package main

import (
    "fmt"
    "errors"
    "os"
)

type BNode struct {
    key string
    value float64
    ltree, rtree *BNode
}

func getMinNodePos(treeList []*BNode) (pos int, err error) {
    if len(treeList) == 0 {
        return -1, errors.New("treeList length is 0")
    }
    pos = -1
    for i, _ := range treeList {
        if pos < 0 {
            pos = i
            continue
        }
        if treeList[pos].value > treeList[i].value {
            pos = i
        }
    }

    return pos, nil
}

func get2MinNodes(treeList []*BNode) (node1, node2 *BNode, newlist []*BNode) {
    if len(treeList) < 2 {
    }
    pos, err := getMinNodePos(treeList)
    if nil != err {
        return nil, nil, treeList
    }
    node1 = treeList[pos]
    newlist = append(treeList[:pos], treeList[pos + 1 :]...)

    pos, err = getMinNodePos(newlist)
    if nil != err {
        return nil, nil, treeList
    }
    node2 = newlist[pos]
    newlist = append(newlist[:pos], newlist[pos + 1 :]...)

    return node1, node2, newlist
}

func makeHuffmanTree(treeList []*BNode) (tree *BNode, err error) {
    if len(treeList) < 1 {
        return nil, errors.New("Error : treeList length is 0")
    }
    if len(treeList) == 1 {
        return treeList[0], nil
    }
    lnode, rnode, newlist := get2MinNodes(treeList)

    newNode := new(BNode)
    newNode.ltree = lnode
    newNode.rtree = rnode

    newNode.value = newNode.ltree.value + newNode.rtree.value
    newNode.key = newNode.ltree.key + newNode.rtree.key;

    newlist = append(newlist, newNode)

    return makeHuffmanTree(newlist)
}

func main() {
    keyList   := []byte    {‘A‘,  ‘B‘, ‘C‘,  ‘D‘,  ‘E‘, ‘F‘,  ‘G‘,  ‘H‘}
    valueList := []float64 {0.12, 0.4, 0.29, 0.90, 0.1, 1.1, 1.23, 0.01}

    treeList := []*BNode   {}
    for i, x := range keyList {
        n := BNode{key:string(x), value:valueList[i]}
        treeList = append(treeList, &n)
    }

    tree, err := makeHuffmanTree(treeList)
    if nil != err {
        fmt.Println(err.Error())
    }

    //TODO you can make it yourself
    //showTree(tree)
}

//叶子结点的哈夫曼编码存储在map m里面
func getHuffmanCode(m map[string]string, tree *BNode){
    if nil == tree {
        return
    }

    showHuffmanCode(m, tree, "")
}

func showHuffmanCode(m map[string]string, node *BNode, e string) {
    if nil == node {
        return
    }
    //左右子结点均为nil，则说明此结点为叶子节点
    if nil == node.ltree && nil == node.rtree {
        m[node.key] = e
    }

    //递归获取左子树上叶子结点的哈夫曼编码
    showHuffmanCode(m, node.ltree, e + "0")

    //递归获取右子树上叶子结点的哈夫曼编码
    showHuffmanCode(m, node.rtree, e + "1")
}

func HuffmanCode(m map[string]string, tree *BNode, strContent string) string {
    if nil == tree{
        return ""
    }
    strEncode := ""
    for _, v := range strContent {
        strEncode += m[string(v)]
    }

    return strEncode
}

func HuffmanDecode(mapTable map[string]string, str string) {
    //把"字符-编码"的map反转一下，变成"编码-字符"的map，便于查找比对。
    mapRTable := make(map[string]string)

    for k, v := range mapTable {
        mapRTable[v] = k
    }

    var strCode string
    getWord := func (b byte) (strWord string, r bool){
        strCode += string(b)
        strWord = mapRTable[strCode]
        if "" == strWord {
            return "", false
        }
        strCode = ""
        return strWord, true
    }

    strDecode := ""
    for _, v := range []byte(str) {
        //每读取一个bit位都要进行一次搜索，目前效率有点儿低哈~.~
        if strWord, b := getWord(v); b {
            //如果匹配成功，则把匹配到的字符追加到结尾
            strDecode += strWord
        }
    }

    fmt.Printf("decode : [%s]\n", strDecode)
}