package tensority

import (
	"github.com/golang/groupcache/lru"

	"github.com/vapor/crypto/sha3pool"
	"github.com/vapor/mining/tensority/cgo_algorithm"
	"github.com/vapor/mining/tensority/go_algorithm"
	"github.com/vapor/protocol/bc"
)

const maxAIHashCached = 64

func calcCacheKey(hash, seed *bc.Hash) *bc.Hash {
	var b32 [32]byte
	sha3pool.Sum256(b32[:], append(hash.Bytes(), seed.Bytes()...))
	key := bc.NewHash(b32)
	return &key
}

// Cache is create for cache the tensority result
type Cache struct {
	lruCache *lru.Cache
}

// NewCache create a cache struct
func NewCache() *Cache {
	return &Cache{lruCache: lru.New(maxAIHashCached)}
}

// AddCache is used for add tensority calculate result
func (a *Cache) AddCache(hash, seed, result *bc.Hash) {
	key := calcCacheKey(hash, seed)
	a.lruCache.Add(*key, result)
}

// RemoveCache clean the cached result
func (a *Cache) RemoveCache(hash, seed *bc.Hash) {
	key := calcCacheKey(hash, seed)
	a.lruCache.Remove(key)
}

// Hash is the real entry for call tensority algorithm
func (a *Cache) Hash(hash, seed *bc.Hash) *bc.Hash {
	key := calcCacheKey(hash, seed)
	if v, ok := a.lruCache.Get(*key); ok {
		return v.(*bc.Hash)
	}
	return algorithm(hash, seed)
}

func algorithm(bh, seed *bc.Hash) *bc.Hash {
	if UseSIMD {
		return cgo_algorithm.SimdAlgorithm(bh, seed)
	} else {
		return go_algorithm.LegacyAlgorithm(bh, seed)
	}
}

var (
	AIHash  = NewCache() // AIHash is created for let different package share same cache
	UseSIMD = false
)