<?php
// This file is part of Moodle - http://moodle.org/
//
// Moodle is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// Moodle is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with Moodle.  If not, see <http://www.gnu.org/licenses/>.

/**
 *
 * Login library file of login/password related Moodle functions.
 *
 * @package    core
 * @subpackage lib
 * @copyright  Catalyst IT
 * @copyright  Peter Bulmer
 * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
 */
define('PWRESET_STATUS_NOEMAILSENT', 1);
define('PWRESET_STATUS_TOKENSENT', 2);
define('PWRESET_STATUS_OTHEREMAILSENT', 3);
define('PWRESET_STATUS_ALREADYSENT', 4);

/**
 *  Processes a user's request to set a new password in the event they forgot the old one.
 *  If no user identifier has been supplied, it displays a form where they can submit their identifier.
 *  Where they have supplied identifier, the function will check their status, and send email as appropriate.
 */
function core_login_process_password_reset_request() {
    global $DB, $OUTPUT, $CFG, $PAGE;
    $systemcontext = context_system::instance();
    $mform = new login_forgot_password_form();

    if ($mform->is_cancelled()) {
        redirect(get_login_url());

    } else if ($data = $mform->get_data()) {
        // Requesting user has submitted form data.
        // Next find the user account in the database which the requesting user claims to own.
        if (!empty($data->username)) {
            // Username has been specified - load the user record based on that.
            $username = core_text::strtolower($data->username); // Mimic the login page process.
            $userparams = array('username' => $username, 'mnethostid' => $CFG->mnet_localhost_id, 'deleted' => 0, 'suspended' => 0);
            $user = $DB->get_record('user', $userparams);
        } else {
            // Try to load the user record based on email address.
            // this is tricky because
            // 1/ the email is not guaranteed to be unique - TODO: send email with all usernames to select the account for pw reset
            // 2/ mailbox may be case sensitive, the email domain is case insensitive - let's pretend it is all case-insensitive.

            $select = $DB->sql_like('email', ':email', false, true, false, '|') .
                    " AND mnethostid = :mnethostid AND deleted=0 AND suspended=0";
            $params = array('email' => $DB->sql_like_escape($data->email, '|'), 'mnethostid' => $CFG->mnet_localhost_id);
            $user = $DB->get_record_select('user', $select, $params, '*', IGNORE_MULTIPLE);
        }

        // Target user details have now been identified, or we know that there is no such account.
        // Send email address to account's email address if appropriate.
        $pwresetstatus = PWRESET_STATUS_NOEMAILSENT;
        if ($user and !empty($user->confirmed)) {
            $userauth = get_auth_plugin($user->auth);
            if (!$userauth->can_reset_password() or !is_enabled_auth($user->auth)
              or !has_capability('moodle/user:changeownpassword', $systemcontext, $user->id)) {
                if (send_password_change_info($user)) {
                    $pwresetstatus = PWRESET_STATUS_OTHEREMAILSENT;
                } else {
                    print_error('cannotmailconfirm');
                }
            } else {
                // The account the requesting user claims to be is entitled to change their password.
                // Next, check if they have an existing password reset in progress.
                $resetinprogress = $DB->get_record('user_password_resets', array('userid' => $user->id));
                if (empty($resetinprogress)) {
                    // Completely new reset request - common case.
                    $resetrecord = core_login_generate_password_reset($user);
                    $sendemail = true;
                } else if ($resetinprogress->timerequested < (time() - $CFG->pwresettime)) {
                    // Preexisting, but expired request - delete old record & create new one.
                    // Uncommon case - expired requests are cleaned up by cron.
                    $DB->delete_records('user_password_resets', array('id' => $resetinprogress->id));
                    $resetrecord = core_login_generate_password_reset($user);
                    $sendemail = true;
                } else if (empty($resetinprogress->timererequested)) {
                    // Preexisting, valid request. This is the first time user has re-requested the reset.
                    // Re-sending the same email once can actually help in certain circumstances
                    // eg by reducing the delay caused by greylisting.
                    $resetinprogress->timererequested = time();
                    $DB->update_record('user_password_resets', $resetinprogress);
                    $resetrecord = $resetinprogress;
                    $sendemail = true;
                } else {
                    // Preexisting, valid request. User has already re-requested email.
                    $pwresetstatus = PWRESET_STATUS_ALREADYSENT;
                    $sendemail = false;
                }

                if ($sendemail) {
                    $sendresult = send_password_change_confirmation_email($user, $resetrecord);
                    if ($sendresult) {
                        $pwresetstatus = PWRESET_STATUS_TOKENSENT;
                    } else {
                        print_error('cannotmailconfirm');
                    }
                }
            }
        }

