<?php
  require_once 'lib/nusoap.php';
  require_once 'DB.php';
  
  $server = new soap_server();
  $server->configureWSDL('statemachine', 'urn:statemachine');
  
  $data_directory = "C:\xampp\htdocs\webservice\data\";  
  $db_connection = DB::connect("mysql://state_machine:password@localhost/state_machines");
  if (DB::isError($db_connection)) 
    stopWithErrorMessage("failed to connect to the database - " . $db_connection->getMessage());
  
  // Register the methods to expose
  $server->register('postMessage',    
      array('stateMachineName' => 'xsd:string', 'message' => 'xsd:string'),
      array('return' => 'xsd:string'),
      'urn:statemachine',             
      'urn:statemachine#postMessage', 
      'rpc',                          
      'encoded',                      
      'send a message to a given state machine. returns the new state'      
  );
  $server->register('getMachineState',    
      array('stateMachineName' => 'xsd:string'),
      array('return' => 'xsd:string'),
      'urn:statemachine',             
      'urn:statemachine#getMachineState', 
      'rpc',                          
      'encoded',                      
      'returns the current state of the automaton'      
  );
  $server->register('getErrorMessage',    
      array('stateMachineName' => 'xsd:string'),
      array('return' => 'xsd:string'),
      'urn:statemachine',             
      'urn:statemachine#getErrorMessage', 
      'rpc',                          
      'encoded',                      
      'returns the error message for a given state machine ("" if no error exists)'      
  );  
  $server->register('resetMachineState',    
      array('stateMachineName' => 'xsd:string'),
      array(),
      'urn:statemachine',             
      'urn:statemachine#resetMachineState', 
      'rpc',                          
      'encoded',                      
      'resets the given state machine'      
  );  
  $server->register('resetAllMachines',    
      array(),
      array(),
      'urn:statemachine',             
      'urn:statemachine#resetMachineState', 
      'rpc',                          
      'encoded',                      
      'resets all the state machines'      
  );    

  $server->service($HTTP_RAW_POST_DATA);

  //send a message to a given state machine. returns the new state
  function postMessage($stateMachineName, $message) {
    if (!preg_match('/^[w-s]+$/', $stateMachineName)) 
      stopWithErrorMessage('state machine name contains illegal characters');
    global $data_directory;
    if (!is_file($data_directory . $stateMachineName . ".xml")) 
      stopWithErrorMessage('specified state machine does not exists');
      
    //load up the state machine
    $stateMachine = loadStateMachineFromFile($data_directory . $stateMachineName . ".xml");
    global $db_connection;
    //from now on we need to be synchronized with other threads - lock the database table
    $db_connection->query('LOCK TABLE lock_table WRITE');
    //synchronize it with the database
    $stateMachine = synchronizeStateMachine($stateMachine, $stateMachineName);
    //now post the message to the state machine
    $stateMachine = postMessageWhilePossible($stateMachine, $message);
    if (is_string($stateMachine)) {
      //an error has occured! store the error message and return the empty string
      $db_connection->query('REPLACE INTO state_machines (machine_state, error_message) VALUES ("", "' . addslashes($stateMachine['currentState']) . 
        '") WHERE machine_name="' . addlashes($stateMachineName) . '"');
      $db_connection->query('UNLOCK TABLES');
      return '';
    } else {
      //everything went ok, store the new state and return it
      $db_connection->query('REPLACE INTO state_machines (machine_state, error_message) VALUES ("' . addslashes($stateMachine['currentState']) . 
        '", "") WHERE machine_name="' . addslashes($stateMachineName) . '"');
      $db_connection->query('UNLOCK TABLES');
      return $stateMachine['currentState'];
    }     
  }
  
  //returns the current state of the automaton
  function getMachineState($stateMachineName) {
    if (!preg_match('/^[w-s]+$/', $stateMachineName)) 
      stopWithErrorMessage('state machine name contains illegal characters');
    global $data_directory;
    if (!is_file($data_directory . $stateMachineName . ".xml")) 
      stopWithErrorMessage('specified state machine does not exists');
      
