const webhookUrl = "https://hooks.slack.com/services/<>/<>/<>";
function postToSlack(message) {

 let payload = {
   "channel":    "#int_general",
   "username":   "Annual Leave Calendar Bot",
   "text":       message
 }

 let options = {
   "method":         "post",
   "contentType":    "application/json",
   "payload":        JSON.stringify(payload)
 };

 console.log(JSON.stringify(payload));
 return UrlFetchApp.fetch(webhookUrl, options)
}

function checkToday(){
 postToSlack("Testing checkToday function...");
}

function checkWeek(){
 postToSlack("Testing checkWeek function...");
}

// CONSTS & VARIABLES //
const startingCellIndex = 3; // we start at A5
let currSheet = undefined;
let currDay = undefined;
let currDayCell = undefined;
const weekDayList = ['Sunday', 'Monday', 'Tuesday', 'Wednesday', 'Thursday', 'Friday', 'Saturday'];

function onOpen() {
 loadSheet();
}

function loadSheet(){
 // We want to get the list of all tabs in the sheet and focus on the newest sheet //
 // this will be the current year //
 let allTabs = SpreadsheetApp.getActiveSpreadsheet().getSheets();
 let yearsList = [];
 for(let i = 0; i < allTabs.length; i++){
   let sheetData = allTabs[i];
   if(hasNumber(sheetData.getSheetName())){
     let year = parseInt(sheetData.getSheetName().split(' ')[0]);
     yearsList.push({
       sheet:  sheetData,
       year:   year
     });
   }
 }

 yearsList = yearsList.sort((a, b) => b.year - a.year);
 let currYear = yearsList[0];
 console.log(`Current Year [${currYear.year}] - ID: ${currYear.sheet.getSheetId()}`);
 currSheet = SpreadsheetApp.getActiveSpreadsheet().setActiveSheet(currYear.sheet);
 // Now we want to focus on the current date //
 currDay = getCurrentDayInYear();
 currDayCell = "A"+(startingCellIndex+currDay);
 console.log(`Current Day's Cell [${currDayCell}]`);
 let currCell = currSheet.getRange(currDayCell);
 SpreadsheetApp.getActiveSpreadsheet().setCurrentCell(currCell);
}

function hasNumber(myString) {
 return /\d/.test(myString);
}

function getCurrentDayInYear(){
 var now = new Date();
 var start = new Date(now.getFullYear(), 0, 0);
 var diff = now - start;
 var oneDay = 1000 * 60 * 60 * 24;
 var day = Math.floor(diff / oneDay);
 return day;
}

function checkToday(){
 if(!currSheet){
   loadSheet();
 }

 const todayRowIndex = (getCurrentDayInYear()+startingCellIndex);
 const valuesForDay = getValuesForDay(todayRowIndex);
 const dayName = weekDayList[new Date(Date.now()).getDay()];
 if(dayName === "Saturday" || dayName === "Sunday"){
   return;
 }

 const dayReport = {
   [dayName]:  valuesForDay
 }
 console.log(dayReport);
}

////////// SPREADSHEET FUNCTIONS //////////////

function getLeaveContext(value){
 let message = "";
 switch(value){
   case "AL":
     message += "Annual Leave (Enjoy)";
     break;
   case "Requested":
     message += "Requested - Not Approved <@manager>";
     break;
 }

 if(message.length === 0){ // << messy hack
   if(value.indexOf('OOO') > -1){
     message += "Out of the Office: "+ value.split('OOO:')[1];
   }
   else if(value !== ''){
     message += "Note: "+ value;
   }
 }

 if(message.length === 0){
   return null;
 }
 return message;}

function getNoOfEmployees(){
 const rangeString = `C3:Z3`; // If you have more than 26 employees then you have to update
 const rangeData = currSheet.getRange(rangeString).getValues();

 for(let i = 0; i < rangeData[0].length; i++){
   var name =  rangeData[0][i];
   if(name === undefined || name === ""){
     return (i+1);
   }
 }
}

function getValuesForDay(rowIndex){
 const currDayCell = "C"+(rowIndex);
 const finalCell = `${numberToEncodedLetter(getNoOfEmployees()+2)}${(rowIndex)}`;
 const rangeString = `${currDayCell}:${finalCell}`;
 const range = currSheet.getRange(rangeString);
 let summary = [];
 for(let i = 0; i < range.getValues().length; i++){
   for(let val = 0; val < range.getValues()[i].length; val++){
     const employeeIndex = `${numberToEncodedLetter(val+3)}3`;
     const employeeName =  currSheet.getRange(employeeIndex).getValues()[0][0];
     const valString = getLeaveContext(range.getValues()[i][val]);
     if(valString !== null){
       summary.push({
         name:   employeeName,
         value:  valString
       });
     }
   }
 }

