package cache

import (
	"encoding/json"
	"errors"
	"fmt"
	"time"

	"github.com/gomodule/redigo/redis"
	"qoobing.com/gomod/log"
)

var (
	ErrNotFound = errors.New("not found")
)

type Cacher[T any] interface {
	GetFromCache(id string) (dat *T, err error)
	SetIntoCache(id string, dat *T) (err error)
}

type Getter[T any] interface {
	GetById(id string) (dat *T, err error)
}

type Config struct {
	UseLocalCache            bool
	LocalCacheLifetimeSecond int64
	UseRedisCache            bool
	RedisCacheConn           redis.Conn
	RedisCacheKeyPrefix      string
	RedisCacheLifetimeSecond int64
}

func NewCache[T any](getter Getter[T], cfg Config) Cacher[T] {
	var c = new(cacher[T])
	// Getter
	c.getter = getter

	// Local cache
	if cfg.UseLocalCache {
		c.localCache = new(localCacher[T])
		c.localCache.cacheItems = map[string]*cacheItem[T]{}
		c.localCache.cacheSecond = time.Duration(cfg.LocalCacheLifetimeSecond) * time.Second
		if c.localCache.cacheSecond.Nanoseconds() <= 0 {
			c.localCache.cacheSecond = 60 * time.Second
		}
	}

	// Redis cache
	if cfg.UseRedisCache && cfg.RedisCacheConn != nil {
		c.redisCache = new(redisCacher[T])
		c.redisCache.rds = cfg.RedisCacheConn
		c.redisCache.cacheSecond = time.Duration(cfg.RedisCacheLifetimeSecond) * time.Second
		if cfg.RedisCacheKeyPrefix == "" {
			panic("redis cache's key prefix must not be null")
		}
		c.redisCache.cachePrefix = fmt.Sprintf("%s-cache-id:", cfg.RedisCacheKeyPrefix)
	} else if cfg.UseRedisCache {
		panic("want to user redis cache, but redis.Conn is nil")
	}

	return c
}

type cacheItem[T any] struct {
	Data       *T        `json:"d"` //cache data
	CreateTime time.Time `json:"t"` //cache create time
}

type localCacher[T any] struct {
	cacheItems  map[string]*cacheItem[T]
	cacheSecond time.Duration
}

type redisCacher[T any] struct {
	rds         redis.Conn
	cachePrefix string
	cacheSecond time.Duration
}

type cacher[T any] struct {
	getter     Getter[T]
	localCache *localCacher[T]
	redisCache *redisCacher[T]
}

func (c *localCacher[T]) GetFromCache(id string) (t *T, err error) {
	var earliestCreateTime = time.Now().Add(-c.cacheSecond)
	if a, ok := c.cacheItems[id]; !ok {
		return nil, ErrNotFound
	} else if earliestCreateTime.Before(a.CreateTime) {
		return a.Data, nil
	}
	//TODO: cocurrent
	delete(c.cacheItems, id)
	return nil, ErrNotFound
}

func (c *localCacher[T]) SetIntoCache(id string, t *T) (err error) {
	c.cacheItems[id] = &cacheItem[T]{
		Data:       t,
		CreateTime: time.Now(),
	}
	fmt.Println("cacheItems", c.cacheItems)
	return nil
}

func (c *redisCacher[T]) GetFromCache(id string) (*T, error) {
	var (
		rds              = c.rds
		redisKey         = c.cachePrefix + id
		redisValue       = ""
		err        error = nil
	)

	// Step 1. read from redis
	if redisValue, err = redis.String(rds.Do("GET", redisKey)); err != nil {
		log.Infof("get cache failed: 'redis return<%s>'", err.Error())
		return nil, ErrNotFound
	}

	// Step 2. decode from string
	a := &cacheItem[T]{}
	if err = json.Unmarshal([]byte(redisValue), a); err != nil {
		log.Errorf("get cache failed: 'json unmarshal failed <%s>'", err.Error())
		return nil, ErrNotFound
	}

