/**
 * TEDxAASTMT application backend (Google Apps Script web app).
 *
 * The page POSTs the application here. We validate it, then append a row to the
 * spreadsheet for the branch the applicant chose (Alamein, Miami or Abuqir).
 * An optional work sample is saved to Google Drive and linked in the sheet.
 */

// ---------- CONFIG ----------
const SHEETS = {
  "Alamein": "1akQXU98v39i0i7rTgvcOStWkcI8gnuRH0JgvxXCUucA",
  "Miami":   "1i9xS-8sOzl8yzgExdpwkr6-jZZWo5yb3MU2ag3FtNeE",
  "Abuqir":  "1HexEQkJD8QZk8LTvG2NdYym0Ynut6zTpMJEHik6sw_k"
};

const TEAMS = ["Coaches", "Operations", "Public Relations", "Media & Marketing", "Human Resources"];
const ALLOWED_EXT = ["pdf", "png", "jpg", "jpeg", "webp", "gif", "doc", "docx", "ppt", "pptx", "mp4", "zip"];
const MAX_FILE_BYTES = 10 * 1024 * 1024;
const UPLOAD_FOLDER = "TEDxAASTMT Applications";
const TIMEZONE = "Africa/Cairo";

const HEADERS = [
  "Timestamp", "Name", "Email", "Registration number", "Phone",
  "College / Major", "Team", "Why do you want to join?", "Work sample"
];

// ---------- ENTRY POINTS ----------
function doGet() {
  return json_({ ok: true, message: "TEDxAASTMT applications endpoint is running." });
}

function doPost(e) {
  const lock = LockService.getScriptLock();
  let locked = false;
  try {
    let data;
    try {
      data = JSON.parse(e.postData.contents);
    } catch (parseErr) {
      return json_({ ok: false, message: "Invalid request." });
    }

    const clean = validate_(data);
    if (clean.error) return json_({ ok: false, message: clean.error });

    lock.waitLock(20000);
    locked = true;

    const sheet = SpreadsheetApp.openById(SHEETS[clean.branch]).getSheets()[0];
    ensureHeader_(sheet);

    if (isDuplicate_(sheet, clean)) {
      return json_({
        ok: false,
        message: "You've already applied to " + clean.team + " at " + clean.branch + " with this registration number."
      });
    }

    let sampleLink = "";
    if (data.sample && data.sample.data) {
      const saved = saveSample_(data.sample, clean);
      if (saved.error) return json_({ ok: false, message: saved.error });
      sampleLink = saved.url;
    }

    sheet.appendRow([
      Utilities.formatDate(new Date(), TIMEZONE, "yyyy-MM-dd HH:mm:ss"),
      safe_(clean.name),
      safe_(clean.email),
      clean.regno,
      clean.phone,
      safe_(clean.college),
      clean.team,
      safe_(clean.why),
      sampleLink
    ]);

    return json_({ ok: true });
  } catch (err) {
    console.error(err);
    return json_({ ok: false, message: "Something went wrong on our side. Please try again." });
  } finally {
    if (locked) lock.releaseLock();
  }
}

// ---------- VALIDATION (mirrors the page, never trust the browser) ----------
function validate_(d) {
  if (!d || typeof d !== "object") return { error: "Invalid request." };

  const s = (v, max) => String(v == null ? "" : v).trim().slice(0, max);
  const out = {
    name: s(d.name, 80),
    email: s(d.email, 120).toLowerCase(),
    regno: s(d.registration_number, 9),
    phone: s(d.phone, 20),
    college: s(d.college, 100),
    team: s(d.team, 40),
    branch: s(d.branch, 20),
    why: s(d.why, 2000)
  };

  if (out.name.length < 3 || /\d/.test(out.name)) return { error: "Please enter a valid full name." };
  if (!/^[^\s@]+@[^\s@]+\.[^\s@]{2,}$/.test(out.email)) return { error: "Please enter a valid email address." };
  if (!/^\d{9}$/.test(out.regno)) return { error: "Registration number must be exactly 9 digits." };
  const phoneDigits = out.phone.replace(/\D/g, "");
  if (phoneDigits.length < 8 || phoneDigits.length > 15) return { error: "Please enter a valid phone number." };
  if (out.college.length < 2) return { error: "Please enter your college or major." };
  if (TEAMS.indexOf(out.team) === -1) return { error: "Please choose a valid team." };
  if (!SHEETS.hasOwnProperty(out.branch)) return { error: "Please choose a valid branch." };
  if (out.why.length < 20) return { error: "Please write at least 20 characters about why you want to join." };
  return out;
}