        // Any email has now been sent.
        // Next display results to requesting user if settings permit.
        echo $OUTPUT->header();

        if (!empty($CFG->protectusernames)) {
            // Neither confirm, nor deny existance of any username or email address in database.
            // Print general (non-commital) message.
            notice(get_string('emailpasswordconfirmmaybesent'), $CFG->wwwroot.'/index.php');
            die; // Never reached.
        } else if (empty($user)) {
            // Protect usernames is off, and we couldn't find the user with details specified.
            // Print failure advice.
            notice(get_string('emailpasswordconfirmnotsent'), $CFG->wwwroot.'/forgot_password.php');
            die; // Never reached.
        } else if (empty($user->email)) {
            // User doesn't have an email set - can't send a password change confimation email.
            notice(get_string('emailpasswordconfirmnoemail'), $CFG->wwwroot.'/index.php');
            die; // Never reached.
        } else if ($pwresetstatus == PWRESET_STATUS_ALREADYSENT) {
            // User found, protectusernames is off, but user has already (re) requested a reset.
            // Don't send a 3rd reset email.
            $stremailalreadysent = get_string('emailalreadysent');
            notice($stremailalreadysent, $CFG->wwwroot.'/index.php');
            die; // Never reached.
        } else if ($pwresetstatus == PWRESET_STATUS_NOEMAILSENT) {
            // User found, protectusernames is off, but user is not confirmed.
            // Pretend we sent them an email.
            // This is a big usability problem - need to tell users why we didn't send them an email.
            // Obfuscate email address to protect privacy.
            $protectedemail = preg_replace('/([^@]*)@(.*)/', '******@$2', $user->email);
            $stremailpasswordconfirmsent = get_string('emailpasswordconfirmsent', '', $protectedemail);
            notice($stremailpasswordconfirmsent, $CFG->wwwroot.'/index.php');
            die; // Never reached.
        } else {
            // Confirm email sent. (Obfuscate email address to protect privacy).
            $protectedemail = preg_replace('/([^@]*)@(.*)/', '******@$2', $user->email);
            // This is a small usability problem - may be obfuscating the email address which the user has just supplied.
            $stremailresetconfirmsent = get_string('emailresetconfirmsent', '', $protectedemail);
            notice($stremailresetconfirmsent, $CFG->wwwroot.'/index.php');
            die; // Never reached.
        }
        die; // Never reached.
    }

    // Make sure we really are on the https page when https login required.
    $PAGE->verify_https_required();

    // DISPLAY FORM.

    echo $OUTPUT->header();
    echo $OUTPUT->box(get_string('passwordforgotteninstructions2'), 'generalbox boxwidthnormal boxaligncenter');
    $mform->display();

    echo $OUTPUT->footer();
}

/**
 * This function processes a user's submitted token to validate the request to set a new password.
 * If the user's token is validated, they are prompted to set a new password.
 * @param string $token the one-use identifier which should verify the password reset request as being valid.
 * @return void
 */
function core_login_process_password_set($token) {
    global $DB, $CFG, $OUTPUT, $PAGE, $SESSION;
    $pwresettime = isset($CFG->pwresettime) ? $CFG->pwresettime : 1800;
    $sql = "SELECT u.*, upr.token, upr.timerequested, upr.id as tokenid
              FROM {user} u
              JOIN {user_password_resets} upr ON upr.userid = u.id
             WHERE upr.token = ?";
    $user = $DB->get_record_sql($sql, array($token));

    $forgotpasswordurl = "{$CFG->httpswwwroot}/login/forgot_password.php";
    if (empty($user) or ($user->timerequested < (time() - $pwresettime - DAYSECS))) {
        // There is no valid reset request record - not even a recently expired one.
        // (suspicious)
        // Direct the user to the forgot password page to request a password reset.
        echo $OUTPUT->header();
        notice(get_string('noresetrecord'), $forgotpasswordurl);
        die; // Never reached.
    }
    if ($user->timerequested < (time() - $pwresettime)) {
        // There is a reset record, but it's expired.
        // Direct the user to the forgot password page to request a password reset.
        $pwresetmins = floor($pwresettime / MINSECS);
        echo $OUTPUT->header();
        notice(get_string('resetrecordexpired', '', $pwresetmins), $forgotpasswordurl);
        die; // Never reached.
    }

    if ($user->auth === 'nologin' or !is_enabled_auth($user->auth)) {
        // Bad luck - user is not able to login, do not let them set password.
        echo $OUTPUT->header();
        print_error('forgotteninvalidurl');
        die; // Never reached.
    }

