package service

import (
	"context"
	"encoding/json"
	"fmt"
	"strconv"
	"time"

	"github.com/redis/go-redis/v9"
	"gorm.io/gorm"

	"spider/internal/model"
)

const settingsCacheKey = "spider:cache:settings"
const settingsCacheTTL = 5 * time.Minute

// SettingsService provides hot-reloadable access to managed_settings.
type SettingsService struct {
	db    *gorm.DB
	redis *redis.Client
}

// NewSettingsService creates a new SettingsService.
func NewSettingsService(db *gorm.DB, rdb *redis.Client) *SettingsService {
	return &SettingsService{db: db, redis: rdb}
}

// Load 从数据库加载所有设置到 Redis 缓存
func (s *SettingsService) Load(ctx context.Context) error {
	var settings []model.ManagedSetting
	if err := s.db.WithContext(ctx).Find(&settings).Error; err != nil {
		return fmt.Errorf("load settings from db: %w", err)
	}

	if len(settings) == 0 {
		// Nothing to cache; ensure any stale cache is cleared.
		return s.redis.Del(ctx, settingsCacheKey).Err()
	}

	fields := make([]interface{}, 0, len(settings)*2)
	for _, setting := range settings {
		fields = append(fields, setting.KeyName, setting.Value)
	}

	pipe := s.redis.Pipeline()
	pipe.HSet(ctx, settingsCacheKey, fields...)
	pipe.Expire(ctx, settingsCacheKey, settingsCacheTTL)
	_, err := pipe.Exec(ctx)
	if err != nil {
		return fmt.Errorf("cache settings to redis: %w", err)
	}
	return nil
}

// Get 获取设置值（先读 Redis 缓存，缓存不存在则读 DB 并回填）
func (s *SettingsService) Get(ctx context.Context, key string) (string, error) {
	// Try cache first.
	val, err := s.redis.HGet(ctx, settingsCacheKey, key).Result()
	if err == nil {
		return val, nil
	}

	// Cache miss or Redis error — fall back to DB.
	var setting model.ManagedSetting
	if err := s.db.WithContext(ctx).Where("key_name = ?", key).First(&setting).Error; err != nil {
		return "", fmt.Errorf("setting %q not found: %w", key, err)
	}

	// Back-fill the cache entry.
	pipe := s.redis.Pipeline()
	pipe.HSet(ctx, settingsCacheKey, key, setting.Value)
	pipe.Expire(ctx, settingsCacheKey, settingsCacheTTL)
	pipe.Exec(ctx) //nolint:errcheck — best-effort

	return setting.Value, nil
}

// GetInt 获取整数类型设置
func (s *SettingsService) GetInt(ctx context.Context, key string, defaultVal int) int {
	raw, err := s.Get(ctx, key)
	if err != nil {
		return defaultVal
	}
	v, err := strconv.Atoi(raw)
	if err != nil {
		return defaultVal
	}
	return v
}

// GetFloat 获取浮点类型设置
func (s *SettingsService) GetFloat(ctx context.Context, key string, defaultVal float64) float64 {
	raw, err := s.Get(ctx, key)
	if err != nil {
		return defaultVal
	}
	v, err := strconv.ParseFloat(raw, 64)
	if err != nil {
		return defaultVal
	}
	return v
}

// GetBool 获取布尔类型设置
func (s *SettingsService) GetBool(ctx context.Context, key string, defaultVal bool) bool {
	raw, err := s.Get(ctx, key)
	if err != nil {
		return defaultVal
	}
	v, err := strconv.ParseBool(raw)
	if err != nil {
		return defaultVal
	}
	return v
}

// GetJSON 获取 JSON 类型设置，解析到 target
func (s *SettingsService) GetJSON(ctx context.Context, key string, target interface{}) error {
	raw, err := s.Get(ctx, key)
	if err != nil {
		return err
	}
	return json.Unmarshal([]byte(raw), target)
}

// Set 更新设置（更新 DB + 清除缓存）
func (s *SettingsService) Set(ctx context.Context, key, value string) error {
	result := s.db.WithContext(ctx).Model(&model.ManagedSetting{}).
		Where("key_name = ?", key).
		Update("value", value)
	if result.Error != nil {
		return fmt.Errorf("update setting %q in db: %w", key, result.Error)
	}
	if result.RowsAffected == 0 {
		return fmt.Errorf("setting %q not found", key)
	}
	// Invalidate cache so next read reloads from DB.
	return s.Invalidate(ctx)
}

// Invalidate 清除缓存，下次读取时从 DB 加载
func (s *SettingsService) Invalidate(ctx context.Context) error {
	return s.redis.Del(ctx, settingsCacheKey).Err()
}