/**
 * Might Learn Premium Sheet API v2.1
 * Bound to the "MightLearn Payments" spreadsheet.
 * Script property: ML_BRIDGE_SECRET (24+ characters).
 * Deployment: Web app, execute as Me; access Anyone for WP server calls.
 * Sheet: Membership Data (A Email, B Phone, C Amount, D Start Date,
 *                         E Expiry Date, F Status, G UTR).
 * Do not publish or log ML_BRIDGE_SECRET.
 */
const ML_MEMBERSHIP_TAB = 'Membership Data';
const ML_TIMEZONE = 'Asia/Kolkata';

function doGet() {
  return mlJson_({ success:true, service:'MightLearn Membership API', version:'2.1' });
}

function doPost(e) {
  try {
    const data = JSON.parse((e && e.postData && e.postData.contents) || '{}');
    const configured = PropertiesService.getScriptProperties().getProperty('ML_BRIDGE_SECRET') || '';
    if (configured.length < 24 || !data.secret || data.secret !== configured) {
      return mlJson_({success:false, message:'Not authorized'});
    }
    if (data.action !== 'checkMembership') {
      return mlJson_({success:false, message:'Unsupported action'});
    }
    const email = String(data.email || '').trim().toLowerCase();
    if (!/^[^\s@]+@[^\s@]+\.[^\s@]+$/.test(email)) {
      return mlJson_({success:false, message:'Invalid email'});
    }
    return mlJson_(mlLookupMembership_(email));
  } catch (err) {
    console.error('Membership lookup failed:', String(err));
    return mlJson_({success:false, message:'Membership lookup error'});
  }
}

function mlLookupMembership_(email) {
  const sheet = SpreadsheetApp.getActiveSpreadsheet().getSheetByName(ML_MEMBERSHIP_TAB);
  if (!sheet) return {success:false, message:'Membership Data tab not found'};
  const last = sheet.getLastRow();
  const now = Date.now();
  let winner = null;
  if (last > 1) {
    const rows = sheet.getRange(2,1,last-1,7).getValues();
    for (let i=0; i<rows.length; i++) {
      const r = rows[i];
      if (String(r[0] || '').trim().toLowerCase() !== email) continue;
      const amount = Number(String(r[2] || '').replace(/[₹,\s]/g,''));
      if (amount !== 9 && amount !== 49) continue;
      const declaredStatus = String(r[5] || '').trim().toLowerCase();
      if (declaredStatus !== 'active') continue;
      const start = mlAsDate_(r[3], false);
      const end = mlAsDate_(r[4], true);
      const utr = String(r[6] || '').trim();
      if (!start || !end || !utr || start.getTime() > now || end.getTime() <= now) continue;
      if (!winner || end.getTime() > winner.end.getTime()) {
        winner = {end:end, plan:amount === 49 ? 'yearly' : 'monthly'};
      }
    }
  }
  return winner ? {
    success:true, active:true, plan:winner.plan,
    expiry:Utilities.formatDate(winner.end,ML_TIMEZONE,"yyyy-MM-dd'T'HH:mm:ssXXX")
  } : {success:true, active:false, plan:'free', expiry:''};
}