	// Step 3. check expire time
	var d = c.cacheSecond
	if d.Nanoseconds() > 0 {
		var earliestCreateTime = time.Now().Add(-c.cacheSecond)
		if a.CreateTime.Before(earliestCreateTime) {
			log.Infof("app(%s) is in redis cache but expired", id)
			return nil, ErrNotFound
		}
	}

	return a.Data, nil
}

func (c *redisCacher[T]) SetIntoCache(id string, t *T) error {
	var (
		rds              = c.rds
		redisKey         = c.cachePrefix + id
		redisValue       = []byte{}
		err        error = nil
	)

	// Step 1. decode from string
	var a = cacheItem[T]{Data: t, CreateTime: time.Now()}
	if redisValue, err = json.Marshal(a); err != nil {
		log.Errorf("set cache failed: 'json marshal failed <%s>'", err.Error())
		return errors.New("set cache failed: 'marshal failed'")
	}

	// Step 2. read from redis
	if _, err = rds.Do("SET", redisKey, string(redisValue)); err != nil {
		log.Errorf("set cache failed: 'redis failed <%s>'", err.Error())
		return errors.New("set cache failed: 'redis failed'")
	}

	return nil
}

func (c *cacher[T]) GetFromCache(id string) (dat *T, err error) {
	// Step 1. check id
	if len(id) < 8 {
		return nil, ErrNotFound
	}

	// Step 2. get from [local]
	if c.localCache != nil {
		if dat, err := c.localCache.GetFromCache(id); err == nil {
			log.Infof("get cache(id:%s) from localCacher success", id)
			return dat, nil
		} else {
			log.Infof("get cache(id:%s) from localCacher failed, try next", id)
		}
	}

	// Step 3. get from [redis]
	if c.redisCache != nil {
		if dat, err := c.redisCache.GetFromCache(id); err == nil {
			if c.localCache != nil {
				log.Infof("set cache(id:%s) to localCache by redisCacher")
				c.localCache.SetIntoCache(id, dat)
			}
			log.Infof("get cache(id:%s) from redisCacher success", id)
			return dat, nil
		} else if c.getter == nil {
			log.Warningf("get cache(id:%s) from all cache failed, and storager is nil, "+
				"trade as not found. may be you forgot set in db ???", id)
			return nil, ErrNotFound
		}
	}
	if c.getter == nil {
		log.Warningf("get cache(id:%s) from all cache failed, and storager is nil, "+
			"trade as not found. may be you forgot set in db ???", id)
		return nil, ErrNotFound
	}

	// Step 4. get from [storager(database or somewhere)]
	dat, err = c.getter.GetById(id)
	if err != nil {
		log.Errorf("cache(id:%s) is not in database, something error: %s", id, err)
		return nil, ErrNotFound
	}
	log.Infof("get cache(id:%s) from exportStorager(maybe database) success", id)

	// Step 5. set to cacha
	if c.localCache != nil {
		c.localCache.SetIntoCache(id, dat)
	}
	if c.redisCache != nil {
		c.redisCache.SetIntoCache(id, dat)
	}

	// Step 6. return
	log.PrintPretty("success cached/return app:", dat)
	return dat, nil
}

func (c *cacher[T]) SetIntoCache(id string, dat *T) (err error) {
	// localCache
	if c.localCache != nil {
		if err = c.localCache.SetIntoCache(id, dat); err != nil {
			log.Infof("set data into localCache failed, err:%s", err)
		} else {
			log.Debugf("success set data into localCache, id: %s", id)
		}
	}

	// redisCache
	if c.redisCache != nil {
		if err = c.redisCache.SetIntoCache(id, dat); err != nil {
			log.Infof("set data into redisCache failed, err:%s", err)
		} else {
			log.Debugf("success set data into redisCache, id: %s", id)
		}
	}
	return nil
}