 // Now we need to check if there is a bank holiday here //
 // if there is, we should set the report to one field instead of reporting "BH" for everyone //
 for(let i = 0; i < summary.length; i++){
   if(summary[i].value.indexOf("BH") > -1){
     summary = [{
       name:   "Report Bot",
       value:  "Monday is a Bank Holiday <!channel>"
     }];
     break;
   }
 }
 console.log("SUMMARY : ["+ rowIndex +"]"+JSON.stringify(summary));
 return summary;
}

function numberToEncodedLetter(number) {
   //Takes any number and converts it into a base (dictionary length) letter combo. 0 corresponds to an empty string.
   //It converts any numerical entry into a positive integer.
   if (isNaN(number)) {return undefined}
   number = Math.abs(Math.floor(number))
   const dictionary = getDictionary()
   let index = number % dictionary.length
   let quotient = number / dictionary.length
   let result
   if (number <= dictionary.length) {return numToLetter(number)}  //Number is within single digit bounds of our encoding letter alphabet
   if (quotient >= 1) {
       //This number was bigger than our dictionary, recursively perform this function until we're done
       if (index === 0) {quotient--}   //Accounts for the edge case of the last letter in the dictionary string
       result = numberToEncodedLetter(quotient)
   }
   if (index === 0) {index = dictionary.length}   //Accounts for the edge case of the final letter; avoids getting an empty string
   return result + numToLetter(index);
}
function numToLetter(number) {
       //Takes a letter between 0 and max letter length and returns the corresponding letter
       if (number > dictionary.length || number < 0) {return undefined}
       if (number === 0) {
           return ''
       } else {
           return dictionary.slice(number - 1, number)
       }
   }
}

function getDictionary() {
   return validateDictionary("ABCDEFGHIJKLMNOPQRSTUVWXYZ")
   function validateDictionary(dictionary) {
       for (let i = 0; i < dictionary.length; i++) {
           if(dictionary.indexOf(dictionary[i]) !== dictionary.lastIndexOf(dictionary[i])) {
               console.log('Error: The dictionary in use has at least one repeating symbol:', dictionary[i])
               return undefined
           }
       }
       return dictionary
   }
}

function sendReport(report){
 const reportKeys =  Object.keys(report);
 let reportString = "\n";
 if(reportKeys.length > 0){
   for(let i = 0; i < reportKeys.length; i++){
     const dayString = reportKeys[i];
     let dayPrefixString = "*"+dayString+"*";
     let dayPayloadString = '';
     if(report[dayString].length === 0){
       reportString += dayPrefixString + '\n' + " Nothing To Report " + '\n';
     }
     else{
       for(let y = 0; y < report[dayString].length; y++){
         const alData = report[dayString][y];
         dayPrefixString += '\n';
      
         const newName = alData.name.padEnd(50-alData.name.length, ' ');
         dayPrefixString += "          "+newName+alData.value;
       }
       reportString += dayPrefixString + '\n';
     }
   }
 }
 postToSlack(reportString);
}

function checkWeek(){
 if(!currSheet){
   loadSheet();
 }

 postToSlack("[Weekly Report]");
 let mondayRowIndex = getRowForMonday();
 let weekReport = {};
 for(let i = 1; i < 6; i++){
   const dayReport = getValuesForDay(mondayRowIndex+(i-1));
   const dayString = weekDayList[i];
   weekReport[dayString] = dayReport;
 }

 console.log(JSON.stringify(weekReport));
 sendReport(weekReport);
}

function getRowForMonday(){
 let currDay = getCurrentDayInYear();
 // Get next Monday //
 for(let i = 0; i < 7; i++){
   const currCell =      (currDay+startingCellIndex+i);
   const rangeString =   `B${(currDay+startingCellIndex+i)}`;
   const currWeekDay =   currSheet.getRange(rangeString).getValues()[0];
   if(currWeekDay == 'Monday'){
     currWeekStartCell = currWeekDay;
     currDay = currCell;
     break;
   }
 }

 console.log("Monday is Cell: "+currDay);
 return currDay;
}