const fs=require("fs");
const path=require("path");
class CntEvent{
	constructor(){
		this.cnt=0;
		this.emptyEvent=[];
		this.encount=this.encount.bind(this);
		this.decount=this.decount.bind(this);
		this.add=this.add.bind(this);
	}
	encount(delta=1){
		this.cnt+=delta;
	}
	decount(){
		if(this.cnt>0)--this.cnt;
		if(this.cnt==0){
			for(let info of this.emptyEvent)info[0](...info[1]);
			this.emptyEvent=[];
		}
	}
	add(cb,...attach){
		this.emptyEvent.push([cb,attach]);
	}
	check(cb,...attach){
		if(this.cnt==0)cb(...attach);
		else this.add(cb,...attach);
	}
}
class LimitedRunner{
	constructor(limit){
		this.limit=limit;
		this.cnt=0;
		this.funcs=[];
	}
	run(func){
		if(this.cnt<this.limit){
			this.cnt++;
			setTimeout(func,0);
		}else{
			this.funcs.push(func);
		}
	}
	done(){
		if(this.cnt>0)this.cnt--;
		if(this.funcs.length>0){
			this.cnt++;
			setTimeout(this.funcs.shift(),0);
		}
	}
	runWithCb(func,...args){
		let cb=args.pop(),self=this;
		function agent(...args){
			self.done();
			return cb.apply(this,args);
		}
		args.push(agent);
		this.run(()=>func(...args));
	}
}
let ioEvent=new CntEvent;
let ioLimit=new LimitedRunner(4096);
function mkdirs(dir,cb){
	ioLimit.runWithCb(fs.stat.bind(fs),dir,(err,stats)=>{
		if(err)mkdirs(path.dirname(dir),()=>fs.mkdir(dir,cb));
		else if(stats.isFile())throw Error(dir+" was created as a file, so we cannot put file into it.");
		else cb();
	});
}
function save(name,content){
	ioEvent.encount();
	mkdirs(path.dirname(name),()=>ioLimit.runWithCb(fs.writeFile.bind(fs),name,content,err=>{
		if(err)throw Error("Save file error: "+err);
		ioEvent.decount();
	}));
}
function get(name,cb,opt={encoding:'utf8'}){
	ioEvent.encount();
	ioLimit.runWithCb(fs.readFile.bind(fs),name,opt,(err,data)=>{
		if(err)throw Error("Read file error: "+err);
		else cb(data);
		ioEvent.decount();
	});
}
function del(name){
	ioEvent.encount();
	ioLimit.runWithCb(fs.unlink.bind(fs),name,ioEvent.decount);
}
function changeExt(name,ext=""){
	return name.slice(0,name.lastIndexOf("."))+ext;
}
function scanDirByExt(dir,ext,cb){
	let result=[],scanEvent=new CntEvent;
	function helper(dir){
		scanEvent.encount();
		ioLimit.runWithCb(fs.readdir.bind(fs),dir,(err,files)=>{
			if(err)throw Error("Scan dir error: "+err);
			for(let file of files){
				scanEvent.encount();
				let name=path.resolve(dir,file);
				fs.stat(name,(err,stats)=>{
					if(err)throw Error("Scan dir error: "+err);
					if(stats.isDirectory())helper(name);
					else if(stats.isFile()&&name.endsWith(ext))result.push(name);
					scanEvent.decount();
				});
			}
			scanEvent.decount();
		});
	}
	scanEvent.add(cb,result);
	helper(dir,ext,scanEvent);
}
function toDir(to,from){//get relative path without posix/win32 problem
	if(from[0]==".")from=from.slice(1);
	if(to[0]==".")to=to.slice(1);
	from=from.replace(/\\/g,'/');to=to.replace(/\\/g,'/');
	let a=Math.min(to.length,from.length);
	for(let i=1,m=Math.min(to.length,from.length);i<=m;i++)if(!to.startsWith(from.slice(0,i))){a=i-1;break;}
	let pub=from.slice(0,a);
	let len=pub.lastIndexOf("/")+1;
	let k=from.slice(len);
	let ret="";
	for(let i=0;i<k.length;i++)if(k[i]=='/')ret+='../';
	return ret+to.slice(len);
}
function commonDir(pathA,pathB){
	if(pathA[0]==".")pathA=pathA.slice(1);
	if(pathB[0]==".")pathB=pathB.slice(1);
	pathA=pathA.replace(/\\/g,'/');pathB=pathB.replace(/\\/g,'/');
	let a=Math.min(pathA.length,pathB.length);
	for(let i=1,m=Math.min(pathA.length,pathB.length);i<=m;i++)if(!pathA.startsWith(pathB.slice(0,i))){a=i-1;break;}
	let pub=pathB.slice(0,a);
	let len=pub.lastIndexOf("/")+1;
	return pathA.slice(0,len);
}
function commandExecute(cb,helper){
	console.time("Total use");
	function endTime(){
		ioEvent.check(()=>console.timeEnd("Total use"));
	}
	let orders=[];
	for(let order of process.argv)if(order.startsWith("-"))orders.push(order.slice(1));
	let iter=process.argv[Symbol.iterator](),nxt=iter.next(),called=false,faster=orders.includes("f"),fastCnt;
	if(faster){
		fastCnt=new CntEvent;
		fastCnt.add(endTime);
	}
	function doNext(){
		let nxt=iter.next();
		while(!nxt.done&&nxt.value.startsWith("-"))nxt=iter.next();
		if(nxt.done){
			if(!called)console.log("Command Line Helper:\n\n"+helper);
			else if(!faster)endTime();
		}else{
			called=true;
			if(faster)fastCnt.encount(),cb(nxt.value,fastCnt.decount,orders),doNext();
			else cb(nxt.value,doNext,orders);
		}
	}
	while(!nxt.done&&!nxt.value.endsWith(".js"))nxt=iter.next();
	doNext();
}
module.exports={mkdirs:mkdirs,get:get,save:save,toDir:toDir,del:del,addIO:ioEvent.add,
	changeExt:changeExt,CntEvent:CntEvent,scanDirByExt:scanDirByExt,commonDir:commonDir,
    commandExecute:commandExecute};