optionally inject receipt submission script

README.md

@@ -15,6 +15,7 @@ The proxy relies on the following environment variables:
 * `PROXY_PORT` -- the port the proxy listens on
 * `BACKEND_PORT` -- the port of the backend application that requests are forwarded to
 * `PAYMENT_POINTER` -- an [Interledger Payment Pointer](https://paymentpointers.org/) string
+* `RECEIPT_SUBMISSION_URL` -- (optional) URL at which to POST [STREAM receipts](https://interledger.org/rfcs/0039-stream-receipts/) for received payment
 
 Reference the [example Deployment](hack/example-deployment.yaml) to see how you might configure these in Kubernetes.
 

config/config.go

@@ -7,9 +7,10 @@ import (
 )
 
 type Config struct {
-	ProxyPort      int
-	BackendPort    int
-	PaymentPointer string
+	ProxyPort            int
+	BackendPort          int
+	PaymentPointer       string
+	ReceiptSubmissionUrl string
 }
 
 func Load() (*Config, error) {
@@ -42,10 +43,13 @@ func Load() (*Config, error) {
 		return nil, fmt.Errorf("PAYMENT_POINTER is required")
 	}
 
+	receiptSubmissionUrl := os.Getenv("RECEIPT_SUBMISSION_URL")
+
 	c := &Config{
-		ProxyPort:      proxyPort,
-		BackendPort:    backendPort,
-		PaymentPointer: paymentPointer,
+		ProxyPort:            proxyPort,
+		BackendPort:          backendPort,
+		PaymentPointer:       paymentPointer,
+		ReceiptSubmissionUrl: receiptSubmissionUrl,
 	}
 
 	return c, nil

config/config_test.go

@@ -26,6 +26,10 @@ func TestConfig(t *testing.T) {
 			if err != nil {
 				t.Error(err)
 			}
+			err = os.Setenv("RECEIPT_SUBMISSION_URL", "https://verifier.com/balances/123:creditReceipt")
+			if err != nil {
+				t.Error(err)
+			}
 
 		})
 
@@ -47,6 +51,10 @@ func TestConfig(t *testing.T) {
 			if cfg.PaymentPointer != "$wallet.example.com/🤑" {
 				t.Errorf("Expected PaymentPointer '%s' to match '$wallet.example.com/🤑'", cfg.PaymentPointer)
 			}
+
+			if cfg.ReceiptSubmissionUrl != "https://verifier.com/balances/123:creditReceipt" {
+				t.Errorf("Expected ReceiptSubmissionUrl '%s' to match 'https://verifier.com/balances/123:creditReceipt'", cfg.ReceiptSubmissionUrl)
+			}
 		})
 
 		when("PROXY_PORT is not provided", func() {
@@ -160,5 +168,23 @@ func TestConfig(t *testing.T) {
 				}
 			})
 		})
+
+		when("RECEIPT_SUBMISSION_URL is not provided", func() {
+			it("uses empty string", func() {
+				err := os.Unsetenv("RECEIPT_SUBMISSION_URL")
+				if err != nil {
+					t.Error(err)
+				}
+
+				cfg, err = config.Load()
+				if err != nil {
+					t.Error(err)
+				}
+
+				if cfg.ReceiptSubmissionUrl != "" {
+					t.Errorf("Expected ReceiptSubmissionUrl '%s' to match \"\"", cfg.ReceiptSubmissionUrl)
+				}
+			})
+		})
 	})
 }

hack/example-deployment.yaml

@@ -31,6 +31,8 @@ spec:
           value: "2368" # default ghost port
         - name: PAYMENT_POINTER
           value: "$wallet.example.com/your-wallet-here"
+        - name: RECEIPT_SUBMISSION_URL
+          value: "https://receipt-verifier.com/balances/id:creditReceipt"
       # Example backend app
       - image: ghost # https://hub.docker.com/_/ghost
         name: ghost-blog

handlers/proxy_handler.go

@@ -14,15 +14,28 @@ import (
 )
 
 type ProxyHandler struct {
-	BackendPort    int
-	PaymentPointer string
+	BackendPort      int
+	PaymentPointer   string
+	ReceiptSubmitter string
+}
+
+func NewProxyHandler(backendPort int, paymentPointer string, receiptSubmissionUrl string) *ProxyHandler {
+	var receiptSubmitter string
+	if receiptSubmissionUrl != "" {
+		receiptSubmitter = fmt.Sprintf(`document.monetization&&document.monetization.addEventListener("monetizationprogress",e=>{const{receipt:t}=e.detail;null!==t&&fetch("%s",{method:"POST",body:t})});`, receiptSubmissionUrl)
+	}
+	return &ProxyHandler{
+		BackendPort:      backendPort,
+		PaymentPointer:   paymentPointer,
+		ReceiptSubmitter: receiptSubmitter,
+	}
 }
 
 func (h *ProxyHandler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
 	url, _ := url.Parse(fmt.Sprintf("http://0.0.0.0:%d", h.BackendPort))
 
 	proxy := httputil.NewSingleHostReverseProxy(url)
-	proxy.ModifyResponse = BuildMonetizationResponseModifier(h.PaymentPointer)
+	proxy.ModifyResponse = BuildMonetizationResponseModifier(h.PaymentPointer, h.ReceiptSubmitter)
 
 	req.URL.Host = url.Host
 	req.URL.Scheme = url.Scheme
@@ -37,7 +50,7 @@ func (h *ProxyHandler) ServeHTTP(resp http.ResponseWriter, req *http.Request) {
 	proxy.ServeHTTP(resp, req)
 }
 
