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<?php
require_once("pgq/PGQ.php");
require_once("pgq/SystemDaemon.php");

/**
* PGQConsumer is a SystemDaemon providing the PGQ SQL API for PHP
* applications, and implementing a simple Consumer model atop of it.
*
* Depending on your needs, please check more specialized classes
* PGQRemoteConsumer and PGQEventRemoteConsumer.
*
* Online references about PGQ are to be found here:
* http://skytools.projects.postgresql.org/doc/pgq-admin.html
* http://skytools.projects.postgresql.org/doc/pgq-sql.html
* http://skytools.projects.postgresql.org/doc/pgq-nodupes.html
*
* http://kaiv.wordpress.com/2007/10/19/skytools-database-scripting-framework-pgq/
*
* http://www.pgcon.org/2008/schedule/events/79.en.html
*
* When implementing a PGQConsumer, you should define following methods:
* - php_error_hook()
* - config()
* - process_event(&$event) --- $event is a PGQEvent
*
* See SystemDaemon header documentation for details about first two
* functions.
*
* The consumer model provided by PGQConsumer works by letting the
* inheriting worker define how to process a single event. The
* function process_event() will get called while in a transaction, so
* don't issue COMMIT or ROLLBACK on $this->pg_src_con.
*
* You should return one of those constants from process_event():
* PGQ_EVENT_OK, PGQ_EVENT_FAILED, PGQ_EVENT_RETRY or PGQ_ABORT_BATCH.
*
* The last will force ROLLBACK, use it when you encounter PostgreSQL
* level errors: the transactions are no more valid, you return
* PGQ_ABORT_BATCH and PGQConsumer will handle: batch is not finished,
* the error is considered not fatal.
*
* When you return PGQ_EVENT_RETRY or PGQ_EVENT_FAILED, PGQConsumer
* will call the matching pgq SQL function to tag the Event. In the
* retry case, PGQConsumer will get $event->retry_delay attribute to
* give to the SQL level API, and in the failed case,
* $event->failed_reason.
*
* PGQConsumer supports same commands as SystemDaemon, and some more:
* install, uninstall, create_queue, drop_queue, register, unregister
* failed, delete <event_id|all>, retry <event_id|all>
*
* See SystemDaemon documentation for using this class at PHP and
* command line levels.
*/

abstract class PGQConsumer extends SystemDaemon
{
  protected $connected = False;
  protected $src_constr;
  protected $pg_src_con;

  protected $cname; // consumer name (pgq consumer id)
  protected $qname; // queue name

  public function __construct($cname, $qname, $argc, $argv, $src_constr)
  {
    $this->cname = $cname;
    $this->qname = $qname;

    $this->commands[] = "install";
    $this->commands[] = "uninstall";
    $this->commands[] = "check";
    $this->commands[] = "create_queue";
    $this->commands[] = "drop_queue";
    $this->commands[] = "register";
    $this->commands[] = "unregister";
    $this->commands[] = "failed";
    $this->commands[] = "delete";
    $this->commands[] = "retry";

    $this->src_constr = $src_constr;

    parent::__construct($argc, $argv);
  }

  /**
* Implement those functions when inheriting from this class.
*/
  public function config() {}

  /**
* Optionnal hooks
*/
  public function preprocess_event($event) {}
  public function postprocess_event($event) {}

  /**
* We overload SystemDaemon::main() in order to support our specific
* commands too.
*/
  public function main($argc, $argv) {
    if( $argc < 2 ) {
      fprintf(STDERR, $this->usage($this->name));
      exit(1);
    }

    switch( $argv[1] )
      {
      case "install":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not install an already running daemon.");
else {
$ret = $this->install();
exit($ret ? 0 : 1);
}
break;

      case "uninstall":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not uninstall a running daemon.");
else {
$ret = $this->uninstall();
exit($ret ? 0 : 1);
}
break;

      case "check":
$pid = $this->getpid();
if( $pid !== False ) {
$this->log->fatal("Daemon already running.");
$this->status();
}
else {
$ret = $this->check();
exit($ret ? 0 : 1);
}
break;

