Moved duplicated code into re-usable library classes

application/controllers/Backend_api.php

@@ -38,6 +38,8 @@ use EA\Engine\Types\Url;
  * @property Customers_Model $customers_model
  * @property Settings_Model $settings_model
  * @property Timezones $timezones
+ * @property Synchronization $synchronization
+ * @property Notifications $notifications
  * @property Roles_Model $roles_model
  * @property Secretaries_Model $secretaries_model
  * @property Admins_Model $admins_model
@@ -283,6 +285,8 @@ class Backend_api extends CI_Controller {
             $this->load->model('customers_model');
             $this->load->model('settings_model');
             $this->load->library('timezones');
+            $this->load->library('synchronization');
+            $this->load->library('notifications');
             $this->load->model('user_model');
 
             // Save customer changes to the database.
@@ -290,10 +294,10 @@ class Backend_api extends CI_Controller {
             {
                 $customer = json_decode($this->input->post('customer_data'), TRUE);
 
-                $required_privilegesileges = ( ! isset($customer['id']))
+                $required_privileges = ( ! isset($customer['id']))
                     ? $this->privileges[PRIV_CUSTOMERS]['add']
                     : $this->privileges[PRIV_CUSTOMERS]['edit'];
-                if ($required_privilegesileges == FALSE)
+                if ($required_privileges == FALSE)
                 {
                     throw new Exception('You do not have the required privileges for this task.');
                 }
@@ -306,17 +310,17 @@ class Backend_api extends CI_Controller {
             {
                 $appointment = json_decode($this->input->post('appointment_data'), TRUE);
 
-                $required_privilegesileges = ( ! isset($appointment['id']))
+                $required_privileges = ( ! isset($appointment['id']))
                     ? $this->privileges[PRIV_APPOINTMENTS]['add']
                     : $this->privileges[PRIV_APPOINTMENTS]['edit'];
-                if ($required_privilegesileges == FALSE)
+                if ($required_privileges == FALSE)
                 {
                     throw new Exception('You do not have the required privileges for this task.');
                 }
 
                 $manage_mode = isset($appointment['id']);
-                // If the appointment does not contain the customer record id, then it
+                // If the appointment does not contain the customer record id, then it means that is is going to be
-                // means that is is going to be inserted. Get the customer's record id.
+                // inserted. Get the customer's record ID.
                 if ( ! isset($appointment['id_users_customer']))
                 {
                     $appointment['id_users_customer'] = $customer['id'];
@@ -348,140 +352,11 @@ class Backend_api extends CI_Controller {
                 'time_format' => $this->settings_model->get_setting('time_format')
             ];
 
-            // Sync appointment changes with Google Calendar.
+            $this->synchronization->sync_appointment_deleted($appointment, $provider);
-            try
+            $this->notifications->notify_appointment_deleted($appointment, $service, $provider, $customer, $settings);
-            {
-                $google_sync = $this->providers_model->get_setting('google_sync',
-                    $appointment['id_users_provider']);
 
-                if ($google_sync == TRUE)
-                {
-                    $google_token = json_decode($this->providers_model->get_setting('google_token',
-                        $appointment['id_users_provider']));
-
-                    $this->load->library('Google_sync');
-                    $this->google_sync->refresh_token($google_token->refresh_token);
-
-                    if ($appointment['id_google_calendar'] == NULL)
-                    {
-                        $google_event = $this->google_sync->add_appointment($appointment, $provider,
-                            $service, $customer, $settings);
-                        $appointment['id_google_calendar'] = $google_event->id;
-                        $this->appointments_model->add($appointment); // Store google calendar id.
-                    }
-                    else
-                    {
-                        $this->google_sync->update_appointment($appointment, $provider,
-                            $service, $customer, $settings);
-                    }
-                }
-            }
-            catch (Exception $exception)
-            {
-                $warnings[] = [
-                    'message' => $exception->getMessage(),
-                    'trace' => config('debug') ? $exception->getTrace() : []
-                ];
-            }
-
-            // Send email notifications to provider and customer.
-            try
-            {
-                $this->config->load('email');
-                $email = new EmailClient($this, $this->config->config);
-
-                $send_provider = $this->providers_model
-                    ->get_setting('notifications', $provider['id']);
-
-                if ( ! $manage_mode)
-                {
-                    $customer_title = new Text(lang('appointment_booked'));
-                    $customer_message = new Text(lang('thank_you_for_appointment'));
-                    $provider_title = new Text(lang('appointment_added_to_your_plan'));
-                    $provider_message = new Text(lang('appointment_link_description'));
-                }
-                else
-                {
-                    $customer_title = new Text(lang('appointment_details_changed'));
-                    $customer_message = new Text('');
-                    $provider_title = new Text(lang('appointment_changes_saved'));
-                    $provider_message = new Text('');
-                }
-
-                $customer_link = new Url(site_url('appointments/index/' . $appointment['hash']));
-                $provider_link = new Url(site_url('backend/index/' . $appointment['hash']));
-
-                $send_customer = $this->settings_model->get_setting('customer_notifications');
-
-                $this->load->library('ics_file');
-                $ics_stream = $this->ics_file->get_stream($appointment, $service, $provider, $customer);
-
-                if ((bool)$send_customer === TRUE)
-                {
-                    $email->sendAppointmentDetails($appointment, $provider,
-                        $service, $customer, $settings, $customer_title,
-                        $customer_message, $customer_link, new Email($customer['email']), new Text($ics_stream));
-                }
-
-                if ($send_provider == TRUE)
-                {
-                    $email->sendAppointmentDetails($appointment, $provider,
-                        $service, $customer, $settings, $provider_title,
-                        $provider_message, $provider_link, new Email($provider['email']), new Text($ics_stream));
-                }
-
-                // Notify admins
-                $admins = $this->admins_model->get_batch();
-
-                foreach($admins as $admin)
-                {
-                    if (!$admin['settings']['notifications'] === '0')
-                    {
-                        continue;
-                    }
-
-                    $email->sendAppointmentDetails($appointment, $provider,
-                        $service, $customer, $settings, $provider_title,
-                        $provider_message, $provider_link, new Email($admin['email']), new Text($ics_stream));
-                }
-
-                // Notify secretaries
-                $secretaries = $this->secretaries_model->get_batch();
-
-                foreach($secretaries as $secretary)
-                {
-                    if (!$secretary['settings']['notifications'] === '0')
-                    {
-                        continue;
-                    }
-
-                    if (in_array($provider['id'], $secretary['providers']))
-                    {
-                        continue;
-                    }
-
-                    $email->sendAppointmentDetails($appointment, $provider,
-                        $service, $customer, $settings, $provider_title,
-                        $provider_message, $provider_link, new Email($secretary['email']), new Text($ics_stream));
-                }
-            }
-            catch (Exception $exception)
-            {
-                $warnings[] = [
-                    'message' => $exception->getMessage(),
-                    'trace' => config('debug') ? $exception->getTrace() : []
-                ];
-            }
-
-            if (empty($warnings))
-            {
             $response = AJAX_SUCCESS;
         }
-            else
-            {
-                $response = ['warnings' => $warnings];
-            }
-        }
         catch (Exception $exception)
         {
             $this->output->set_status_header(500);
@@ -1032,10 +907,10 @@ class Backend_api extends CI_Controller {
             $this->load->model('customers_model');
             $customer = json_decode($this->input->post('customer'), TRUE);
 