    //load up the state machine
    $stateMachine = loadStateMachineFromFile($data_directory . $stateMachineName . ".xml");
    //synchronize it with the database
    $stateMachine = synchronizeStateMachine($stateMachine, $stateMachineName);
    //return the current state
    return $stateMachine['currentState'];
  }
  
  //returns the error message for a given state machine ('' if no error exists)
  function getErrorMessage($stateMachineName) {
    if (!preg_match('/^[w-s]+$/', $stateMachineName)) 
      stopWithErrorMessage('state machine name contains illegal characters');
    global $db_connection;
    return $db_connection->getOne("SELECT error_message FROM state_machines WHERE machine_name="" . addslashes($stateMachineName) . """);
  }
  
  //resets the given state machine
  function resetMachineState($stateMachineName) {
    if (!preg_match('/^[w-s]+$/', $stateMachineName)) 
      stopWithErrorMessage('state machine name contains illegal characters');
    global $db_connection;
    $db_connection->query('DELETE FROM state_machines WHERE machine_name="' . addslashes($stateMachineName) . '"');
  }
  
  //resets all the state machines
  function resetAllMachines() {
    global $db_connection;
    $db_connection->query('DELETE FROM state_machines');
  }
  
  //internal helper function which outputs the error message to the header and then exits
  function stopWithErrorMessage($error_message) {
    header("HTTP/1.1 500 Internal Server Error: " . $error_message, true, 500);
    exit;     
  }
  
  //internal helper function - synchronizes the state of a an automaton with the one stored in the databas
  //(if it's stored there)
  function synchronizeStateMachine($state_machine, $stateMachineName) {
    global $db_connection;
    $machine_state = $db_connection->getRow("SELECT * FROM state_machines WHERE machine_name="" . addslashes($stateMachineName) . """);
    if (is_array($machine_state)) {
      //it is present in the database, try to synchronize with it
      if ( ('' == $machine_state['machine_state']) || array_key_exists($machine_state['machine_state'], $state_machine['states'])) {
        $state_machine['currentState'] = $machine_state['machine_state'];
        return $state_machine;
      } else {
        stopWithErrorMessage("Erroneous state in the database: " . $machine_state['machine_state']);        
        exit;
      }
    }
    //it's not present in the database, leave it as it is
    return $state_machine;
  }
  
  //internal helper function. Checks if the given node has the specified attribute
  //if not, returns null, if it does, it returns it
  function getAttributeOrNull($node, $attr_name) {
    if ($node->hasAttribute($attr_name))
      return $node->getAttribute($attr_name);
    return null;      
  }
  
  //internal helper function. Extract and validate the action elements from
  //a node (message or state). Return an array structure on success,
  //an error messag (string) on failure
  function extractActions($parent_node, $states_list, $state_name, $message_name) {
    //process the probable actions - make sure that the sum of the probabilities if 1.0
    //when no probaility is specified, the remaining probability is distributed between them
    $error_message_suffix = ('' == $message_name) ? '' : " at message '$message_name'";
    $actions = $parent_node->getElementsByTagName('action');
    $result = array();
    $probability_sum = 0.0; $actions_with_no_probability = 0;
    foreach ($actions as $action) {
      $new_action = array();
      if (null !== ($action_probability = getAttributeOrNull($action, 'probability'))) {
        if ($action_probability <= 0)
          return "Negative probability of action in state '$state_name'$error_message_suffix";
        $probability_sum += 0.0 + $action_probability;
        $new_action['probability'] = 0.0 + $action_probability;
      } else {
        ++$actions_with_no_probability;
      }
      if (null === ($action_wait_before = getAttributeOrNull($action, 'waitBefore'))) {
        $new_action['waitBefore'] = 0;
      } else {
        if ($action_wait_before < 0)
          return "Negative 'waitBefore' of action in state '$state_name'$error_message_suffix";
        $new_action['waitBefore'] = intval($action_wait_before);
      }
      if (null === ($action_wait_after = getAttributeOrNull($action, 'waitAfter'))) {
        $new_action['waitAfter'] = 0;
      } else {
        if ($action_wait_after < 0)
          return "Negative 'waitAfter' of action in state '$state_name'$error_message_suffix";
        $new_action['waitAfter'] = intval($action_wait_after);
      }     
      if (null === ($action_next_state = getAttributeOrNull($action, 'nextState')))
        return "Unspecified nextState in state '$state_name'$error_message_suffix";
      if (!array_key_exists($action_next_state, $states_list))
        return "Invalid nextState specified in action at state '$state_name'$error_message_suffix: '$action_next_state'";
      $new_action['nextState'] = $action_next_state;
                  
