feat(captain): align custom tool limits

internal/service/captain_custom_tool_service.go

@@ -3,9 +3,12 @@ package service
 import (
 	"bytes"
 	"context"
+	"crypto/rand"
 	"encoding/json"
+	"errors"
 	"fmt"
 	"io"
+	"math/big"
 	"net/http"
 	"regexp"
 	"strings"
@@ -25,6 +28,14 @@ type CaptainCustomToolService struct {
 	httpClient  HTTPDoer
 }
 
+const (
+	maxCaptainCustomToolsPerAccount = 15
+	maxCaptainCustomToolSlugLength  = 64
+	customToolSlugCollisionSuffix   = 7
+)
+
+var ErrCaptainCustomToolLimitExceeded = errors.New("You can create a maximum of 15 custom tools per account")
+
 type HTTPDoer interface {
 	Do(req *http.Request) (*http.Response, error)
 }
@@ -89,6 +100,14 @@ type UpdateCustomToolRequest struct {
 
 // Create creates a new CaptainCustomTool.
 func (s *CaptainCustomToolService) Create(ctx context.Context, accountID uint, req *CreateCustomToolRequest) (*model.CaptainCustomTool, error) {
+	count, err := s.toolRepo.CountByAccount(ctx, accountID)
+	if err != nil {
+		return nil, fmt.Errorf("count custom tools: %w", err)
+	}
+	if count >= maxCaptainCustomToolsPerAccount {
+		return nil, ErrCaptainCustomToolLimitExceeded
+	}
+
 	// Default values
 	httpMethod := req.HTTPMethod
 	if httpMethod == "" {
@@ -100,7 +119,10 @@ func (s *CaptainCustomToolService) Create(ctx context.Context, accountID uint, r
 	}
 	slug := req.Slug
 	if slug == "" {
-		slug = customToolSlug(req.Title)
+		slug, err = s.uniqueCustomToolSlug(ctx, accountID, req.Title)
+		if err != nil {
+			return nil, err
+		}
 	}
 
 	tool := &model.CaptainCustomTool{
@@ -265,14 +287,54 @@ func applyCustomToolUpdate(tool *model.CaptainCustomTool, req *UpdateCustomToolR
 	}
 }
 
+func (s *CaptainCustomToolService) uniqueCustomToolSlug(ctx context.Context, accountID uint, title string) (string, error) {
+	baseSlug := customToolSlug(title)
+	if !s.customToolSlugExists(ctx, accountID, baseSlug) {
+		return baseSlug, nil
+	}
+
+	truncated := truncateString(baseSlug, maxCaptainCustomToolSlugLength-customToolSlugCollisionSuffix)
+	for i := 0; i < 5; i++ {
+		candidate := truncated + "_" + randomLowerAlphanumeric(6)
+		if !s.customToolSlugExists(ctx, accountID, candidate) {
+			return candidate, nil
+		}
+	}
+	return "", fmt.Errorf("slug generation failed")
+}
+
+func (s *CaptainCustomToolService) customToolSlugExists(ctx context.Context, accountID uint, slug string) bool {
+	_, err := s.toolRepo.GetBySlug(ctx, accountID, slug)
+	return err == nil
+}
+
 func customToolSlug(title string) string {
 	slug := strings.ToLower(strings.TrimSpace(title))
-	slug = regexp.MustCompile(`[^a-z0-9]+`).ReplaceAllString(slug, "-")
-	slug = strings.Trim(slug, "-")
-	if slug == "" {
-		return "custom-tool"
+	slug = regexp.MustCompile(`[^a-z0-9]+`).ReplaceAllString(slug, "_")
+	slug = strings.Trim(slug, "_")
+	return truncateString("custom_"+slug, maxCaptainCustomToolSlugLength)
+}
+
+func truncateString(value string, maxLen int) string {
+	if len(value) <= maxLen {
+		return value
 	}
-	return slug
+	return value[:maxLen]
+}
+
+func randomLowerAlphanumeric(length int) string {
+	const alphabet = "abcdefghijklmnopqrstuvwxyz0123456789"
+	var b strings.Builder
+	b.Grow(length)
+	for i := 0; i < length; i++ {
+		n, err := rand.Int(rand.Reader, big.NewInt(int64(len(alphabet))))
+		if err != nil {
+			b.WriteByte(alphabet[time.Now().UnixNano()%int64(len(alphabet))])
+			continue
+		}
+		b.WriteByte(alphabet[n.Int64()])
+	}
+	return b.String()
 }
 
 // --- Tool Execution ---