Enhance MTProxy checker by introducing a new -probe mode deep-strict for stricter response validation. Update README and Docker documentation to clarify probing modes, exit codes, and the new MTPROXY_TDLIB_HELPER and MTPROXY_TDLIB_TIMEOUT environment variables for external helper integration. Refactor connection handling and error reporting to improve robustness and clarity in response verification.

internal/tdlibexec/tdlibexec.go

@@ -0,0 +1,112 @@
+// Package tdlibexec runs an optional external helper (e.g. Node + TDLib) for proxy verification.
+// Contract: helper argv = [helperPath, proxyURL]; stdout must contain a JSON line:
+//
+//	{"ok":true,"error":"","exit_code":0}
+package tdlibexec
+
+import (
+	"bytes"
+	"context"
+	"encoding/json"
+	"errors"
+	"fmt"
+	"os/exec"
+	"strings"
+	"time"
+)
+
+// Result is the parsed outcome of a helper invocation.
+type Result struct {
+	OK         bool
+	ExitCode   int
+	Error      string
+	DurationMs int64
+}
+
+type jsonLine struct {
+	OK       bool   `json:"ok"`
+	Error    string `json:"error"`
+	ExitCode int    `json:"exit_code"`
+}
+
+// Run executes helperPath with a single argument proxyURL and parses the last JSON object from stdout.
+func Run(ctx context.Context, helperPath, proxyURL string) (Result, error) {
+	start := time.Now()
+	ms := func() int64 { return time.Since(start).Milliseconds() }
+
+	if strings.TrimSpace(helperPath) == "" {
+		return Result{}, errors.New("empty helper path")
+	}
+
+	cmd := exec.CommandContext(ctx, helperPath, proxyURL)
+	var stdout, stderr bytes.Buffer
+	cmd.Stdout = &stdout
+	cmd.Stderr = &stderr
+
+	err := cmd.Run()
+	duration := ms()
+
+	if ctx.Err() != nil {
+		return Result{OK: false, ExitCode: 4, Error: "tdlib helper: " + ctx.Err().Error(), DurationMs: duration}, ctx.Err()
+	}
+
+	if err == nil {
+		r, perr := parseStdout(stdout.Bytes(), stderr.Bytes(), duration)
+		if perr != nil {
+			return Result{OK: false, ExitCode: 1, Error: perr.Error(), DurationMs: duration}, nil
+		}
+		return r, nil
+	}
+
+	var ee *exec.ExitError
+	if errors.As(err, &ee) {
+		if r, perr := parseStdout(stdout.Bytes(), stderr.Bytes(), duration); perr == nil {
+			if r.ExitCode == 0 && !r.OK {
+				r.ExitCode = ee.ExitCode()
+			}
+			if r.ExitCode == 0 && !r.OK {
+				r.ExitCode = 2
+			}
+			return r, nil
+		}
+		msg := strings.TrimSpace(stdout.String())
+		if msg == "" {
+			msg = strings.TrimSpace(stderr.String())
+		}
+		if msg == "" {
+			msg = err.Error()
+		}
+		code := ee.ExitCode()
+		if code < 0 || code > 4 {
+			code = 2
+		}
+		return Result{OK: false, ExitCode: code, Error: msg, DurationMs: duration}, nil
+	}
+
+	return Result{}, fmt.Errorf("tdlib helper: %w", err)
+}
+
+func parseStdout(stdout, stderr []byte, duration int64) (Result, error) {
+	lines := strings.Split(string(stdout), "\n")
+	for i := len(lines) - 1; i >= 0; i-- {
+		line := strings.TrimSpace(lines[i])
+		if line == "" || line[0] != '{' {
+			continue
+		}
+		var j jsonLine
+		if err := json.Unmarshal([]byte(line), &j); err != nil {
+			continue
+		}
+		if j.ExitCode == 0 && !j.OK {
+			j.ExitCode = 2
+		}
+		if j.Error == "" && !j.OK {
+			j.Error = "tdlib reported failure"
+		}
+		return Result{OK: j.OK, ExitCode: j.ExitCode, Error: j.Error, DurationMs: duration}, nil
+	}
+	if len(stderr) > 0 {
+		return Result{}, fmt.Errorf("no json in stdout: stderr=%s", strings.TrimSpace(string(stderr)))
+	}
+	return Result{}, fmt.Errorf("no json line in helper stdout")
+}