-            $required_privilegesileges = ( ! isset($customer['id']))
+            $required_privileges = ( ! isset($customer['id']))
                 ? $this->privileges[PRIV_CUSTOMERS]['add']
                 : $this->privileges[PRIV_CUSTOMERS]['edit'];
-            if ($required_privilegesileges == FALSE)
+            if ($required_privileges == FALSE)
             {
                 throw new Exception('You do not have the required privileges for this task.');
             }
@@ -1105,10 +980,10 @@ class Backend_api extends CI_Controller {
             $this->load->model('services_model');
             $service = json_decode($this->input->post('service'), TRUE);
 
-            $required_privilegesileges = ( ! isset($service['id']))
+            $required_privileges = ( ! isset($service['id']))
                 ? $this->privileges[PRIV_SERVICES]['add']
                 : $this->privileges[PRIV_SERVICES]['edit'];
-            if ($required_privilegesileges == FALSE)
+            if ($required_privileges == FALSE)
             {
                 throw new Exception('You do not have the required privileges for this task.');
             }
@@ -1215,10 +1090,10 @@ class Backend_api extends CI_Controller {
             $this->load->model('services_model');
             $category = json_decode($this->input->post('category'), TRUE);
 
-            $required_privilegesileges = ( ! isset($category['id']))
+            $required_privileges = ( ! isset($category['id']))
                 ? $this->privileges[PRIV_SERVICES]['add']
                 : $this->privileges[PRIV_SERVICES]['edit'];
-            if ($required_privilegesileges == FALSE)
+            if ($required_privileges == FALSE)
             {
                 throw new Exception('You do not have the required privileges for this task.');
             }

application/controllers/api/v1/Appointments.php

@@ -37,6 +37,8 @@ use EA\Engine\Types\NonEmptyText;
  * @property Customers_Model $customers_model
  * @property Settings_Model $settings_model
  * @property Timezones $timezones
+ * @property Notifications $notifications
+ * @property Synchronization $synchronization
  * @property Roles_Model $roles_model
  * @property Secretaries_Model $secretaries_model
  * @property Admins_Model $admins_model
@@ -59,6 +61,12 @@ class Appointments extends API_V1_Controller {
     {
         parent::__construct();
         $this->load->model('appointments_model');
+        $this->load->model('services_model');
+        $this->load->model('providers_model');
+        $this->load->model('customers_model');
+        $this->load->model('settings_model');
+        $this->load->library('synchronization');
+        $this->load->library('notifications');
         $this->parser = new \EA\Engine\Api\V1\Parsers\Appointments;
     }
 
@@ -109,8 +117,6 @@ class Appointments extends API_V1_Controller {
      */
     public function post()
     {
-        $this->load->model('services_model');
-
         try
         {
             // Insert the appointment to the database.
@@ -138,6 +144,20 @@ class Appointments extends API_V1_Controller {
 
             $id = $this->appointments_model->add($appointment);
 
