New whatismydns feature (#29)

router/dns.go

@@ -0,0 +1,85 @@
+package router
+
+import (
+	"fmt"
+	"net"
+	"net/http"
+	"strings"
+
+	validator "github.com/dcarrillo/whatismyip/internal/validator/uuid"
+	"github.com/dcarrillo/whatismyip/service"
+	"github.com/gin-gonic/gin"
+	"github.com/google/uuid"
+	"github.com/patrickmn/go-cache"
+)
+
+type DNSJSONResponse struct {
+	DNS dnsData `json:"dns"`
+}
+type dnsData struct {
+	IP              string `json:"ip"`
+	Country         string `json:"country"`
+	AsnOrganization string `json:"provider"`
+}
+
+// TODO
+// Implement a proper vhost manager instead of using a middleware
+func GetDNSDiscoveryHandler(store *cache.Cache, domain string, redirectPort string) gin.HandlerFunc {
+	return func(ctx *gin.Context) {
+		if !strings.HasSuffix(ctx.Request.Host, domain) {
+			ctx.Next()
+			return
+		}
+
+		if ctx.Request.Host == domain {
+			ctx.Redirect(http.StatusFound, fmt.Sprintf("http://%s.%s%s", uuid.New().String(), domain, redirectPort))
+			ctx.Abort()
+			return
+		}
+
+		handleDNS(ctx, store)
+		ctx.Abort()
+	}
+}
+
+func handleDNS(ctx *gin.Context, store *cache.Cache) {
+	d := strings.Split(ctx.Request.Host, ".")[0]
+	if !validator.IsValid(d) {
+		ctx.String(http.StatusNotFound, http.StatusText(http.StatusNotFound))
+		return
+	}
+
+	v, found := store.Get(d)
+	if !found {
+		ctx.String(http.StatusNotFound, http.StatusText(http.StatusNotFound))
+		return
+	}
+
+	ipStr, ok := v.(string)
+	if !ok {
+		ctx.String(http.StatusNotFound, http.StatusText(http.StatusNotFound))
+		return
+	}
+
+	ip := net.ParseIP(ipStr)
+	if ip == nil {
+		ctx.String(http.StatusNotFound, http.StatusText(http.StatusNotFound))
+		return
+	}
+
+	geo := service.Geo{IP: ip}
+	j := DNSJSONResponse{
+		DNS: dnsData{
+			IP:              ipStr,
+			Country:         geo.LookUpCity().Country.Names["en"],
+			AsnOrganization: geo.LookUpASN().AutonomousSystemOrganization,
+		},
+	}
+
+	switch ctx.NegotiateFormat(gin.MIMEPlain, gin.MIMEHTML, gin.MIMEJSON) {
+	case gin.MIMEJSON:
+		ctx.JSON(http.StatusOK, j)
+	default:
+		ctx.String(http.StatusOK, fmt.Sprintf("%s (%s / %s)\n", j.DNS.IP, j.DNS.Country, j.DNS.AsnOrganization))
+	}
+}