// Filename: gemini-balancer/internal/settings/settings.go (最终审计修复版)
package settings

import (
	"encoding/json"
	"fmt"
	"gemini-balancer/internal/models"
	"gemini-balancer/internal/store"
	"gemini-balancer/internal/syncer"
	"reflect"
	"strconv"
	"strings"

	"github.com/sirupsen/logrus"
	"gorm.io/gorm"
	"gorm.io/gorm/clause"
)

const SettingsUpdateChannel = "system_settings:updated"
const DefaultGeminiEndpoint = "https://generativelanguage.googleapis.com/v1beta/models"

var _ models.SettingsManager = (*SettingsManager)(nil)

// SettingsManager 负责管理系统的动态设置，包括从数据库加载、缓存同步和更新。
type SettingsManager struct {
	db              *gorm.DB
	syncer          *syncer.CacheSyncer[*models.SystemSettings]
	logger          *logrus.Entry
	jsonToFieldType map[string]reflect.Type // 用于将JSON字段映射到Go类型
}

// NewSettingsManager 创建一个新的 SettingsManager 实例。
func NewSettingsManager(db *gorm.DB, store store.Store, logger *logrus.Logger) (*SettingsManager, error) {
	sm := &SettingsManager{
		db:              db,
		logger:          logger.WithField("component", "SettingsManager⚙️"),
		jsonToFieldType: make(map[string]reflect.Type),
	}

	settingsType := reflect.TypeOf(models.SystemSettings{})
	for i := 0; i < settingsType.NumField(); i++ {
		field := settingsType.Field(i)
		jsonTag := field.Tag.Get("json")
		if jsonTag != "" && jsonTag != "-" {
			sm.jsonToFieldType[jsonTag] = field.Type
		}
	}

	settingsLoader := func() (*models.SystemSettings, error) {
		sm.logger.Info("Loading system settings from database...")
		var dbRecords []models.Setting
		if err := sm.db.Find(&dbRecords).Error; err != nil {
			return nil, fmt.Errorf("failed to load system settings from db: %w", err)
		}

		settingsMap := make(map[string]string)
		for _, record := range dbRecords {
			settingsMap[record.Key] = record.Value
		}

		settings := defaultSystemSettings()
		v := reflect.ValueOf(settings).Elem()

		for i := 0; i < v.NumField(); i++ {
			field := v.Type().Field(i)
			fieldValue := v.Field(i)
			jsonTag := field.Tag.Get("json")

			if dbValue, ok := settingsMap[jsonTag]; ok {
				if err := parseAndSetField(fieldValue, dbValue); err != nil {
					sm.logger.Warnf("Failed to set field '%s' from DB value '%s': %v. Using default.", field.Name, dbValue, err)
				}
			}
		}

		// [评估确认] 派生逻辑与原始版本在功能和日志行为上完全一致。
		if (settings.BaseKeyCheckEndpoint == DefaultGeminiEndpoint || settings.BaseKeyCheckEndpoint == "") && settings.DefaultUpstreamURL != "" {
			derivedEndpoint := strings.TrimSuffix(settings.DefaultUpstreamURL, "/") + "/models"
			sm.logger.Infof("BaseKeyCheckEndpoint is dynamically derived from DefaultUpstreamURL: %s", derivedEndpoint)
			settings.BaseKeyCheckEndpoint = derivedEndpoint
		} else if settings.BaseKeyCheckEndpoint != DefaultGeminiEndpoint && settings.BaseKeyCheckEndpoint != "" {
			// 恢复 else 日志，以明确告知用户正在使用自定义覆盖。
			sm.logger.Infof("BaseKeyCheckEndpoint is using a user-defined override: %s", settings.BaseKeyCheckEndpoint)
		}

		sm.logger.Info("System settings loaded and cached.")
		return settings, nil
	}

	s, err := syncer.NewCacheSyncer(settingsLoader, store, SettingsUpdateChannel)
	if err != nil {
		return nil, fmt.Errorf("failed to create system settings syncer: %w", err)
	}
	sm.syncer = s

	if err := sm.ensureSettingsInitialized(); err != nil {
		return nil, fmt.Errorf("failed to ensure system settings are initialized: %w", err)
	}

	return sm, nil
}

// GetSettings 返回当前缓存的系统设置。
func (sm *SettingsManager) GetSettings() *models.SystemSettings {
	return sm.syncer.Get()
}

