module PlainApm
  ##
  # Tracks current revision of the app.
  #
  # This enables per-deploy metrics segmentation and checking
  # for performance regressions.
  module Hooks
    class Deploy
      include EventAttributes

      ##
      # Collect once, immediately on install.
      def install
        collect
      end

      def collect
        result = git_revision || hg_revision || return

        _, attrs = attributes_from_deploy(*result)

        Agent.collect(attrs)
      end

      private

      # TODO: other deploy mechanisms
      #
      # Also, we might not be in the app root.
      def git_revision
        return unless File.exist?(".git")

        rev = `git rev-parse --short=8 HEAD`.strip

        return if rev.empty?

        ["git", rev]
      rescue Error::ENOENT # No git installed
        nil
      end

      def hg_revision
        return unless File.exist?(".hg")

        rev = `hg log -l 1 -r . -T '{node}'`.strip

        return if rev.empty?

        ["hg", rev]
      rescue Error::ENOENT # No mercurial installed
        nil
      end
    end
  end
end