candidate" with files that contain the commit log of single
#   authors that have at least one commit in each 3 month time span in the last
#   12 months.
# - A subdir "pm_candidate" with files that contain the commit log of single
#   authors that have at least one commit in each 3 month time span in the last
#   18 months (only commits from 12 to 18 months back are in the file so only
#   what's not already in the dev log).
#
# Github commit graphs can be used to somewhat double check against:
#   https://github.com/wesnoth/wesnoth/graphs/contributors?from=2020-04-24&to=2021-10-24&type=c
# Though the graph just shows the default branch (master) while this script
# considers master and stable branches (1.*).
#
# Expects GNU date for the date calculations.


# stable release date in ISO 8601 format
release_date=${1-2021-10-24}

# location of wesnoth repo checkout, default to current dir
repo_dir=${2-.}


git -C "$repo_dir" rev-parse --git-dir >/dev/null 2>&1 || { printf '"%s" is not a git repository!\n' "$repo_dir" >&2; exit 1; }

start_date=$(date -d "$release_date - 18 months - 1 week" +%F)
year=${release_date%%-*}
output_dir=wesnoth-election-"$year"
# calculate start and end UNIX epoch for 3 month time spans with a week grace period
date6=$(date -d "$release_date - 18 months" +%s) date6s=$(date -d "$release_date - 18 months - 1 week" +%s) date6e=$(date -d "$release_date - 15 months+1 week" +%s)
date5=$(date -d "$release_date - 15 months" +%s) date5s=$(date -d "$release_date - 15 months - 1 week" +%s) date5e=$(date -d "$release_date - 12 months+1 week" +%s)
date4=$(date -d "$release_date - 12 months" +%s) date4s=$(date -d "$release_date - 12 months - 1 week" +%s) date4e=$(date -d "$release_date -  9 months+1 week" +%s)
date3=$(date -d "$release_date -  9 months" +%s) date3s=$(date -d "$release_date -  9 months - 1 week" +%s) date3e=$(date -d "$release_date -  6 months+1 week" +%s)
date2=$(date -d "$release_date -  6 months" +%s) date2s=$(date -d "$release_date -  6 months - 1 week" +%s) date2e=$(date -d "$release_date -  3 months+1 week" +%s)
date1=$(date -d "$release_date -  3 months" +%s) date1s=$(date -d "$release_date -  3 months - 1 week" +%s) date1e=$(date -d "$release_date" +%s)
commitlog=commits-by-author.log

#printf '%s - %s\n' "$date1s" "$date1e" "$date2s" "$date2e" "$date3s" "$date3e" "$date4s" "$date4e"

mkdir "$output_dir" || exit
cd "$output_dir" || exit

# get all commits in tsv-format: <author> <commit date as UNIX epoch> <relative commit date> <commit hash> <subject> (<committer>)
# GIT_TEST_DATE_NOW makes the relative dates relative to that timestamp
gitlog() {
	GIT_TEST_DATE_NOW=$date1e git -C "$repo_dir" log --branches=master --branches='1.*' $'--pretty=format:%an\t%ct\t%ci (%cr)\t%h\t%s\t(%cn)' --before="$release_date" "$@"
}
gitlog --since="$start_date" | sort > "$commitlog"

# get authors with commits in each time span
declare -A span1 span2 span3 span4 span5 span6
while IFS=$'\t' read -r author date rest
do
	author=${author,,}
	# there is no a >= b so need to write ! a < b
	if [[ ! $date < $date1s && ! $date > $date1e ]]; then span1[$author]=1; continue; fi
	if [[ ! $date < $date2s && ! $date > $date2e ]]; then span2[$author]=1; continue; fi
	if [[ ! $date < $date3s && ! $date > $date3e ]]; then span3[$author]=1; continue; fi
	if [[ ! $date < $date4s && ! $date > $date4e ]]; then span4[$author]=1; continue; fi
	if [[ ! $date < $date5s && ! $date > $date5e ]]; then span5[$author]=1; continue; fi
	if [[ ! $date < $date6s && ! $date > $date6e ]]; then span6[$author]=1; continue; fi
done < "$commitlog"

# check for at least one commit in the last 4 3 month time spans
dev_candidate() { [[ ${span1[$author]+exists} && ${span2[$author]+exists} && ${span3[$author]+exists} && ${span4[$author]+exists} ]]; }
# check for at least one commit in the last 6 3 month time spans
pm_candidate() { [[ ${span1[$author]+exists} && ${span2[$author]+exists} && ${span3[$author]+exists} && ${span4[$author]+exists} && ${span5[$author]+exists} && ${span6[$author]+exists} ]]; }

mkdir {dev,pm}_candidate || exit

print_commit() {
	if [[ $1 ]]
	then
		# print timestamp if date crosses a 3 month date limit
		if [[ $1 < $date1 && ! $2 < $date1 ]]
		then
			printf '%(%F %T)T 3 months back\n' "$date1"
		elif [[ $1 < $date2 && ! $2 < $date2 ]]
		then
			printf '%(%F %T)T 6 months back\n' "$date2"
		elif [[ $1 < $date3 && ! $2 < $date3 ]]
		then
			printf '%(%F %T)T 9 months back\n' "$date3"
		elif [[ $1 < $date4 && ! $2 < $date4 ]]
		then
			printf '%(%F %T)T 12 months back\n' "$date4"
		elif [[ $1 < $date5 && ! $2 < $date5 ]]
		then
			printf '%(%F %T)T 15 months back\n' "$date5"
		elif [[ $1 < $date6 && ! $2 < $date6 ]]
		then
			printf '%(%F %T)T 18 months back\n' "$date6"
		fi
	fi
	printf '%s\t%s\n' "$3" "$4"
}

# write commits of each active dev candidate to its own file, write commits in the extended project manager period to a separate pm file
# appending each commit instead of opening the file just once so we don't get empty files for authors not passing the checks.
prev_date= prev_author=
while IFS=$'\t' read -r author date rest
do
	author=${author,,}
	if [[ $prev_author != $author ]]
	then
		prev_date=
	fi
	prev_author=$author

	if [[ ! $date > $date4s ]]
	then
		if pm_candidate "$author"
		then
			print_commit "$prev_date" "$date" "$author" "$rest" >> "pm_candidate/$author"
			prev_date=$date
		fi
		continue
	fi

	if dev_candidate "$author"
	then
		print_commit "$prev_date" "$date" "$author" "$rest" >> "dev_candidate/$author"
		prev_date=$date
	fi
done < "$commitlog"