Allow subscriptions to be removed

lib/ferrum/client.rb

@@ -26,6 +26,10 @@ def on(event, &block)
       @client.on(event_name(event), &block)
     end
 
+    def off(event, id)
+      @client.off(event_name(event), id)
+    end
+
     def subscribed?(event)
       @client.subscribed?(event_name(event))
     end
@@ -99,6 +103,10 @@ def on(event, &block)
       @subscriber.on(event, &block)
     end
 
+    def off(event, id)
+      @subscriber.off(event, id)
+    end
+
     def subscribed?(event)
       @subscriber.subscribed?(event)
     end

lib/ferrum/client/subscriber.rb

@@ -23,6 +23,11 @@ def <<(message)
 
       def on(event, &block)
         @on[event] << block
+        @on[event].index(block)
+      end
+
+      def off(event, id)
+        @on[event].delete_at(id)
         true
       end
 

lib/ferrum/page.rb

@@ -379,6 +379,19 @@ def on(name, &block)
       end
     end
 
+    def off(name, id)
+      case name
+      when :dialog
+        client.off("Page.javascriptDialogOpening", id)
+      when :request
+        client.off("Fetch.requestPaused", id)
+      when :auth
+        client.off("Fetch.authRequired", id)
+      else
+        client.off(name, id)
+      end
+    end
+
     def subscribed?(event)
       client.subscribed?(event)
     end

spec/page_spec.rb

@@ -194,4 +194,42 @@
       expect(page.device_pixel_ratio).to eq(2)
     end
   end
+
+  describe "#on" do
+    it "subscribes to an event" do
+      message = nil
+
+      page.on("Runtime.consoleAPICalled") do |params|
+        message = params.dig("args", 0, "value")
+      end
+
+      page.evaluate("console.log('hello')")
+      expect(message).to eq("hello")
+    end
+  end
+
+  describe "#off" do
+    it "unsubscribes a specific event handler" do
+      message_a = nil
+      message_b = nil
+
+      a = page.on("Runtime.consoleAPICalled") do |params|
+        message_a = params.dig("args", 0, "value")
+      end
+
+      page.on("Runtime.consoleAPICalled") do |params|
+        message_b = params.dig("args", 0, "value")
+      end
+
+      page.evaluate("console.log('hello')")
+      expect(message_a).to eq("hello")
+      expect(message_b).to eq("hello")
+
+      page.off("Runtime.consoleAPICalled", a)
+      page.evaluate("console.log('goodbye')")
+
+      expect(message_a).to eq("hello")
+      expect(message_b).to eq("goodbye")
+    end
+  end
 end