"use strict";

var cmn=require("../$common.js"),
    persist=require("node-persist"),
    crypto=require("crypto"),
    http=require("http"),
    https=require("https"),
    URL=require("url"),
    child_process=require("child_process");

var moddir=null;

persist=persist.create({
	dir:"persist/changes",
	continuous:false,
	interval:false
});
persist.initSync();

//urls: map(url => URLobject)
//url: String
//URLobject: {url, timeline: [[Date, hash, contents]]}
var urls=persist.getItemSync("urls");
if(!urls){
	urls={};
	persist.setItemSync("urls",urls);
} else {
	(function(){
		var url,i;
		for(url in urls){
			for(i=0;i<urls[url].timeline.length;i++){
				urls[url].timeline[i][0]=new Date(urls[url].timeline[i][0]);
			}
		}
	})();
}
//gsettings: {notify: null/{to: "email", interval: ms}}
var gsettings=persist.getItemSync("gsettings");
if(!gsettings){
	gsettings={notify: null};
	persist.setItemSync("gsettings",gsettings);
}

if(gsettings.notify){
	scheduleNotify();
}

var notifyIsScheduled=false;
function scheduleNotify(){
	if(notifyIsScheduled){
		console.log("WARNING: requesting notify schedule when already scheduled");
		return;
	}
	notifyIsScheduled=true;
	var timeoutFunc=function(){
		if(!gsettings.notify){
			notifyIsScheduled=false;
			return;
		}
		performNotify(gsettings.notify,function(){
			performCleanup();
			if(gsettings.notify){
				setTimeout(timeoutFunc,gsettings.notify.interval);
			} else {
				notifyIsScheduled=false;
			}
		});
	};
	setTimeout(timeoutFunc,gsettings.notify.interval);
}


function URLobject(url){
	if(!(this instanceof URLobject))return new URLobject(url);
	this.url=url;
	this.timeline=[];
}

function fetch(method,url,data/*?*/,cb){
	var cbcalled=false;

	if(!cb){
		cb=data;
		data=undefined;
		if(!cb)throw new Error("No callback passed to fetch");
	}

	try {
		url=URL.parse(url);
	} catch(e){
		cb(-1,null);
		return;
	}

	var httpclass;
	switch(url.protocol){
		case "http:": httpclass=http; break;
		case "https:": httpclass=https; break;
		default:
			cb(-1,null);
			return;
	}

	url.method=method;

	var req=httpclass.request(url,function(res){
		var body="";
		res.on("data",function(data){
			body+=data;
		});
		res.on("end",function(){
			if(!cbcalled)cb(res.statusCode,body);
			cbcalled=true;
		});
		res.on("error",function(err){
			if(!cbcalled)cb(-1,err);
			cbcalled=true;
		});
	});
	req.on("error",function(err){
		if(!cbcalled)cb(-1,err);
		cbcalled=true;
	});
	if(data)req.write(data);
	req.end();
}

var refresh_persist_timeout=null;

function refreshURLs(cb){
	var hashes={};
	var i;
	var url;
	var nwaiting=0;
	for(url in urls){
		console.log("Fetching <"+url+">");
		nwaiting++;
		fetch("GET",url,function(url,status,body){
			nwaiting--;
			console.log("Got <"+url+">; status = "+status);
			if(status==-1){
				hashes[url]=[new Date(),null,null];
			} else {
				var hash=crypto.createHash("sha256");
				hash.update(body);
				hashes[url]=[new Date(),hash.digest("hex"),body];
			}

			if(!urls[url]){
				console.log("WARNING: url <"+url+"> from hashes not found in urls!");
			} else {
				//var last=urls[url].timeline[urls[url].timeline.length-1];
				//if(last==undefined||hashes[url][1]==null||hashes[url][1]!=last[1]){
					urls[url].timeline.push(hashes[url]);
				//}
			}

			if(nwaiting==0&&cb)process.nextTick(cb);

			if(refresh_persist_timeout!=null)clearTimeout(refresh_persist_timeout);
			refresh_persist_timeout=setTimeout(function(){
				persist.setItemSync("urls",urls);
				console.log("(persisted after refresh)")
				refresh_persist_timeout=null;
			},2000);
		}.bind(null,url));
	}
}

function collectLastHashes(){
	var lasthashes={};
	for(url in urls){
		if(urls[url].timeline.length==0){
			lasthashes[url]=null;
		} else {
			lasthashes[url]=urls[url].timeline[urls[url].timeline.length-1][1];
		}
	}
	return lasthashes;
}