+            $service = $this->services_model->get_row($appointment['id_services']);
+            $provider = $this->providers_model->get_row($appointment['id_users_provider']);
+            $customer = $this->customers_model->get_row($appointment['id_users_customer']);
+            $settings = [
+                'company_name' => $this->settings_model->get_setting('company_name'),
+                'company_email' => $this->settings_model->get_setting('company_email'),
+                'company_link' => $this->settings_model->get_setting('company_link'),
+                'date_format' => $this->settings_model->get_setting('date_format'),
+                'time_format' => $this->settings_model->get_setting('time_format')
+            ];
+
+            $this->synchronization->sync_appointment_saved($appointment, $service, $provider, $customer, $settings, FALSE);
+            $this->notifications->notify_appointment_saved($appointment, $service, $provider, $customer, $settings, FALSE);
+
             // Fetch the new object from the database and return it to the client.
             $batch = $this->appointments_model->get_batch('id = ' . $id);
             $response = new Response($batch);
@@ -174,6 +194,21 @@ class Appointments extends API_V1_Controller {
             $updatedAppointment['id'] = $id;
             $id = $this->appointments_model->add($updatedAppointment);
 
+            $service = $this->services_model->get_row($updatedAppointment['id_services']);
+            $provider = $this->providers_model->get_row($updatedAppointment['id_users_provider']);
+            $customer = $this->customers_model->get_row($updatedAppointment['id_users_customer']);
+            $settings = [
+                'company_name' => $this->settings_model->get_setting('company_name'),
+                'company_email' => $this->settings_model->get_setting('company_email'),
+                'company_link' => $this->settings_model->get_setting('company_link'),
+                'date_format' => $this->settings_model->get_setting('date_format'),
+                'time_format' => $this->settings_model->get_setting('time_format')
+            ];
+
+            $this->synchronization->sync_appointment_saved($updatedAppointment, $service, $provider, $customer, $settings, TRUE);
+            $this->notifications->notify_appointment_saved($updatedAppointment, $service, $provider, $customer, $settings, TRUE);
+
+
             // Fetch the updated object from the database and return it to the client.
             $batch = $this->appointments_model->get_batch('id = ' . $id);
             $response = new Response($batch);
@@ -194,8 +229,23 @@ class Appointments extends API_V1_Controller {
     {
         try
         {
+            $appointment = $this->appointments_model->get_row($id);
+            $service = $this->services_model->get_row($appointment['id_services']);
+            $provider = $this->providers_model->get_row($appointment['id_users_provider']);
+            $customer = $this->customers_model->get_row($appointment['id_users_customer']);
+            $settings = [
+                'company_name' => $this->settings_model->get_setting('company_name'),
+                'company_email' => $this->settings_model->get_setting('company_email'),
+                'company_link' => $this->settings_model->get_setting('company_link'),
+                'date_format' => $this->settings_model->get_setting('date_format'),
+                'time_format' => $this->settings_model->get_setting('time_format')
+            ];
+
             $this->appointments_model->delete($id);
 
+            $this->synchronization->sync_appointment_deleted($appointment, $provider);
+            $this->notifications->notify_appointment_deleted($appointment, $service, $provider, $customer, $settings);
+
             $response = new Response([
                 'code' => 200,
                 'message' => 'Record was deleted successfully!'

