#!/bin/bash
set -eu

self="$(basename "$BASH_SOURCE")"
cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"

# get the most recent commit which modified any of "$@"
fileCommit() {
	git log -1 --format='format:%H' HEAD -- "$@"
}

# get the most recent commit which modified "$1/Dockerfile" or any file COPY'd from "$1/Dockerfile"
dirCommit() {
	local dir="$1"; shift
	(
		cd "$dir"
		fileCommit \
			Dockerfile \
			$(git show HEAD:./Dockerfile | awk '
				toupper($1) == "COPY" {
					for (i = 2; i < NF; i++) {
						print $i
					}
				}
			')
	)
}

cat <<-EOH
# this file is generated via https://github.com/docker-library/rails/blob/$(fileCommit "$self")/$self

Maintainers: Tianon Gravi <admwiggin@gmail.com> (@tianon),
             Joseph Ferguson <yosifkit@gmail.com> (@yosifkit)
GitRepo: https://github.com/docker-library/rails.git
EOH

# prints "$2$1$3$1...$N"
join() {
	local sep="$1"; shift
	local out; printf -v out "${sep//%/%%}%s" "$@"
	echo "${out#$sep}"
}

commit="$(dirCommit .)"

fullVersion="$(git show "$commit":Dockerfile | awk '$1 == "ENV" && $2 == "RAILS_VERSION" { print $3; exit }')"

versionAliases=()
while [ "${fullVersion%.*}" != "$fullVersion" ]; do
	versionAliases+=( $fullVersion )
	fullVersion="${fullVersion%.*}"
done
versionAliases+=( $fullVersion latest )

echo
cat <<-EOE
	Tags: $(join ', ' "${versionAliases[@]}")
	GitCommit: $commit
EOE

for variant in onbuild; do
	commit="$(dirCommit "$variant")"

	variantAliases=( "$variant" )

	echo
	cat <<-EOE
		Tags: $(join ', ' "${variantAliases[@]}")
		GitCommit: $commit
		Directory: $variant
	EOE
done
