update.sh

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

cd "$(dirname "$(readlink -f "$BASH_SOURCE")")"

versions=( "$@" )
if [ ${#versions[@]} -eq 0 ]; then
	versions=( */ )
fi
versions=( "${versions[@]%/}" )

releasesPage="$(curl -fsSL 'https://www.ruby-lang.org/en/downloads/releases/')"
newsPage="$(curl -fsSL 'https://www.ruby-lang.org/en/news/')" # occasionally, releases don't show up on the Releases page (see https://github.com/ruby/www.ruby-lang.org/blob/master/_data/releases.yml)
# TODO consider parsing https://github.com/ruby/www.ruby-lang.org/blob/master/_data/downloads.yml as well

latest_gem_version() {
	curl -fsSL "https://rubygems.org/api/v1/gems/$1.json" | sed -r 's/^.*"version":"([^"]+)".*$/\1/'
}

# https://github.com/docker-library/ruby/issues/246
rubygems='3.0.3'
declare -A newEnoughRubygems=(
	[2.6]=1 # 2.6.3 => gems 3.0.3 (https://github.com/ruby/ruby/blob/v2_6_3/lib/rubygems.rb#L12)
	[2.7]=1 # 2.7.0-preview2 => gems 3.1.0.pre1 (https://github.com/ruby/ruby/blob/v2_7_0_preview1/lib/rubygems.rb#L12)
)
# TODO once all versions are in this family of "new enough", remove RUBYGEMS_VERSION code entirely

for version in "${versions[@]}"; do
	rcGrepV='-v'
	rcVersion="${version%-rc}"
	if [ "$rcVersion" != "$version" ]; then
		rcGrepV=
	fi

	IFS=$'\n'; allVersions=( $(
		curl -fsSL --compressed "https://cache.ruby-lang.org/pub/ruby/$rcVersion/" \
			| grep -oE '["/]ruby-'"$rcVersion"'.[^"]+\.tar\.xz' \
			| sed -r 's!^["/]ruby-([^"]+)[.]tar[.]xz!\1!' \
			| grep $rcGrepV -E 'preview|rc' \
			| sort -ruV
	) ); unset IFS

	fullVersion=
	shaVal=
	for tryVersion in "${allVersions[@]}"; do
		if \
			{
				versionReleasePage="$(grep "<td>Ruby $tryVersion</td>" -A 2 <<<"$releasesPage" | awk -F '"' '$1 == "<td><a href=" { print $2; exit }')" \
					&& [ "$versionReleasePage" ] \
					&& shaVal="$(curl -fsSL "https://www.ruby-lang.org/$versionReleasePage" |tac|tac| grep "ruby-$tryVersion.tar.xz" -A 5 | awk '$1 == "SHA256:" { print $2; exit }')" \
					&& [ "$shaVal" ]
			} \
			|| {
				versionReleasePage="$(echo "$newsPage" | grep -oE '<a href="[^"]+">Ruby '"$tryVersion"' Released</a>' | cut -d'"' -f2)" \
					&& [ "$versionReleasePage" ] \
					&& shaVal="$(curl -fsSL "https://www.ruby-lang.org/$versionReleasePage" |tac|tac| grep "ruby-$tryVersion.tar.xz" -A 5 | awk '$1 == "SHA256:" { print $2; exit }')" \
					&& [ "$shaVal" ]
			} \
		; then
			fullVersion="$tryVersion"
			break
		fi
	done

	if [ -z "$fullVersion" ]; then
		echo >&2 "warning: cannot determine sha for $version (tried all of ${allVersions[*]}); skipping"
		continue
	fi

	echo "$version: $fullVersion; $shaVal"

	for v in \
		{focal,bionic,xenial} \
	; do
		dir="$version/$v"
		variant="$(basename "$v")"

		[ -d "$dir" ] || continue

		case "$variant" in
			*) template='ubuntu'; tag="$variant" ;;
		esac
		template="Dockerfile-${template}.template"

		sed -r \
			-e 's!%%VERSION%%!'"$version"'!g' \
			-e 's!%%FULL_VERSION%%!'"$fullVersion"'!g' \
			-e 's!%%SHA256%%!'"$shaVal"'!g' \
			-e 's!%%RUBYGEMS%%!'"$rubygems"'!g' \
			-e 's/^(FROM (ubuntu|buildpack-deps)):.*/\1:'"$tag"'/' \
			"$template" > "$dir/Dockerfile"

		if [ -n "${newEnoughRubygems[$rcVersion]:-}" ]; then
			sed -ri -e '/RUBYGEMS_VERSION/d' "$dir/Dockerfile"
		fi
	done
done