var cmn=require("../$common.js"),
    fs=require("fs"),
    mkdirp=require("mkdirp");

var moddir;
var dbdir=cmn.persistdir+"/zelfoverhoor";
mkdirp.sync(dbdir);

var accounts=require("./accounts.json");

var SHUFFLE_QUESTIONS=false;

// {<id>: {q: "question", a: "answer"}}
var questiondb={};
// {<id>: {id, name, description, questions: [<question_id>]}}
var questionsets={};
// {<username>: [<set_id>]}
var userlists={};

function uniqidstr(validp){
	for(var len=6;;len++){
		var str="";
		for(var i=0;i<len;i++)str+=String.fromCharCode(97+Math.random()*26|0);
		if(validp(str))return str;
	}
}

var persistDB=(function(){
	var qdbCache=null,qsetsCache=null,ulCache=null;
	return function persistDB(){
		var s=JSON.stringify(questiondb);
		if(s!=qdbCache){
			qdbCache=s;
			fs.writeFile(dbdir+"/questiondb.json",s,function(err){
				if(err)console.log("write questiondb.json:",err);
			});
		}
		s=JSON.stringify(questionsets);
		if(s!=qsetsCache){
			qsetsCache=s;
			fs.writeFile(dbdir+"/questionsets.json",s,function(err){
				if(err)console.log("write questionsets.json:",err);
			});
		}
		s=JSON.stringify(userlists);
		if(s!=ulCache){
			ulCache=s;
			fs.writeFile(dbdir+"/userlists.json",s,function(err){
				if(err)console.log("write userlists.json:",err);
			});
		}
	};
})();

function shuffle(a){
	var j,v,i;
	for(var i=a.length-1;i>0;i--){
		j=Math.floor(Math.random()*(i+1));
		v=a[i]; a[i]=a[j]; a[j]=v;
	}
}

function checkQsetJson(json,errfunc){
	var qset;
	try {
		qset=JSON.parse(json);
	} catch(e){
		errfunc("Invalid json received");
		return null;
	}
	if(!qset.name||typeof qset.name!="string"||
			!qset.description||typeof qset.description!="string"||
			!qset.questions||!Array.isArray(qset.questions)){
		errfunc("Invalid data received");
		return null;
	}
	var i;
	for(i=0;i<qset.questions.length;i++){
		if(!qset.questions[i].q||typeof qset.questions[i].q!="string"||
				!qset.questions[i].a||typeof qset.questions[i].a!="string"){
			errfunc("Invalid question data received");
			return null;
		}
	}
	return qset;
}

function canAccessFile(fname){
	try {
		fs.accessSync(fname,fs.constants.F_OK|fs.constants.R_OK|fs.constants.W_OK);
		return true;
	} catch(e) {
		return false;
	}
}

module.exports=function(app,io,_moddir){
	moddir=_moddir;

	if(canAccessFile(dbdir+"/questiondb.json")&&canAccessFile(dbdir+"/questionsets.json")&&canAccessFile(dbdir+"/userlists.json")){
		questiondb=JSON.parse(fs.readFileSync(dbdir+"/questiondb.json"));
		questionsets=JSON.parse(fs.readFileSync(dbdir+"/questionsets.json"));
		userlists=JSON.parse(fs.readFileSync(dbdir+"/userlists.json"));
	} else {
		console.log("newly creating zelfoverhoor db");
		questiondb={};
		questionsets={};
		userlists={};
		persistDB();
	}

	app.all("/zelfoverhoor*",function(req,res,next){
		res.header("Cache-Control","private, no-cache, no-store, must-revalidate");
		res.header("Expires","-1");
		res.header("Pragma","no-cache");
		next();
	});

	app.get("/zelfoverhoor",function(req,res){
		res.sendFile(moddir+"/index.html");
	});