application/libraries/Availability.php

@@ -0,0 +1,552 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.4.0
+ * ---------------------------------------------------------------------------- */
+
+
+/**
+ * Class Availability
+ *
+ * Handles the availability generation of providers, based on their working plan and their schedule.
+ */
+class Availability {
+    /**
+     * @var CI_Controller
+     */
+    protected $CI;
+
+    /**
+     * Availability constructor.
+     */
+    public function __construct()
+    {
+        $this->CI =& get_instance();
+        $this->CI->load->model('providers_model');
+        $this->CI->load->model('secretaries_model');
+        $this->CI->load->model('secretaries_model');
+        $this->CI->load->model('admins_model');
+        $this->CI->load->model('appointments_model');
+        $this->CI->load->model('settings_model');
+        $this->CI->load->library('ics_file');
+    }
+
+    /**
+     * Get the available hours of a provider.
+     *
+     * @param string $date Selected date (Y-m-d).
+     * @param array $service Service record.
+     * @param array $provider Provider record.
+     * @param int|null $exclude_appointment_id Exclude an appointment from the availability generation.
+     *
+     * @return array
+     *
+     * @throws Exception
+     */
+    public function get_available_hours($date, $service, $provider, $exclude_appointment_id = NULL)
+    {
+        $available_periods = $this->get_available_periods($date, $provider, $exclude_appointment_id);
+
+        $available_hours = $this->generate_available_hours($date, $service, $available_periods);
+
+        if ($service['attendants_number'] > 1)
+        {
+            $available_hours = $this->consider_multiple_attendants($date, $service, $provider);
+        }
+
+        return $this->consider_book_advance_timeout($date, $available_hours, $provider);
+    }
+
+    /**
+     * Get an array containing the free time periods (start - end) of a selected date.
+     *
+     * This method is very important because there are many cases where the system needs to know when a provider is
+     * available for an appointment. This method will return an array that belongs to the selected date and contains
+     * values that have the start and the end time of an available time period.
+     *
+     * @param string $date Select date string.
+     * @param array $provider Provider record.
+     * @param int|null $exclude_appointment_id Exclude an appointment from the availability generation.
+     *
+     * @return array Returns an array with the available time periods of the provider.
+     *
+     * @throws Exception
+     */
+    public function get_available_periods(
+        $date,
+        $provider,
+        $exclude_appointment_id = NULL
+    )
+    {
+        // Get the service, provider's working plan and provider appointments.
+        $working_plan = json_decode($provider['settings']['working_plan'], TRUE);
+
+        // Get the provider's working plan exceptions.
+        $working_plan_exceptions = json_decode($provider['settings']['working_plan_exceptions'], TRUE);
+
+        $conditions = [
+            'id_users_provider' => $provider['id'],
+        ];
+
+        // Sometimes it might be necessary to exclude an appointment from the calculation (e.g. when editing an
+        // existing appointment).
+        if ($exclude_appointment_id)
+        {
+            $conditions['id !='] = $exclude_appointment_id;
+        }
+
+        $appointments = $this->CI->appointments_model->get_batch($conditions);
+
+        // Find the empty spaces on the plan. The first split between the plan is due to a break (if any). After that
+        // every reserved appointment is considered to be a taken space in the plan.
+        $date_working_plan = $working_plan[strtolower(date('l', strtotime($date)))];
+
+        // Search if the $date is an custom availability period added outside the normal working plan.
+        if (isset($working_plan_exceptions[$date]))
+        {
+            $date_working_plan = $working_plan_exceptions[$date];
+        }
+
+        $periods = [];
+
+        if (isset($date_working_plan['breaks']))
+        {
+            $periods[] = [
+                'start' => $date_working_plan['start'],
+                'end' => $date_working_plan['end']
+            ];
+
+            $day_start = new DateTime($date_working_plan['start']);
+            $day_end = new DateTime($date_working_plan['end']);
+
+            // Split the working plan to available time periods that do not contain the breaks in them.
+            foreach ($date_working_plan['breaks'] as $index => $break)
+            {
+                $break_start = new DateTime($break['start']);
+                $break_end = new DateTime($break['end']);
+
+                if ($break_start < $day_start)
+                {
+                    $break_start = $day_start;
+                }
+
+                if ($break_end > $day_end)
+                {
+                    $break_end = $day_end;
+                }
+
+                if ($break_start >= $break_end)
+                {
+                    continue;
+                }
+
+                foreach ($periods as $key => $period)
+                {
+                    $period_start = new DateTime($period['start']);
+                    $period_end = new DateTime($period['end']);
+
+                    $remove_current_period = FALSE;
+
+                    if ($break_start > $period_start && $break_start < $period_end && $break_end > $period_start)
+                    {
+                        $periods[] = [
+                            'start' => $period_start->format('H:i'),
+                            'end' => $break_start->format('H:i')
+                        ];
+
+                        $remove_current_period = TRUE;
+                    }
+
+                    if ($break_start < $period_end && $break_end > $period_start && $break_end < $period_end)
+                    {
+                        $periods[] = [
+                            'start' => $break_end->format('H:i'),
+                            'end' => $period_end->format('H:i')
+                        ];
+
+                        $remove_current_period = TRUE;
+                    }
+
+                    if ($break_start == $period_start && $break_end == $period_end)
+                    {
+                        $remove_current_period = TRUE;
+                    }
+
+                    if ($remove_current_period)
+                    {
+                        unset($periods[$key]);
+                    }
+                }
+            }
+        }
+
+        // Break the empty periods with the reserved appointments.
+        foreach ($appointments as $appointment)
+        {
+            foreach ($periods as $index => &$period)
+            {
+                $appointment_start = new DateTime($appointment['start_datetime']);
+                $appointment_end = new DateTime($appointment['end_datetime']);
+
+                if ($appointment_start >= $appointment_end)
+                {
