static_google_map.rb

class StaticGoogleMap
  URL_TEMPLATE = "http://maps.google.com/maps/api/staticmap?%s"
  COLOURS      = %w(red white green brown blue orange gray purple yellow black)
  LABELS       = ('A'..'Z').to_a
  
  def initialize(options = {})
    @addresses = []
    @width, @height = options.fetch(:width, 540), options.fetch(:height, 400)
    @params = returning({}) do |p|
      p[:sensor]  = false
      p[:size]    = "#{@width}x#{@height}"
      p[:maptype] = options.fetch(:type, "roadmap")
    end
  end

  def <<(address)
    @addresses << address
  end
  
  def to_url
    params = @params.to_param
    params << "&"
    params << build_marker_params
    URL_TEMPLATE % params
  end
  
  def self.for_address(address, opts = {})
    map = self.new(opts.reverse_merge(:zoom => 15))
    map << address
    map.to_url
  end
  
  def self.for_addresses(*addresses)
    map = self.new(addresses.extract_options!)
    addresses.flatten.each { |a| map << a }
    map.to_url
  end
  
  protected
  
  def build_marker_params
    params = []
    @addresses.each_with_index do |address, index|
      return "markers=#{to_ll @addresses.first}" if @addresses.size == 1
      color = COLOURS[index % COLOURS.size]
      label = LABELS[index % LABELS.size]
      params << "markers=color:#{color}|label:#{label}|#{to_ll(address)}"
    end
    params.join("&")
  end
  
  def to_ll(address)
    "#{address.lat},#{address.lng}"
  end
  
end