module BomRadarComposite

# File lib/bom_radar_composite.rb, line 55
def dominant_background_index(background_counts)
  return 0 if background_counts[0].to_i.positive?

  background_counts.max_by { |index, count| [count, -index] }&.first || 2
end

# File lib/bom_radar_composite.rb, line 26
def downsample(background:, rain:, width: BomRadarConfig::MAP_WIDTH, height: BomRadarConfig::MAP_HEIGHT)
  block_h = background[:height].to_f / height
  block_w = background[:width].to_f / width

  Array.new(height) do |row|
    Array.new(width) do |col|
      y0 = (row * block_h).floor
      y1 = [((row + 1) * block_h).ceil - 1, background[:height] - 1].min
      x0 = (col * block_w).floor
      x1 = [((col + 1) * block_w).ceil - 1, background[:width] - 1].min

      rain_indices = []
      background_counts = Hash.new(0)
      (y0..y1).each do |y|
        (x0..x1).each do |x|
          rain_indices << rain[:grid][y][x]
          bg_index = background[:grid][y][x]
          background_counts[bg_index] += 1 if bg_index.between?(0, 2)
        end
      end

      peak = peak_rain_index(rain_indices)
      next peak if peak

      dominant_background_index(background_counts)
    end
  end
end

# File lib/bom_radar_composite.rb, line 14
def merge_cell(background_index:, rain_index:)
  rain = rain_index.to_i
  return rain if rain >= BomRadarConfig::RAIN_MIN_INDEX

  background_index.to_i
end

# File lib/bom_radar_composite.rb, line 21
def peak_rain_index(indices)
  rain = Array(indices).select { |index| index.to_i >= BomRadarConfig::RAIN_MIN_INDEX }
  rain.max
end