	app.get("/zelfoverhoor/qs/:id",function(req,res){
		var qset=questionsets[req.params.id];
		if(qset==null){
			res.status(404).sendFile(moddir+"/notfound.html");
			return;
		}
		var list=[];
		for(var i=0;i<qset.questions.length;i++){
			list.push(questiondb[qset.questions[i]]);
		}
		var resset={"id": qset.id, "name": qset.name, "description": qset.description, "questions": list};
		if(SHUFFLE_QUESTIONS)shuffle(resset.questions);
		fs.readFile(moddir+"/qs.html",function(err,data){
			if(err)throw err;
			res.send(String(data)
				.replace("<!-- ###ID### -->",req.params.id)
				.replace("/*###QUESTIONSET###*/",JSON.stringify(resset)));
		});
	});
	app.get("/zelfoverhoor/qsdata/:id",function(req,res){
		var qset=questionsets[req.params.id];
		if(qset==null){
			res.status(404).send("ID not found");
			return;
		}
		var list=[];
		for(var i=0;i<qset.questions.length;i++){
			list.push(questiondb[qset.questions[i]]);
		}
		var resset={"id": qset.id, "name": qset.name, "description": qset.description, "questions": list};
		res.send(JSON.stringify(resset));
	});

	app.use(["/zelfoverhoor/docent","/zelfoverhoor/docent/*"],cmn.authgen(accounts));
	app.get("/zelfoverhoor/docent",function(req,res){
		fs.readFile(moddir+"/docent.html",function(err,data){
			if(err)throw err;
			res.send(String(data)
				.replace(/<!-- ###NAME### -->/g,req.authuser));
		});
	});
	app.get("/zelfoverhoor/docent/sets",function(req,res){
		if(userlists[req.authuser]==null){
			userlists[req.authuser]=[];
		}
		var ul=userlists[req.authuser];
		var list=[];
		for(var i=0;i<ul.length;i++){
			list.push(questionsets[ul[i]]);
		}
		res.send(JSON.stringify(list));
	});
	app.post("/zelfoverhoor/docent/addset",function(req,res){
		var qset=checkQsetJson(req.body,function(err){res.status(400).send(err);});
		if(qset==null)return;
		var ids=[],id;
		for(i=0;i<qset.questions.length;i++){
			id=uniqidstr(function(s){return questiondb[s]==null;});
			questiondb[id]={"q": qset.questions[i].q, "a": qset.questions[i].a};
			ids.push(id);
		}
		var setid=uniqidstr(function(s){return questionsets[s]==null;});
		questionsets[setid]={"id": setid, "name": qset.name, "description": qset.description, "questions": ids};
		if(userlists[req.authuser]==null){
			userlists[req.authuser]=[];
		}
		userlists[req.authuser].push(setid);
		persistDB();
		res.send(setid);
	});
	app.post("/zelfoverhoor/docent/editset/:id",function(req,res){
		var setid=req.params.id;
		if(questionsets[setid]==null){
			res.status(404).send("ID not found");
			return;
		}
		if(userlists[req.authuser].indexOf(setid)==-1){
			res.status(403).send("ID does not belong to you");
			return;
		}
		var qset=checkQsetJson(req.body,function(err){res.status(400).send(err);});
		if(qset==null)return;
		var ids=[],id;
		for(i=0;i<qset.questions.length;i++){
			id=uniqidstr(function(s){return questiondb[s]==null;});
			questiondb[id]={"q": qset.questions[i].q, "a": qset.questions[i].a};
			ids.push(id);
		}
		questionsets[setid]={"id": setid, "name": qset.name, "description": qset.description, "questions": ids};
		persistDB();
		res.send(setid);
	});
	app.post("/zelfoverhoor/docent/deleteset",function(req,res){
		var setid=req.body;
		if(!setid||typeof setid!="string"){
			res.status(400).send("Invalid id received");
			return;
		}
		if(!userlists[req.authuser]){
			userlists[req.authuser]=[];
		}
		var ul=userlists[req.authuser];
		var found=false;
		for(var i=0;i<ul.length;i++){
			if(ul[i]==setid){
				ul.splice(i,1);
				found=true;
				break;
			}
		}
		if(!found){
			res.status(404).send("ID not found");
			return;
		}
		delete questionsets[setid];
		persistDB();
		res.send();
	});

	app.post("/zelfoverhoor/error",function(req,res){
		if(typeof req.body=="string"){
			fs.appendFile(dbdir+"/errors.txt",new Date().toString()+" "+req.body+"\n",function(err){
				if(err)console.log(err);
			});
		}
		res.send();
	});

	app.get("/zelfoverhoor/docent/docent.js",function(req,res){
		res.sendFile(moddir+"/docent.js");
	});

	app.get("/zelfoverhoor/qs.js",function(req,res){
		res.sendFile(moddir+"/qs.js");
	});
	app.get("/zelfoverhoor/style.css",function(req,res){
		res.sendFile(moddir+"/style.css");
	});
};