url.go

package main

import (
    "fmt"
    "math/rand"
    "net/http"

    "github.com/gin-gonic/gin"
    "gorm.io/driver/sqlite"
    "gorm.io/gorm"
)

type ShortURL struct {
    ID      uint   `gorm:"primary_key"`
    Short   string `gorm:"unique"`
    Long    string `gorm:"unique"`
}

var db *gorm.DB

func main() {
    // Connect to the database
    var err error
    db, err = gorm.Open(sqlite.Open("urlshortener.db"), &gorm.Config{})
    if err != nil {
        panic("failed to connect database")
    }

    // Auto-migrate the schema
    db.AutoMigrate(&ShortURL{})

    // Create a new Gin router
    router := gin.Default()

    // Register the route for shortening URLs
    router.POST("/shorten", shortenURL)

    // Register the route for redirecting short URLs
    router.GET("/:shortURL", redirectURL)

    // Start the server
    router.Run(":8080")
}

func shortenURL(c *gin.Context) {
    // Get the long URL from the POST request
    longURL := c.PostForm("url")

    // Generate a random short URL
    shortURL := generateShortURL()

    // Add the short URL and long URL to the database
    db.Create(&ShortURL{Short: shortURL, Long: longURL})

    // Return the short URL to the user
    c.JSON(http.StatusOK, gin.H{
        "short_url": fmt.Sprintf("http://localhost:8080/%s", shortURL),
    })
}

func redirectURL(c *gin.Context) {
    // Get the short URL from the request
    shortURL := c.Param("shortURL")

    // Look up the long URL in the database
    var s ShortURL
    db.Where("short = ?", shortURL).First(&s)
    if s.Long == "" {
        // Short URL not found, return a 404 error
        c.JSON(http.StatusNotFound, gin.H{
            "error": "Short URL not found",
        })
        return
    }

    // Redirect the user to the long URL
    c.Redirect(http.StatusMovedPermanently, s.Long)
}

func generateShortURL() string {
    // Generate a random 6-character string
    var letters = []rune("abcdefghijklmnopqrstuvwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789")
    b := make([]rune, 6)
    for i := range b {
        b[i] = letters[rand.Intn(len(letters))]
    }
    return string(b)
}



This code adds a ShortURL struct and a db variable to manage the database using GORM. When a user submits a long URL to the /shorten route, the code creates a new ShortURL object and adds it to the database using db.Create(). When a user visits a short URL, the code looks up the corresponding ShortURL object in the database using db.Where().First() and redirects the user to the long URL.

Note that this implementation is still very basic and doesn't include error handling or validation of user input. But it should give you a good starting point for building your own URL shortener with GORM!