+                    continue;
+                }
+
+                $period_start = new DateTime($date . ' ' . $period['start']);
+                $period_end = new DateTime($date . ' ' . $period['end']);
+
+                if ($appointment_start <= $period_start && $appointment_end <= $period_end && $appointment_end <= $period_start)
+                {
+                    // The appointment does not belong in this time period, so we  will not change anything.
+                    continue;
+                }
+                else
+                {
+                    if ($appointment_start <= $period_start && $appointment_end <= $period_end && $appointment_end >= $period_start)
+                    {
+                        // The appointment starts before the period and finishes somewhere inside. We will need to break
+                        // this period and leave the available part.
+                        $period['start'] = $appointment_end->format('H:i');
+                    }
+                    else
+                    {
+                        if ($appointment_start >= $period_start && $appointment_end < $period_end)
+                        {
+                            // The appointment is inside the time period, so we will split the period into two new
+                            // others.
+                            unset($periods[$index]);
+
+                            $periods[] = [
+                                'start' => $period_start->format('H:i'),
+                                'end' => $appointment_start->format('H:i')
+                            ];
+
+                            $periods[] = [
+                                'start' => $appointment_end->format('H:i'),
+                                'end' => $period_end->format('H:i')
+                            ];
+                        }
+                        else if ($appointment_start == $period_start && $appointment_end == $period_end)
+                        {
+                            unset($periods[$index]); // The whole period is blocked so remove it from the available periods array.
+                        }
+                        else
+                        {
+                            if ($appointment_start >= $period_start && $appointment_end >= $period_start && $appointment_start <= $period_end)
+                            {
+                                // The appointment starts in the period and finishes out of it. We will need to remove
+                                // the time that is taken from the appointment.
+                                $period['end'] = $appointment_start->format('H:i');
+                            }
+                            else
+                            {
+                                if ($appointment_start >= $period_start && $appointment_end >= $period_end && $appointment_start >= $period_end)
+                                {
+                                    // The appointment does not belong in the period so do not change anything.
+                                    continue;
+                                }
+                                else
+                                {
+                                    if ($appointment_start <= $period_start && $appointment_end >= $period_end && $appointment_start <= $period_end)
+                                    {
+                                        // The appointment is bigger than the period, so this period needs to be removed.
+                                        unset($periods[$index]);
+                                    }
+                                }
+                            }
+                        }
+                    }
+                }
+            }
+        }
+
+        return array_values($periods);
+    }
+
+
+    /**
+     * Calculate the available appointment hours.
+     *
+     * Calculate the available appointment hours for the given date. The empty spaces
+     * are broken down to 15 min and if the service fit in each quarter then a new
+     * available hour is added to the "$available_hours" array.
+     *
+     * @param string $date Selected date (Y-m-d).
+     * @param array $service Service record.
+     * @param array $empty_periods Empty periods as generated by the "get_provider_available_time_periods"
+     * method.
+     *
+     * @return array Returns an array with the available hours for the appointment.
+     *
+     * @throws Exception
+     */
+    protected function generate_available_hours(
+        $date,
+        $service,
+        $empty_periods
+    )
+    {
+        $available_hours = [];
+
+        foreach ($empty_periods as $period)
+        {
+            $start_hour = new DateTime($date . ' ' . $period['start']);
+            $end_hour = new DateTime($date . ' ' . $period['end']);
+            $interval = $service['availabilities_type'] === AVAILABILITIES_TYPE_FIXED ? (int)$service['duration'] : 15;
+
+            $current_hour = $start_hour;
+            $diff = $current_hour->diff($end_hour);
+
+            while (($diff->h * 60 + $diff->i) >= (int)$service['duration'])
+            {
+                $available_hours[] = $current_hour->format('H:i');
+                $current_hour->add(new DateInterval('PT' . $interval . 'M'));
+                $diff = $current_hour->diff($end_hour);
+            }
+        }
+
+        return $available_hours;
+    }
+
+    /**
+     * Get multiple attendants hours.
+     *
+     * This method will add the additional appointment hours whenever a service accepts multiple attendants.
+     *
+     * @param string $date Selected date (Y-m-d).
+     * @param array $service Service record.
+     * @param array $provider Provider record.
+     *
+     * @return array Returns the available hours array.
+     *
+     * @throws Exception
+     */
+    protected function consider_multiple_attendants(
+        $date,
+        $service,
+        $provider
+    )
+    {
+        $unavailability_events = $this->CI->appointments_model->get_batch([
+            'is_unavailable' => TRUE,
+            'DATE(start_datetime)' => $date,
+            'id_users_provider' => $provider['id']
+        ]);
+
+        $working_plan = json_decode($provider['settings']['working_plan'], TRUE);
+        $working_day = strtolower(date('l', strtotime($date)));
+        $working_hours = $working_plan[$working_day];
+
+        $periods = [
+            [
+                'start' => new DateTime($date . ' ' . $working_hours['start']),
+                'end' => new DateTime($date . ' ' . $working_hours['end'])
+            ]
+        ];
+
+        $periods = $this->remove_breaks($date, $periods, $working_hours['breaks']);
+        $periods = $this->remove_unavailability_events($periods, $unavailability_events);
+
+        $hours = [];
+
+        $interval_value = $service['availabilities_type'] == AVAILABILITIES_TYPE_FIXED ? $service['duration'] : '15';
+        $interval = new DateInterval('PT' . (int)$interval_value . 'M');
+        $duration = new DateInterval('PT' . (int)$service['duration'] . 'M');
