# frozen_string_literal: true

require 'digest/md5'

MESSAGE = <<MARKDOWN
## Reviewer roulette

Changes that require review have been detected! A merge request is normally
reviewed by both a reviewer and a maintainer in its primary category (e.g.
~frontend or ~backend), and by a maintainer in all other categories.
MARKDOWN

CATEGORY_TABLE_HEADER = <<MARKDOWN

To spread load more evenly across eligible reviewers, Danger has picked a candidate for each
review slot, based on their timezone. Feel free to
[override these selections](https://about.gitlab.com/handbook/engineering/projects/#gitlab)
if you think someone else would be better-suited, or the chosen person is unavailable.

To read more on how to use the reviewer roulette, please take a look at the
[Engineering workflow](https://about.gitlab.com/handbook/engineering/workflow/#basics)
and [code review guidelines](https://docs.gitlab.com/ee/development/code_review.html).
Please consider assigning a reviewer or maintainer who is a
[domain expert](https://about.gitlab.com/handbook/engineering/projects/#gitlab) in the area of the merge request.

Once you've decided who will review this merge request, mention them as you
normally would! Danger does not automatically notify them for you.

| Category | Reviewer | Maintainer |
| -------- | -------- | ---------- |
MARKDOWN

UNKNOWN_FILES_MESSAGE = <<MARKDOWN

These files couldn't be categorised, so Danger was unable to suggest a reviewer.
Please consider creating a merge request to
[add support](https://gitlab.com/gitlab-org/gitlab/blob/master/lib/gitlab/danger/helper.rb)
for them.
MARKDOWN

OPTIONAL_REVIEW_TEMPLATE = "%{role} review is optional for %{category}".freeze
NOT_AVAILABLE_TEMPLATE = 'No %{role} available'.freeze
TIMEZONE_EXPERIMENT = true

def mr_author
  roulette.team.find { |person| person.username == gitlab.mr_author }
end

def note_for_category_role(spin, role)
  if spin.optional_role == role
    return OPTIONAL_REVIEW_TEMPLATE % { role: role.capitalize, category: helper.label_for_category(spin.category) }
  end

  spin.public_send(role)&.markdown_name(timezone_experiment: TIMEZONE_EXPERIMENT, author: mr_author) || NOT_AVAILABLE_TEMPLATE % { role: role } # rubocop:disable GitlabSecurity/PublicSend
end

def markdown_row_for_spin(spin)
  reviewer_note = note_for_category_role(spin, :reviewer)
  maintainer_note = note_for_category_role(spin, :maintainer)

  "| #{helper.label_for_category(spin.category)} | #{reviewer_note} | #{maintainer_note} |"
end

changes = helper.changes_by_category

# Ignore any files that are known but uncategorized. Prompt for any unknown files
changes.delete(:none)
# To reinstate roulette for documentation, remove this line.
changes.delete(:docs)
categories = changes.keys - [:unknown]

# Ensure to spin for database reviewer/maintainer when ~database is applied (e.g. to review SQL queries)
categories << :database if gitlab.mr_labels.include?('database') && !categories.include?(:database)

if changes.any?
  project = helper.project_name
  branch_name = gitlab.mr_json['source_branch']

  markdown(MESSAGE)

  roulette_spins = roulette.spin(project, categories, branch_name, timezone_experiment: TIMEZONE_EXPERIMENT)
  rows = roulette_spins.map do |spin|
    # MR includes QA changes, but also other changes, and author isn't an SET
    if spin.category == :qa && categories.size > 1 && mr_author && !mr_author.reviewer?(project, spin.category, [])
      spin.optional_role = :maintainer
    end

    spin.optional_role = :maintainer if spin.category == :test

    markdown_row_for_spin(spin)
  end

  markdown(CATEGORY_TABLE_HEADER + rows.join("\n")) unless rows.empty?

  unknown = changes.fetch(:unknown, [])
  markdown(UNKNOWN_FILES_MESSAGE + helper.markdown_list(unknown)) unless unknown.empty?
end