      $result[] = $new_action;
    }
    //now redistribute the remaining probability :)
    if ($actions_with_no_probability > 0) {
      foreach (array_keys($result) as $action_key) {
        if (!array_key_exists('probability', $result[$action_key])) {
          $result[$action_key]['probability'] = (1.0 - $probability_sum) / $actions_with_no_probability;
        }
      }
    }
    //finally sum up the probability and check it (must be 1.0)
    $probability_sum = 0.0;
    foreach ($result as $action)
      $probability_sum += $action['probability'];
    if (abs(1.0 - $probability_sum) > 0.001)
      return "The sum of probabilities for state '$state_name'$error_message_suffix is way off from 1.0"; 
    
    return $result;
  }

  //returns a structure which completly describes the state machine
  //returns a string with an error message if the XML failed to follow
  //the rules
  function loadStateMachine($state_machine_xml) {
    $doc = new DOMDocument();
    $doc->loadXML($state_machine_xml);    
    
    //this will be the result is all goes well
    $result = array();
    
    //find all the valid message
    $xpath = new DOMXPath($doc);
    $valid_messages = array();
    foreach ($xpath->query('//stateMachine/messages/message') as $valid_message) {
      if (null === getAttributeOrNull($valid_message, 'name'))
        return "Found message element which doesn't have the 'name' attribute!";
      $valid_messages[getAttributeOrNull($valid_message, 'name')] = 1;
    } 
    if (0 >= count($valid_messages))
      return 'No valid message names found!';   
          
    //now parse states
    $result['states'] = array();
    $states = $doc->getElementsByTagName('state');
    if (0 >= $states->length)
      return 'No state elements found!';
    
    //first store the state names so that we can validate them later on
    foreach ($states as $state) {
      if (null === ($state_name = getAttributeOrNull($state, 'name')))
        return 'Found state with no name!';
      if (array_key_exists($state_name, $result['states']))
        return "Found state with duplicate name: '$state_name'";
      $result['states'][$state_name] = array();
    }
    
    foreach ($states as $state) {
      //validate the basic parameters for the state
      $state_name = getAttributeOrNull($state, 'name');
      if (null === ($state_type = getAttributeOrNull($state, 'type')))
        return 'Found state with no type!';
      if ( ('message' != $state_type) && ('auto' != $state_type) )
        return "Found state with invalid type: '$state_type'";
        
      //save the validated stuff
      $result['states'][$state_name]['type'] = $state_type;
      
      //process the available state transitions
      if ('message' == $state_type) {
        $messages = $state->getElementsByTagName('message');
        $result['states'][$state_name]['messages'] = array();
        foreach ($messages as $message) {
          //message name: - it should exists, - it should be valid and - it shouldn't be used before (in this state)
          if (null === ($message_name = getAttributeOrNull($message, 'name')))
            return "Found message with no name in state '$state_name'";
          if (!array_key_exists($message_name, $valid_messages))
            return "Found invalid message name '$message_name' in state '$state_name'";
          if (array_key_exists($message_name, $result['states'][$state_name]['messages']))          
            return "Found duplicate message name '$message_name' in state '$state_name'";
          $result['states'][$state_name]['messages'][$message_name] = array();
          
