From 8eb3873d27ffb679eddc2a2f230b5a58f9d6708a Mon Sep 17 00:00:00 2001
From: samosvalishe <samosvalishe@users.noreply.github.com>
Date: Tue, 4 Aug 2026 10:37:08 +0300
Subject: [PATCH] =?UTF-8?q?fix(captcha):=20=D1=80=D0=B0=D0=B7=D0=BD=D0=BE?=
 =?UTF-8?q?=D1=81=D0=B8=D1=82=D1=8C=20=D0=BF=D0=BE=D0=BF=D1=8B=D1=82=D0=BA?=
 =?UTF-8?q?=D0=B8=20=D1=81=D0=BB=D0=B0=D0=B9=D0=B4=D0=B5=D1=80=D0=B0=20?=
 =?UTF-8?q?=D0=BF=D0=BE=20=D0=B4=D0=BE=D1=80=D0=BE=D0=B6=D0=BA=D0=B5?=
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Соседние кандидаты отличаются одним свапом и получают почти равный скор,
поэтому топ-2 ранжирования - всегда пара соседей, и вторая попытка
промахивается вместе с первой. Вторая берётся не ближе трёх позиций от первой,
с откатом на соседей, если дальних кандидатов не хватило.
---
 .../vk/internal/captcha/captcha_test.go       | 46 +++++++++++++++++++
 .../provider/vk/internal/captcha/slider.go    | 34 ++++++++++++--
 2 files changed, 76 insertions(+), 4 deletions(-)

diff --git a/internal/provider/vk/internal/captcha/captcha_test.go b/internal/provider/vk/internal/captcha/captcha_test.go
index 55379da..b6d00a0 100644
--- a/internal/provider/vk/internal/captcha/captcha_test.go
+++ b/internal/provider/vk/internal/captcha/captcha_test.go
@@ -137,3 +137,49 @@ func TestCaptchaDomainFromRedirectURI(t *testing.T) {
 		})
 	}
 }
+
+func TestPickSliderAttempts(t *testing.T) {
+	tests := []struct {
+		name    string
+		indexes []int
+		limit   int
+		want    []int
+	}{
+		{
+			name:    "skips neighbours of the top guess",
+			indexes: []int{20, 19, 21, 18, 40, 5},
+			limit:   2,
+			want:    []int{20, 40},
+		},
+		{
+			name:    "falls back to neighbours when nothing is far enough",
+			indexes: []int{20, 19, 21},
+			limit:   3,
+			want:    []int{20, 19, 21},
+		},
+		{
+			name:    "limit above candidate count",
+			indexes: []int{7},
+			limit:   4,
+			want:    []int{7},
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			guesses := make([]sliderGuess, 0, len(tt.indexes))
+			for _, idx := range tt.indexes {
+				guesses = append(guesses, sliderGuess{Index: idx})
+			}
+			got := pickSliderAttempts(guesses, tt.limit)
+			if len(got) != len(tt.want) {
+				t.Fatalf("len = %d, want %d", len(got), len(tt.want))
+			}
+			for i := range tt.want {
+				if got[i].Index != tt.want[i] {
+					t.Fatalf("attempts = %v, want %v", got, tt.want)
+				}
+			}
+		})
+	}
+}
diff --git a/internal/provider/vk/internal/captcha/slider.go b/internal/provider/vk/internal/captcha/slider.go
index 3025027..374192e 100644
--- a/internal/provider/vk/internal/captcha/slider.go
+++ b/internal/provider/vk/internal/captcha/slider.go
@@ -11,6 +11,7 @@ import (
 	_ "image/jpeg" // регистрация JPEG-декодера для image.Decode
 	"math"
 	"runtime"
+	"slices"
 	"sort"
 	"strconv"
 	"strings"
@@ -75,6 +76,7 @@ func (s *captchaSession) solveSliderCaptcha(
 	if limit <= 0 {
 		return "", errors.New("slider has no attempts available")
 	}
+	attempts := pickSliderAttempts(guesses, limit)
 	s.logger().Debugf("[Captcha] slider guesses ranked: total=%d limit=%d", len(guesses), limit)
 
 	if err := s.sendComponentDone(sessionToken); err != nil {
@@ -87,15 +89,15 @@ func (s *captchaSession) solveSliderCaptcha(
 	if !s.profile.Touch() {
 		handle = approachFrom(s.profile, s.layout, handle)
 	}
-	for i := 0; i < limit; i++ {
-		s.logger().Debugf("[Captcha] slider attempt %d/%d (guess #%d)", i+1, limit, guesses[i].Index)
+	for i, guess := range attempts {
+		s.logger().Debugf("[Captcha] slider attempt %d/%d (guess #%d)", i+1, len(attempts), guess.Index)
 		answerData, err := json.Marshal(struct {
 			Value []int `json:"value"`
-		}{Value: guesses[i].Swaps})
+		}{Value: guess.Swaps})
 		if err != nil {
 			return "", err
 		}
-		target := s.layout.sliderTarget(guesses[i].Index, len(guesses))
+		target := s.layout.sliderTarget(guess.Index, len(guesses))
 		g := gesture{
 			from:   handle,
 			to:     target,
@@ -352,6 +354,30 @@ func rankSliderGuesses(img image.Image, gridSize int, swaps []int) ([]sliderGues
 	return guesses, nil
 }
 
+// pickSliderAttempts разносит попытки по дорожке: соседние кандидаты отличаются
+// одним свапом и получают почти равный скор, поэтому вторая попытка рядом с
+// первой промахивается вместе с ней.
+func pickSliderAttempts(guesses []sliderGuess, limit int) []sliderGuess {
+	const minGap = 3
+	out := make([]sliderGuess, 0, limit)
+	taken := func(index, gap int) bool {
+		return slices.ContainsFunc(out, func(g sliderGuess) bool {
+			return absInt(g.Index-index) < gap
+		})
+	}
+	for _, gap := range []int{minGap, 1} {
+		for _, g := range guesses {
+			if len(out) == limit {
+				return out
+			}
+			if !taken(g.Index, gap) {
+				out = append(out, g)
+			}
+		}
+	}
+	return out
+}
+
 func activeSwapsForIndex(swaps []int, index int) []int {
 	if index <= 0 {
 		return []int{}