update-hashes

#!/usr/bin/env ruby
#
# Usage: update-hashes VERSION
#
# VERSION should be a supported Go version available for download.

require 'json'
require 'net/http'
require 'tempfile'

def rewrite_file(name, mode)
  r = File.open(name, "r")
  w = Tempfile.new(name, ".")
  yield r, w
  r.close
  w.chmod(mode)
  File.rename(w.path, r.path)
end

def update_main_repo(version, hashes)
  rewrite_file("build_dockers.bsh", 0755) do |r, w|
    puts "Processing build_dockers.bsh"
    arch = nil
    in_arch = false
    while line = r.gets
      case line
      when /^(: \$\{GOLANG_VERSION:=)(?:[0-9.]+)(\})/
        w.puts "#{$1}#{version}#{$2}"
      when /case "\$GOLANG_ARCH" in/
        in_arch = true
        w.puts line
      when /^\s+([a-z0-9-]+)\)/
        arch = $1 if in_arch
        w.puts line
      when /^(.*\$\{GOLANG_SHA256:=)(?:[a-f0-9]+)(\})/
        w.puts "#{$1}#{hashes[arch]}#{$2}"
      when /^esac/
        in_arch = false
        w.puts line
      else
        w.puts line
      end
    end
  end
end

def update_dockerfile(name, version, hashes)
  rewrite_file(name, 0644) do |r, w|
    puts "Processing #{name}"
    while line = r.gets
      case line
      when /^ARG GOLANG_VERSION=/
        w.puts "ARG GOLANG_VERSION=#{version}"
      when /^ARG GOLANG_SHA256=/
        w.puts "ARG GOLANG_SHA256=#{hashes['amd64']}"
      else
        w.puts line
      end
    end
  end
end

def fetch_hashes(version)
  uri = URI('https://go.dev/dl/?mode=json')
  res = Net::HTTP.get(uri)
  data = JSON.parse(res)
  ver = data.select { |v| v["version"] == "go#{version}" }.first
  return nil unless ver && ver["files"]
  ver["files"].select { |e| e["os"] == "linux" }.map { |e| [e["arch"], e["sha256"]] }.to_h
end

version = ARGV[0]
hashes = fetch_hashes(version)
if hashes.nil?
  $stderr.puts "Cannot find version #{version}"
  exit 2
end
update_main_repo(version, hashes)
Dir.glob("*.Dockerfile").each do |f|
  update_dockerfile(f, version, hashes)
end