// ---------- SHEET HELPERS ----------
function ensureHeader_(sheet) {
  if (sheet.getLastRow() === 0) {
    sheet.appendRow(HEADERS);
    sheet.getRange(1, 1, 1, HEADERS.length)
      .setFontWeight("bold")
      .setBackground("#EB0028")
      .setFontColor("#ffffff");
    sheet.setFrozenRows(1);
    // Keep registration number and phone as text so leading zeros / "+" survive.
    sheet.getRange("D:E").setNumberFormat("@");
    sheet.setColumnWidths(1, HEADERS.length, 160);
    sheet.setColumnWidth(8, 420);
  }
}

function isDuplicate_(sheet, clean) {
  const last = sheet.getLastRow();
  if (last < 2) return false;
  const rows = sheet.getRange(2, 4, last - 1, 4).getValues(); // columns D..G
  for (let i = 0; i < rows.length; i++) {
    if (String(rows[i][0]).trim() === clean.regno && String(rows[i][3]).trim() === clean.team) return true;
  }
  return false;
}

// Stops values like =IMPORTXML(...) from being run as formulas in the sheet.
function safe_(v) {
  const t = String(v);
  return /^[=+\-@]/.test(t) ? "'" + t : t;
}

// ---------- FILE UPLOAD ----------
function saveSample_(sample, clean) {
  const original = String(sample.name || "sample").slice(0, 120);
  const ext = original.indexOf(".") > -1 ? original.split(".").pop().toLowerCase() : "";
  if (ALLOWED_EXT.indexOf(ext) === -1) return { error: "That file type isn't supported." };

  const bytes = Utilities.base64Decode(String(sample.data));
  if (bytes.length > MAX_FILE_BYTES) return { error: "The file is too large. Please keep it under 10 MB." };

  const safeName = original.replace(/[^\w.\- ]/g, "_");
  const fileName = clean.regno + "_" + clean.team.replace(/[^\w]/g, "") + "_" + safeName;
  const blob = Utilities.newBlob(bytes, sample.type || "application/octet-stream", fileName);

  const file = getBranchFolder_(clean.branch).createFile(blob);
  return { url: file.getUrl() };
}

function getBranchFolder_(branch) {
  const root = getOrCreateFolder_(DriveApp.getRootFolder(), UPLOAD_FOLDER);
  return getOrCreateFolder_(root, branch);
}

function getOrCreateFolder_(parent, name) {
  const it = parent.getFoldersByName(name);
  return it.hasNext() ? it.next() : parent.createFolder(name);
}

// ---------- RESPONSE ----------
function json_(obj) {
  return ContentService.createTextOutput(JSON.stringify(obj)).setMimeType(ContentService.MimeType.JSON);
}

// ---------- ONE-TIME HELPERS (run from the editor) ----------
// Run this once so Google asks you to approve access to Sheets and Drive.
function authorize() {
  Object.keys(SHEETS).forEach(function (branch) {
    console.log(branch + ": " + SpreadsheetApp.openById(SHEETS[branch]).getName());
  });
  console.log("Drive folder: " + getOrCreateFolder_(DriveApp.getRootFolder(), UPLOAD_FOLDER).getUrl());
}

// Optional: sends a fake application to the Alamein sheet so you can test.
function testSubmit() {
  const result = doPost({
    postData: {
      contents: JSON.stringify({
        name: "Test Applicant",
        email: "test@example.com",
        registration_number: "123456789",
        phone: "+201000000000",
        college: "Computer Engineering",
        team: "Coaches",
        branch: "Alamein",
        why: "This is a test application to check the sheet connection.",
        sample: null
      })
    }
  });
  console.log(result.getContent());
}