Initial commit

lib/carto/google_maps_api.rb

@@ -0,0 +1,62 @@
+require 'base64'
+require 'openssl'
+
+module Carto
+  class GoogleMapsApi
+    STATIC_IMAGE_BASE_URL = 'https://maps.googleapis.com/maps/api/staticmap'.freeze
+
+    def sign_url(user, url)
+      raise 'User does not have Google configured' unless user.google_maps_query_string.present?
+      if user.google_maps_client_id.present? && user.google_maps_private_key.present?
+        # Add client=xxx + signature
+        client_id_signed_url(user, url)
+      else
+        # Just add key=xxx
+        key_signed_url(user, url)
+      end
+    end
+
+    def build_static_image_url(center:, map_type:, size:, zoom:, style:)
+      style_string = parse_basemap_styles(style)
+      STATIC_IMAGE_BASE_URL + "?center=#{center}&mapType=#{map_type}&size=#{size}#{style_string}&zoom=#{zoom}"
+    end
+
+    private
+
+    def client_id_signed_url(user, url)
+      uri = URI.parse("#{url}&#{user.google_maps_query_string}")
+      payload_to_sign = uri.path + '?' + uri.query
+      signature = hmac(user.google_maps_private_key, payload_to_sign)
+
+      "#{uri}&signature=#{signature}"
+    end
+
+    def key_signed_url(user, url)
+      "#{url}&#{user.google_maps_query_string}"
+    end
+
+    def hmac(key, data)
+      binary_key = Base64.urlsafe_decode64(key)
+      binary_signature = OpenSSL::HMAC.digest(OpenSSL::Digest.new('sha1'), binary_key, data)
+      Base64.urlsafe_encode64(binary_signature)
+    end
+
+    def parse_basemap_styles(style_json)
+      return '' unless style_json
+      styles = style_json.map do |style_definition|
+        style_parts = []
+        style_parts << "feature:#{style_definition[:featureType] || 'all'}"
+        style_parts << "element:#{style_definition[:elementType] || 'all'}"
+        style_parts += parse_stylers(style_definition[:stylers])
+        '&style=' + style_parts.join('|')
+      end
+      styles.join('')
+    end
+
+    def parse_stylers(stylers)
+      stylers.flat_map do |styler|
+        styler.map { |k, v| "#{k}:#{v.to_s.gsub('#', '0x')}" }
+      end
+    end
+  end
+end