package lrucache

import (
	"errors"
	"github.com/creachadair/cityhash"
	"github.com/hashicorp/golang-lru"
	"globalfintech/golib/tlog"
	"time"
)

// API
var (
	Nil        error = errors.New("cache: nil")
	ErrExpTime error = errors.New("args error, expTime must be > 0")
	dbs        map[int]*lru.Cache
)

func Set(key string, value interface{}) error {
	return SetEx(key, value, 86400)
}

func SetEx(key string, value interface{}, exp int) error {
	return setEx(key, value, exp)
}

func Get(key string) (interface{}, error) {
	return get(key)
}

func Del(key string) error {
	return del(key)
}

// internal

func init() {
	if dbs == nil {
		dbs = make(map[int]*lru.Cache, 1024)
		for i := 0; i < 1024; i++ {
			dbs[i], _ = lru.New(3000)
		}
	}
	go flush()
}

func flush() {
	i := 0
	for range time.NewTicker(time.Minute).C {
		start := time.Now()
		shard := i % 1024
		db, _ := dbs[shard]
		keys := db.Keys()
		for _, key := range keys {
			if keyS, ok := key.(string); ok {
				getByDb(keyS, db)
			}
		}
		i++
		tlog.Infof("FlushKey||time=%s||shard=%d||old=%d||new=%d", time.Since(start), shard, len(keys), db.Len())
	}
}

type item struct {
	d interface{}
	t int
}

func setEx(key string, value interface{}, exp int) error {
	if exp < 1 {
		return ErrExpTime
	}

	db, _ := dbs[hash(key)]
	db.Add(key, &item{d: value, t: int(time.Now().Unix()) + exp})
	return nil
}

func get(key string) (interface{}, error) {
	db, _ := dbs[hash(key)]
	return getByDb(key, db)
}

func getByDb(key string, db *lru.Cache) (interface{}, error) {
	if value, ok := db.Get(key); ok {
		if item, ok := value.(*item); ok {
			if item.t >= int(time.Now().Unix()) {
				return item.d, nil
			} else {
				delByDb(key, db)
			}
		}
	}
	return nil, Nil
}

func del(key string) error {
	db, _ := dbs[hash(key)]
	return delByDb(key, db)
}

func delByDb(key string, db *lru.Cache) error {
	db.Remove(key)
	return nil
}

func hash(key string) int {
	return int(cityhash.Hash32([]byte(key)) % 1024)
}