/** @OnlyCurrentDoc */

/**
 * Guest confirmations: emails everyone who fills in your Squarespace
 * form a copy of their answers. Setup guide:
 * https://pengon.dev/blog/squarespace-form-confirmation-email/
 * Change SENDER_NAME and REPLY_TO below and save. Then reload the
 * sheet and click Guest confirmations > Turn on.
 */

var CONFIG = {
  // Shown as the sender's name. The email itself comes from the Gmail
  // account that turns this on.
  SENDER_NAME: 'Your business name',
  // Where guests' replies go: usually your own address.
  REPLY_TO: 'you@example.com',
  SUBJECT: 'Thanks! Here is a copy of your answers',
  INTRO: "Thanks, we've received your submission. Here is a copy of your answers:",
  OUTRO: 'If anything needs changing, just reply to this email.',
  // How often to look for new submissions: 1, 5, 10, 15 or 30 minutes.
  CHECK_EVERY_MINUTES: 5,
  DAILY_LIMIT: 50,
  ONE_PER_EMAIL_HOURS: 24,
  SKIP_IF_LINKS: true,
  // Column headers to leave out of the email, e.g. ['Submitted On'].
  HIDE_COLUMNS: [],
};

var LOG_SHEET_NAME = 'Confirmations sent';
var LOG_HEADERS = ['Logged at', 'Row key', 'Guest email', 'Status'];
// A burst of "new" rows (a pasted import, say) is handled a few at a time.
var MAX_PER_RUN = 20;
var EMAIL_RE = /^[^\s@<>()",;]+@[^\s@<>()",;]+\.[a-z]{2,}$/i;
var LINK_RE = /https?:\/\/|www\.|\b(?:bit\.ly|t\.me|tinyurl\.com|goo\.gl)\//i;
var HOUR_MS = 60 * 60 * 1000;

// -- Menu actions ------------------------------------------------------

function onOpen() {
  SpreadsheetApp.getUi()
    .createMenu('Guest confirmations')
    .addItem('Turn on', 'turnOn')
    .addItem('Send me a test email', 'sendTestEmail')
    .addItem('Turn off', 'turnOff')
    .addToUi();
}

function turnOn() {
  checkConfig_();
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var log = logSheet_(ss);
  var data = readSubmissions_(ss);
  var known = readLog_(log).keys;
  var now = new Date();

  // Everything already in the sheet predates this switch: mark it done.
  var entries = [];
  data.rows.forEach(function (row) {
    var key = rowKey_(row);
    if (!key || known[key]) return;
    known[key] = true;
    entries.push([now, key, findEmail_(data.headers, row), 'existing before turn-on, not emailed']);
  });
  appendLogRows_(log, entries);

  removeTriggers_();
  ScriptApp.newTrigger('processNewSubmissions')
    .timeBased()
    .everyMinutes(CONFIG.CHECK_EVERY_MINUTES)
    .create();

  notify_(
    'Guest confirmations are on',
    'New submissions get a copy within ' + CONFIG.CHECK_EVERY_MINUTES + ' minutes. ' +
      entries.length + ' earlier submission(s) were marked as done and will not be emailed.'
  );
}

function turnOff() {
  removeTriggers_();
  notify_('Guest confirmations are off', 'No more copies will be sent until you turn it on again.');
}

/** Emails YOU (REPLY_TO) what the latest guest would get, so you can check the wording. */
function sendTestEmail() {
  checkConfig_();
  var ss = SpreadsheetApp.getActiveSpreadsheet();
  var data = readSubmissions_(ss);
  if (!data.rows.length) {
    notify_('Nothing to preview yet', 'Submit your form once, then try again.');
    return;
  }
  var latest = data.rows[data.rows.length - 1];
  sendCopy_(CONFIG.REPLY_TO, data.headers, latest, ss.getSpreadsheetTimeZone(), '[Test] ');
  notify_('Test email sent', 'Check ' + CONFIG.REPLY_TO + '. It shows the latest submission.');
}

// -- The trigger -------------------------------------------------------

/** Runs every CHECK_EVERY_MINUTES: emails guests whose rows are new. */
function processNewSubmissions() {
  var lock = LockService.getScriptLock();
  if (!lock.tryLock(10000)) return; // a previous run is still going
  try {
    var ss = SpreadsheetApp.getActiveSpreadsheet();
    var log = logSheet_(ss);
    var data = readSubmissions_(ss);
    var history = readLog_(log);
    var tz = ss.getSpreadsheetTimeZone();
    var now = new Date();
    var sentToday = history.sentTimes.filter(function (t) {
      return t > now.getTime() - 24 * HOUR_MS;
    }).length;

    var entries = [];
    for (var i = 0; i < data.rows.length && entries.length < MAX_PER_RUN; i++) {
      var row = data.rows[i];
      var key = rowKey_(row);
      if (!key || history.keys[key]) continue;
      history.keys[key] = true;

