module BomRadarRender

# File lib/bom_radar_render.rb, line 34
def image_cell_to_map_cell(image_row, image_col, map_width: BomRadarConfig::MAP_WIDTH,
                           map_height: BomRadarConfig::MAP_HEIGHT)
  row = (image_row * map_height.to_f / BomRadarConfig::IMAGE_SIZE).floor.clamp(0, map_height - 1)
  col = (image_col * map_width.to_f / BomRadarConfig::IMAGE_SIZE).floor.clamp(0, map_width - 1)
  [row, col]
end

# File lib/bom_radar_render.rb, line 18
def image_pixel_for(lat, lon, site:)
  centre = [site[:lat], site[:lon]]
  distance_km = GeoLookup.distance_km(centre, [lat, lon])
  return nil if distance_km > site[:range_km]

  bearing = Geocoder::Calculations.bearing_between(centre, [lat, lon])
  fraction = distance_km / site[:range_km].to_f
  radius_px = fraction * (BomRadarConfig::IMAGE_SIZE / 2.0 - 1.0)
  radians = bearing * Math::PI / 180.0
  centre_px = BomRadarConfig::IMAGE_SIZE / 2.0
  col = centre_px + Math.sin(radians) * radius_px
  row = centre_px - Math.cos(radians) * radius_px
  [row.round.clamp(0, BomRadarConfig::IMAGE_SIZE - 1),
   col.round.clamp(0, BomRadarConfig::IMAGE_SIZE - 1)]
end

# File lib/bom_radar_render.rb, line 41
def lat_lon_to_cell(lat, lon, site:, map_width: BomRadarConfig::MAP_WIDTH,
                    map_height: BomRadarConfig::MAP_HEIGHT)
  pixel = image_pixel_for(lat, lon, site: site)
  return nil unless pixel

  image_cell_to_map_cell(pixel[0], pixel[1], map_width: map_width, map_height: map_height)
end

# File lib/bom_radar_render.rb, line 49
def overlay_label(grid, row, col, label)
  text = label.to_s[0, 6]
  return if text.empty?

  width = grid.first.length
  start_col = [col - (text.length / 2), 0].max
  end_col = [start_col + text.length - 1, width - 1].min
  actual = text[0, end_col - start_col + 1]

  actual.chars.each_with_index do |char, index|
    target_col = start_col + index
    next if target_col >= width
    next if grid[row][target_col].match?(/[A-Za-z+]/)

    grid[row][target_col] = char
  end
end

# File lib/bom_radar_render.rb, line 67
def place_town_labels(char_grid, site:, product_id:)
  BomRadarTowns.for_product(product_id).each do |town|
    cell = lat_lon_to_cell(town[:lat], town[:lon], site: site)
    next unless cell

    row, col = cell
    overlay_label(char_grid, row, col, "+#{town[:name]}")
  end
  char_grid
end

# File lib/bom_radar_render.rb, line 91
def render_map(grid_data, site:, product_id:, query_lat: nil, query_lon: nil, background_data: nil)
  composite = !background_data.nil?
  downsampled = if composite
                  BomRadarComposite.downsample(background: background_data, rain: grid_data)
                else
                  BomRadarImage.downsample(grid_data)
                end
  char_grid = downsampled.map(&:dup)
  center = nil

  if query_lat && query_lon
    cell = lat_lon_to_cell(query_lat, query_lon, site: site)
    center = cell if cell
  end

  char_fn = composite ? BomRadarImage.method(:char_for_merged) : BomRadarImage.method(:char_for_index)
  char_grid = char_grid.map { |row| row.map { |index| char_fn.call(index) } }
  place_town_labels(char_grid, site: site, product_id: product_id)

  if center
    row, col = center
    char_grid[row][col] = BomRadarConfig::CENTER_CHAR
  end

  lines = char_grid.map(&:join)
  colored = BomRadarImage.colorize_lines(lines, grid: downsampled, center: center, merged: composite)
  summaries = town_summaries(grid_data, site: site, product_id: product_id)

  { lines: colored, summaries: summaries, downsampled: downsampled, center: center }
end

# File lib/bom_radar_render.rb, line 78
def town_summaries(grid, site:, product_id:)
  BomRadarTowns.for_product(product_id).filter_map do |town|
    pixel = image_pixel_for(town[:lat], town[:lon], site: site)
    next unless pixel

    index = grid[:grid][pixel[0]][pixel[1]]
    intensity = BomRadarImage.display_intensity(index)
    next unless intensity

    "+#{town[:name]} — #{intensity}"
  end
end