package cache

import (
	"electricity_bill_calc/global"
	"fmt"
	"strings"
	"time"

	"github.com/rueian/rueidis"
)

const (
	TAG_ENTITY   = "ENTITY"
	TAG_COUNT    = "COUNT"
	TAG_SEARCH   = "SEARCH"
	TAG_EXISTS   = "CHECK"
	TAG_SESSION  = "SESSION"
	TAG_RELATION = "RELATION"
)

// 向Redis缓存中保存一个数据
// ! 如果需要长期保存一个数据，那么需要向expires传入0。
func Cache[T interface{}](key string, value *T, expires time.Duration) error {
	var err error
	if expires > 0 {
		setCmd := global.RedisConn.B().Set().
			Key(key).Value(rueidis.JSON(value)).
			ExSeconds(int64(expires.Seconds())).
			Build()
		err = global.RedisConn.Do(global.Ctx, setCmd).Error()
	} else {
		setCmd := global.RedisConn.B().Set().
			Key(key).Value(rueidis.JSON(value)).
			Build()
		err = global.RedisConn.Do(global.Ctx, setCmd).Error()
	}
	return err
}

// 从Redis缓存中获取一个数据
func Retreive[T interface{}](key string) (*T, error) {
	getCmd := global.RedisConn.B().Get().Key(key).Build()
	result := global.RedisConn.Do(global.Ctx, getCmd)
	if result.Error() != nil {
		if rueidis.IsRedisNil(result.Error()) {
			return nil, nil
		} else {
			return nil, result.Error()
		}
	}
	value := new(T)
	err := result.DecodeJSON(value)
	if err != nil {
		return nil, err
	}
	return value, nil
}

// 检查Redis缓存中是否存在指定键的记录
func Exists(key string) (bool, error) {
	existsCmd := global.RedisConn.B().Exists().Key(key).Build()
	result := global.RedisConn.Do(global.Ctx, existsCmd)
	if result.Error() != nil {
		return false, result.Error()
	}
	count, err := result.AsInt64()
	return count > 0, err
}

// 从Redis缓存中删除指定键
// ! 如果指定键已不存在，那么本函数一样会返回false
func Delete(key string) (bool, error) {
	deleteCmd := global.RedisConn.B().Del().Key(key).Build()
	result := global.RedisConn.Do(global.Ctx, deleteCmd)
	if result.Error() != nil {
		return false, result.Error()
	}
	count, err := result.AsInt64()
	return count > 0, err
}

func dissembleScan(result rueidis.RedisResult) (int64, []string, error) {
	var (
		err    error
		cursor int64
		keys   = make([]string, 0)
	)
	results, err := result.ToArray()
	if err != nil {
		return -1, keys, err
	}
	cursor, err = results[0].AsInt64()
	if err != nil {
		return -1, keys, err
	}
	keys, err = results[1].AsStrSlice()
	if err != nil {
		return -1, keys, err
	}
	return cursor, keys, err
}

// 从Redis缓存中批量删除符合pattern的键，这里的pattern直接使用Redis的pattern规则
func DeleteAll(pattern string) error {
	var (
		err    error
		cursor int64
		keys   = make([]string, 0)
		sKeys  []string
	)
	for {
		scanCmd := global.RedisConn.B().Scan().Cursor(cursor).Match(pattern).Count(20).Build()
		results := global.RedisConn.Do(global.Ctx, scanCmd)
		cursor, sKeys, err = dissembleScan(results)
		if err != nil {
			return err
		}
		keys = append(keys, sKeys...)
		if cursor == 0 {
			break
		}
	}

	delCmd := global.RedisConn.B().Del().Key(keys...).Build()
	err = global.RedisConn.Do(global.Ctx, delCmd).Error()
	return err
}

// 生成用于Redis存储的键
func CacheKey(category string, ids ...string) string {
	var b strings.Builder
	b.WriteString(category)
	for _, s := range ids {
		fmt.Fprintf(&b, ":%s", s)
	}
	return b.String()
}