ameeuw23 · August 3, 2019 20:30 · Oct 10, 2018 · Oct 10, 2018 · Oct 10, 2018
diff --git a/README.md b/README.md
@@ -7,6 +7,11 @@ _id=$client_id port=8081 go run main.go
 
 ```
 2018/10/10 12:57:57 Using port: 8081
+```
+
+Now navigate to http://localhost:8081/start/ to begin the flow. 
+
+```
 2018/10/10 12:57:58 URL: /oauth2/authorized?custom_param=1&code=xyz&state=state
 2018/10/10 12:57:58 map[custom_param:[1] code:[xyz] state:[state]]
 ```
diff --git a/README.md b/README.md
@@ -0,0 +1,12 @@
+Running the example:
+
+```
+base_url=https://gitlab.your-host client_secret=$client_secret client
+_id=$client_id port=8081 go run main.go
+```
+
+```
+2018/10/10 12:57:57 Using port: 8081
+2018/10/10 12:57:58 URL: /oauth2/authorized?custom_param=1&code=xyz&state=state
+2018/10/10 12:57:58 map[custom_param:[1] code:[xyz] state:[state]]
+```
diff --git a/main.go b/main.go
@@ -0,0 +1,88 @@
+package main
+
+import (
+	"fmt"
+	"log"
+	"net/http"
+	"net/url"
+	"os"
+	"strconv"
+	"time"
+)
+
+func main() {
+
+	router := http.NewServeMux()
+	router.HandleFunc("/start/", MakeStartHandler())
+	router.HandleFunc("/oauth2/", MakeOAuth2Handler())
+	router.HandleFunc("/home/", MakeHomepageHandler())
+
+	timeout := time.Second * 10
+	port := 8080
+	if v, exists := os.LookupEnv("port"); exists {
+		val, _ := strconv.Atoi(v)
+		port = val
+	}
+
+	log.Printf("Using port: %d\n", port)
+
+	s := &http.Server{
+		Addr:           fmt.Sprintf(":%d", port),
+		Handler:        router,
+		ReadTimeout:    timeout,
+		WriteTimeout:   timeout,
+		MaxHeaderBytes: 1 << 20,
+	}
+
+	log.Fatal(s.ListenAndServe())
+}
+
+func MakeStartHandler() func(http.ResponseWriter, *http.Request) {
+
+	// http://localhost:8081/start
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		redirectRaw := "http://localhost:8081/oauth2/authorized"
+		redirectURI, _ := url.Parse(redirectRaw)
+		rQuery := redirectURI.Query()
+		rQuery.Set("custom_param", "1")
+		redirectURI.RawQuery = rQuery.Encode()
+
+		redirect, _ := url.Parse(os.Getenv("base_url") + "/oauth/authorize")
+		q := redirect.Query()
+		q.Set("client_id", os.Getenv("client_id"))
+		q.Set("response_type", "code")
+		q.Set("state", "state")
+		q.Set("redirect_uri", redirectURI.String())
+
+		redirect.RawQuery = q.Encode()
+
+		w.Write([]byte(`<html><head></head>Redirecting.. <a href="redirect">to login</a>. <script>window.location.replace("` + redirect.String() + `");</script></html>`))
+	}
+}
+func MakeHomepageHandler() func(http.ResponseWriter, *http.Request) {
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		w.Write([]byte("OK"))
+	}
+}
+
+func MakeOAuth2Handler() func(http.ResponseWriter, *http.Request) {
+
+	return func(w http.ResponseWriter, r *http.Request) {
+		log.Printf("URL: %s", r.URL)
+		if r.URL.Path != "/oauth2/authorized" {
+			w.WriteHeader(http.StatusUnauthorized)
+			w.Write([]byte("Unauthorized OAuth callback."))
+			return
+		}
+
+		if r.Body != nil {
+			defer r.Body.Close()
+		}
+
+		log.Println(r.URL.Query())
+
+		w.Write([]byte(fmt.Sprintf("OK, got a code: %s", r.URL.Query().Get("code"))))
+	}
+}