const SHEET_USERS = 'Users';
const SHEET_EXAMS = 'Exams';
const SHEET_QUESTIONS = 'Questions';
const SHEET_RESULTS = 'Results';

function setupAwal() {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const sheetsInfo = [
    { name: SHEET_USERS, headers: ['id', 'username', 'password', 'role'] },
    { name: SHEET_EXAMS, headers: ['id', 'title', 'status'] },
    { name: SHEET_QUESTIONS, headers: ['id', 'exam_id', 'text', 'opt_a', 'opt_b', 'opt_c', 'opt_d', 'answer', 'image_url'] },
    { name: SHEET_RESULTS, headers: ['id', 'exam_id', 'student', 'score', 'is_cheated', 'timestamp'] }
  ];

  sheetsInfo.forEach(info => {
    let sheet = ss.getSheetByName(info.name);
    if (!sheet) {
      sheet = ss.insertSheet(info.name);
      sheet.appendRow(info.headers);
      sheet.getRange("A1:Z1").setFontWeight("bold").setBackground("#f3f4f6");
      sheet.setFrozenRows(1);
    }
  });

  // Inject Dummy Data if Users sheet is empty (only header exists)
  const userSheet = ss.getSheetByName(SHEET_USERS);
  if (userSheet.getLastRow() === 1) {
    userSheet.appendRow(['u1', 'admin', '123', 'admin']);
    userSheet.appendRow(['u2', 'user', '123', 'student']);
  }
  
  return "Setup Berhasil! Silakan deploy sebagai Web App.";
}

function doPost(e) {
  const lock = LockService.getScriptLock();
  try {
    lock.waitLock(10000);
    const action = e.parameter.action;
    
    if (action === 'login') return handleLogin(e.parameter);
    if (action === 'save_exam_full') return handleSaveExamFull(e.parameter);
    if (action === 'submit_result') return handleSubmitResult(e.parameter);
    if (action === 'upload_image') return handleUploadImage(e.parameter);
    
    return ContentService.createTextOutput(JSON.stringify({status: 'error', message: 'Unknown action'})).setMimeType(ContentService.MimeType.JSON);
    
  } catch (err) {
    return ContentService.createTextOutput(JSON.stringify({status: 'error', message: err.message})).setMimeType(ContentService.MimeType.JSON);
  } finally {
    lock.releaseLock();
  }
}

// Untuk menghindari error OPTIONS/CORS preflight
function doGet(e) {
  return ContentService.createTextOutput("Examify Backend Active").setMimeType(ContentService.MimeType.TEXT);
}

function handleLogin(p) {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  
  // Validate User
  const users = ss.getSheetByName(SHEET_USERS).getDataRange().getValues();
  let user = null;
  for (let i = 1; i < users.length; i++) {
    if (String(users[i][1]) === String(p.username) && String(users[i][2]) === String(p.password)) {
      user = { id: users[i][0], username: users[i][1], role: users[i][3] };
      break;
    }
  }
  
  if (!user) return createJSONResponse({status: 'error', message: 'Username / Password salah!'});

  // Fetch all related data in one go to avoid multiple roundtrips
  const exams = getSheetDataAsObjects(ss.getSheetByName(SHEET_EXAMS));
  const questions = getSheetDataAsObjects(ss.getSheetByName(SHEET_QUESTIONS));
  const results = getSheetDataAsObjects(ss.getSheetByName(SHEET_RESULTS));

  return createJSONResponse({
    status: 'success',
    user: user,
    exams: exams,
    questions: questions,
    results: results
  });
}

function handleSaveExamFull(p) {
  const ss = SpreadsheetApp.getActiveSpreadsheet();
  const examSheet = ss.getSheetByName(SHEET_EXAMS);
  const qSheet = ss.getSheetByName(SHEET_QUESTIONS);
  
  // 1. Upsert Exam
  const exams = examSheet.getDataRange().getValues();
  let examFoundIndex = -1;
  for(let i = 1; i < exams.length; i++) {
    if(exams[i][0] === p.exam_id) { examFoundIndex = i + 1; break; }
  }
  
  if(examFoundIndex > 0) {
    examSheet.getRange(examFoundIndex, 2).setValue(p.title);
  } else {
    examSheet.appendRow([p.exam_id, p.title, 'active']);
  }
  
  // 2. Overwrite Questions for this exam (Delete old, insert new)
  // Delete old
  const qData = qSheet.getDataRange().getValues();
  for(let i = qData.length - 1; i >= 1; i--) {
    if(qData[i][1] === p.exam_id) qSheet.deleteRow(i + 1);
  }
  
  // Insert new
  const newQs = JSON.parse(p.questions);
  if(newQs.length > 0) {
    const rowsToInsert = newQs.map(q => [q.id, q.exam_id, q.text, q.opt_a, q.opt_b, q.opt_c, q.opt_d, q.answer, q.image_url || '']);
    // Batch insert for performance
    qSheet.getRange(qSheet.getLastRow() + 1, 1, rowsToInsert.length, 9).setValues(rowsToInsert);
  }
  
  return createJSONResponse({status: 'success'});
}

function handleSubmitResult(p) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(SHEET_RESULTS);
  const isCheated = p.is_cheated === 'true' || p.is_cheated === true;
  sheet.appendRow([
    p.id, 
    p.exam_id, 
    p.student, 
    Number(p.score), 
    isCheated, 
    new Date().toISOString()
  ]);
  
  return createJSONResponse({status: 'success'});
}

function getSheetDataAsObjects(sheet) {
  if (sheet.getLastRow() <= 1) return [];
  const data = sheet.getDataRange().getValues();
  const headers = data[0];
  const result = [];
  
  for (let i = 1; i < data.length; i++) {
    const obj = {};
    for (let j = 0; j < headers.length; j++) {
      obj[headers[j]] = data[i][j];
    }
    result.push(obj);
  }
  return result;
}

function createJSONResponse(data) {
  return ContentService.createTextOutput(JSON.stringify(data)).setMimeType(ContentService.MimeType.JSON);
}

/* PLACEHOLDER: FUNGSI CRUD BARU */

function handleUploadImage(p) {
  try {
    const base64Data = p.base64.split(',')[1];
    const blob = Utilities.newBlob(Utilities.base64Decode(base64Data), p.mimeType || 'image/jpeg', p.filename || ('img_' + Date.now() + '.jpg'));
    
    const folderName = 'Examify_Uploads';
    let folders = DriveApp.getFoldersByName(folderName);
    let folder = folders.hasNext() ? folders.next() : DriveApp.createFolder(folderName);
    
    const file = folder.createFile(blob);
    file.setSharing(DriveApp.Access.ANYONE_WITH_LINK, DriveApp.Permission.VIEW);
    
    const fileId = file.getId();
    const fileUrl = `https://drive.google.com/uc?export=view&id=${fileId}`; // Direct view link
    
    return createJSONResponse({status: 'success', url: fileUrl});
  } catch (err) {
    return createJSONResponse({status: 'error', message: err.message});
  }
}