github-update.rb

require 'net/http'
require 'uri'
require 'json'

# Get release info from github
# Extracted into a class so it can be shared by multiple formulae.

class GithubUpdate
  # net::http doesn't handle redirects, so we have to handle them
  # here. It also doesnt have raise_for_status (like python requests)
  # so we check the http response code and raise if its not a redirect
  # or a 200.
  def self.get_with_redirect(uri)
    for _ in 1..20
      # Ruby <3 includes net/http <0.1.1 where get_response doesn't take
      # headers. Macos includes ruby 2.6.0, and to avoid users having to
      # update ruby in order to brew install this package, we must make
      # sure the library calls used are compatible with net/http v0.1.0
      request = Net::HTTP::Get.new(uri)
      using_token = false
      # Homebrew seems to santize its environment variables, so we have to
      # use a hombrew recognised environment variable.
      if ENV.include? 'HOMEBREW_GITHUB_PACKAGE_TOKEN' and not(ENV['HOMEBREW_GITHUB_PACKAGE_TOKEN'].empty?)
        using_token = true
        # While github allows unauthenticated requests, the rate limit is low
        # and easily hit in CI systems. To avoid this, we allow a GITHUB_TOKEN
        # to be specified.
        request["Authorization"] = "token #{ENV['HOMEBREW_GITHUB_PACKAGE_TOKEN']}"
      end
      response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) { |http|
        http.request(request)
      }
      redirect = response.header['location']
      if redirect != nil
        uri = URI.parse(response.header['location'])
      elsif response.code == 200.to_s
        return response
      else
        body = response.body
        if body.include? "rate limit"
          if using_token
            raise "Github rate limit exceeded :( "\
                  "A token was provided, check its valid and has quota."
          else
            raise "Github rate limit exceeded :( "\
                  "Rate limits are higher for authenticated users so try with a "\
                  "Github Personal Access Token eg: " \
                  "HOMEBREW_GITHUB_PACKAGE_TOKEN=YOUR_PAT_HERE brew install ... "
          end
        else
          raise "Failed to fetch #{response.uri} Code: #{response.code} Response: #{response.body}."
        end
      end
    end
    raise "Too many redirects fetching #{uri}"
  end

  def self.getLatestRelease(repo)

    # Can't use graphql unauthenticated, so have to use v3/REST API.

    # Find the latest release
    releases_uri = URI.parse("https://api.github.com/repos/#{repo}/releases")
    releases_response = self.get_with_redirect(releases_uri)
    releases = JSON.parse(releases_response.body)
    raise "No GitHub releases found for repo #{repo}" if releases.empty?
    latest = releases[0]

    ver = latest["tag_name"].delete_prefix("v")

    # Get list of artifacts from release
    artifacts_uri = URI.parse(latest["assets_url"])
    artifacts_response = self.get_with_redirect(artifacts_uri)
    artifacts_json = JSON.parse(artifacts_response.body)

    # Find hashes file generated by goreleaser in list of release assets
    hashes_artifact_matches = artifacts_json.filter do |a|
      a['name'].include? "SHA256SUMS"
    end
    if hashes_artifact_matches.empty?
      raise "SHA256SUMS asset not found attached to github release #{releases_uri}"
    end
    hashes_artifact = hashes_artifact_matches[0]

    # Download Hashes file
    hashes_uri = URI.parse(hashes_artifact['browser_download_url'])
    hashes_response = self.get_with_redirect(hashes_uri)
    hashes_txt = hashes_response.body

    # Parse hashes file into { filename => {'hash' => hash}}
    artifacts = {}
    for line in hashes_txt.split("\n") do
      hash, file = line.split()
      artifacts[file] = {"hash" => hash}
    end

    # Add download url to each artifact
    # After this loop we have { filename => {'hash' => hash, 'url' => url}}
    for artifact in artifacts_json do
      name = artifact['name']
      if artifacts.key? name
          artifacts[name]['url'] = artifact['browser_download_url']
      end
    end
    return ver, artifacts
  end

  # Map homebrew to goreleaser arch types
  def self.arch(type)
    return {
      "intel" => "amd64",
      "arm" => "arm64"
    }[String(type)]
  end
end