      var email = findEmail_(data.headers, row);
      var status = skipReason_(data.headers, row, email, history, sentToday, now);
      if (!status) {
        try {
          sendCopy_(email, data.headers, row, tz, '');
          status = 'sent';
          sentToday++;
          history.lastSent[email.toLowerCase()] = now.getTime();
        } catch (err) {
          // Usually Gmail's daily quota. Log it and stop; later rows are
          // left for the next run rather than all failing the same way.
          entries.push([now, key, email, 'error: ' + String((err && err.message) || err).slice(0, 200)]);
          break;
        }
      }
      entries.push([now, key, email, status]);
    }
    appendLogRows_(log, entries);
  } finally {
    lock.releaseLock();
  }
}

/**
 * Why this row must not be emailed, or '' if it may be. A form that
 * emails whatever address is typed into it can be abused to send mail
 * to strangers in your name, so: one copy per address per
 * ONE_PER_EMAIL_HOURS, at most DAILY_LIMIT a day (Gmail's own cap is
 * about 100), and nothing for submissions with links (spam nearly always
 * has one). Rows already in the sheet at Turn on are never emailed.
 */
function skipReason_(headers, row, email, history, sentToday, now) {
  if (!email) return 'skipped: no valid email address';
  if (CONFIG.SKIP_IF_LINKS && hasLink_(row)) return 'skipped: contains a link';
  var last = history.lastSent[email.toLowerCase()];
  if (last && now.getTime() - last < CONFIG.ONE_PER_EMAIL_HOURS * HOUR_MS) {
    return 'skipped: already sent to this address recently';
  }
  if (sentToday >= CONFIG.DAILY_LIMIT) return 'skipped: daily limit reached';
  return '';
}

// -- The email ---------------------------------------------------------

function sendCopy_(to, headers, row, tz, subjectPrefix) {
  var msg = buildMessage_(headers, row, tz);
  MailApp.sendEmail({
    to: to,
    subject: subjectPrefix + CONFIG.SUBJECT,
    body: msg.text,
    htmlBody: msg.html,
    name: CONFIG.SENDER_NAME,
    replyTo: CONFIG.REPLY_TO,
  });
}

/** Every answered question, in the form's order, as plain text and HTML. */
function buildMessage_(headers, row, tz) {
  var hidden = CONFIG.HIDE_COLUMNS.map(function (h) {
    return String(h).trim().toLowerCase();
  });
  var answers = [];
  headers.forEach(function (header, i) {
    var label = String(header).trim() || 'Answer';
    var value = displayValue_(row[i], tz);
    if (value === '' || hidden.indexOf(label.toLowerCase()) !== -1) return;
    answers.push({ label: label, value: value });
  });

  var name = findFirstName_(headers, row);
  var greeting = name ? 'Hi ' + name + ',' : 'Hello,';

  var text = [greeting, '', CONFIG.INTRO, '']
    .concat(answers.map(function (a) { return a.label + ': ' + a.value; }))
    .concat(['', CONFIG.OUTRO])
    .join('\n');

  var cell = 'padding:6px 0;vertical-align:top;';
  var html =
    '<div style="font-family:Arial,Helvetica,sans-serif;font-size:15px;line-height:1.5;color:#222">' +
    '<p>' + escapeHtml_(greeting) + '</p>' +
    '<p>' + escapeHtml_(CONFIG.INTRO) + '</p>' +
    '<table cellpadding="0" cellspacing="0" style="border-collapse:collapse;margin:8px 0 16px">' +
    answers.map(function (a) {
      return '<tr><td style="' + cell + 'padding-right:16px;color:#666">' + escapeHtml_(a.label) +
        '</td><td style="' + cell + '">' + escapeHtml_(a.value).replace(/\n/g, '<br>') + '</td></tr>';
    }).join('') +
    '</table>' +
    '<p>' + escapeHtml_(CONFIG.OUTRO) + '</p>' +
    '</div>';

  return { text: text, html: html };
}

function displayValue_(value, tz) {
  if (isDate_(value)) return Utilities.formatDate(value, tz, 'd MMM yyyy, HH:mm');
  if (value === true) return 'Yes';
  if (value === false) return 'No';
  return value === null || value === undefined ? '' : String(value).trim();
}

// -- Reading the sheet -------------------------------------------------

/** The tab Squarespace writes to: the first one that isn't our log. */
function readSubmissions_(ss) {
  var sheet = ss.getSheets().filter(function (s) {
    return s.getName() !== LOG_SHEET_NAME;
  })[0];
  if (!sheet) throw new Error('No submissions tab found in this spreadsheet.');
  var values = sheet.getDataRange().getValues();
  return { headers: values[0] || [], rows: values.slice(1) };
}

