//ref https://github.com/DeanThompson/syncmap/blob/master/syncmap.go

package shardmap

import (
	"sync"
    "fmt"
)

const (
	DEF_SHARD_CNT = 32

	BKDR_SEED = 131 // 31 131 1313 13131 131313 etc...
)

type shardItem struct {
	sync.RWMutex

	data map[string]interface{}
}

type ShardMap struct {
	shardCnt uint8
	shards   []*shardItem
}

var Count = make(chan int)

type wfOp func(a, b string) float32 

/**
* @param uint8, shardCnt must be pow of two
*/
func New(shardCnt uint8) *ShardMap {
	if !isPowOfTwo(shardCnt) {
		shardCnt = DEF_SHARD_CNT
	}

	s := &ShardMap{
		shardCnt: shardCnt,
		shards:   make([]*shardItem, shardCnt),
	}

	for i, _ := range s.shards {
		s.shards[i] = &shardItem{
			data: make(map[string]interface{}),
		}
	}

	return s
}

func (s *ShardMap) Get(key string) (interface{}, bool) {
	si := s.locate(key)

	si.RLock()
	value, ok := si.data[key]
	si.RUnlock()
	return value, ok
}

func (s *ShardMap) Set(key string, value interface{}) {
	si := s.locate(key)

	si.Lock()
	si.data[key] = value
	si.Unlock()
}

func (s *ShardMap) Del(key string) {
	si := s.locate(key)

	si.Lock()
	delete(si.data, key)
	si.Unlock()
}

type kvItem struct {
	key   string
	value interface{}
}

// modify by long.
func (s *ShardMap) Walk(wf wfOp, cfrom string) {

    var wg sync.WaitGroup
    var second float32 

	for _, si := range s.shards {
        //fmt.Println(len(si.data))
        wg.Add(1)
		go func(s *shardItem, fw wfOp, cf string) {
            defer wg.Done()
			s.RLock()
			for _, v := range s.data {
                if cv, ok := v.(string); ok {
                 second = fw(cf,cv)
                 fmt.Println(second)
                }
			}
			s.RUnlock()
		}(si,wf, cfrom)
	}

    wg.Wait()
}

func (s * ShardMap)GetLen() int {
    var slen  int
    for i:= 0 ; i<int(s.shardCnt); i++{
        slen += len(s.shards[i].data)
    } 
    return slen
}

func (s *ShardMap) locate(key string) *shardItem {
	i := bkdrHash(key) & uint32(s.shardCnt-1)

	return s.shards[i]
}

func isPowOfTwo(x uint8) bool {
	return x != 0 && (x&(x-1) == 0)
}

//https://www.byvoid.com/blog/string-hash-compare/
func bkdrHash(str string) uint32 {
	var h uint32

	for _, c := range str {
		h = h*BKDR_SEED + uint32(c)
	}

	return h
}