/* Signs in the user */
router.post("/sign_in", function (req, res , next) {
  var username = req.body.username;
  var password = req.body.password;
  password = sha256(password);
  var token = "";
  //Checks if username and password match
  query.checkUsernamePassword(username, password).then(function (row) {
      if(row === undefined){
          throw "Username and password doesnt match";
      }
      return row.id;
  }).then(function (userId) {
      //Check if user is already logged in.
      return query.isUserLoggedIn(userId);
  }).then(function (rows) {
      //Signs out if user is logged in.
      if(rows[0] !== undefined){
          return query.signOut(rows[0].token);
      }
  }).then(function() {
      //Signs the user in.
      var letters = "abcdefghiklmnopqrstuvwwxyzABCDEFGHIJKLMNOPQRSTUVWXYZ1234567890";
      for (var i = 0 ; i < 36 ; ++i) {
        token += letters[Math.floor(Math.random() * letters.length)];
      }
      return query.signIn(username, token);
  }).then(function (){
      res.send(getResponseObject(true, "Success signing in", token))
  }).catch(function (error) {
      console.log(error);
      res.send(getResponseObject(false, "error signing in"));
  });
});