/** Prefers a column whose header says email; falls back to any cell that is one. */
function findEmail_(headers, row) {
  var byHeader = [];
  var rest = [];
  headers.forEach(function (h, i) {
    (/e-?mail/i.test(String(h)) ? byHeader : rest).push(i);
  });
  var order = byHeader.concat(rest);
  for (var k = 0; k < order.length; k++) {
    var value = String(row[order[k]] === undefined ? '' : row[order[k]]).trim();
    if (EMAIL_RE.test(value)) return value;
  }
  return '';
}

function findFirstName_(headers, row) {
  for (var i = 0; i < headers.length; i++) {
    var h = String(headers[i]).trim();
    if (/first\s*name/i.test(h) || /^(full\s*)?name$/i.test(h)) {
      var first = String(row[i] || '').trim().split(/\s+/)[0];
      if (first) return first;
    }
  }
  return '';
}

function hasLink_(row) {
  return row.some(function (cell) {
    var text = String(cell === undefined || cell === null ? '' : cell);
    return !EMAIL_RE.test(text.trim()) && LINK_RE.test(text);
  });
}

/**
 * Identifies a submission across runs. Built from the row's non-empty
 * values, sorted, so adding a field to the form later (a new, empty
 * column on old rows) doesn't make every old row look new.
 */
function rowKey_(row) {
  var parts = row
    .map(function (v) {
      return isDate_(v) ? v.toISOString() : String(v === null || v === undefined ? '' : v).trim();
    })
    .filter(function (s) { return s !== ''; })
    .sort();
  if (!parts.length) return '';
  var bytes = Utilities.computeDigest(
    Utilities.DigestAlgorithm.SHA_256,
    JSON.stringify(parts),
    Utilities.Charset.UTF_8
  );
  return bytes
    .map(function (b) { return ('0' + (b & 0xff).toString(16)).slice(-2); })
    .join('')
    .slice(0, 32);
}

// -- The log tab -------------------------------------------------------

function logSheet_(ss) {
  var log = ss.getSheetByName(LOG_SHEET_NAME);
  if (log) return log;
  log = ss.insertSheet(LOG_SHEET_NAME, ss.getSheets().length);
  log.appendRow(LOG_HEADERS);
  log.setFrozenRows(1);
  return log;
}

function readLog_(log) {
  var history = { keys: {}, sentTimes: [], lastSent: {} };
  log.getDataRange().getValues().slice(1).forEach(function (r) {
    var key = String(r[1] || '');
    if (key) history.keys[key] = true;
    if (r[3] !== 'sent' || !isDate_(r[0])) return;
    var t = r[0].getTime();
    var email = String(r[2] || '').toLowerCase();
    history.sentTimes.push(t);
    if (!history.lastSent[email] || history.lastSent[email] < t) history.lastSent[email] = t;
  });
  return history;
}

function appendLogRows_(log, entries) {
  if (!entries.length) return;
  log.getRange(log.getLastRow() + 1, 1, entries.length, LOG_HEADERS.length).setValues(entries);
}

// -- Helpers -----------------------------------------------------------

function checkConfig_() {
  var problems = [];
  if (!CONFIG.SENDER_NAME || CONFIG.SENDER_NAME === 'Your business name') {
    problems.push('SENDER_NAME: put your business name');
  }
  if (!EMAIL_RE.test(String(CONFIG.REPLY_TO)) || CONFIG.REPLY_TO === 'you@example.com') {
    problems.push('REPLY_TO: put the address guests should reply to');
  }
  if ([1, 5, 10, 15, 30].indexOf(CONFIG.CHECK_EVERY_MINUTES) === -1) {
    problems.push('CHECK_EVERY_MINUTES: must be 1, 5, 10, 15 or 30');
  }
  if (problems.length) {
    throw new Error('Fill in CONFIG at the top of the script first. ' + problems.join('; '));
  }
}

function removeTriggers_() {
  ScriptApp.getProjectTriggers().forEach(function (t) {
    if (t.getHandlerFunction() === 'processNewSubmissions') ScriptApp.deleteTrigger(t);
  });
}

/** A pop-up when run from the sheet's menu; a log line when run from the editor. */
function notify_(title, message) {
  try {
    var ui = SpreadsheetApp.getUi();
    ui.alert(title, message, ui.ButtonSet.OK);
  } catch (e) {
    console.log(title + ': ' + message);
  }
}

function isDate_(value) {
  return Object.prototype.toString.call(value) === '[object Date]' && !isNaN(value.getTime());
}

function escapeHtml_(s) {
  return String(s)
    .replace(/&/g, '&amp;')
    .replace(/</g, '&lt;')
    .replace(/>/g, '&gt;')
    .replace(/"/g, '&quot;');
}