wip: extract tarball downloading into separate command

bin/download-tarball

@@ -0,0 +1,46 @@
+#!/usr/bin/env ruby
+# frozen_string_literal: true
+
+require 'optparse'
+
+require_relative '../lib/download_tarball'
+require_relative '../lib/errors'
+
+options = {
+  repo: 'emacs-mirror/emacs',
+  output: File.expand_path('../tarballs', __dir__),
+  log_level: :info
+}
+
+OptionParser.new do |opts|
+  opts.banner = <<~TXT
+    Usage: ./download-tarball [options] <branch/tag/sha>
+
+    Download a tarball of given GitHub repository branch, tag, or SHA.
+
+    Options:
+  TXT
+
+  opts.on('-r', '--repo STRING',
+          "GitHub repository (default: #{options[:repo]})") do |v|
+    options[:repo] = v
+  end
+
+  opts.on('-o', '--output DIR', 'Directory to save tarball in ' \
+          "(default: #{options[:output]})") do |v|
+    options[:output] = v
+  end
+
+  opts.on('-l', '--log-level LEVEL', 'Log level ' \
+          "(default: #{options[:log_level]})") do |v|
+    options[:log_level] = v.to_sym
+  end
+end.parse!
+
+begin
+  tarball = DownloadTarball.new(ref: ARGV[0], **options).perform
+
+  puts tarball.to_yaml
+rescue Error => e
+  handle_error(e)
+end

lib/commit.rb

@@ -0,0 +1,29 @@
+# frozen_string_literal: true
+
+require 'yaml'
+
+class Commit
+  attr_reader :sha
+  attr_reader :time
+
+  def initialize(sha:, time:)
+    @sha = sha
+    @time = time
+  end
+
+  def sha_short
+    sha[0..6]
+  end
+
+  def to_hash
+    {
+      'sha' => sha,
+      'sha_short' => sha_short,
+      'time' => time
+    }
+  end
+
+  def to_yaml
+    to_hash.to_yaml
+  end
+end

lib/common.rb

@@ -0,0 +1,19 @@
+# frozen_string_literal: true
+
+require 'net/http'
+
+module Common
+  private
+
+  def run_cmd(*args)
+    info "executing: #{args.join(' ')}"
+    system(*args) || err("Exit code: #{$CHILD_STATUS.exitstatus}")
+  end
+
+  def http_get(url)
+    response = Net::HTTP.get_response(URI.parse(url))
+    return unless response.code == '200'
+
+    response.body
+  end
+end

lib/download_tarball.rb

@@ -0,0 +1,83 @@
+# frozen_string_literal: true
+
+require 'fileutils'
+require 'json'
+require 'time'
+
+require_relative './common'
+require_relative './commit'
+require_relative './output'
+require_relative './tarball'
+
+class DownloadTarball
+  include Common
+  include Output
+
+  logger_name 'download-tarball'
+
+  TARBALL_URL = 'https://github.com/%s/tarball/%s'
+  COMMIT_URL = 'https://api.github.com/repos/%s/commits/%s'
+
+  attr_reader :ref
+  attr_reader :repo
+  attr_reader :output
+  attr_reader :log_level
+
+  def initialize(ref:, repo:, output:, log_level:)
+    @ref = ref
+    @repo = repo
+    @output = output
+    @log_level = log_level
+
+    err 'branch/tag/sha argument cannot be empty' if ref.nil? || ref.empty?
+  end
+
+  def perform
+    FileUtils.mkdir_p(output)
+    tarball = Tarball.new(file: target, commit: commit)
+
+    if File.exist?(target)
+      info "#{filename} already exists locally, attempting to use."
+      return tarball
+    end
+
+    info 'Downloading tarball from GitHub. This could take a while, ' \
+         'please be patient.'
+    result = run_cmd('curl', '-L', url, '-o', target)
+    err 'Download failed.' if !result || !File.exist?(target)
+
+    tarball
+  end
+
+  def url
+    @url ||= format(TARBALL_URL, repo, commit.sha)
+  end
+
+  def filename
+    @filename ||= "#{repo.gsub(/[^\w]/, '-')}-#{commit.sha_short}.tgz"
+  end
+
+  def target
+    @target ||= File.join(output, filename)
+  end
+
+  def commit
+    return @commit if @commit
+
+    info "Fetching info for git ref: #{ref}"
+    url = format(COMMIT_URL, repo, ref)
+    commit_json = http_get(url)
+    err "Failed to get commit info about: #{ref}" if commit_json.nil?
+
+    parsed = JSON.parse(commit_json)
+    commit = Commit.new(
+      sha: parsed&.dig('sha'),
+      time: Time.parse(parsed&.dig('commit', 'committer', 'date'))
+    )
+
+    err 'Failed to get commit SHA' if commit.sha.nil? || commit.sha.empty?
+    err 'Failed to get commit time' if commit.time.nil?
+
+    @commit = commit
+  end
+end

lib/errors.rb

@@ -0,0 +1,8 @@
+# frozen_string_literal: true
+
+def handle_error(err)
+  warn "ERROR: #{err.message}"
+  Process.exit 1
+end
+
+class Error < StandardError; end

lib/output.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+require 'forwardable'
+require 'logger'
+
+require_relative './errors'
+
+module Output
+  extend Forwardable
+
+  def self.included(base)
+    base.extend(ClassMethods)
+  end
+
+  module ClassMethods
+    def logger_name(name = nil)
+      return @logger_name if name.nil?
+
+      @logger_name = name
+    end
+  end
+
+  def_delegators :logger, :debug, :info, :warn, :error, :fatal, :unkonwn
+
+  def err(msg = nil)
+    raise Error, msg
+  end
+
+  private
+
+  # override to set custom log level
+  def log_level
+    :info
+  end
+
+  def logger
+    @logger ||= Logger.new($stderr).tap do |l|
+      l.progname = self.class.logger_name
+      l.level = log_level
+      l.formatter = log_formatter
+    end
+  end
+
+  def log_formatter
+    proc do |severity, _datetime, progname, msg|
+      "==> [#{progname}] #{severity}: #{msg}\n"
+    end
+  end
+end

lib/tarball.rb

@@ -0,0 +1,24 @@
+# frozen_string_literal: true
+
+require 'yaml'
+
+class Tarball
+  attr_reader :file
+  attr_reader :commit
+
+  def initialize(file:, commit:)
+    @file = file
+    @commit = commit
+  end
+
+  def to_hash
+    {
+      'file' => file,
+      'commit' => commit.to_hash
+    }
+  end
+
+  def to_yaml
+    to_hash.to_yaml
+  end
+end