短链

将内容生成一个key或者id的短链

const md5=require('./md5')
const fs=require('fs-extra');

//分割符号和字符长度
class ShortName{
    constructor({splitCode,tagLen,tagDir}){
        this.splitCode=splitCode||'<,>';
        this.tagLen=tagLen||3;
        this.tagDir=tagDir||__dirname+'/db/';
        fs.ensureDirSync(this.tagDir);
    }
    //查找
    async _find(name){
        const mstr= md5(String(name));
        let tag=mstr.substring(0,this.tagLen);
        if(tag[0]==='0'){
            tag=parseInt(tag,16).toString(16)
        }
        const tagPath=this.tagDir+tag;
        if(fs.existsSync(tagPath)) {
            const arr=fs.readFileSync(tagPath).toString().split(this.splitCode)
            const i=arr.indexOf(name);
            if(i>-1){
                return [tag,i];
            }else{
                return [tag,-1];
            }
        }
        return [tag,-2]
    }
    //保存字符
    async _save(name) {
        if(typeof name==='undefined'||name.indexOf(this.splitCode)>-1){
            return -1
        }
        const posArr=await this._find(name);
        const tagPath=this.tagDir+posArr[0];
        if(posArr[1]===-2){
            fs.writeFileSync(tagPath,name);
            posArr[1]=0;
        }else if(posArr[1]===-1){
            const arr=fs.readFileSync(tagPath).toString().split(this.splitCode);
            posArr[1]=arr.length;
            arr.push(name);
            fs.writeFileSync(tagPath,arr.join(this.splitCode))
        }
        return posArr;
    }

    //保存后返回16进制id
    async saveKey(name) {
        const posArr=await this._save(name);
        return this.PosToKey(posArr);
    }
    //保存后返回10进制id
    async saveId(name) {
        const key=await this.saveKey(name);
        return this.KeyToId(key)
    }
    //获取id，16进制
     PosToKey(posArr){
        if(posArr[1]>-1){
            return posArr[0]+'v'+posArr[1].toString(16)
        }else{
            return -1
        }
    }
    //获取id，16进制
     KeyToPos(key){
        const posArr=key.split('v')
        if(posArr.length>1){
            return posArr;
        }else{
            return -1;
        }
    }
    //key转id
    KeyToId(key){
        if(key===-1){
            return -1;
        }
        return parseInt(key,32)
    }
    //id转key
    IdToKey(id){
        return id.toString(32);
    }
    //获取id
    async getId(name) {
        const posArr=await this._find(name)
        return this.KeyToId(this.PosToKey(posArr));
    }
    //获取key
    async getKey(name) {
        const posArr=await this._find(name)
        return this.PosToKey(posArr);
    }
    //用key获取内容
    async getNameByKey(key){
        const posArr=this.KeyToPos(key)
        if(posArr!==-1){
            const tagPath=this.tagDir+posArr[0];
            if(fs.existsSync(tagPath)) {
                const arr=fs.readFileSync(tagPath).toString().split(this.splitCode);
                return arr[posArr[1]]
            }
        }
        return null;
    }
    //用id获取内容
    async getNameById(id){
        const key=this.IdToKey(id)
        return await this.getNameByKey(key)
    }
}
module.exports=ShortName