Add telegram api

telegram/api/addresses.go

@@ -0,0 +1,106 @@
+package api
+
+import (
+	"bufio"
+	"fmt"
+	"net"
+	"regexp"
+	"strconv"
+	"strings"
+
+	"github.com/9seconds/mtg/conntypes"
+)
+
+const (
+	addressesURLV4 = "https://core.telegram.org/getProxyConfig"   // nolint: gas
+	addressesURLV6 = "https://core.telegram.org/getProxyConfigV6" // nolint: gas
+)
+
+var addressesProxyForSplitter = regexp.MustCompile(`\s+`)
+
+func AddressesV4() (map[conntypes.DC][]string, conntypes.DC, error) {
+	return getAddresses(addressesURLV4)
+}
+
+func AddressesV6() (map[conntypes.DC][]string, conntypes.DC, error) {
+	return getAddresses(addressesURLV6)
+}
+
+func getAddresses(url string) (map[conntypes.DC][]string, conntypes.DC, error) {
+	resp, err := request(url)
+	if err != nil {
+		return nil, 0, fmt.Errorf("cannot get http response: %w", err)
+	}
+	defer resp.Close()
+
+	scanner := bufio.NewScanner(resp)
+	data := map[conntypes.DC][]string{}
+
+	var defaultDC = conntypes.DCDefaultIdx
+	for scanner.Scan() {
+		text := strings.TrimSpace(scanner.Text())
+		switch {
+		case strings.HasPrefix(text, "#"):
+			continue
+
+		case strings.HasPrefix(text, "proxy_for"):
+			addr, idx, err := addressesParseProxyFor(text)
+			if err != nil {
+				return nil, 0, fmt.Errorf("cannot parse 'proxy_for' section: %w", err)
+			}
+			if addresses, ok := data[idx]; ok {
+				data[idx] = append(addresses, addr)
+			} else {
+				data[idx] = []string{addr}
+			}
+
+		case strings.HasPrefix(text, "default"):
+			idx, err := addressesParseDefault(text)
+			if err != nil {
+				return nil, 0, fmt.Errorf("cannot parse 'default' section: %w", err)
+			}
+			defaultDC = idx
+		}
+	}
+
+	err = scanner.Err()
+	if err != nil {
+		return nil, 0, fmt.Errorf("cannot parse http response: %w", err)
+	}
+
+	return data, defaultDC, nil
+}
+
+func addressesParseProxyFor(text string) (string, conntypes.DC, error) {
+	chunks := addressesProxyForSplitter.Split(text, 3)
+	if len(chunks) != 3 || chunks[0] != "proxy_for" {
+		return "", 0, fmt.Errorf("incorrect config %s", text)
+	}
+
+	dc, err := strconv.ParseInt(chunks[1], 10, 16)
+	if err != nil {
+		return "", 0, fmt.Errorf("incorrect config '%s': %w", text, err)
+	}
+
+	addr := strings.TrimRight(chunks[2], ";")
+	if _, _, err = net.SplitHostPort(addr); err != nil {
+		return "", 0, fmt.Errorf("incorrect config '%s': %w", text, err)
+	}
+
+	return addr, conntypes.DC(dc), nil
+}
+
+func addressesParseDefault(text string) (conntypes.DC, error) {
+	chunks := addressesProxyForSplitter.Split(text, 2)
+	if len(chunks) != 2 || chunks[0] != "default" {
+		return 0, fmt.Errorf("incorrect config '%s'", text)
+	}
+
+	dcString := strings.TrimRight(chunks[1], ";")
+	dc, err := strconv.ParseInt(dcString, 10, 16)
+	if err != nil {
+		return 0, fmt.Errorf("incorrect config '%s': %w", text, err)
+	}
+
+	return conntypes.DC(dc), nil
+}

telegram/api/api.go

@@ -0,0 +1,38 @@
+package api
+
+import (
+	"fmt"
+	"io"
+	"io/ioutil"
+	"net/http"
+	"time"
+)
+
+const (
+	apiUserAgent   = "mtg"
+	apiHTTPTimeout = 30 * time.Second
+)
+
+var httpClient = http.Client{
+	Timeout: apiHTTPTimeout,
+}
+
+func request(url string) (io.ReadCloser, error) {
+	req, err := http.NewRequest("GET", url, nil)
+	if err != nil {
+		panic(err)
+	}
+	req.Header.Set("Accept", "text/plan")
+	req.Header.Set("User-Agent", apiUserAgent)
+
+	resp, err := httpClient.Do(req)
+	if err != nil {
+		if resp != nil {
+			io.Copy(ioutil.Discard, resp.Body)
+			resp.Body.Close()
+		}
+		return nil, fmt.Errorf("cannot perform a request: %w", err)
+	}
+
+	return resp.Body, err
+}

telegram/api/secret.go

@@ -0,0 +1,23 @@
+package api
+
+import (
+	"fmt"
+	"io/ioutil"
+)
+
+const secretURL = "https://core.telegram.org/getProxySecret" // nolint: gas
+
+func Secret() ([]byte, error) {
+	resp, err := request(secretURL)
+	if err != nil {
+		return nil, fmt.Errorf("cannot access telegram server: %w", err)
+	}
+	defer resp.Close()
+
+	secret, err := ioutil.ReadAll(resp)
+	if err != nil {
+		return nil, fmt.Errorf("cannot read response: %w", err)
+	}
+
+	return secret, nil
+}