source: trunk/grails-app/services/dbnp/modules/ModuleCommunicationService.groovy @ 1561

/**
 * SynchronizationService Service
 * 
 * Description of my service
 *
 * @author  your email (+name?)
 * @since       2010mmdd
 * @package     ???
 *
 * Revision information:
 * $Rev: 1517 $
 * $Author: s.h.sikkema@gmail.com $
 * $Date: 2011-02-14 09:56:17 +0000 (ma, 14 feb 2011) $
 */
package dbnp.modules

import dbnp.studycapturing.*
import grails.converters.*
import javax.servlet.http.HttpServletResponse
import org.codehaus.groovy.grails.commons.ConfigurationHolder

class ModuleCommunicationService implements Serializable {
        boolean transactional = false
        def authenticationService
        def moduleNotificationService

        /**
         * Cache containing the contents of different URLs. These urls are
         * saved per user, since the data could be different for different users.
         */
        def cache = [:]

        /**
         * Number of seconds to save the data in cache
         */
        def numberOfSecondsInCache = ConfigurationHolder.config.modules.cacheDuration ? Integer.valueOf( ConfigurationHolder.config.modules.cacheDuration.toString() ) : 300;

        /**
         * Sends a notification to assay modules that some part of a study has changed.
         * 
         * Only modules that have the notify flag set to true will be notified. They will be notified on the URL
         * 
         * [moduleUrl]/rest/notifyStudyChange?studyToken=abc
         * 
         * Errors that occur when calling this URL are ignored. The module itself is responsible of
         * maintaining a synchronized state.
         * 
         * @param study
         * @return
         */
        def invalidateStudy( def study ) {
                moduleNotificationService.invalidateStudy( study );
        }

        /**
         * Checks whether a specific method on a module is reachable and returns a SC_OK response code. 
         * 
         * This method will return false if a method returns an error (including 403 and 401 errors) or
         * a redirect
         * 
         * @param moduleUrl             URL of the module
         * @param path                  Path of the rest method on that module. If omitted, the module reachablility itself is tested
         * @return                              True if the module is reachable, false otherwise
         */
        def isModuleReachable(moduleUrl, path = "") {
                def connection = ( moduleUrl + path ).toURL().openConnection()
                try {
                        return connection.responseCode == HttpServletResponse.SC_OK
                } catch(e) {
                        return false
                }
        }

        /**
         * Calls a rest method on a module
         * 
         * @param consumer      Consumer of that specific module
         * @param restUrl       Full URL for the method to call
         * @return                      JSON    JSON object of the parsed text
         */
        def callModuleRestMethodJSON( consumer, restUrl ) throws Exception {
                if (!authenticationService.isLoggedIn()) {
                        // should not happen because we can only get here when a user is
                        // logged in...
                        throw new Exception('User is not logged in.')
                }

                // Check whether the url is present in cache
                def cacheData = retrieveFromCache( restUrl );
                if( cacheData && cacheData[ "success" ] )
                        return cacheData[ "contents" ];
                else if( cacheData && !cacheData[ "success" ] )
                        throw new Exception( "Error while fetching data from " + restUrl + " (from cache): " + cacheData[ "error" ] )

                // create a random session token that will be used to allow to module to
                // sync with gscf prior to presenting the measurement data
                def sessionToken = UUID.randomUUID().toString()

                // put the session token to work
                authenticationService.logInRemotely( consumer, sessionToken, authenticationService.getLoggedInUser() )

                // Append the sessionToken to the URL
                def url = restUrl
                if( restUrl.indexOf( '?' ) > 0 ) {
                        // The url itself also has parameters
                        url += '&sessionToken=' + sessionToken
                } else {
                        // The url itself doesn't have parameters
                        url += '?sessionToken=' + sessionToken
                }

                // Perform a call to the url
                def restResponse
                try {
                        def textResponse = url.toURL().getText()
                        log.trace "GSCF call to " + consumer + " URL: " + url
                        log.trace "GSCF response: " + textResponse
                        restResponse = JSON.parse( textResponse )
                } catch (Exception e) {
                        storeErrorInCache( restUrl, e.getMessage() );
                        throw new Exception( "An error occurred while fetching " + url + ".", e )
                } finally {
                        // Dispose of the ephemeral session token
                        authenticationService.logOffRemotely(consumer, sessionToken)
                }

                // Store the response in cache
                storeInCache( restUrl, restResponse );
                
                return restResponse
        }

        /**
         * Checks whether a specific url exists in cache
         * @param url   URL to call
         * @return              true if the url is present in cache
         */
        def existsInCache( url ) {
                return retrieveFromCache( url ) == null;
        }

        /**
         * Retrieves the contents of a specific URL from cache
         * @param url   URL to call
         * @return              JSON object with the contents of the URL or null if the url doesn't exist in cache
         */
        def retrieveFromCache( url ) {
                def user = authenticationService.getLoggedInUser();
                def userId = user ? user.id : -1;
                
                if( cache[ userId ] && cache[ userId ][ url ] && ( System.currentTimeMillis() - cache[ userId ][ url ][ "timestamp" ] ) < numberOfSecondsInCache * 1000 ) {
                        return cache[ userId ][ url ];
                } else {
                        return null;
                }
        }

        /**
         * Store the retrieved contents from a url in cache
         * @param url           URL that has been called
         * @param contents      Contents of the URL
         */
        def storeInCache( url, contents ) {
                def user = authenticationService.getLoggedInUser();
                def userId = user ? user.id : -1;

                if( !cache[ userId ] )
                        cache[ userId ] = [:]

                cache[ userId ][ url ] = [
                        "timestamp": System.currentTimeMillis(),
                        "success": true,
                        "contents": contents
                ];
        }
        
        /**
        * Store the retrieved error from a url in cache
        * @param url            URL that has been called
        * @param contents       Contents of the URL
        */
   def storeErrorInCache( url, error ) {
           def user = authenticationService.getLoggedInUser();
           def userId = user ? user.id : -1;

           if( !cache[ userId ] )
                   cache[ userId ] = [:]

           cache[ userId ][ url ] = [
                   "timestamp": System.currentTimeMillis(),
                   "success": false,
                   "error": error
           ];
   }

}