var ss = SpreadsheetApp.getActiveSpreadsheet();
var Date,Systolic,Diastolic,history,user,msg,sheet;

function doGet(e){
if (e.parameter.history == "DisplayData") {
    return ReadSheetData(e);
}}

function doPost(e) {
  addUser(e, sheet);
  msg = " ";
  if (e.parameter.action == 'register') {
    user = e.parameter.user;
    if (ss.getSheetByName(user) == null) {
      sheet = ss.insertSheet(user);
      sheet.appendRow(["Date", "Systolic", "Diastolic"]);
      msg = "New User Added";
    } else {
      msg = "User already exists";
    }
  }

  else if(e.parameter.action == 'login') {
    user = e.parameter.user;
    sheet = ss.getSheetByName(user);
      if (sheet != null){
        msg = "Sheet accessed";
    } else {
      msg = "User not found";
    }
  }
  
  addUser(e, user);
  
  return ContentService.createTextOutput(msg);
}

function addUser(e,user) {
  sheet = ss.getSheetByName(user);
  if (sheet) {
    Date = e.parameter.Date;
    Systolic = e.parameter.Systolic;
    Diastolic = e.parameter.Diastolic;
    sheet.appendRow([Date, Systolic, Diastolic]);
  } 
  else {
    Logger.log("Sheet not found for user: " + user);}
}


function ReadSheetData() {
  sheet = ss.getSheetByName(user);
  var lastRow = sheet.getLastRow();
  var valueRange = sheet.getRange(lastRow, 2, 1, 3).getValues()[0]; //start row, start column, end row, end column

  var outData = [];
    Date = valueRange[0];
    Systolic = valueRange[1];
    Diastolic = valueRange[2];
    outData.push([Date.toDateString(),Systolic,Diastolic]);

  var outString = ContentService.createTextOutput(JSON.stringify(outData));
  Logger.log(outData);
  return outString;
}