# Builds the rotating banner "badges" that sit alongside the ranked leaderboard.
# The banner picks one at a time or cycles through the whole list.
#
# Three kinds, matching the client's brief:
#   #1 encouragement  "Ketch-up <Country>!"            bottom 10 featured countries
#   #2 new_players    "Yay! New players in <Country>"  countries with recent sign-ups
#                     "<N> new players in <Country>!"   (benchmark variant)
#   #3 participation  "<Country>, every tomato counts!" everyone not covered above
#
# Tunables — the client's example numbers, adjust freely:
class LeaderboardBadges
  NEW_PLAYER_WINDOW   = 24.hours       # #2: "new players in the last X hours"
  BENCHMARKS          = [100, 50, 10]  # #2: highest crossed threshold wins
  ENCOURAGEMENT_COUNT = 10             # #1: rotate across the bottom N

  # leaderboard: the array returned by LeaderboardScore.call (already ranked).
  def self.call(leaderboard)
    new(leaderboard).call
  end

  def initialize(leaderboard)
    @leaderboard = leaderboard
  end

  # At most three badges — one random pick of each type. The pick changes on
  # each cache refresh, so the banner naturally rotates through countries.
  def call
    [
      new_player_badges.sample,
      encouragement_badges.sample,
      participation_badges.sample
    ].compact
  end

  private

  # #2 — countries that gained new players (started sessions) within the window.
  def new_player_badges
    new_player_counts.map do |code, count|
      benchmark = BENCHMARKS.find { |b| count >= b }
      message = if benchmark
        "#{benchmark} new players in #{country_name(code)}!"
      else
        "Yay! New players in #{country_name(code)}"
      end
      badge(:new_players, code, message)
    end
  end

  # #1 — encouragement for the bottom N countries that are actually playing.
  def encouragement_badges
    bottom_featured.map do |code|
      badge(:encouragement, code, "Ketch-up #{country_name(code)}!")
    end
  end

  # #3 — everyone not featured on the leaderboard and not covered by #1 or #2.
  def participation_badges
    covered = (new_player_counts.keys + bottom_featured).to_set
    unfeatured_codes.reject { |code| covered.include?(code) }.map do |code|
      badge(:participation, code, "#{country_name(code)}, every tomato counts!")
    end
  end

  # Countries with at least one tomato — the ones "on" the leaderboard.
  def featured
    @featured ||= @leaderboard.select { |row| row[:tomatoes].to_i.positive? }
  end

  # @leaderboard is ranked high→low, so the last N featured are the bottom N.
  def bottom_featured
    @bottom_featured ||= featured.last(ENCOURAGEMENT_COUNT).map { |row| code_of(row) }
  end

  def unfeatured_codes
    featured_set = featured.map { |row| code_of(row) }.to_set
    @leaderboard.map { |row| code_of(row) }.reject { |code| featured_set.include?(code) }
  end

  def new_player_counts
    @new_player_counts ||= Player
      .where(country: known_codes)
      .where(created_at: NEW_PLAYER_WINDOW.ago..)
      .group(:country).count
  end

  def known_codes
    @known_codes ||= I18n.t("countries").keys.map(&:to_s)
  end

  def code_of(row)
    row[:country_code].to_s.downcase
  end

  def country_name(code)
    I18n.t("countries.#{code}", default: code.to_s.upcase)
  end

  def badge(type, code, message)
    { type: type.to_s, country_code: code.to_s.upcase, message: message }
  end
end