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

//
// Constants
//
let DATA_LOCATION = "dataDir/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);