# 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 randomly picked
a candidate for each review slot. Feel free to override this selection if you
think someone else would be better-suited, or the chosen person is unavailable.

Once you've decided who will review this merge request, mention them as you
normally would! Danger does not (yet?) 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-ce/blob/master/lib/gitlab/danger/helper.rb)
for them.
MARKDOWN

def spin_for_category(team, project, category, branch_name)
  rng = Random.new(Digest::MD5.hexdigest(branch_name).to_i(16))

  reviewers = team.select { |member| member.reviewer?(project, category) }
  traintainers = team.select { |member| member.traintainer?(project, category) }
  maintainers = team.select { |member| member.maintainer?(project, category) }

  # TODO: take CODEOWNERS into account?
  # https://gitlab.com/gitlab-org/gitlab-ce/issues/57653

  # Make traintainers have triple the chance to be picked as a reviewer
  reviewer = spin_for_person(reviewers + traintainers + traintainers, random: rng)
  maintainer = spin_for_person(maintainers, random: rng)

  "| #{helper.label_for_category(category)} | #{reviewer&.markdown_name} | #{maintainer&.markdown_name} |"
end

# Known issue: If someone is rejected due to OOO, and then becomes not OOO, the
# selection will change on next spin
def spin_for_person(people, random:)
  person = nil
  people = people.dup

  people.size.times do
    person = people.sample(random: random)

    break person unless out_of_office?(person)

    people -= [person]
  end

  person
end

def out_of_office?(person)
  username = CGI.escape(person.username)
  api_endpoint = "https://gitlab.com/api/v4/users/#{username}/status"
  response = HTTParty.get(api_endpoint) # rubocop:disable Gitlab/HTTParty

  if response.code == 200
    response["message"]&.match(/OOO/i)
  else
    false # this is no worse than not checking for OOO
  end
rescue
  false
end

def build_list(items)
  list = items.map { |filename| "* `#{filename}`" }.join("\n")

  if items.size > 10
    "\n<details>\n\n#{list}\n\n</details>"
  else
    list
  end
end

changes = helper.changes_by_category

# Ignore any files that are known but uncategorized. Prompt for any unknown files
changes.delete(:none)
categories = changes.keys - [:unknown]

# Single codebase MRs are reviewed using a slightly different process, so we
# disable the review roulette for such MRs.
# CSS Clean up MRs are reviewed using a slightly different process, so we
# disable the review roulette for such MRs.
if changes.any? && !gitlab.mr_labels.include?('single codebase') && !gitlab.mr_labels.include?('CSS cleanup')
  # Strip leading and trailing CE/EE markers
  canonical_branch_name = gitlab
                            .mr_json['source_branch']
                            .gsub(/^[ce]e-/, '')
                            .gsub(/-[ce]e$/, '')

  team =
    begin
      helper.project_team
    rescue => err
      warn("Reviewer roulette failed to load team data: #{err.message}")
      []
    end

  # Exclude the MR author from the team for selection purposes
  team.delete_if { |teammate| teammate.username == gitlab.mr_author }

  project = helper.project_name
  unknown = changes.fetch(:unknown, [])

  rows = categories.map { |category| spin_for_category(team, project, category, canonical_branch_name) }

  markdown(MESSAGE)
  markdown(CATEGORY_TABLE_HEADER + rows.join("\n")) unless rows.empty?
  markdown(UNKNOWN_FILES_MESSAGE + build_list(unknown)) unless unknown.empty?
end