Multi-Channel Notification

import (
    "context"
    "log"
    "os"

    "github.com/gopackx/go-notification/notification"
    "github.com/gopackx/go-notification/channel/mail/mailgun"
    "github.com/gopackx/go-notification/channel/whatsapp/waha"
    "github.com/gopackx/go-notification/channel/database"
    "github.com/gopackx/go-notification/message/mail"
    "github.com/gopackx/go-notification/message/whatsapp"

    "database/sql"
    _ "github.com/lib/pq"
)

type User struct {
    ID            int64
    Name          string
    Email         string
    Phone         string // E.164
    WantsMail     bool
    WantsWhatsApp bool
}

func (u User) RouteNotificationFor(channel string) any {
    switch channel {
    case "mail":     return u.Email
    case "whatsapp": return u.Phone
    case "database": return u.ID
    }
    return nil
}

type OrderShipped struct {
    OrderID     string
    TrackingURL string
}

func (n OrderShipped) Via(notifiable notification.Notifiable) []string {
    u := notifiable.(User)
    channels := []string{"database"} // always in-app
    if u.WantsMail     { channels = append(channels, "mail") }
    if u.WantsWhatsApp { channels = append(channels, "whatsapp") }
    return channels
}

func (n OrderShipped) ToMail(_ notification.Notifiable) *mail.Message {
    return mail.NewMessage().
        Subject("Your order shipped").
        Greeting("Hey,").
        Line("Your order " + n.OrderID + " is on its way.").
        Action("Track package", n.TrackingURL)
}

func (n OrderShipped) ToWhatsApp(_ notification.Notifiable) *whatsapp.Message {
    return whatsapp.NewMessage().
        Text("📦 Your order *" + n.OrderID + "* shipped. Track it: " + n.TrackingURL)
}

func (n OrderShipped) ToDatabase(_ notification.Notifiable) map[string]any {
    return map[string]any{
        "type":         "order.shipped",
        "order_id":     n.OrderID,
        "tracking_url": n.TrackingURL,
    }
}

func main() {
    db, err := sql.Open("postgres", os.Getenv("DATABASE_URL"))
    if err != nil { panic(err) }

    notifier := notification.New(notification.Config{
        OnError: func(_ context.Context, err notification.Error) {
            log.Printf("send failed: channel=%s err=%v", err.Channel, err.Err)
        },
    })

    notifier.RegisterChannel("mail", mailgun.New(mailgun.Config{
        Domain: "mg.example.com",
        APIKey: os.Getenv("MAILGUN_API_KEY"),
        From:   "noreply@example.com",
    }))

    notifier.RegisterChannel("whatsapp", waha.New(waha.Config{
        BaseURL:   "http://localhost:3000",
        APIKey:    os.Getenv("WAHA_API_KEY"),
        SessionID: "default",
    }))

    dbChannel := database.New(database.Config{
        DB:     db,
        Driver: database.DriverPostgres,
    })
    if err := dbChannel.AutoMigrate(context.Background()); err != nil {
        panic(err)
    }
    notifier.RegisterChannel("database", dbChannel)

    user := User{
        ID: 1, Name: "Dani", Email: "dani@example.com",
        Phone: "+628123456789",
        WantsMail: true, WantsWhatsApp: true,
    }

    ctx := context.Background()
    if err := notifier.Send(ctx, user, OrderShipped{
        OrderID: "A-1024",
        TrackingURL: "https://example.com/track/A-1024",
    }); err != nil {
        log.Fatal(err)
    }

    notifier.Close(ctx)
}