Add fetching of addresses from proxyGetConfig endpoint

mtglib/internal/dc/public_config_updater.go

@@ -0,0 +1,93 @@
+package dc
+
+import (
+	"bufio"
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"regexp"
+	"strconv"
+)
+
+var publicConfigRe = regexp.MustCompile(`^\s*proxy_for\s+(\d+)\s+(\S+?)?;\s*$`)
+
+type PublicConfigUpdater struct {
+	updater
+
+	http *http.Client
+	tg   *Telegram
+}
+
+func (p PublicConfigUpdater) Run(ctx context.Context, url, network string) {
+	p.run(ctx, func() error {
+		req, err := http.NewRequestWithContext(ctx, http.MethodGet, url, nil)
+		if err != nil {
+			panic(err)
+		}
+
+		resp, err := p.http.Do(req)
+		if err != nil {
+			if resp != nil {
+				io.Copy(io.Discard, resp.Body)
+				resp.Body.Close()
+			}
+			return fmt.Errorf("cannot fetch url %s: %w", url, err)
+		}
+
+		if resp.StatusCode >= http.StatusBadRequest {
+			return fmt.Errorf("unexpected status code from %s: %d", url, resp.StatusCode)
+		}
+
+		scanner := bufio.NewScanner(resp.Body)
+		addrs := map[int][]Addr{}
+
+		for scanner.Scan() {
+			matches := publicConfigRe.FindStringSubmatch(scanner.Text())
+			if len(matches) != 3 {
+				continue
+			}
+
+			dc, err := strconv.Atoi(matches[1])
+			if err != nil {
+				continue
+			}
+
+			switch dc {
+			// this is a list of DC we currently support. Other are ignored.
+			case 203: // CDN DC
+				p.logger.Info(fmt.Sprintf("found %s address for DC %d", matches[2], dc))
+				addrs[dc] = append(addrs[dc], Addr{
+					Network: network,
+					Address: matches[2],
+				})
+			}
+		}
+
+		if err := scanner.Err(); err != nil {
+			return fmt.Errorf("cannot read response body from %s: %w", url, err)
+		}
+
+		p.tg.lock.Lock()
+		defer p.tg.lock.Unlock()
+
+		if network == "tcp4" {
+			p.tg.view.publicConfigs.v4 = addrs
+		} else {
+			p.tg.view.publicConfigs.v6 = addrs
+		}
+
+		return nil
+	})
+}
+
+func NewPublicConfigUpdater(tg *Telegram, logger Logger, client *http.Client) PublicConfigUpdater {
+	return PublicConfigUpdater{
+		updater: updater{
+			logger: logger,
+			period: PublicConfigUpdateEach,
+		},
+		http: client,
+		tg:   tg,
+	}
+}