#!/usr/bin/env bash
set -Eeuo pipefail

declare -A aliases=(
	[5.1-rc]='rc'
	[5.0]='5 latest'
	[4.2]='4'
)

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

versions=( */ )
versions=( "${versions[@]%/}" )

# sort version numbers with highest first
IFS=$'\n'; versions=( $(echo "${versions[*]}" | sort -rV) ); unset IFS

# 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/tianon/docker-qemu/blob/$(fileCommit "$self")/$self

Maintainers: Tianon Gravi <admwiggin@gmail.com> (@tianon)
GitRepo: https://github.com/tianon/docker-qemu.git
EOH

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

for version in "${versions[@]}"; do
	commit="$(dirCommit "$version")"

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

	rcVersion="${version%-rc}"

	versionAliases=()
	while [ "$fullVersion" != "$rcVersion" -a "${fullVersion%[.]*}" != "$fullVersion" ]; do
		versionAliases+=( $fullVersion )
		fullVersion="${fullVersion%[.]*}"
	done
	versionAliases+=(
		$version
		${aliases[$version]:-}
	)

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