module MatchingBundle

# File lib/matching_bundle.rb, line 7
def find_or_install_matching_version(gemfile_content)
  requirements = bundler_requirements(gemfile_content)
  return if requirements.empty? # just use whatever

  if version = find_matching_local_bundler_version(requirements)
    warn "Using installed bundler #{version}"
    return version
  end

  unless version = find_matching_remote_bundler_version(requirements)
    warn "No remote version of bundler satisfies #{requirements.join(", ")}"
    return
  end

  warn "Installing bundler #{version}"
  abort unless system "gem", "install", "bundler", "-v", version
  version
end

# File lib/matching_bundle.rb, line 52
def bundler_requirements(gemfile_content)
  requirements =
    gemfile_content.
      split("Current Bundler version").first.to_s.
      scan(/^\s*bundler \((.*)\)/).flatten.
      flat_map { |r| r.split(", ") }

  # saw 2.2.16 fail on 2.2.3 ... so we need exact match
  if gemfile_content =~ /BUNDLED WITH\n\s+(.*)/
    requirements << "= #{$1}"
  end

  requirements
end

# File lib/matching_bundle.rb, line 34
def find_matching_local_bundler_version(requirements)
  find_satisfied(requirements, installed_bundler_versions)
end

# File lib/matching_bundle.rb, line 28
def find_matching_remote_bundler_version(requirements)
  json = open('https://rubygems.org/api/v1/versions/bundler.json').read
  versions = JSON.load(json).map { |v| v["number"] }
  find_satisfied(requirements, versions)
end

# File lib/matching_bundle.rb, line 38
def find_satisfied(requirements, versions)
  requirement = Gem::Requirement.new(*requirements)
  version = versions.map { |v| Gem::Version.new(v) }.sort!.reverse!.find do |version|
    requirement.satisfied_by? version
  end
  version.to_s if version
end

# File lib/matching_bundle.rb, line 46
def installed_bundler_versions
  Gem::Specification.
    find_all { |s| s.name == 'bundler' }.
    map { |spec| spec.version.to_s }
end