import express from 'express'
import cors from 'cors'
import Database from 'better-sqlite3';
import fs from "fs"



const HOST = '0.0.0.0'
const PORT = '17058'
const fileDir = "./temp";
const dbPath = './miaoShare.db'
// 上传文件最大大小：200MB
const uploadMaxSize=200*1024*1024
// 一天的毫秒数
const millisecondsOfTheDay = parseInt(24*3600*1000)
// 文件3天过期
const LifeOfFile=millisecondsOfTheDay*3
// const LifeOfFile=0

// 数据库相关
const db = new Database(dbPath, { verbose: null });
db.prepare(`CREATE TABLE IF NOT EXISTS id2fileName (
    id CHAR(8) PRIMARY KEY NOT NULL UNIQUE,
    fileName TEXT NOT NULL,
    timestamp INT NOT NULL,
    freeze tinyint(1) NOT NULL,
    downloadCredit INT NOT NULL
);`).run()
const stmt_getFileName = db.prepare(`SELECT fileName FROM id2fileName WHERE id = ?`)
const stmt_getTimestamp = db.prepare(`SELECT timestamp FROM id2fileName WHERE id = ?`)
const stmt_getFreeze = db.prepare(`SELECT freeze FROM id2fileName WHERE id = ?`)
const stmt_getDownloadCredit = db.prepare(`SELECT downloadCredit FROM id2fileName WHERE id = ?`)
const stmt_getFreezenIDs = db.prepare(`SELECT id FROM id2fileName WHERE freeze = 1`)
const stmt_insertId2FileName = db.prepare(`INSERT INTO id2fileName (id, fileName, timestamp, freeze, downloadCredit) VALUES (?, ?, ?, ?, ?)`)
const stmt_deleteExpireData = db.prepare(`DELETE FROM id2fileName WHERE freeze=1`)
const stmt_freezeExpireData = db.prepare(`UPDATE id2fileName SET freeze=1 WHERE timestamp < ? OR downloadCredit < 1`)
const stmt_updateDownloadCredit = db.prepare(`UPDATE id2fileName SET downloadCredit=downloadCredit-1 WHERE id = ?`)

const db_insert = (id,fileName,downloadCredit)=>{
    stmt_insertId2FileName.run(id,fileName,parseInt(Date.now()),0,downloadCredit)
}
const db_getFileName = (id)=>{
    try{
        if(stmt_getFreeze.get(id)['freeze'] == 1)return null
        return stmt_getFileName.get(id)['fileName']
    }catch(e){
        return null
    }
}
// 检查是否可下载
const db_downloadable = (id)=>{
    try{
        // 懒
        if(stmt_getDownloadCredit.get(id)['downloadCredit'] < 1)return false
        if(stmt_getFreeze.get(id)['freeze'] == 1)return false
        return true
    }catch(e){
        return false
    }
}
const db_updateDownloadCredit = (id)=>{
    try{
        stmt_updateDownloadCredit.run(id)
        return true
    }catch(e){
        return false
    }
}

const db_getTimestamp = (id)=>{
    return stmt_getTimestamp.get(id)['timestamp']
}

// 更新存储的文件，删除已经被冻结的文件以及相关记录，然后冻结过期文件
const updateFiles = ()=>{
    try{
        let rows = stmt_getFreezenIDs.all()
        stmt_deleteExpireData.run()
        for(let row of rows){
            let fileName = row['id']
            let path = fileDir + '/' + fileName
            try{
                fs.unlink(path,(e)=>{if(e)throw e})
            }catch(e){
                console.log(e)
                continue
            }
        }
        stmt_freezeExpireData.run(parseInt(Date.now()) - LifeOfFile)
    }catch(e){
        console.log(e)
        return
    }
}
updateFiles()
// 3小时更新一次
setInterval(updateFiles,1000*3600*3)


var app = express();
app.use(cors());
var tempMap = {}

if (!fs.existsSync(fileDir)) {
    fs.mkdirSync(fileDir);
}

function generateId(){
    var returnStr = "",
        range = 8,
        charStr = 'ABCDEFGHIJKLMNOPQRSTUVWXYZ0123456789';
 
    for(var i=0; i<range; i++){
        var index = Math.round(Math.random() * 35);
        returnStr += charStr.substring(index,index+1);
    }
    return returnStr;
}

// 上传文件接口
function uploadFile(req, res, fileName, downloadCredit){
    let id = generateId();
    const fileStream = fs.createWriteStream(fileDir + '/' + id);
    db_insert(id,fileName,downloadCredit)
    // tempMap[id] = fileName;
    // console.log(tempMap);
    req.pipe(fileStream);
    res.on('data',(c)=>{console.log(c)})
    req.on("end", function () {
        fileStream.end();
        res.statusCode = 200;
        res.end(id);
    });
    req.on("error", err => {
        fileStream.end();
        res.statusCode = 500;
        res.end("File save failed: " + err.message);
    });
}

function downloadFile(req, res, fileId){
    try {
        if(db_downloadable(fileId) == false){
            res.writeHead(404);
            res.end(null);
            return
        }
        db_updateDownloadCredit(fileId)
        var fileName = db_getFileName(fileId)
        if(fileName == null){
            res.writeHead(404);
            res.end(null);
            return
        }
        let data = fs.readFileSync(fileDir + '/' + fileId);
        res.writeHead(200, {
            "Content-Type": "application/octet-stream ",
            "File-Name": fileName,
            'Content-Length':data.length,
        });
        res.end(data);
    } catch (err) {
        console.log(err);
        res.writeHead(404);
        res.end(null);
    }
}

// 设置一些通用的中间件
// app.use(bodyParser.json());
// app.use(bodyParser.urlencoded({extended: true}));

// app.all()
app.post('/file/upload', function(req, res){
	res.header("Access-Control-Allow-Origin", "*");
	res.header("Access-Control-Allow-Headers", "*");
	res.header("Access-Control-Allow-Methods", "POST");
	res.header("Access-Control-Expose-Headers", "File-Name");
	var fileSize = parseInt(req.get('Content-Length'))
    var fileName = req.query.fileName;
    var downloadCredit = parseInt(req.query.downloadCredit);
    if(downloadCredit == -1)downloadCredit = 2147483647
    if(!fileName){
        res.statusCode = 500;
        res.end("FileName Not Found");
    }else if(fileSize > uploadMaxSize){
        res.statusCode = 500;
        res.end("Maximum size limit exceeded");
    }
    else{
        uploadFile(req, res, fileName, downloadCredit);
    }
});

app.get('/file/download', function(req, res){
	res.header("Access-Control-Allow-Origin", "*");
	res.header("Access-Control-Allow-Headers", "*");
	res.header("Access-Control-Allow-Methods", "GET");
	res.header("Access-Control-Expose-Headers", "File-Name");
    var fileId = req.query.fileName;
    if(!fileId){
        res.statusCode = 500;
        res.end("FileName Not Found");
    }else{
        downloadFile(req, res, fileId);
    }
});

// 启动服务器
app.listen(PORT, HOST, function(){
    // console.log('Example app listening on port ' + PORT + '.');
});