feat: refactor app in a separate package

internal/app/nameservers.go

@@ -0,0 +1,108 @@
+package app
+
+import (
+	"fmt"
+	"net"
+	"net/url"
+
+	"github.com/mr-karan/doggo/pkg/config"
+	"github.com/mr-karan/doggo/pkg/models"
+)
+
+// LoadNameservers reads all the user given
+// nameservers and loads to App.
+func (app *App) LoadNameservers() error {
+	for _, srv := range app.QueryFlags.Nameservers {
+		ns, err := initNameserver(srv)
+		if err != nil {
+			return fmt.Errorf("error parsing nameserver: %s", srv)
+		}
+		// check if properly initialised.
+		if ns.Address != "" && ns.Type != "" {
+			app.Nameservers = append(app.Nameservers, ns)
+		}
+	}
+
+	// Set `ndots` to the user specified value.
+	app.ResolverOpts.Ndots = app.QueryFlags.Ndots
+	// fallback to system nameserver
+	// in case no nameserver is specified by user.
+	if len(app.Nameservers) == 0 {
+		ns, ndots, search, err := getDefaultServers()
+		if err != nil {
+			return fmt.Errorf("error fetching system default nameserver")
+		}
+		// `-1` indicates the flag is not set.
+		// use from config if user hasn't specified any value.
+		if app.ResolverOpts.Ndots == -1 {
+			app.ResolverOpts.Ndots = ndots
+		}
+		if len(search) > 0 && app.QueryFlags.UseSearchList {
+			app.ResolverOpts.SearchList = search
+		}
+		app.Nameservers = append(app.Nameservers, ns...)
+	}
+	// if the user hasn't given any override of `ndots` AND has
+	// given a custom nameserver. Set `ndots` to 1 as the fallback value
+	if app.ResolverOpts.Ndots == -1 {
+		app.ResolverOpts.Ndots = 0
+	}
+	return nil
+}
+
+func initNameserver(n string) (models.Nameserver, error) {
+	// Instantiate a UDP resolver with default port as a fallback.
+	ns := models.Nameserver{
+		Type:    models.UDPResolver,
+		Address: net.JoinHostPort(n, models.DefaultUDPPort),
+	}
+	u, err := url.Parse(n)
+	if err != nil {
+		return ns, err
+	}
+	if u.Scheme == "https" {
+		ns.Type = models.DOHResolver
+		ns.Address = u.String()
+	}
+	if u.Scheme == "tls" {
+		ns.Type = models.DOTResolver
+		if u.Port() == "" {
+			ns.Address = net.JoinHostPort(u.Hostname(), models.DefaultTLSPort)
+		} else {
+			ns.Address = net.JoinHostPort(u.Hostname(), u.Port())
+		}
+	}
+	if u.Scheme == "tcp" {
+		ns.Type = models.TCPResolver
+		if u.Port() == "" {
+			ns.Address = net.JoinHostPort(u.Hostname(), models.DefaultTCPPort)
+		} else {
+			ns.Address = net.JoinHostPort(u.Hostname(), u.Port())
+		}
+	}
+	if u.Scheme == "udp" {
+		ns.Type = models.UDPResolver
+		if u.Port() == "" {
+			ns.Address = net.JoinHostPort(u.Hostname(), models.DefaultUDPPort)
+		} else {
+			ns.Address = net.JoinHostPort(u.Hostname(), u.Port())
+		}
+	}
+	return ns, nil
+}
+
+func getDefaultServers() ([]models.Nameserver, int, []string, error) {
+	dnsServers, ndots, search, err := config.GetDefaultServers()
+	if err != nil {
+		return nil, 0, nil, err
+	}
+	servers := make([]models.Nameserver, 0, len(dnsServers))
+	for _, s := range dnsServers {
+		ns := models.Nameserver{
+			Type:    models.UDPResolver,
+			Address: net.JoinHostPort(s, models.DefaultUDPPort),
+		}
+		servers = append(servers, ns)
+	}
+	return servers, ndots, search, nil
+}