+
+        foreach ($periods as $period)
+        {
+            $slot_start = clone $period['start'];
+            $slot_end = clone $slot_start;
+            $slot_end->add($duration);
+
+            while ($slot_end <= $period['end'])
+            {
+                // Check reserved attendants for this time slot and see if current attendants fit.
+                $appointment_attendants_number = $this->CI->appointments_model->get_attendants_number_for_period(
+                    $slot_start,
+                    $slot_end,
+                    $service['id']
+                );
+
+                if ($appointment_attendants_number < $service['attendants_number'])
+                {
+                    $hours[] = $slot_start->format('H:i');
+                }
+
+                $slot_start->add($interval);
+                $slot_end->add($interval);
+            }
+        }
+
+        return $hours;
+    }
+
+    /**
+     * Remove breaks from available time periods.
+     *
+     * @param string $selected_date Selected data (Y-m-d format).
+     * @param array $periods Time periods of the current date.
+     * @param array $breaks Breaks array for the current date.
+     *
+     * @return array Returns the available time periods without the breaks.
+     * @throws Exception
+     */
+    public function remove_breaks($selected_date, $periods, $breaks)
+    {
+        if ( ! $breaks)
+        {
+            return $periods;
+        }
+
+        foreach ($breaks as $break)
+        {
+            $break_start = new DateTime($selected_date . ' ' . $break['start']);
+            $break_end = new DateTime($selected_date . ' ' . $break['end']);
+
+            foreach ($periods as &$period)
+            {
+                $period_start = $period['start'];
+                $period_end = $period['end'];
+
+                if ($break_start <= $period_start && $break_end >= $period_start && $break_end <= $period_end)
+                {
+                    // left
+                    $period['start'] = $break_end;
+                    continue;
+                }
+
+                if ($break_start >= $period_start && $break_start <= $period_end && $break_end >= $period_start && $break_end <= $period_end)
+                {
+                    // middle
+                    $period['end'] = $break_start;
+                    $periods[] = [
+                        'start' => $break_end,
+                        'end' => $period_end
+                    ];
+                    continue;
+                }
+
+                if ($break_start >= $period_start && $break_start <= $period_end && $break_end >= $period_end)
+                {
+                    // right
+                    $period['end'] = $break_start;
+                    continue;
+                }
+
+                if ($break_start <= $period_start && $break_end >= $period_end)
+                {
+                    // break contains period
+                    $period['start'] = $break_end;
+                    continue;
+                }
+            }
+        }
+
+        return $periods;
+    }
+
+    /**
+     * Remove the unavailability entries from the available time periods of the selected date.
+     *
+     * @param array $periods Available time periods.
+     * @param array $unavailability_events Unavailability events of the current date.
+     *
+     * @return array Returns the available time periods without the unavailability events.
+     *
+     * @throws Exception
+     */
+    public function remove_unavailability_events($periods, $unavailability_events)
+    {
+        foreach ($unavailability_events as $unavailability_event)
+        {
+            $unavailability_start = new DateTime($unavailability_event['start_datetime']);
+            $unavailability_end = new DateTime($unavailability_event['end_datetime']);
+
+            foreach ($periods as &$period)
+            {
+                $period_start = $period['start'];
+                $period_end = $period['end'];
+
+                if ($unavailability_start <= $period_start && $unavailability_end >= $period_start && $unavailability_end <= $period_end)
+                {
+                    // left
+                    $period['start'] = $unavailability_end;
+                    continue;
+                }
+
+                if ($unavailability_start >= $period_start && $unavailability_start <= $period_end && $unavailability_end >= $period_start && $unavailability_end <= $period_end)
+                {
+                    // middle
+                    $period['end'] = $unavailability_start;
+                    $periods[] = [
+                        'start' => $unavailability_end,
+                        'end' => $period_end
+                    ];
+                    continue;
+                }
+
+                if ($unavailability_start >= $period_start && $unavailability_start <= $period_end && $unavailability_end >= $period_end)
+                {
+                    // right
+                    $period['end'] = $unavailability_start;
+                    continue;
+                }
+
+                if ($unavailability_start <= $period_start && $unavailability_end >= $period_end)
+                {
+                    // Unavailability contains period
+                    $period['start'] = $unavailability_end;
+                    continue;
+                }
+            }
+        }
+
+        return $periods;
+    }
+
+    /**
+     * Consider the book advance timeout and remove available hours that have passed the threshold.
+     *
+     * If the selected date is today, remove past hours. It is important  include the timeout before booking
+     * that is set in the back-office the system. Normally we might want the customer to book an appointment
+     * that is at least half or one hour from now. The setting is stored in minutes.
+     *
+     * @param string $selected_date The selected date.
+     * @param array $available_hours Already generated available hours.
+     * @param array $provider Provider information.
+     *
+     * @return array Returns the updated available hours.
+     *
+     * @throws Exception
+     */
+    protected function consider_book_advance_timeout($selected_date, $available_hours, $provider)
+    {
+        $provider_timezone = new DateTimeZone($provider['timezone']);
+
+        $book_advance_timeout = $this->CI->settings_model->get_setting('book_advance_timeout');
+
+        $threshold = new DateTime('+' . $book_advance_timeout . ' minutes', $provider_timezone);
+
+        foreach ($available_hours as $index => $value)
+        {
+            $available_hour = new DateTime($selected_date . ' ' . $value, $provider_timezone);
+
+            if ($available_hour->getTimestamp() <= $threshold->getTimestamp())
+            {
+                unset($available_hours[$index]);
+            }
+        }
+
+        $available_hours = array_values($available_hours);
+        sort($available_hours, SORT_STRING);
+        return array_values($available_hours);
+    }
+}

