Support exchange shortened URLs (#133)

* feat: support shortened exchange urls

* feat: add shortener processing for exchange /a/:id conventions

main.go

@@ -55,6 +55,23 @@ func main() {
 	r.GET("/q/:id", routes.RedirectShortenedOverflowURL)
 	r.GET("/q/:id/:answerId", routes.RedirectShortenedOverflowURL)
 
+	exchangeRouter := r.Group("/exchange/:sub")
+	{
+		exchangeRouter.GET("/questions/:id/:title", routes.ViewQuestion)
+		exchangeRouter.GET("/questions/:id", func(c *gin.Context) {
+			// redirect user to the question with the title
+			c.Redirect(302, fmt.Sprintf("/exchange/%s/questions/%s/placeholder", c.Param("sub"), c.Param("id")))
+		})
+		exchangeRouter.GET("/questions/:id/:title/:answerId", func(c *gin.Context) {
+			// redirect user to the answer with the title
+			c.Redirect(302, fmt.Sprintf("/exchange/%s/questions/%s/%s#%s", c.Param("sub"), c.Param("id"), c.Param("title"), c.Param("answerId")))
+		})
+		exchangeRouter.GET("/q/:id/:answerId", routes.RedirectShortenedOverflowURL)
+		exchangeRouter.GET("/q/:id", routes.RedirectShortenedOverflowURL)
+		exchangeRouter.GET("/a/:id/:answerId", routes.RedirectShortenedOverflowURL)
+		exchangeRouter.GET("/a/:id", routes.RedirectShortenedOverflowURL)
+	}
+
 	r.GET("/questions/:id", func(c *gin.Context) {
 		// redirect user to the question with the title
 		c.Redirect(302, fmt.Sprintf("/questions/%s/placeholder", c.Param("id")))
@@ -64,15 +81,6 @@ func main() {
 		// redirect user to the answer with the title
 		c.Redirect(302, fmt.Sprintf("/questions/%s/%s#%s", c.Param("id"), c.Param("title"), c.Param("answerId")))
 	})
-	r.GET("/exchange/:sub/questions/:id/:title", routes.ViewQuestion)
-	r.GET("/exchange/:sub/questions/:id", func(c *gin.Context) {
-		// redirect user to the question with the title
-		c.Redirect(302, fmt.Sprintf("/exchange/%s/questions/%s/placeholder", c.Param("sub"), c.Param("id")))
-	})
-	r.GET("/exchange/:sub/questions/:id/:title/:answerId", func(c *gin.Context) {
-		// redirect user to the answer with the title
-		c.Redirect(302, fmt.Sprintf("/exchange/%s/questions/%s/%s#%s", c.Param("sub"), c.Param("id"), c.Param("title"), c.Param("answerId")))
-	})
 
 	r.GET("/proxy", routes.GetImage)
 

src/routes/shortened.go

@@ -4,6 +4,7 @@ import (
 	"fmt"
 	"net/http"
 	"os"
+	"strings"
 
 	"github.com/gin-gonic/gin"
 	"github.com/go-resty/resty/v2"
@@ -12,6 +13,7 @@ import (
 func RedirectShortenedOverflowURL(c *gin.Context) {
 	id := c.Param("id")
 	answerId := c.Param("answerId")
+	sub := c.Param("sub")
 
 	// fetch the stack overflow URL
 	client := resty.New()
@@ -21,7 +23,13 @@ func RedirectShortenedOverflowURL(c *gin.Context) {
 		}),
 	)
 
-	resp, err := client.R().Get(fmt.Sprintf("https://www.stackoverflow.com/a/%s/%s", id, answerId))
+	domain := "www.stackoverflow.com"
+	if strings.Contains(sub, ".") {
+		domain = sub
+	} else if sub != "" {
+		domain = fmt.Sprintf("%s.stackexchange.com", sub)
+	}
+	resp, err := client.R().Get(fmt.Sprintf("https://%s/a/%s/%s", domain, id, answerId))
 	if err != nil {
 		c.HTML(400, "home.html", gin.H{
 			"errorMessage": "Unable to fetch stack overflow URL",
@@ -41,5 +49,10 @@ func RedirectShortenedOverflowURL(c *gin.Context) {
 	// get the redirect URL
 	location := resp.Header().Get("Location")
 
-	c.Redirect(302, fmt.Sprintf("%s%s", os.Getenv("APP_URL"), location))
+	redirectPrefix := os.Getenv("APP_URL")
+	if sub != "" {
+		redirectPrefix += fmt.Sprintf("/exchange/%s", sub)
+	}
+
+	c.Redirect(302, fmt.Sprintf("%s%s", redirectPrefix, location))
 }