iflrandevu/doc/thesis/snippets/google_sync_algorithm.php

<?php
/**
 * Full synchronization of appointments between Google 
 * Calendar and Easy!Appointments.
 * 
 * This method will completely sync the appointments of a provider 
 * with his Google Calendar account. The sync period needs to be 
 * relatively small, because a lot of API calls might be necessary 
 * and this will lead to consuming the Google limit for the Calendar 
 * API usage.
 * 
 * @param numeric $provider_id Provider record to be synced.
 */
public function sync($provider_id = NULL) {
	try {
		// The user must be logged in.
		$this->load->library('session');
		if ($this->session->userdata('user_id') == FALSE) return;
		
		if ($provider_id === NULL) {
			throw new Exception('Provider id not specified.');
		}
		
		$this->load->model('appointments_model');
		$this->load->model('providers_model');
		$this->load->model('services_model');
		$this->load->model('customers_model');
		$this->load->model('settings_model');
		
		$provider = $this->providers_model->get_row($provider_id);
		
		// Check whether the selected provider has google sync enabled.
		$google_sync = $this->providers_model
				->get_setting('google_sync', $provider['id']);
		if (!$google_sync) {
			throw new Exception('The selected provider has not the  '
					. 'Google synchronization setting enabled.');
		}
		
		$google_token = json_decode($this->providers_model
				->get_setting('google_token', $provider['id']));
		$this->load->library('google_sync');
		$this->google_sync->refresh_token($google_token->refresh_token);
		
		// Fetch provider's appointments that belong to the sync 
		// time period. 
		$sync_past_days = $this->providers_model
				->get_setting('sync_past_days', $provider['id']);
		$sync_future_days = $this->providers_model
				->get_setting('sync_future_days', $provider['id']);
		$start = strtotime('-' . $sync_past_days 
				. ' days', strtotime(date('Y-m-d')));
		$end = strtotime('+' . $sync_future_days 
				. ' days', strtotime(date('Y-m-d')));
		
		$where_clause = array(
			'start_datetime >=' => date('Y-m-d H:i:s', $start),
			'end_datetime <=' => date('Y-m-d H:i:s', $end),
			'id_users_provider' => $provider['id']
		);
		
		$appointments = 
				$this->appointments_model->get_batch($where_clause);
		
		$company_settings = array(
			'company_name' => $this->settings_model
					->get_setting('company_name'),
			'company_link' => $this->settings_model
					->get_setting('company_link'),
			'company_email' => $this->settings_model
					->get_setting('company_email')
		);
		
		// Sync each appointment with Google Calendar by following 
		// the project's sync protocol (see documentation).
		foreach($appointments as $appointment) {
			if ($appointment['is_unavailable'] == FALSE) {
				$service = $this->services_model
						->get_row($appointment['id_services']);
				$customer = $this->customers_model
						->get_row($appointment['id_users_customer']);
			} else {
				$service = NULL;
				$customer = NULL;
			}

			// If current appointment not synced yet, add to gcal.
			if ($appointment['id_google_calendar'] == NULL) {
				$google_event = $this->google_sync
						->add_appointment($appointment, $provider,
						$service, $customer, $company_settings);
				$appointment['id_google_calendar'] = $google_event->id;
				$this->appointments_model->add($appointment);// Save gcal id
			} else {
				// Appointment is synced with google calendar.
				try {
					$google_event = $this->google_sync
							->get_event($appointment['id_google_calendar']);
					
					if ($google_event->status == 'cancelled') {
						throw new Exception('Event is cancelled, remove the '
								. 'record from Easy!Appointments.');
					}
					
					// If gcal event is different from e!a appointment 
					// then update e!a record.
					$is_different = FALSE;
					$appt_start = strtotime($appointment['start_datetime']);
					$appt_end = strtotime($appointment['end_datetime']);
					$event_start = 
						strtotime($google_event->getStart()->getDateTime());
					$event_end = 
						strtotime($google_event->getEnd()->getDateTime());

					if ($appt_start != $event_start 
							|| $appt_end != $event_end) {
						$is_different = TRUE;
					}

					if ($is_different) {
						$appointment['start_datetime'] = 
								date('Y-m-d H:i:s', $event_start);
						$appointment['end_datetime'] = 
								date('Y-m-d H:i:s', $event_end);
						$this->appointments_model->add($appointment);
					}
					
				} catch(Exception $exc) {
					// Appointment not found on gcal, delete from e!a.
					$this->appointments_model->delete($appointment['id']);
					$appointment['id_google_calendar'] = NULL; 
				}
			}
		}
		
		// :: ADD GCAL EVENTS THAT ARE NOT PRESENT ON E!A
		$events = $this->google_sync->get_sync_events($start, $end);
		
		foreach($events->getItems() as $event) {
			$results = $this->appointments_model->get_batch(
					array('id_google_calendar' => $event->getId()));
			if (count($results) == 0) {
				// Record doesn't exist in E!A, so add the event now.
				$appointment = array(
					'start_datetime' => date('Y-m-d H:i:s', 
							strtotime($event->start->getDateTime())),
					'end_datetime' => date('Y-m-d H:i:s', 
							strtotime($event->end->getDateTime())),
					'is_unavailable' => TRUE,
					'notes' => $event->getSummary() 
							. ' ' . $event->getDescription(),
					'id_users_provider' => $provider_id,
					'id_google_calendar' => $event->getId(),
					'id_users_customer' => NULL,
					'id_services' => NULL,
				);
				$this->appointments_model->add($appointment);
			}
		}
		
		echo json_encode(AJAX_SUCCESS);
		
	} catch(Exception $exc) {
		echo json_encode(array(
			'exceptions' => array($exc)
		));
	}
}