From b5fdfcb49c70f61116116aa2fd62f8ee0500f050 Mon Sep 17 00:00:00 2001
From: Alvie Rahman <alvierahman90@gmail.com>
Date: Wed, 21 Sep 2022 20:52:40 +0100
Subject: [PATCH] implement conditional redirects

---
 main.go | 93 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
 1 file changed, 87 insertions(+), 6 deletions(-)

diff --git a/main.go b/main.go
index 864e312..7b76a5a 100644
--- a/main.go
+++ b/main.go
@@ -24,6 +24,9 @@ import (
 	"log"
 	"net/http"
 	"os"
+	"strconv"
+	"strings"
+	"time"
 
 	"github.com/go-redis/redis/v8"
 	"github.com/gorilla/mux"
@@ -83,7 +86,7 @@ func indexHandler(w http.ResponseWriter, r *http.Request) {
 		alt_condition,
 	)
 
-	formstring := command+":"+shortlink+":"+redirect+":"+alt_condition+":"+alt_redirect
+	formstring := command + ":" + shortlink + ":" + redirect + ":" + alt_condition + ":" + alt_redirect
 
 	fmt.Println("formstring: " + formstring)
 
@@ -110,7 +113,21 @@ func indexHandler(w http.ResponseWriter, r *http.Request) {
 		ctx := context.Background()
 		_, err := client.Get(ctx, shortlink).Result()
 		if err == redis.Nil {
-			err = client.Set(ctx, shortlink, shortlink, 0).Err()
+			err = client.Set(ctx, shortlink+":redirect", shortlink, 0).Err()
+			if err != nil {
+				fmt.Println(err)
+				w.WriteHeader(500)
+				w.Write([]byte("500 Internal Server Error"))
+				return
+			}
+			err = client.Set(ctx, shortlink+":altcondition", alt_condition, 0).Err()
+			if err != nil {
+				fmt.Println(err)
+				w.WriteHeader(500)
+				w.Write([]byte("500 Internal Server Error"))
+				return
+			}
+			err = client.Set(ctx, shortlink+":altredirect", alt_redirect, 0).Err()
 
 			if err != nil {
 				fmt.Println(err)
@@ -139,7 +156,15 @@ func indexHandler(w http.ResponseWriter, r *http.Request) {
 
 	if command == "delete" {
 		ctx := context.Background()
-		if err := client.Del(ctx, shortlink).Err(); err != nil {
+		if err := client.Del(ctx, shortlink+":redirect").Err(); err != nil {
+			w.WriteHeader(500)
+			w.Write([]byte("500 Internal Server Error"))
+		}
+		if err := client.Del(ctx, shortlink+":altredirect").Err(); err != nil {
+			w.WriteHeader(500)
+			w.Write([]byte("500 Internal Server Error"))
+		}
+		if err := client.Del(ctx, shortlink+":altcondition").Err(); err != nil {
 			w.WriteHeader(500)
 			w.Write([]byte("500 Internal Server Error"))
 		}
@@ -176,7 +201,9 @@ func shortlinkHandler(w http.ResponseWriter, r *http.Request) {
 	fmt.Println("shortlinkHandler called")
 	shortlink := string(mux.Vars(r)["shortlink"])
 	ctx := context.Background()
-	redirect, err := client.Get(ctx, shortlink).Result()
+	client.Incr(ctx, shortlink + ":hits")
+
+	redirect, err := client.Get(ctx, shortlink+":redirect").Result()
 	fmt.Printf("shortlink: %v, redirect: %v\n", shortlink, redirect)
 	if err == redis.Nil {
 		w.WriteHeader(404)
@@ -184,13 +211,67 @@ func shortlinkHandler(w http.ResponseWriter, r *http.Request) {
 		return
 	} else if err != nil {
 		fmt.Println(err)
+		fmt.Println(0)
 		w.WriteHeader(500)
 		w.Write([]byte("500 Internal Server Error"))
 		return
 	}
 
-	http.Redirect(w, r, redirect, 302)
-	return
+	altcondition, err := client.Get(ctx, shortlink+":altcondition").Result()
+	if err == redis.Nil {
+		http.Redirect(w, r, redirect, 302)
+		return
+	} else if err != nil {
+		fmt.Println(err)
+		fmt.Println(1)
+		w.WriteHeader(500)
+		w.Write([]byte("500 Internal Server Error"))
+		return
+	}
+
+	altredirect, err := client.Get(ctx, shortlink+":altredirect").Result()
+	if err == redis.Nil {
+		http.Redirect(w, r, redirect, 302)
+		return
+	} else if err != nil {
+		fmt.Println(err)
+		fmt.Println(2)
+		w.WriteHeader(500)
+		w.Write([]byte("500 Internal Server Error"))
+		return
+	}
+
+	altcondition_split := strings.Split(altcondition, ",")
+	ac_varname := altcondition_split[0]
+	ac_operator := altcondition_split[1]
+	ac_required_value, _ := strconv.Atoi(altcondition_split[2])
+
+	var ac_varval int
+
+	if ac_varname != "timestamp" {
+		ac_varvalstr, err := client.Get(ctx, shortlink+":"+ac_varname).Result()
+		if err == redis.Nil {
+			ac_varval = 0
+		} else if err != nil {
+			fmt.Println(err)
+			fmt.Println(3)
+			w.WriteHeader(500)
+			w.Write([]byte("500 Internal Server Error"))
+			return
+		} else {
+			ac_varval, _ = strconv.Atoi(ac_varvalstr)
+		}
+	} else {
+		ac_varval = int(time.Now().Unix())
+	}
+
+	if (ac_operator == "eq" && ac_varval == ac_required_value) ||
+		(ac_operator == "gt" && ac_varval > ac_required_value) ||
+		(ac_operator == "lt" && ac_varval < ac_required_value) {
+		http.Redirect(w, r, altredirect, 307)
+	} else {
+		http.Redirect(w, r, redirect, 307)
+	}
 }
 
 func getSha256HMACSignature(secret []byte, data string) string {