      case "create_queue":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not create queue for an already running daemon.");
else {
if( $this->connect() === False ) {
exit(3);
}
else {
$ret = $this->create_queue();
$this->disconnect();
exit($ret ? 0 : 1);
}
}
break;

      case "drop_queue":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not drop queue for a running daemon.");
else {
if( $this->connect() === False ) {
exit(3);
}
else {
$ret = $this->drop_queue();
$this->disconnect();
exit($ret ? 0 : 1);
}
}
break;

      case "register":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not register already running daemon.");
else {
if( $this->connect() === False ) {
exit(3);
}
else {
$ret = $this->register();
$this->disconnect();

exit($ret ? 0 : 1);
}
}
break;

      case "unregister":
$pid = $this->getpid();
if( $pid !== False )
$this->log->fatal("Can not unregister already running daemon.");
else {
$force = False;
if( $argc >= 3 ) {
$force = ($argv[2] == "--force");

if( $force != True ) {
$this->log->fatal("unregister [--force]");
exit(1);
}
}

if( $this->connect() === False ) {
exit(3);
}
else {
if( $force )
$ret = $this->force_unregister();
else {
if( $this->check_unregister() )
$ret = $this->force_unregister();
else
$ret = False;
}

$this->disconnect();

exit($ret ? 0 : 1);
}
}
break;

      case "failed":
if( $this->connect() === False ) {
exit(3);
}
else {
$events = $this->failed_event_list();
if( $events !== False )
foreach( $events as $event ) {
echo $event."\n";
}
else
$this->log->warning("Failed event list is empty.");
$this->disconnect();
exit(0);
}
break;

      case "delete":
if( $argc < 3 ) {
$this->log->fatal("delete <event_id> [<event_id> ...]");
exit(1);
}

if( $this->connect() === False ) {
exit(3);
}
else {
if( $argv[2] == "all" )
$this->failed_event_delete_all();
else {
for($i = 2; $i < $argc; $i++) {
$this->failed_event_delete($argv[$i]);
}
}
$this->disconnect();
exit(0);
}
break;

      case "retry":
if( $argc < 3 ) {
$this->log->fatal("delete <event_id> [<event_id> ...]");
exit(1);
}
if( $this->connect() === False ) {
exit(3);
}
else {
if( $argv[2] == "all" )
$this->failed_event_retry_all();
else {
for($i = 2; $i < $argc; $i++) {
$this->failed_event_retry($argv[$i]);
}
}
$this->disconnect();
exit(0);
}
break;

      default:
/**
* Support daemon commands: start, stop, reload, restart, ...
*/
parent::main($argc, $argv);
break;
      }
  }

  /**
* Check installation is ok before to run.
*/
  public function run() {
    if( $this->check() )
      parent::run();
    else
      $this->stop();
  }

  /**
* Stop is called either at normal exit or when receiving an error,
* PHP errors included.
*/
  public function stop() {
    if( $this->connected ) {
      $this->rollback();
      $this->disconnect();
    }
    parent::stop();
  }

  /**
* Process available batches, sleeping only when next_batch() returns null.
*
* We want to consume empty batches as fast as possible to avoid
* lagging behind.
*
* Sleep only when next_batch() is null.
* null: no more batches awaiting us to process, we sleep
* True: successfully processed a batch, have it processed
* False: failed to get next_batch, sleep (temp. failure?)
*
* The sleeping is cared about at SystemDaemon level, in run()
* method, between process() calls.
*/
  public function process()
  {
    $sleep = False;

    if( $this->connect() === False ) {
      // Can't connect to database, transient error: return to sleep
      return;
    }

    while( ! $sleep && ! $this->killed ) {
      $batch_id = $this->next_batch();

      switch( $batch_id ) {
      case null:
$this->log->verbose("PGQConsumer.process: next_batch is null, sleep.");
$sleep = True;
break;

      case False:
$this->log->verbose("PGQConsumer.process: failed to get batch.");
break;

      case True:
$this->log->verbose("PGQConsumer.process: \$this->process_batch(%d).",
$batch_id);

