feat: add ai gateway foundation

backend/internal/ai/gateway.go

@@ -0,0 +1,45 @@
+package ai
+
+import (
+	"errors"
+
+	"gorm.io/gorm"
+	"senlinai-agent/backend/internal/domain"
+)
+
+type Gateway struct {
+	db        *gorm.DB
+	systemKey string
+}
+
+type SelectedKey struct {
+	Provider string
+	APIKey   string
+	KeyType  string
+}
+
+func NewGateway(database *gorm.DB, systemKey string) *Gateway {
+	return &Gateway{db: database, systemKey: systemKey}
+}
+
+func (g *Gateway) SelectKey(userID uint) (SelectedKey, error) {
+	var userKey domain.AIKey
+	if err := g.db.Where("user_id = ?", userID).First(&userKey).Error; err == nil {
+		return SelectedKey{Provider: userKey.Provider, APIKey: userKey.EncryptedAPIKey, KeyType: "user"}, nil
+	}
+	if g.systemKey == "" {
+		return SelectedKey{}, errors.New("no ai key available")
+	}
+	return SelectedKey{Provider: "openai", APIKey: g.systemKey, KeyType: "system"}, nil
+}
+
+func (g *Gateway) RecordCall(userID uint, provider string, usedKeyType string, action string, status string, errText string) error {
+	return g.db.Create(&domain.AICallLog{
+		UserID:      userID,
+		Provider:    provider,
+		UsedKeyType: usedKeyType,
+		Action:      action,
+		Status:      status,
+		Error:       errText,
+	}).Error
+}

backend/internal/ai/gateway_test.go

@@ -0,0 +1,79 @@
+package ai
+
+import (
+	"fmt"
+	"testing"
+
+	"github.com/glebarez/sqlite"
+	"github.com/stretchr/testify/require"
+	"gorm.io/gorm"
+	"senlinai-agent/backend/internal/domain"
+)
+
+func TestSelectKeyPrefersUserKey(t *testing.T) {
+	database := newTestDB(t)
+	require.NoError(t, database.Create(&domain.AIKey{UserID: 3, Provider: "openai", EncryptedAPIKey: "user-key"}).Error)
+	gateway := NewGateway(database, "system-key")
+
+	selected, err := gateway.SelectKey(3)
+
+	require.NoError(t, err)
+	require.Equal(t, "user", selected.KeyType)
+	require.Equal(t, "user-key", selected.APIKey)
+}
+
+func TestSelectKeyFallsBackToSystemKey(t *testing.T) {
+	database := newTestDB(t)
+	gateway := NewGateway(database, "system-key")
+
+	selected, err := gateway.SelectKey(3)
+
+	require.NoError(t, err)
+	require.Equal(t, "system", selected.KeyType)
+	require.Equal(t, "system-key", selected.APIKey)
+}
+
+func TestSelectKeyReturnsErrorWhenNoKeyAvailable(t *testing.T) {
+	database := newTestDB(t)
+	gateway := NewGateway(database, "")
+
+	_, err := gateway.SelectKey(3)
+
+	require.ErrorContains(t, err, "no ai key available")
+}
+
+func TestRecordCallStoresAuditFields(t *testing.T) {
+	database := newTestDB(t)
+	gateway := NewGateway(database, "system-key")
+
+	require.NoError(t, gateway.RecordCall(3, "openai", "system", "inbox_analyze", "failed", "rate limited"))
+
+	var log domain.AICallLog
+	require.NoError(t, database.First(&log).Error)
+	require.Equal(t, uint(3), log.UserID)
+	require.Equal(t, "openai", log.Provider)
+	require.Equal(t, "system", log.UsedKeyType)
+	require.Equal(t, "inbox_analyze", log.Action)
+	require.Equal(t, "failed", log.Status)
+	require.Equal(t, "rate limited", log.Error)
+}
+
+func TestCreateAISession(t *testing.T) {
+	database := newTestDB(t)
+	service := NewSessionService(database)
+
+	session, err := service.Create(7, 3, "报价分析")
+
+	require.NoError(t, err)
+	require.Equal(t, uint(7), session.ProjectID)
+	require.Equal(t, uint(3), session.CreatedBy)
+	require.Equal(t, "报价分析", session.Title)
+}
+
+func newTestDB(t *testing.T) *gorm.DB {
+	t.Helper()
+	database, err := gorm.Open(sqlite.Open(fmt.Sprintf("file:%s?mode=memory&cache=shared", t.Name())), &gorm.Config{})
+	require.NoError(t, err)
+	require.NoError(t, domain.AutoMigrate(database))
+	return database
+}

backend/internal/ai/sessions.go

@@ -0,0 +1,26 @@
+package ai
+
+import (
+	"errors"
+	"strings"
+
+	"gorm.io/gorm"
+	"senlinai-agent/backend/internal/domain"
+)
+
+type SessionService struct {
+	db *gorm.DB
+}
+
+func NewSessionService(database *gorm.DB) *SessionService {
+	return &SessionService{db: database}
+}
+
+func (s *SessionService) Create(projectID uint, userID uint, title string) (*domain.AISession, error) {
+	title = strings.TrimSpace(title)
+	if title == "" {
+		return nil, errors.New("session title is required")
+	}
+	session := &domain.AISession{ProjectID: projectID, CreatedBy: userID, Title: title}
+	return session, s.db.Create(session).Error
+}