          $result['states'][$state_name]['messages'][$message_name]['actions'] = 
            extractActions($message, $result['states'], $state_name, $message_name);
          if (is_string($result['states'][$state_name]['messages'][$message_name]['actions']))
            //an error has occured
            return $result['states'][$state_name]['messages'][$message_name]['actions'];
        }       
      } else {
        //load the actions we can chose from
        $result['states'][$state_name]['actions'] = 
          extractActions($state, $result['states'], $state_name, '');
        if (is_string($result['states'][$state_name]['actions']))
          //an error has occurred
          return $result['states'][$state_name]['actions'];
      }
    }
      
    //get the starting state and make sure that it's a valid state
    if (null === ($initial_state = getAttributeOrNull($doc->documentElement, 'initialState')))
      return 'Document has no initial state!';      
    if (!array_key_exists($initial_state, $result['states']))
      return 'Initial state is invalid!';   
    $result['currentState'] = $initial_state;   
    
    return $result;
  }
  
  function loadStateMachineFromFile($file_machine) {
    $xml_file_contents = file_get_contents($file_machine);
    if (get_magic_quotes_gpc()) $xml_file_contents = stripslashes($xml_file_contents);
    return loadStateMachine($xml_file_contents);
  }
  
  //applies a given message to a given state machine. it executes the specified waits
  //returns the modified state machine. If an error occured, the currentState will be set to ''
  function internalPostMessage($state_machine, $message = '') {
    //print "Applying message: '$message'n";
    //print "Current state: $state_machine[currentState]n";
    
    //we are in an invalid state - we can't do anything
    if (!array_key_exists($state_machine['currentState'], $state_machine['states']))
      return $state_machine;
        
    if ('message' == $state_machine['states'][$state_machine['currentState']]['type']) {
      if (!array_key_exists($message, $state_machine['states'][$state_machine['currentState']]['messages'])) {
        //this message can not be applied now
        $state_machine['currentState'] = '';
        return $state_machine;
      }
      $actions = $state_machine['states'][$state_machine['currentState']]['messages'][$message]['actions'];
    } else {
      $actions = $state_machine['states'][$state_machine['currentState']]['actions'];
    }
        
    //now chose an action, by "throwing a dice"
    $rand_value = rand(0, 32768) / 32768;
    $action_to_execute = null;
    foreach ($actions as $action) {
      $action_to_execute = $action;
      if ($rand_value <= $action['probability'])        
        break;      
      $rand_value -= $action['probability'];
    }   
    
    //print "Going to state $action[nextState]n";
    //now execute the action        
    sleep(intval($action['waitBefore'] / 1000 + 0.5));
    $state_machine['currentState'] = $action['nextState'];    
    sleep(intval($action['waitAfter'] / 1000 + 0.5));
    //print "Gone to state $action[nextState]n";   
    
    return $state_machine;
  }
  
  //the same as above, however it continues while possible after the first move
  //(while the current state is an automatic one)
  function postMessageWhilePossible($state_machine, $message) {
    //process any automatic statest BEFORE
    while ( ('' != $state_machine['currentState']) &&
      ('auto' == $state_machine['states'][$state_machine['currentState']]['type']) ) {
      $state_machine = internalPostMessage($state_machine);
    }
    if ('' != $state_machine['currentState'])
      $state_machine = internalPostMessage($state_machine, $message);
    //process any automatic statest AFTER
    while ( ('' != $state_machine['currentState']) &&
      ('auto' == $state_machine['states'][$state_machine['currentState']]['type']) ) {
      $state_machine = internalPostMessage($state_machine);
    }
    return $state_machine;
  } 
?>

<stateMachine initialState="Off">
  <messages>
    <message name="Flip" />
  </messages>
  <state name="Off" type="message">
    <message name="Flip">
      <action probability="0.5" nextState="Transient" />
      <action probability="0.5" nextState="Off" />
    </message>
  </state>
  <state name="Transient" type="auto">
    <action probability="0.9" nextState="On" waitBefore="1000" />
    <action probability="0.1" nextState="Off" waitBefore="1000" />  
  </state>
  <state name="On" type="message">
    <message name="Flip">
      <action nextState="Off" />  
    </message>
  </state>
</stateMachine>