From 868b49685825df218f2e9c5e67ad75b73c0a68a4 Mon Sep 17 00:00:00 2001
From: Tom Andrade <wolvie@gmail.com>
Date: Mon, 18 Mar 2019 14:12:13 +0100
Subject: [PATCH] shortener initial version

---
 main.go | 148 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 148 insertions(+)
 create mode 100644 main.go

diff --git a/main.go b/main.go
new file mode 100644
index 0000000..b4dc9ec
--- /dev/null
+++ b/main.go
@@ -0,0 +1,148 @@
+package main
+
+import (
+	"flag"
+	"log"
+	"math/rand"
+	"net/url"
+	"regexp"
+	"time"
+
+	"github.com/gomodule/redigo/redis"
+	"github.com/hoisie/web"
+)
+
+const letterBytes = "abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789" // Base strings for RandStringBytesMaskImprSrc
+const (
+	letterIdxBits = 6                    // 6 bits to represent a letter index
+	letterIdxMask = 1<<letterIdxBits - 1 // All 1-bits, as many as letterIdxBits
+	letterIdxMax  = 63 / letterIdxBits   // # of letter indices fitting in 63 bits
+)
+
+var domain string
+var redisServer string
+var listenAddr string
+var src = rand.NewSource(time.Now().UnixNano())
+var pool = newPool()
+
+func newPool() *redis.Pool {
+	return &redis.Pool{
+		// Maximum number of idle connections in the pool.
+		MaxIdle: 10,
+		// max number of connections
+		MaxActive: 1200,
+		// Dial is an application supplied function for creating and
+		// configuring a connection.
+		Dial: func() (redis.Conn, error) {
+			c, err := redis.Dial("tcp", redisServer)
+			if err != nil {
+				panic(err.Error())
+			}
+			return c, err
+		},
+	}
+}
+
+// ping tests connectivity for redis (PONG should be returned)
+func ping(c redis.Conn) error {
+	// Send PING command to Redis
+	// PING command returns a Redis "Simple String"
+	// Use redis.String to convert the interface type to string
+	_, err := redis.String(c.Do("PING"))
+	if err != nil {
+		return err
+	}
+	// fmt.Printf("PING Response = %s\n", s)
+	// Output: PONG
+	return nil
+}
+
+// get executes the redis GET command
+func get(c redis.Conn, key string) (bool, string) {
+	s, err := redis.String(c.Do("GET", key))
+	if err == redis.ErrNil {
+		return false, ""
+	} else if err != nil {
+		return false, ""
+	} else {
+		return true, s
+	}
+}
+
+// set executes the redis SET command
+func set(c redis.Conn, url, suffix string) error {
+	_, err := c.Do("SET", suffix, url)
+	if err != nil {
+		return err
+	}
+	return nil
+}
+
+func redirect(ctx *web.Context, val string) {
+	r, _ := regexp.Compile("[a-zA-Z0-9]+")
+	key := r.FindString(val)
+	conn := pool.Get()
+	defer conn.Close()
+	status, url := get(conn, key)
+	if status {
+		ctx.Redirect(302, url)
+	} else {
+		ctx.NotFound("URL don't exist")
+	}
+}
+
+func shortner(ctx *web.Context) {
+	// return fmt.Sprintf("%v\n", ctx.Params)
+	u, err := url.ParseRequestURI(ctx.Params["url"])
+	if err != nil {
+		ctx.Abort(400, "Bad URL")
+	} else {
+		suffix := RandStringBytesMaskImprSrc(10)
+		// nURL := "https://" + domain + "/" + suffix
+		conn := pool.Get()
+		defer conn.Close()
+		for {
+			status, _ := get(conn, suffix)
+			if status {
+				suffix = RandStringBytesMaskImprSrc(10)
+			} else {
+				break
+			}
+		}
+		err := set(conn, u.String(), suffix)
+		if err != nil {
+			ctx.Abort(500, "Internal Error")
+		} else {
+			ctx.WriteString("URL shortened at: https://" + domain + "/" + suffix)
+		}
+	}
+}
+
+// RandStringBytesMaskImprSrc Generate random string for URL
+func RandStringBytesMaskImprSrc(n int) string {
+	b := make([]byte, n)
+	// A src.Int63() generates 63 random bits, enough for letterIdxMax characters!
+	for i, cache, remain := n-1, src.Int63(), letterIdxMax; i >= 0; {
+		if remain == 0 {
+			cache, remain = src.Int63(), letterIdxMax
+		}
+		if idx := int(cache & letterIdxMask); idx < len(letterBytes) {
+			b[i] = letterBytes[idx]
+			i--
+		}
+		cache >>= letterIdxBits
+		remain--
+	}
+	return string(b)
+}
+
+func main() {
+	flag.StringVar(&domain, "domain", "localhost", "Domain to write to the URLs")
+	flag.StringVar(&redisServer, "redis", "localhost:6379", "ip/hostname of the redis server to connect")
+	flag.StringVar(&listenAddr, "addr", "localhost:8080", "Address to listen for connections")
+	flag.Parse()
+	web.Post("/", shortner)
+	web.Get("/(.*)", redirect)
+	log.Printf("Domain: %s, Redis: %s\n", domain, redisServer)
+	web.Run(listenAddr)
+}