application/libraries/Notifications.php

@@ -0,0 +1,227 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.4.0
+ * ---------------------------------------------------------------------------- */
+
+use EA\Engine\Notifications\Email as EmailClient;
+use EA\Engine\Types\Email;
+use EA\Engine\Types\Text;
+use EA\Engine\Types\Url;
+
+/**
+ * Class Notifications
+ *
+ * Handles the system notifications (mostly related to scheduling changes).
+ */
+class Notifications {
+    /**
+     * @var CI_Controller
+     */
+    protected $CI;
+
+    /**
+     * Notifications constructor.
+     */
+    public function __construct()
+    {
+        $this->CI =& get_instance();
+        $this->CI->load->model('providers_model');
+        $this->CI->load->model('secretaries_model');
+        $this->CI->load->model('secretaries_model');
+        $this->CI->load->model('admins_model');
+        $this->CI->load->model('appointments_model');
+        $this->CI->load->model('settings_model');
+        $this->CI->load->library('ics_file');
+    }
+
+    /**
+     * Send the required notifications, related to an appointment creation/modification.
+     *
+     * @param array $appointment Appointment record.
+     * @param array $service Service record.
+     * @param array $provider Provider record.
+     * @param array $customer Customer record.
+     * @param array $settings Required settings for the notification content.
+     * @param bool|false $manage_mode
+     */
+    public function notify_appointment_saved($appointment, $service, $provider, $customer, $settings, $manage_mode = FALSE)
+    {
+        // Send email notifications to customer and provider.
+        try
+        {
+            $this->CI->config->load('email');
+
+            $email = new EmailClient($this->CI, $this->CI->config->config);
+
+            if ($manage_mode === FALSE)
+            {
+                $customer_title = new Text(lang('appointment_booked'));
+                $customer_message = new Text(lang('thank_you_for_appointment'));
+                $provider_title = new Text(lang('appointment_added_to_your_plan'));
+                $provider_message = new Text(lang('appointment_link_description'));
+
+            }
+            else
+            {
+                $customer_title = new Text(lang('appointment_changes_saved'));
+                $customer_message = new Text('');
+                $provider_title = new Text(lang('appointment_details_changed'));
+                $provider_message = new Text('');
+            }
+
+            $customer_link = new Url(site_url('appointments/index/' . $appointment['hash']));
+            $provider_link = new Url(site_url('backend/index/' . $appointment['hash']));
+
+            $send_customer = filter_var(
+                $this->CI->settings_model->get_setting('customer_notifications'),
+                FILTER_VALIDATE_BOOLEAN);
+
+
+            $ics_stream = $this->CI->ics_file->get_stream($appointment, $service, $provider, $customer);
+
+            if ($send_customer === TRUE)
+            {
+                $email->sendAppointmentDetails($appointment, $provider,
+                    $service, $customer, $settings, $customer_title,
+                    $customer_message, $customer_link, new Email($customer['email']), new Text($ics_stream));
+            }
+
+            $send_provider = filter_var(
+                $this->CI->providers_model->get_setting('notifications', $provider['id']),
+                FILTER_VALIDATE_BOOLEAN);
+
+            if ($send_provider === TRUE)
+            {
+                $email->sendAppointmentDetails($appointment, $provider,
+                    $service, $customer, $settings, $provider_title,
+                    $provider_message, $provider_link, new Email($provider['email']), new Text($ics_stream));
+            }
+
+            // Notify admins
+            $admins = $this->CI->admins_model->get_batch();
+
+            foreach ($admins as $admin)
+            {
+                if ( ! $admin['settings']['notifications'] === '0')
+                {
+                    continue;
+                }
+
+                $email->sendAppointmentDetails($appointment, $provider,
+                    $service, $customer, $settings, $provider_title,
+                    $provider_message, $provider_link, new Email($admin['email']), new Text($ics_stream));
+            }
+
+            // Notify secretaries
+            $secretaries = $this->CI->secretaries_model->get_batch();
+
+            foreach ($secretaries as $secretary)
+            {
+                if ( ! $secretary['settings']['notifications'] === '0')
+                {
+                    continue;
+                }
+
+                if (in_array($provider['id'], $secretary['providers']))
+                {
+                    continue;
+                }
+
+                $email->sendAppointmentDetails($appointment, $provider,
+                    $service, $customer, $settings, $provider_title,
+                    $provider_message, $provider_link, new Email($secretary['email']), new Text($ics_stream));
+            }
+        }
+        catch (Exception $exception)
+        {
+            log_message('error', $exception->getMessage());
+            log_message('error', $exception->getTraceAsString());
+        }
+    }
+
+    /**
+     * Send the required notifications, related to an appointment removal.
+     *
+     * @param array $appointment Appointment record.
+     * @param array $service Service record.
+     * @param array $provider Provider record.
+     * @param array $customer Customer record.
+     * @param array $settings Required settings for the notification content.
+     */
+    public function notify_appointment_deleted($appointment, $service, $provider, $customer, $settings)
+    {
+        // Send email notification to customer and provider.
+        try
+        {
+            $email = new EmailClient($this->CI, $this->CI->config->config);
+
+            $send_provider = filter_var($this->CI->providers_model->get_setting('notifications', $provider['id']),
+                FILTER_VALIDATE_BOOLEAN);
+
+            if ($send_provider === TRUE)
+            {
+                $email->sendDeleteAppointment($appointment, $provider,
+                    $service, $customer, $settings, new Email($provider['email']),
+                    new Text($this->CI->input->post('cancel_reason')));
+            }
+
+            $send_customer = filter_var(
+                $this->CI->settings_model->get_setting('customer_notifications'),
+                FILTER_VALIDATE_BOOLEAN);
+
+            if ($send_customer === TRUE)
+            {
+                $email->sendDeleteAppointment($appointment, $provider,
+                    $service, $customer, $settings, new Email($customer['email']),
+                    new Text($this->CI->input->post('cancel_reason')));
+            }
+
+            // Notify admins
+            $admins = $this->CI->admins_model->get_batch();
+
+            foreach ($admins as $admin)
+            {
+                if ( ! $admin['settings']['notifications'] === '0')
+                {
+                    continue;
+                }
+
+                $email->sendDeleteAppointment($appointment, $provider,
+                    $service, $customer, $settings, new Email($admin['email']),
+                    new Text($this->CI->input->post('cancel_reason')));
+            }
+
+            // Notify secretaries
+            $secretaries = $this->CI->secretaries_model->get_batch();
+
+            foreach ($secretaries as $secretary)
+            {
+                if ( ! $secretary['settings']['notifications'] === '0')
+                {
+                    continue;
+                }
+
+                if (in_array($provider['id'], $secretary['providers']))
+                {
+                    continue;
+                }
+
+                $email->sendDeleteAppointment($appointment, $provider,
+                    $service, $customer, $settings, new Email($secretary['email']),
+                    new Text($this->CI->input->post('cancel_reason')));
+            }
+        }
+        catch (Exception $exception)
+        {
+            $exceptions[] = $exception;
+        }
+    }
+}

