From 10805ef2d5b9b924fe096db00eba4d46f601bd7c Mon Sep 17 00:00:00 2001
From: Sergey Chubaryan <serghio2@yandex.ru>
Date: Mon, 5 Aug 2024 09:58:45 +0300
Subject: [PATCH] add shortlink generator and handlers

---
 main.go                            |  9 +++++
 src/handlers/shortlink_handlers.go | 61 ++++++++++++++++++++++++++++++
 src/services/shortlink_service.go  | 60 +++++++++++++++++++++++++++++
 3 files changed, 130 insertions(+)
 create mode 100644 src/handlers/shortlink_handlers.go
 create mode 100644 src/services/shortlink_service.go

diff --git a/main.go b/main.go
index 1ed5c95..1c7d398 100644
--- a/main.go
+++ b/main.go
@@ -90,6 +90,11 @@ func main() {
 			ActionTokenRepo: actionTokenRepo,
 		},
 	)
+	linkService := services.NewShortlinkSevice(
+		services.NewShortlinkServiceParams{
+			Cache: repo.NewCacheInmem[string, string](7 * 24 * 60 * 60),
+		},
+	)
 
 	if !debugMode {
 		gin.SetMode(gin.ReleaseMode)
@@ -99,6 +104,10 @@ func main() {
 	r.Use(middleware.NewRequestLogMiddleware(logger))
 	r.Use(gin.Recovery())
 
+	linkGroup := r.Group("/s")
+	linkGroup.POST("/new", handlers.NewShortlinkCreateHandler(linkService))
+	linkGroup.GET("/:linkId", handlers.NewShortlinkResolveHandler(linkService))
+
 	userGroup := r.Group("/user")
 	userGroup.POST("/create", handlers.NewUserCreateHandler(userService))
 	userGroup.POST("/login", handlers.NewUserLoginHandler(userService))
diff --git a/src/handlers/shortlink_handlers.go b/src/handlers/shortlink_handlers.go
new file mode 100644
index 0000000..f228e8e
--- /dev/null
+++ b/src/handlers/shortlink_handlers.go
@@ -0,0 +1,61 @@
+package handlers
+
+import (
+	"backend/src/services"
+	"encoding/json"
+	"fmt"
+	"net/url"
+
+	"github.com/gin-gonic/gin"
+)
+
+type shortlinkCreateOutput struct {
+	Link string `json:"link"`
+}
+
+func NewShortlinkCreateHandler(shortlinkService services.ShortlinkService) gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		rawUrl := ctx.Query("url")
+		if rawUrl == "" {
+			ctx.AbortWithError(400, fmt.Errorf("no url param"))
+			return
+		}
+
+		u, err := url.Parse(rawUrl)
+		if err != nil {
+			ctx.Data(500, "plain/text", []byte(err.Error()))
+			return
+		}
+		u.Scheme = "https"
+
+		linkId, err := shortlinkService.CreateLink(u.String())
+		if err != nil {
+			ctx.Data(500, "plain/text", []byte(err.Error()))
+			return
+		}
+
+		resultBody, err := json.Marshal(shortlinkCreateOutput{
+			Link: "https:/nucrea.ru/s/" + linkId,
+		})
+		if err != nil {
+			ctx.AbortWithError(500, err)
+			return
+		}
+
+		ctx.Data(200, "application/json", resultBody)
+	}
+}
+
+func NewShortlinkResolveHandler(shortlinkService services.ShortlinkService) gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		linkId := ctx.Param("linkId")
+
+		linkUrl, err := shortlinkService.GetLink(linkId)
+		if err != nil {
+			ctx.AbortWithError(500, err)
+			return
+		}
+
+		ctx.Redirect(301, linkUrl)
+	}
+}
diff --git a/src/services/shortlink_service.go b/src/services/shortlink_service.go
new file mode 100644
index 0000000..d3f2469
--- /dev/null
+++ b/src/services/shortlink_service.go
@@ -0,0 +1,60 @@
+package services
+
+import (
+	"backend/src/repo"
+	"fmt"
+	"math/rand"
+	"strings"
+	"time"
+)
+
+type ShortlinkService interface {
+	CreateLink(in string) (string, error)
+	GetLink(id string) (string, error)
+}
+
+type NewShortlinkServiceParams struct {
+	Endpoint string
+	Cache    repo.Cache[string, string]
+}
+
+func NewShortlinkSevice(params NewShortlinkServiceParams) ShortlinkService {
+	return &shortlinkService{
+		cache: params.Cache,
+	}
+}
+
+type shortlinkService struct {
+	cache repo.Cache[string, string]
+}
+
+func (s *shortlinkService) randomStr() string {
+	src := rand.NewSource(time.Now().UnixMicro())
+	randGen := rand.New(src)
+
+	builder := strings.Builder{}
+	for i := 0; i < 9; i++ {
+		offset := 0x41
+		if randGen.Int()%2 == 1 {
+			offset = 0x61
+		}
+
+		byte := offset + (randGen.Int() % 26)
+		builder.WriteRune(rune(byte))
+	}
+	return builder.String()
+}
+
+func (s *shortlinkService) CreateLink(in string) (string, error) {
+	str := s.randomStr()
+	s.cache.Set(str, in, 7*24*60*60)
+	return str, nil
+}
+
+func (s *shortlinkService) GetLink(id string) (string, error) {
+	val, ok := s.cache.Get(id)
+	if !ok {
+		return "", fmt.Errorf("link does not exist or expired")
+	}
+	return val, nil
+}