ManageIQ/miq_bot

class PrMergeabilityChecker
  include Sidekiq::Worker
  sidekiq_options :queue => :miq_bot

  include BranchWorkerMixin

  LABEL = "unmergeable".freeze

  def perform(branch_id)
    return unless find_branch(branch_id, :pr)
    logger.info("Determining mergeability of PR #{branch.fq_pr_number}.")

    process_mergeability
  end

  private

  def tag
    "<pr-mergeability-checker />"
  end

  def unmergeable_comment
    "#{tag}This pull request is not mergeable. Please rebase and repush."
  end

  def process_mergeability
    was_mergeable       = branch.mergeable?
    currently_mergeable = branch.git_service.mergeable?

    if was_mergeable && !currently_mergeable
      write_to_github
      apply_label
    elsif !was_mergeable && currently_mergeable
      remove_comments
      remove_label
    end

    # Update columns directly to avoid collisions wrt the serialized column issue
    branch.update_columns(:mergeable => currently_mergeable)
  end

  def remove_comments
    comment_ids = GithubService.issue_comments(fq_repo_name, branch.pr_number).select do |com|
      com.user.login == Settings.github_credentials.username && com.body.start_with?(tag)
    end.map(&:id)

    GithubService.delete_comments(fq_repo_name, comment_ids)
  end

  def write_to_github
    logger.info("Updating PR #{branch.fq_pr_number} with mergability comment.")

    GithubService.add_comment(
      fq_repo_name,
      branch.pr_number,
      unmergeable_comment
    )
  end

  def apply_label
    logger.info("Updating PR #{branch.fq_pr_number} with label #{LABEL.inspect}.")

    GithubService.add_labels_to_an_issue(fq_repo_name, branch.pr_number, [LABEL])
  end

  def remove_label
    logger.info("Updating PR #{branch.fq_pr_number} removing label #{LABEL.inspect}.")
    GithubService.remove_label(fq_repo_name, branch.pr_number, LABEL)
  rescue Octokit::NotFound
    # This label is not currently applied, skip
  end
end