#!/usr/bin/env node
const firebase_app=require("firebase-admin/app")
const firebase_messaging=require("firebase-admin/messaging")
const util=require("util");

// Potential TODO's:
// - Use collapseKey to collect notifications for particular rooms
//   - But note that you cannot have more than 4 collapseKeys at a time;
//     correctly managing this requires synchronisation between app and server
//     of exactly what keys have disappeared in the meantime

firebase_app.initializeApp({
	credential:firebase_app.cert(require("./firebaseServiceAccountKey.json")),
	databaseURL:"https://tomsg-83196.firebaseio.com",
});

const fieldConverters=new Map([
	["token",(b)=>b.toString()],
	["user",(b)=>b.toString()],
	["to_user",(b)=>b.toString()],
	["room",(b)=>b.toString()],
	["message",(b)=>b.toString()],
	["timestamp",(b)=>b.toString()],  // Nanosecond timestamps are too close to 52-bit range
	["online",(b)=>parseInt(b.toString(),10)],
]);

function typeConvertFields(fields){
	for(const key of fields.keys()){
		const conv=fieldConverters.get(key);
		if(conv!=undefined)fields.set(key,conv(fields.get(key)));
	}
}

function readFields(buffer){
	const fields=new Map();
	if(buffer.length==0)return fields;
	let cursor=0;
	while(true){
		let idx=buffer.indexOf(32,cursor);
		if(idx==-1){
			console.error("ERR: Incomplete field in input line");
			return null;
		}
		const key=String(buffer.slice(cursor,idx));
		cursor=idx+1;

		idx=buffer.indexOf(32,cursor);
		if(idx==-1){
			console.error("ERR: Incomplete field in input line");
			return null;
		}
		const arglen=parseInt(String(buffer.slice(cursor,idx)),10);
		if(arglen<0||arglen==null||isNaN(arglen)){
			console.error("ERR: Invalid length in input line");
			return null;
		}
		cursor=idx+1;

		if(cursor+arglen>buffer.length){
			console.error("ERR: Length larger than remaining line in input line");
			return null;
		}
		const arg=buffer.slice(cursor,cursor+arglen);
		cursor+=arglen;

		fields.set(key,arg);

		if(cursor==buffer.length)break;
		if(buffer[cursor]!=32){
			console.error("ERR: No space after argument in input line");
			return null;
		}
		cursor++;
	}
	return fields;
}

function processMessage(type,fields){
	switch(type){
		case "message":
			const user=fields.get("user");
			const to_user=fields.get("to_user");
			const room=fields.get("room");
			const message=fields.get("message");
			const token=fields.get("token");
			const payload={
				notification: {
					title: room + " (" + user + ")",
					body: message,
				},
				data: {
					user: user,
					room: room,
					message: message,
				}
			};
			const options={
				collapseKey: "tomsg-collapseKey",
			};
			firebase_messaging.getMessaging().sendToDevice(token,payload,options)
				.then((response)=>{
					const result=response.results[0];
					const realToken=result.canonicalRegistrationToken;
					if(result.error){
						console.error("JS: Send error:",result.error.errorInfo);
						console.log("delete_token "+to_user+" "+token);
					} else if(realToken&&realToken!=token){
						console.log("delete_token "+to_user+" "+token);
						console.log("add_token "+to_user+" "+realToken);
					}
				})
				.catch((err)=>{
					console.error("JS: Early send error:",err);
				});
			break;

		default:
			console.error("JS: Unknown type '"+type+"'");
	}
}

function handleInputLine(buffer){
	let idx=buffer.indexOf(32);
	if(idx==-1){
		console.error("ERR: No space in input line");
		return;
	}
	const type=String(buffer.slice(0,idx));
	const fields=readFields(buffer.slice(idx+1));
	if(fields==null)return;
	typeConvertFields(fields);
	processMessage(type,fields);
}


{
	let buffer=null;
	process.stdin.on("data",(data)=>{
		const prevlen=buffer==null?0:buffer.length;
		if(buffer)buffer=Buffer.concat([buffer,data]);
		else buffer=data;
		let cursor=0;
		let lfidx=buffer.indexOf(10,prevlen);
		while(lfidx!=-1){
			handleInputLine(buffer.slice(cursor,lfidx));
			cursor=lfidx+1;
			lfidx=buffer.indexOf(10,cursor);
		}
		if(cursor>=buffer.length)buffer=null;
		else buffer=Buffer.from(buffer.slice(cursor));
	});
}

console.error("Firebase js plugin loaded!");