-func BuildMonetizationResponseModifier(paymentPointer string) func(*http.Response) error {
+func BuildMonetizationResponseModifier(paymentPointer string, receiptSubmitter string) func(*http.Response) error {
 	return func(r *http.Response) error {
 		if !contentTypeIsHTML(r) {
 			log.Println("Content-Type is not HTML")
@@ -51,7 +64,7 @@ func BuildMonetizationResponseModifier(paymentPointer string) func(*http.Respons
 		}
 		defer r.Body.Close()
 
-		insertMonetizationMeta(doc, paymentPointer)
+		insertInHead(doc, paymentPointer, receiptSubmitter)
 		buf := bytes.NewBuffer([]byte{})
 		html.Render(buf, doc)
 
@@ -61,6 +74,21 @@ func BuildMonetizationResponseModifier(paymentPointer string) func(*http.Respons
 	}
 }
 
+func insertInHead(n *html.Node, paymentPointer string, receiptSubmitter string) {
+	if n.Type == html.ElementNode && n.Data == "head" {
+		insertMonetizationMeta(n, paymentPointer)
+		if receiptSubmitter != "" {
+			insertReceiptSubmitter(n, receiptSubmitter)
+		}
+
+		return
+	}
+
+	for c := n.FirstChild; c != nil; c = c.NextSibling {
+		insertInHead(c, paymentPointer, receiptSubmitter)
+	}
+}
+
 func insertMonetizationMeta(n *html.Node, paymentPointer string) {
 	if n.Type == html.ElementNode && n.Data == "head" {
 		n.AppendChild(&html.Node{
@@ -71,12 +99,20 @@ func insertMonetizationMeta(n *html.Node, paymentPointer string) {
 				{Key: "content", Val: paymentPointer},
 			},
 		})
-
-		return
 	}
+}
 
-	for c := n.FirstChild; c != nil; c = c.NextSibling {
-		insertMonetizationMeta(c, paymentPointer)
+func insertReceiptSubmitter(n *html.Node, receiptSubmitter string) {
+	if n.Type == html.ElementNode && n.Data == "head" {
+		script := html.Node{
+			Type: html.ElementNode,
+			Data: "script",
+		}
+		script.AppendChild(&html.Node{
+			Type: html.TextNode,
+			Data: receiptSubmitter,
+		})
+		n.AppendChild(&script)
 	}
 }
 

handlers/proxy_handler_test.go

@@ -16,32 +16,36 @@ import (
 func TestAddWebMonetizationMeta(t *testing.T) {
 	spec.Run(t, "TestBuildMonetizationResponseModifier", func(t *testing.T, when spec.G, it spec.S) {
 		var response *http.Response
-		var proxyHandler handlers.ProxyHandler
-		var addWebMonetizationMetaFunc func(*http.Response) error
+		var proxyHandler *handlers.ProxyHandler
+		var proxyScriptHandler *handlers.ProxyHandler
+		var addWmMetaFunc func(*http.Response) error
+		var addWmMetaAndScriptFunc func(*http.Response) error
+		expectedScript :=
+			`<script>document.monetization&&document.monetization.addEventListener("monetizationprogress",e=>{const{receipt:t}=e.detail;null!==t&&fetch("https://verifier.com/balances/123:creditReceipt",{method:"POST",body:t})});</script>`
 
 		it.Before(func() {
-			proxyHandler = handlers.ProxyHandler{
-				BackendPort:    1337,
-				PaymentPointer: "$wallet.example.com/🤑",
-			}
-			addWebMonetizationMetaFunc = handlers.BuildMonetizationResponseModifier(proxyHandler.PaymentPointer)
+			proxyHandler = handlers.NewProxyHandler(1337, "$wallet.example.com/🤑", "")
+			addWmMetaFunc = handlers.BuildMonetizationResponseModifier(proxyHandler.PaymentPointer, proxyHandler.ReceiptSubmitter)
+			proxyScriptHandler = handlers.NewProxyHandler(1337, "$wallet.example.com/🤑", "https://verifier.com/balances/123:creditReceipt")
+			addWmMetaAndScriptFunc = handlers.BuildMonetizationResponseModifier(proxyScriptHandler.PaymentPointer, proxyScriptHandler.ReceiptSubmitter)
 		})
 
 		when("the response is not HTML", func() {
+			bodyString := "console.log('hello world')"
 			it.Before(func() {
 				response = &http.Response{
 					StatusCode: 200,
 					ProtoMajor: 1,
 					ProtoMinor: 1,
 					Header:     make(http.Header),
-					Body:       ioutil.NopCloser(bytes.NewBufferString("console.log('hello world')")),
+					Body:       ioutil.NopCloser(bytes.NewBufferString(bodyString)),
 				}
 
 				response.Header.Set("Content-Type", mime.TypeByExtension(".js"))
 			})
 
 			it("does not modify the response", func() {
-				if err := addWebMonetizationMetaFunc(response); err != nil {
+				if err := addWmMetaFunc(response); err != nil {
 					t.Error(err)
 				}
 