application/libraries/Synchronization.php

@@ -0,0 +1,120 @@
+<?php defined('BASEPATH') or exit('No direct script access allowed');
+
+/* ----------------------------------------------------------------------------
+ * Easy!Appointments - Open Source Web Scheduler
+ *
+ * @package     EasyAppointments
+ * @author      A.Tselegidis <alextselegidis@gmail.com>
+ * @copyright   Copyright (c) 2013 - 2020, Alex Tselegidis
+ * @license     http://opensource.org/licenses/GPL-3.0 - GPLv3
+ * @link        http://easyappointments.org
+ * @since       v1.4.0
+ * ---------------------------------------------------------------------------- */
+
+/**
+ * Class Synchronization
+ *
+ * Handles the external calendar synchronization.
+ */
+class Synchronization {
+    /**
+     * @var CI_Controller
+     */
+    protected $CI;
+
+    /**
+     * Synchronization constructor.
+     */
+    public function __construct()
+    {
+        $this->CI =& get_instance();
+        $this->CI->load->model('providers_model');
+        $this->CI->load->model('appointments_model');
+        $this->CI->load->library('google_sync');
+    }
+
+    /**
+     * Synchronize changes made to the appointment with external calendars.
+     *
+     * @param array $appointment Appointment record.
+     * @param array $service Service record.
+     * @param array $provider Provider record.
+     * @param array $customer Customer record.
+     * @param array $settings Required settings for the notification content.
+     * @param bool|false $manage_mode True if the appointment is being edited.
+     */
+    public function sync_appointment_saved($appointment, $service, $provider, $customer, $settings, $manage_mode = FALSE)
+    {
+        try
+        {
+            $google_sync = filter_var(
+                $this->CI->providers_model->get_setting('google_sync', $appointment['id_users_provider']),
+                FILTER_VALIDATE_BOOLEAN
+            );
+
+            if ($google_sync === TRUE)
+            {
+                $google_token = json_decode(
+                    $this->CI->providers_model->get_setting('google_token', $appointment['id_users_provider']));
+
+                $this->CI->load->library('google_sync');
+
+                $this->CI->google_sync->refresh_token($google_token->refresh_token);
+
+                if ($manage_mode === FALSE)
+                {
+                    // Add appointment to Google Calendar.
+                    $google_event = $this->CI->google_sync->add_appointment($appointment, $provider,
+                        $service, $customer, $settings);
+                    $appointment['id_google_calendar'] = $google_event->id;
+                    $this->CI->appointments_model->add($appointment);
+                }
+                else
+                {
+                    // Update appointment to Google Calendar.
+                    $appointment['id_google_calendar'] = $this->CI->appointments_model
+                        ->get_value('id_google_calendar', $appointment['id']);
+
+                    $this->CI->google_sync->update_appointment($appointment, $provider,
+                        $service, $customer, $settings);
+                }
+            }
+        }
+        catch (Exception $exception)
+        {
+            log_message('error', $exception->getMessage());
+            log_message('error', $exception->getTraceAsString());
+        }
+    }
+
+    /**
+     * Synchronize removal of an appointment with external calendars.
+     *
+     * @param array $appointment Appointment record.
+     * @param array $provider Provider record.
+     */
+    public function sync_appointment_deleted($appointment, $provider)
+    {
+        if ($appointment['id_google_calendar'] != NULL)
+        {
+            try
+            {
+                $google_sync = filter_var(
+                    $this->CI->providers_model->get_setting('google_sync', $appointment['id_users_provider']),
+                    FILTER_VALIDATE_BOOLEAN);
+
+                if ($google_sync === TRUE)
+                {
+                    $google_token = json_decode($this->CI->providers_model->get_setting('google_token', $provider['id']));
+                    $this->CI->load->library('Google_sync');
+                    $this->CI->google_sync->refresh_token($google_token->refresh_token);
+                    $this->CI->google_sync->delete_appointment($provider, $appointment['id_google_calendar']);
+                }
+            }
+            catch (Exception $exception)
+            {
+                $exceptions[] = $exception;
+            }
+        }
+    }
+}