//
// Dependencies
//
let http = require('http');
let fs   = require('fs');

//
// Constants
//
let DATA_LOCATION     = 'data'; // both the url root and the location of data file
let DATA_LOCATION_LEN = DATA_LOCATION.length;
let DATA_FILE         = __dirname + '/' + DATA_LOCATION;
let PORT              = 1280;

//
// Load store file
//
let store = {}; // deafult empty object
let json='';
try {
    let json = fs.readFileSync(DATA_FILE);
    store = JSON.parse(json);
    console.log('Read store file');
} catch (e) { // lazy error handling
    console.log('Could not load store file.  Using empty array.');
}


//
// Flush to store file on exit
//
let flush = function()
{
    console.log('Flushing data to file [' + DATA_FILE + ']\n');
    fs.writeFileSync(DATA_FILE, JSON.stringify(store));
};

let handleInterrupt = function() { flush(); process.exit(); };

process.on('SIGINT',  handleInterrupt);
process.on('SIGTERM', handleInterrupt);
process.on('SIGHUP',  flush); // HUP flushes to file but keeps the server running


//
// If request URI is prefixed with the value of DATA_LOCATION, we treat incoming request as a REST request
// Otherwise we serve the file referenced by the URI
//
let serveFile = function(loc, req, resp) {
    let fullPath = __dirname + '/' + loc;
    console.log('Trying to serve file at [' + fullPath + ']');

    if (req.method !== 'GET') { // read only!
        resp.writeHead(405);
        resp.write('Unsupported method\n');
        resp.end();
    } else if (fs.existsSync(fullPath)) {
        resp.writeHead(200);
        fs.createReadStream(fullPath).pipe(resp);
    } else {
        resp.writeHead(404);
        resp.write('Not Found\n');
        resp.end();
    }
};

let serveRestData = function(urlPath, req, resp) {
    console.log(req.method + ' request for path [' + urlPath + ']');

    switch (req.method) {

        case 'GET':
			let exactMatch=!urlPath.endsWith('/');
			let matchFound=false;
			
			if (exactMatch) { // assumes that only a single resource has this ID.
				console.log("  - Exact Match.");
				if (store.hasOwnProperty(urlPath)) {
					resp.writeHead(200, { 'Content-Type' : 'application/json' });
					resp.write(JSON.stringify(store[urlPath]) + '\n');
					matchFound=true;
				}
			} else {
				console.log("  - All Matches.");
				let matches=[];
				Object.keys(store).forEach(theKey=>{
				if (theKey.startsWith(urlPath)){
					matches.push(store[theKey]);
					matchFound=true;
				}
				});
			
				if (matchFound) {
					resp.writeHead(200, { 'Content-Type' : 'application/json' });
					resp.write(JSON.stringify(matches));
				} 
			}
			
			if (!matchFound) {
				console.log("  - Match NOT found.");
                resp.writeHead(404, { 'Content-Type' : 'application/json' });
                resp.write('{"success":false, "error":"Not Found"}');
            } else {
				console.log("  - Match found.");
			}
            resp.end();
            break;

        case 'PUT':
		    json = '';
            req.on('data', function(chunk) { json += chunk; });
            req.on('end', function() {
                try {
                    let data = JSON.parse(json);
                    store[urlPath] = data;
                    resp.writeHead(201, { 'Content-Type' : 'application/json' });
					resp.write('{"success":true}');
                } catch (e) {
                    resp.writeHead(400, { 'Content-Type' : 'application/json' });
                    resp.write('{"success":false, "error":"Invalid JSON"}');
                }
                resp.end();
				flush();
            });
            break;
		
		
        case 'POST':
            json = '';
            req.on('data', function(chunk) { json += chunk; });
            req.on('end', function() {
                try {
                    let data = JSON.parse(json);
                    if (data.ID === undefined) {
                        resp.writeHead(400, { 'Content-Type' : 'application/json' });
                        resp.write('{"success":false, "error":"The ID Field needs to be given"}');
                    } else { 
                        // make sure the ID from the data is used as the final resource Identifier, 
                        // even if the URL has none or says different.
                        let re=new RegExp("/[^/]*$");
                        urlPath=urlPath.replace(re,"");
                        urlPath=urlPath+"/"+data.ID;
                        console.log("  - storing with resource key: [" + urlPath + "]");

                        store[urlPath] = data;

                        resp.writeHead(201, { 'Content-Type' : 'application/json' });
                        resp.write(JSON.stringify(store[urlPath]));
                    }
                } catch (e) {
                    resp.writeHead(400, { 'Content-Type' : 'application/json' });
                    resp.write('{"success":false, "error":"Invalid JSON"}');
                }
                resp.end();
				flush();
            });
            break;
			
		case 'PATCH':
            json = '';
            req.on('data', function(chunk) { json += chunk; });
            req.on('end', function() {
                try {
                    let data = JSON.parse(json);
					Object.keys(data).forEach(theKey=>{
					store[urlPath][theKey] = data[theKey]	
					});
                    
                    resp.writeHead(201, { 'Content-Type' : 'application/json' });
					resp.write('{"success":true}');
                } catch (e) {
                    resp.writeHead(400, { 'Content-Type' : 'application/json' });
                    resp.write('{"success":false, "error":"Invalid JSON"}');
                }
                resp.end();
				flush();
            });
            break;
		
			
		case 'OPTIONS':
		    resp.end();
			break;

        case 'DELETE':
            if (store.hasOwnProperty(urlPath)) {
                delete store[urlPath];
                resp.writeHead(204, { 'Content-Type' : 'application/json' });
				resp.write('{"success":true}');
            } else {
                resp.writeHead(404, { 'Content-Type' : 'application/json' });
				resp.write('{"success":false, "error":"Not Found"}');
            }
            resp.end();
			flush();
            break;

        default:
            resp.writeHead(405, { 'Content-Type' : 'application/json' });
			resp.write('{"success":false, "error":"Unsupported method"}');
            resp.end();
    }

};

//
// Listen for connections
//
http.createServer(function(req, resp) {
	// CORS headers
	resp.setHeader('Access-Control-Allow-Origin', '*'); 
	resp.setHeader('Access-Control-Allow-Headers', 'X-Request-With, content-type'); 
	resp.setHeader('Vary', 'Origin');
	
	resp.setHeader('Access-Control-Allow-Methods','GET, PATCH, POST, PUT, DELETE, OPTIONS');
	
	console.log('Serving [' + req.url + ']');
   
    if (req.url  === '/') { // server index file
        serveFile('index.html', req, resp);
	} else { // rest request
        serveRestData(req.url, req, resp);
    }

}).listen(PORT);