@@ -50,9 +54,23 @@ func TestAddWebMonetizationMeta(t *testing.T) {
 					t.Error(err)
 				}
 
-				bodyString := string(bodyBytes)
-				if strings.Contains(bodyString, "<meta name=\"monetization\" content=\"$wallet.example.com/🤑\"/>") {
-					t.Error(fmt.Sprintf("<meta> tag was added: %s", bodyString))
+				if string(bodyBytes) != bodyString {
+					t.Error(fmt.Sprintf("response was modified: %s", bodyString))
+				}
+			})
+
+			it("does not modify the response with a script", func() {
+				if err := addWmMetaAndScriptFunc(response); err != nil {
+					t.Error(err)
+				}
+
+				bodyBytes, err := ioutil.ReadAll(response.Body)
+				if err != nil {
+					t.Error(err)
+				}
+
+				if string(bodyBytes) != bodyString {
+					t.Error(fmt.Sprintf("response was modified: %s", bodyString))
 				}
 			})
 		})
@@ -72,7 +90,23 @@ func TestAddWebMonetizationMeta(t *testing.T) {
 				})
 
 				it("adds the monetization <meta> tag", func() {
-					if err := addWebMonetizationMetaFunc(response); err != nil {
+					if err := addWmMetaFunc(response); err != nil {
+						t.Error(err)
+					}
+
+					bodyBytes, err := ioutil.ReadAll(response.Body)
+					if err != nil {
+						t.Error(err)
+					}
+
+					bodyString := string(bodyBytes)
+					if !strings.Contains(bodyString, "<head><meta name=\"monetization\" content=\"$wallet.example.com/🤑\"/></head>") {
+						t.Error(fmt.Sprintf("<meta> tag not added: %s", bodyString))
+					}
+				})
+
+				it("adds the monetization <meta> tag and receipt submission <script>", func() {
+					if err := addWmMetaAndScriptFunc(response); err != nil {
 						t.Error(err)
 					}
 
@@ -85,6 +119,10 @@ func TestAddWebMonetizationMeta(t *testing.T) {
 					if !strings.Contains(bodyString, "<meta name=\"monetization\" content=\"$wallet.example.com/🤑\"/>") {
 						t.Error(fmt.Sprintf("<meta> tag not added: %s", bodyString))
 					}
+
+					if !strings.Contains(bodyString, expectedScript) {
+						t.Error(fmt.Sprintf("<script> tag not added: %s", bodyString))
+					}
 				})
 			})
 
@@ -102,7 +140,7 @@ func TestAddWebMonetizationMeta(t *testing.T) {
 				})
 
 				it("adds the monetization <meta> tag and <head> tag", func() {
-					if err := addWebMonetizationMetaFunc(response); err != nil {
+					if err := addWmMetaFunc(response); err != nil {
 						t.Error(err)
 					}
 
@@ -116,6 +154,26 @@ func TestAddWebMonetizationMeta(t *testing.T) {
 						t.Error(fmt.Sprintf("<meta> tag not added: %s", bodyString))
 					}
 				})
+
+				it("adds the monetization <meta>, receipt submission <script>, and <head> tags", func() {
+					if err := addWmMetaAndScriptFunc(response); err != nil {
+						t.Error(err)
+					}
+
+					bodyBytes, err := ioutil.ReadAll(response.Body)
+					if err != nil {
+						t.Error(err)
+					}
+
+					bodyString := string(bodyBytes)
+					if !strings.Contains(bodyString, "<meta name=\"monetization\" content=\"$wallet.example.com/🤑\"/>") {
+						t.Error(fmt.Sprintf("<meta> tag not added: %s", bodyString))
+					}
+
+					if !strings.Contains(bodyString, expectedScript) {
+						t.Error(fmt.Sprintf("<script> tag not added: %s", bodyString))
+					}
+				})
 			})
 		})
 	})

main.go

@@ -15,10 +15,7 @@ func main() {
 		log.Fatal(err)
 	}
 
-	proxyHandler := &handlers.ProxyHandler{
-		BackendPort:    cfg.BackendPort,
-		PaymentPointer: cfg.PaymentPointer,
-	}
+	proxyHandler := handlers.NewProxyHandler(cfg.BackendPort, cfg.PaymentPointer, cfg.ReceiptSubmissionUrl)
 
 	mux := http.NewServeMux()
 	mux.Handle("/", proxyHandler)