    // Check this isn't guest user.
    if (isguestuser($user)) {
        print_error('cannotresetguestpwd');
    }

    // Token is correct, and unexpired.
    $mform = new login_set_password_form(null, null, 'post', '', 'autocomplete="yes"');
    $data = $mform->get_data();
    if (empty($data)) {
        // User hasn't submitted form, they got here directly from email link.
        // Next, display the form.
        $setdata = new stdClass();
        $setdata->username = $user->username;
        $setdata->username2 = $user->username;
        $setdata->token = $user->token;
        $mform->set_data($setdata);
        $PAGE->verify_https_required();
        echo $OUTPUT->header();
        echo $OUTPUT->box(get_string('setpasswordinstructions'), 'generalbox boxwidthnormal boxaligncenter');
        $mform->display();
        echo $OUTPUT->footer();
        return;
    } else {
        // User has submitted form.
        // Delete this token so it can't be used again.
        $DB->delete_records('user_password_resets', array('id' => $user->tokenid));
        $userauth = get_auth_plugin($user->auth);
        if (!$userauth->user_update_password($user, $data->password)) {
            print_error('errorpasswordupdate', 'auth');
        }
        // Reset login lockout (if present) before a new password is set.
        login_unlock_account($user);
        // Clear any requirement to change passwords.
        unset_user_preference('auth_forcepasswordchange', $user);
        unset_user_preference('create_password', $user);

        if (!empty($user->lang)) {
            // Unset previous session language - use user preference instead.
            unset($SESSION->lang);
        }
        complete_user_login($user); // Triggers the login event.

        $user = $DB->get_record('user', array('id' => $user->id), '*', MUST_EXIST);
        \core\event\user_password_updated::create_from_user($user, true)->trigger();

        $urltogo = core_login_get_return_url();
        unset($SESSION->wantsurl);
        redirect($urltogo, get_string('passwordset'), 1);
    }
}

/** Create a new record in the database to track a new password set request for user.
 * @param object $user the user record, the requester would like a new password set for.
 * @return record created.
 */
function core_login_generate_password_reset ($user) {
    global $DB;
    $resetrecord = new stdClass();
    $resetrecord->timerequested = time();
    $resetrecord->userid = $user->id;
    $resetrecord->token = random_string(32);
    $resetrecord->id = $DB->insert_record('user_password_resets', $resetrecord);
    return $resetrecord;
}

/**  Determine where a user should be redirected after they have been logged in.
 * @return string url the user should be redirected to.
 */
function core_login_get_return_url() {
    global $CFG, $SESSION, $USER;
    // Prepare redirection.
    if (user_not_fully_set_up($USER)) {
        $urltogo = $CFG->wwwroot.'/user/edit.php';
        // We don't delete $SESSION->wantsurl yet, so we get there later.

    } else if (isset($SESSION->wantsurl) and (strpos($SESSION->wantsurl, $CFG->wwwroot) === 0
            or strpos($SESSION->wantsurl, str_replace('http://', 'https://', $CFG->wwwroot)) === 0)) {
        $urltogo = $SESSION->wantsurl;    // Because it's an address in this site.
        unset($SESSION->wantsurl);
    } else {
        // No wantsurl stored or external - go to homepage.
        $urltogo = $CFG->wwwroot.'/';
        unset($SESSION->wantsurl);
    }

    // If the url to go to is the same as the site page, check for default homepage.
    if ($urltogo == ($CFG->wwwroot . '/')) {
        $homepage = get_home_page();
        // Go to my-moodle page instead of site homepage if defaulthomepage set to homepage_my.
        if ($homepage == HOMEPAGE_MY && !is_siteadmin() && !isguestuser()) {
            if ($urltogo == $CFG->wwwroot or $urltogo == $CFG->wwwroot.'/' or $urltogo == $CFG->wwwroot.'/index.php') {
                $urltogo = $CFG->wwwroot.'/my/';
            }
        }
    }
    return $urltogo;
}
