feat(links): create basic link shortening algo

internal/services/link.go

@@ -2,8 +2,13 @@ package services
 
 import (
 	"context"
+	"crypto/rand"
+	"encoding/base64"
+	"errors"
 	"maot-shortner/internal/domain"
 	"maot-shortner/internal/repositories"
+	"strings"
+	"time"
 )
 
 type LinkService struct {
@@ -19,3 +24,40 @@ func NewLinkService(repo repositories.LinkRepository) *LinkService {
 func (s *LinkService) GetLinks(ctx context.Context) ([]*domain.Link, error) {
 	return s.repo.GetLinks(ctx)
 }
+
+func (s *LinkService) CreateLink(ctx context.Context, longUrl string, redirectCode *string) (*domain.Link, error) {
+	if !strings.Contains(longUrl, "http://") && !strings.Contains(longUrl, "https://") {
+		return nil, errors.New("Invalid URL")
+	}
+
+	var shortUrl string
+
+	if redirectCode != nil {
+		shortUrl = *redirectCode
+	} else {
+		shortUrl = generateShortCode(5)
+	}
+
+	link := &domain.Link{
+		LongURL:   longUrl,
+		ShortURL:  shortUrl,
+		CreatedAt: time.Now(),
+	}
+
+	return s.repo.CreateLink(ctx, link)
+}
+
+func generateShortCode(length int) string {
+	b := make([]byte, length)
+	rand.Read(b)
+	if _, err := rand.Read(b); err != nil {
+		return ""
+	}
+
+	return base64.RawURLEncoding.EncodeToString(b)
+}
+
+func (s *LinkService) GetLink(ctx context.Context, shortUrl string) (*domain.Link, error) {
+
+	return s.repo.GetLinkByShortCode(ctx, shortUrl)
+}