/**
 * Convert date cells as India-local calendar dates. Expiry date-only cells are
 * valid until the END of that day, instead of expiring at 00:00 at its start.
 * Handles genuine Sheets Date values, dd/MM/yyyy, yyyy-MM-dd and timestamps.
 */
function mlAsDate_(value, endOfDay) {
  if (value == null || value === '') return null;
  const isDate = value instanceof Date && !isNaN(value.getTime());
  if (isDate) {
    const d = new Date(value.getTime());
    // Date-only cells commonly have midnight in the spreadsheet's time zone.
    // Use the displayed date as the authoritative calendar date.
    const datePart = Utilities.formatDate(d, ML_TIMEZONE, 'yyyy-MM-dd');
    const timePart = Utilities.formatDate(d, ML_TIMEZONE, 'HH:mm:ss');
    if (timePart === '00:00:00') return mlIndianDate_(datePart, !!endOfDay);
    return d;
  }
  const s = String(value).trim();
  let m = s.match(/^(\d{1,2})[\/-](\d{1,2})[\/-](\d{4})$/);
  if (m) return mlIndianDate_([m[3],m[2].padStart(2,'0'),m[1].padStart(2,'0')].join('-'), !!endOfDay);
  m = s.match(/^(\d{4})-(\d{1,2})-(\d{1,2})$/);
  if (m) return mlIndianDate_([m[1],m[2].padStart(2,'0'),m[3].padStart(2,'0')].join('-'), !!endOfDay);
  m = s.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})\s+(\d{1,2}):(\d{2})(?::(\d{2}))?$/);
  if (m) return mlIndianDate_(`${m[3]}-${m[2].padStart(2,'0')}-${m[1].padStart(2,'0')}`, false, `${m[4].padStart(2,'0')}:${m[5]}:${m[6]||'00'}`);
  const parsed = new Date(s); // ISO 8601 timestamps with offsets
  return isNaN(parsed.getTime()) ? null : parsed;
}
function mlIndianDate_(ymd, endOfDay, time) {
  const m = ymd.match(/^(\d{4})-(\d{2})-(\d{2})$/);
  if (!m) return null;
  const year=+m[1], month=+m[2], day=+m[3];
  const valid = new Date(Date.UTC(year,month-1,day));
  if (valid.getUTCFullYear() !== year || valid.getUTCMonth() !== month-1 || valid.getUTCDate() !== day) return null;
  const hm = time || (endOfDay ? '23:59:59' : '00:00:00');
  // Indian Standard Time is UTC+05:30 and has no DST.
  const d = new Date(`${ymd}T${hm}+05:30`);
  return isNaN(d.getTime()) ? null : d;
}
function mlJson_(data) {
  return ContentService.createTextOutput(JSON.stringify(data))
    .setMimeType(ContentService.MimeType.JSON);
}

/**
 * Diagnostic: run manually in Apps Script editor. No secrets or full emails
 * are logged. It checks EVERY used row independently from the logged-in user.
 * Output: Executions > Logs. Does not change any Sheet data.
 */
function diagnoseMembershipRows() {
  const book = SpreadsheetApp.getActiveSpreadsheet();
  const sheet = book.getSheetByName(ML_MEMBERSHIP_TAB);
  console.log('Spreadsheet: ' + book.getName());
  console.log('Membership tab found: ' + !!sheet);
  if (!sheet) return;
  const last=sheet.getLastRow();
  console.log('Data rows: ' + Math.max(0,last-1));
  if (last < 2) return;
  const rows=sheet.getRange(2,1,last-1,7).getValues();
  const now=Date.now();
  rows.forEach((r,i)=>{
    const email=String(r[0]||'').trim().toLowerCase();
    const amount=Number(String(r[2]||'').replace(/[₹,\s]/g,''));
    const status=String(r[5]||'').trim().toLowerCase();
    const start=mlAsDate_(r[3],false), end=mlAsDate_(r[4],true);
    const utr=String(r[6]||'').trim();
    const reasons=[];
    if (!email) reasons.push('missing email');
    if (![9,49].includes(amount)) reasons.push('invalid amount');
    if (status!=='active') reasons.push('status not Active');
    if (!start) reasons.push('invalid start date');
    if (!end) reasons.push('invalid expiry date');
    if (!utr) reasons.push('missing UTR');
    if (start && start.getTime()>now) reasons.push('not started');
    if (end && end.getTime()<=now) reasons.push('expired');
    const masked = email ? email.slice(0,2)+'***@'+(email.split('@')[1]||'') : '(empty)';
    console.log('Row '+(i+2)+' | '+masked+' | amount='+amount+' | status='+status+
      ' | expiry='+(end?Utilities.formatDate(end,ML_TIMEZONE,'yyyy-MM-dd HH:mm:ss'):'invalid')+
      ' | '+(reasons.length?reasons.join(', '):'VALID ACTIVE MEMBERSHIP'));
  });
}