let satitm_directory = require('./config/ldap.js');
let ldap = require('ldapjs');
// Search for a user in the directory
async function queryUser(upn, attributes) {
  return new Promise((resolve, reject) => {
    let opts = {
      filter: `(userPrincipalName=${upn})`,
      scope: 'sub',
      attributes: attributes
    };
    satitm_directory.search('DC=ad,DC=satitm,DC=chula,DC=ac,DC=th', opts, function(err, ldapRes) {
      ldapRes.on('searchEntry', function(entry) {
        console.log('entry: ' + JSON.stringify(entry.object));
        resolve(entry.object);
      });
      ldapRes.on('error', function(err) {
        console.error('error: ' + err.message);
        reject(err);
      });
      ldapRes.on('end', function(result) {
        console.log('status: ' + result.status);
      });
    });
  });
}

async function setPrimaryParent(student_upn, parent_upn) {
  try {
    // Query the student's LDAP entry
    let studentAttributes = ['primaryParent'];
    let student = await queryUser(student_upn, studentAttributes);
    let primaryParent = student.primaryParent;
    // If the primary parent is not set, set it to the parent's UPN
    if (!primaryParent) {
      let change = new ldap.Change({
        operation: 'add',
        modification: {
          primaryParent: parent_upn
        }
      });
      let dn = student.dn;
      satitm_directory.modify(dn, change, function(err) {
        if (err) {
          console.error(err);
          throw err;
        }
      });
    }
    // If the primary parent is already set, return an error
    else {
      throw new Error('Primary parent already set');
    }
  } catch (err) {
    console.error(err);
    throw err;
  }
}


// 0: Unkown, 1: Student, 2: Parent
const USER_TYPE = {
  UNKNOWN: 0,
  STUDENT: 1,
  PARENT: 2
};

// Determine the type of user
// Student is in OU=Students,OU=Users,DC=ad,DC=satitm,DC=chula,DC=ac,DC=th 
// Parent is in OU=Parents,OU=Users,DC=ad,DC=satitm,DC=chula,DC=ac,DC=th
function getUserType(req, res) {
  // The user's DN is present in the session as req.user.dn
  // To convert DN to OU, remove from first CN= to first ,
  let ou = req.user.dn.substring(req.user.dn.indexOf(',') + 1);
  console.log('OU:', ou);
  if (ou === 'OU=Students,DC=ad,DC=satitm,DC=chula,DC=ac,DC=th') {
    return USER_TYPE.STUDENT;
  }
  else if (ou === 'OU=Parents,DC=ad,DC=satitm,DC=chula,DC=ac,DC=th') {
    return USER_TYPE.PARENT;
  }
  else {
    return USER_TYPE.UNKNOWN;
  }
}

async function getPrimaryParent(student_upn) {
  try {
    // Query primaryParent attribute in the student's LDAP entry
    let attributes = ['primaryParent'];
    let student = await queryUser(student_upn, attributes);
    let primaryParent = student.primaryParent;
    return primaryParent;
  } catch (err) {
    console.error(err);
    throw err;
  }
}

module.exports = {
    queryUser: queryUser,
    getUserType: getUserType,
    setPrimaryParent: setPrimaryParent,
    USER_TYPE: USER_TYPE
};