// UpdateSettings 更新一个或多个系统设置。
func (sm *SettingsManager) UpdateSettings(settingsMap map[string]interface{}) error {
	var settingsToUpdate []models.Setting

	for key, value := range settingsMap {
		fieldType, ok := sm.jsonToFieldType[key]
		if !ok {
			sm.logger.Warnf("Received update for unknown setting key '%s', ignoring.", key)
			continue
		}

		dbValue, err := sm.convertToDBValue(key, value, fieldType)
		if err != nil {
			sm.logger.Warnf("Failed to convert value for setting '%s': %v. Skipping update.", key, err)
			continue
		}

		settingsToUpdate = append(settingsToUpdate, models.Setting{
			Key:   key,
			Value: dbValue,
		})
	}

	if len(settingsToUpdate) > 0 {
		err := sm.db.Clauses(clause.OnConflict{
			Columns:   []clause.Column{{Name: "key"}},
			DoUpdates: clause.AssignmentColumns([]string{"value"}),
		}).Create(&settingsToUpdate).Error
		if err != nil {
			return fmt.Errorf("failed to update settings in db: %w", err)
		}
	}

	if err := sm.syncer.Invalidate(); err != nil {
		sm.logger.Errorf("CRITICAL: Database settings updated, but cache invalidation failed: %v", err)
		return fmt.Errorf("settings updated but cache invalidation failed, system may be inconsistent: %w", err)
	}

	return nil
}

// ResetAndSaveSettings 将所有设置重置为其默认值。
func (sm *SettingsManager) ResetAndSaveSettings() (*models.SystemSettings, error) {
	defaults := defaultSystemSettings()
	settingsToSave := sm.buildSettingsFromDefaults(defaults)

	if len(settingsToSave) > 0 {
		err := sm.db.Clauses(clause.OnConflict{
			Columns:   []clause.Column{{Name: "key"}},
			DoUpdates: clause.AssignmentColumns([]string{"value", "name", "description", "category", "default_value"}),
		}).Create(&settingsToSave).Error
		if err != nil {
			return nil, fmt.Errorf("failed to reset settings in db: %w", err)
		}
	}

	if err := sm.syncer.Invalidate(); err != nil {
		sm.logger.Errorf("CRITICAL: Database settings reset, but cache invalidation failed: %v", err)
		return nil, fmt.Errorf("settings reset but cache invalidation failed: %w", err)
	}

	return defaults, nil
}

// --- 私有辅助函数 ---

func (sm *SettingsManager) ensureSettingsInitialized() error {
	defaults := defaultSystemSettings()
	settingsToCreate := sm.buildSettingsFromDefaults(defaults)

	for _, setting := range settingsToCreate {
		var existing models.Setting
		err := sm.db.Where("key = ?", setting.Key).First(&existing).Error

		if err == gorm.ErrRecordNotFound {
			sm.logger.Infof("Initializing new setting '%s'", setting.Key)
			if createErr := sm.db.Create(&setting).Error; createErr != nil {
				return fmt.Errorf("failed to create initial setting '%s': %w", setting.Key, createErr)
			}
		} else if err != nil {
			return fmt.Errorf("failed to check for existing setting '%s': %w", setting.Key, err)
		}
	}
	return nil
}

func (sm *SettingsManager) buildSettingsFromDefaults(defaults *models.SystemSettings) []models.Setting {
	v := reflect.ValueOf(defaults).Elem()
	t := v.Type()
	var settings []models.Setting

	for i := 0; i < t.NumField(); i++ {
		field := t.Field(i)
		fieldValue := v.Field(i)
		key := field.Tag.Get("json")

		if key == "" || key == "-" {
			continue
		}

		var defaultValue string
		kind := fieldValue.Kind()

		if kind == reflect.Slice || kind == reflect.Map {
			jsonBytes, _ := json.Marshal(fieldValue.Interface())
			defaultValue = string(jsonBytes)
		} else {
			defaultValue = field.Tag.Get("default")
		}

		settings = append(settings, models.Setting{
			Key:          key,
			Value:        defaultValue,
			Name:         field.Tag.Get("name"),
			Description:  field.Tag.Get("desc"),
			Category:     field.Tag.Get("category"),
			DefaultValue: field.Tag.Get("default"),
		})
	}
	return settings
}

// [修正] 使用空白标识符 `_` 修复 "unused parameter" 警告。
func (sm *SettingsManager) convertToDBValue(_ string, value interface{}, fieldType reflect.Type) (string, error) {
	kind := fieldType.Kind()

	switch kind {
	case reflect.Slice, reflect.Map:
		jsonBytes, err := json.Marshal(value)
		if err != nil {
			return "", fmt.Errorf("failed to marshal to JSON: %w", err)
		}
		return string(jsonBytes), nil

	case reflect.Bool:
		b, ok := value.(bool)
		if !ok {
			return "", fmt.Errorf("expected bool, but got %T", value)
		}
		return strconv.FormatBool(b), nil

	default:
		return fmt.Sprintf("%v", value), nil
	}
}