function sendMail(tomail,body,cb){
	var proc=child_process.spawn("sendmail",[tomail],{stdio:["pipe",process.stdout,process.stderr]});
	proc.stdin.error(function(e){
		console.log(e);
		cb(e);
	});
	proc.stdin.write(body,function(){
		proc.stdin.end();
		cb();
	});
}

function constructMailBody(tomail,diffs){
	var body="To: "+tomail+"\n"+
	         "From: changes <changes_module@tomsmeding.com>\n"+
	         "Subject: changes notification mail\n\n"+
	         "The <a href=\"http://tomsmeding.com/changes\">changes</a> module recorded "+
	           "some changes in watched webpages.\n"+
	         "The URLs and their old and new content hashes are shown below.\n\n";
	var i;
	for(i=0;i<diffs.length;i++){
		body+="- <a href=\""+diffs[i].url+"\">"+diffs[i].url+"</a>\n"+
		      "  was: "+diffs[i].oldhash+"\n"+
		      "  now: "+diffs[i].newhash+"\n";
	}
	body+="\n\n"+
	      "- webserver\n";
	return body;
}

function performNotify(settings,cb){
	var oldhashes=collectLastHashes();
	refreshURLs(function(){
		var newhashes=collectLastHashes();
		var diffs=[]; // [{url, oldhash, newhash}]
		for(url in newhashes){
			if(newhashes[url]==oldhashes[url])continue;
			diffs.push({
				url: url,
				oldhash: oldhashes[url],
				newhash: newhashes[url]
			});
		}
		sendMail(settings.to,constructMailBody(settings.to,diffs),cb);
	});
}

function performCleanup(){
	//keep only the last hash and the last different hash intact
	//(if there is no different hash, delete everything but the last)
	for(url in urls){
		if(urls[url].timeline.length<=2)continue;
		var i,lasthash,prevhash=null,prevhashidx=-1,tllen;
		tllen=urls[url].timeline.length;
		lasthash=urls[url].timeline[tllen-1][1];
		for(i=tllen-2;i>=0;i--){
			if(urls[url].timeline[i][1]!=lasthash){
				prevhash=urls[url].timeline[i][1];
				prevhashidx=i;
				break;
			}
		}
		if(prevhash==null){
			urls[url].timeline.splice(0,tllen-1);
		} else {
			urls[url].timeline.splice(prevhashidx+1,tllen-prevhashidx-2);
			urls[url].timeline.splice(0,prevhashidx);
		}
	}
}


module.exports=function(app,io,_moddir){
	moddir=_moddir;
	app.all(["/changes","/changes/*"],cmn.authgen());
	app.get("/changes",function(req,res){
		res.sendFile(moddir+"/changes.html");
	});
	app.get("/changes/urls",function(req,res){
		var list=[];
		var url;
		for(url in urls)list.push(url);
		res.json(list);
	});
	app.get("/changes/url",function(req,res){
		var url=req.query.url;
		if(!urls[url]){
			res.status(404);
			res.send("URL not found in watch list");
			return;
		}
		res.json(urls[url]);
	});
	app.post("/changes/url",function(req,res){
		var url=req.body;
		urls[url]=new URLobject(url);
		persist.setItemSync("urls",urls);
		// refreshURLs();
		res.send();
	});
	app.delete("/changes/url",function(req,res){
		var url=req.body;
		if(!urls[url]){
			res.status(404);
			res.send("URL not found in watch list");
			return;
		}
		delete urls[url];
		persist.setItemSync("urls",urls);
		res.send();
	});
	app.delete("/changes/url/history",function(req,res){
		var param;
		try {param=JSON.parse(req.body);}
		catch(e){
			res.status(400);
			res.send("Invalid JSON sent");
		}
		var url=param.url;
		var todate=new Date(param.todate);
		if(!urls[url]){
			res.status(404);
			res.send("URL not found in watch list");
			return;
		}
		if(todate.getTime()==NaN){
			res.status(400);
			res.send("Invalid time sent");
		}
		var tl=urls[url].timeline;
		var i;
		for(i=0;i<tl.length;i++){
			if(tl[i][0]<=todate){
				tl.splice(i,1);
				i--;
			}
		}
		persist.setItemSync("urls",urls);
		res.status(200);
		res.send();
	});
	app.post("/changes/refresh",function(req,res){
		refreshURLs();
		res.send();
	});
};