Deployment Steps

1. Open Google Apps Script: Go to your Google Sheet: Tire Management Sheet. Click on Extensions > Apps Script. This will open the Apps Script editor.
2. Add the Code: If there is any existing code in the Code.gs file, delete it. Copy the entire content from the code block below and paste it into the editor. Save the project (File > Save, or Ctrl+S/Cmd+S).
3. Deploy as a Web App: Click the Deploy button in the top-right corner and select New deployment. Click the gear icon next to "Select type" and choose Web app.
4. Configure Deployment:
   • Description: Tire Management API (or something similar).
   • Execute as: Me (your Google account).
   • Who has access: Anyone (This is crucial for JSONP to work from the web app).
   Click Deploy.
5. Authorize Permissions: Google will ask for authorization. Click Review permissions. Choose your Google account. You may see a warning screen. Click Advanced, then click Go to [Your Project Name] (unsafe). Click Allow to grant the necessary permissions.
6. Get the URL: After deployment, you will get a Web app URL. Important: The URL in this application's code is already set to the one you provided. If you create a brand new script project and get a different URL, you would need to update the APP_SCRIPT_URL constant at the top of the script in this file. If you are re-deploying to the same script project, the URL should remain the same.
7. Redeploying Changes: If you ever change the script, you must create a new deployment version. Click Deploy > Manage deployments, select your deployment, click the pencil icon (Edit), choose New version, and click Deploy.

Code.gs (Copy this code)

var sheetId = "1VrRsDBy4-9qYxP2xeNrFBdLc6CnXV8qKPh95rtXGMJQ";
var sheetName = "TireData";

// Helper function to get or create the sheet
function getSheet() {
  var spreadsheet = SpreadsheetApp.openById(sheetId);
  var sheet = spreadsheet.getSheetByName(sheetName);
  if (!sheet) {
    sheet = spreadsheet.insertSheet(sheetName);
    var initialHeaders = [
      "timestamp", "vehicleId", "fleet", "checkDate", "checkMileage", "technicianNotes",
      "FL_brand", "FL_size", "FL_serial", "FL_installDate", "FL_installMileage", "FL_tread_g1", "FL_tread_g2", "FL_tread_g3", "FL_pressure_std", "FL_pressure_act", "FL_photo",
      "FR_brand", "FR_size", "FR_serial", "FR_installDate", "FR_installMileage", "FR_tread_g1", "FR_tread_g2", "FR_tread_g3", "FR_pressure_std", "FR_pressure_act", "FR_photo",
      "RL_brand", "RL_size", "RL_serial", "RL_installDate", "RL_installMileage", "RL_tread_g1", "RL_tread_g2", "RL_tread_g3", "RL_pressure_std", "RL_pressure_act", "RL_photo",
      "RR_brand", "RR_size", "RR_serial", "RR_installDate", "RR_installMileage", "RR_tread_g1", "RR_tread_g2", "RR_tread_g3", "RR_pressure_std", "RR_pressure_act", "RR_photo"
    ];
    sheet.appendRow(initialHeaders);
  }
  return sheet;
}

function doGet(e) {
  // This check prevents errors when the script is run directly from the editor
  // or when the URL is visited without parameters.
  if (!e || !e.parameter || !e.parameter.action) {
    return HtmlService.createHtmlOutput(
      "
Tire Management System Backend
" +
      "
This script is running correctly. It is the backend for the Tire Management web application.
" +
      "
It should not be run directly from the Apps Script editor. Please access the web application to use it.
" +
      "
If you are setting this up for the first time, please follow the deployment instructions provided in the web app's HTML file.
"
    );
  }
  
  var callback = e.parameter.callback;
  var action = e.parameter.action;
  var response;

  try {
    if (action == "write") {
      response = writeData(e);
    } else if (action == "read") {
      response = readData();
    } else {
      response = { status: "error", message: "Invalid action specified." };
    }
  } catch (error) {
    // Log the full error for debugging
    Logger.log("Error in doGet: " + error.toString() + "\nStack: " + error.stack);
    response = { status: "error", message: "An error occurred: " + error.message, details: error.stack };
  }

  // Return as JSONP
  var jsonResponse = JSON.stringify(response);
  if (callback) {
    return ContentService.createTextOutput(callback + "(" + jsonResponse + ")").setMimeType(ContentService.MimeType.JAVASCRIPT);
  } else {
    return ContentService.createTextOutput(jsonResponse).setMimeType(ContentService.MimeType.JSON);
  }
}

function writeData(e) {
  var sheet = getSheet(); // Use the helper to ensure sheet exists
  var headers = sheet.getRange(1, 1, 1, sheet.getLastColumn()).getValues()[0];

  var newRow = headers.map(function(header) {
    if (header === "timestamp") {
      return new Date();
    }
    return e.parameter[header] || ""; // Default to empty string if param is missing
  });

  sheet.appendRow(newRow);
  
  return { status: "success", message: "Data saved successfully." };
}

function readData() {
  var sheet = getSheet(); // Use the helper to ensure sheet exists
  var range = sheet.getDataRange();
  var values = range.getValues();

  if (values.length < 2) {
    return { status: "success", data: [] }; // No data rows
  }

  var headers = values[0];
  var data = [];

  for (var i = 1; i < values.length; i++) {
    var rowObject = {};
    for (var j = 0; j < headers.length; j++) {
      var header = headers[j];
      var value = values[i][j];
      // Format dates nicely
      if (value instanceof Date) {
        if (header.toLowerCase().includes('date')) {
           rowObject[header] = value.toISOString().split('T')[0];
        } else {
           rowObject[header] = value.toISOString();
        }
      } else {
         rowObject[header] = value;
      }
    }
    data.push(rowObject);
  }

  return { status: "success", data: data };
}