$this->process_batch($batch_id);
break;
      }
    }
    $this->disconnect();
  }

  /**
* We want that all events of a same batch to have been either
* processed or postponed by the end of this loop, so we only
* COMMIT; when no error arise.
*/
  public function process_batch($batch_id) {
    $events = $this->preprocess_batch($batch_id);

    if( $events === False) {
$this->log->verbose("PGQConsumer.preprocess_batch got not events (False).");
      return False;
    }

    /**
* Event processing loop!
*/
    $abort_batch = False;

    foreach( $events as $event ) {
      if( $abort_batch )
break;

      if( $this->preprocess_event($event) === PGQ_ABORT_BATCH ) {
$abort_batch = True;
      }
      else {
$tag = $event->tag( $this->process_event($event) );
$this->log->verbose("PGQConsumer.process_batch processed event %d of batch %d, tag %d",
$event->id, $batch_id, $tag);

switch( $tag ) {
case PGQ_ABORT_BATCH:
$this->log->verbose("PGQConsumer.process_batch got PGQ_ABORT_BATCH");
$abort_batch = True;
break;

case PGQ_EVENT_FAILED:
$this->event_failed($batch_id, $event);
break;

case PGQ_EVENT_RETRY:
$this->event_retry($batch_id, $event);
break;

case PGQ_EVENT_OK:
break;
}

if( ! $abort_batch ) {
if( $this->postprocess_event($event) === PGQ_ABORT_BATCH) {
$this->log->verbose("PGQConsumer.postprocess_event(%d) abort batches", $event->id);
$abort_batch = True;
}
}
      }
    }
    return $this->postprocess_batch($batch_id, $abort_batch);
  }

  /**
* Prepare batch processing, returns PGQEvent list or False if
* empty.
*
* Exists as a separate function for implementers to accomodate
* easily, see PGQRemoteConsumer.
*/
  public function preprocess_batch($batch_id) {
    pg_query($this->pg_src_con, "BEGIN;");

    $events = $this->get_batch_events($batch_id);

    if( $events === False ) {
      // batch with no event
      $this->log->debug("PGQConsumer.preprocess_batch got no events");
      $this->finish_batch($batch_id);
      pg_query($this->pg_src_con, "COMMIT;");
      return False;
    }
    $this->log->debug("PGQConsumer.preprocess_batch got %d events", count($events));
    return $events;
  }

  /**
* Conclude batch processing, COMMIT or ROLLBACK if $abort_batch,
* and call finish_batch().
*/
  public function postprocess_batch($batch_id, $abort_batch = False) {
    if( $abort_batch) {
     $this->log->warning("PGQConsumer.postprocess_batch aborts: ROLLBACK");
      $this->rollback();
      return False;
    }

    if( $this->finish_batch($batch_id) === False )
      $this->log->warning("Could not mark batch id %d as finished", $batch_id);

    pg_query($this->pg_src_con, "COMMIT;");
    return True;
  }

  /**
* print out deamon status, and detailed queue informations
*/
  public function status() {
    $pid = $this->getpid();
    if( $pid === False )
      printf("PGQConsumer %s is not running.\n", $this->name);
    else {
      printf("PGQConsumer %s is running with pid %d\n", $this->name, $pid);

      if( $this->connect() === False ) {
return;
      }
      $status = $this->get_consumer_info();
      foreach( $status as $k => $v)
printf("%s: %s\n", $k, $v);

      $this->disconnect();
    }
  }

  /**
* Consumer installation: create the queue and register consumer.
*/
  protected function install() {
    if( $this->connect() === False )
      return False;

    pg_query($this->pg_src_con, "BEGIN;");
    $ret = $this->create_queue();

    if( $ret ) {
      $ret = $this->register();
    }
    pg_query($this->pg_src_con, "COMMIT;");

    $this->disconnect();
    return $ret;
  }

  /**
* Consumer uninstall: unregister the consumer and drop the queue
*/
  protected function uninstall() {
    if( $this->connect() === False )
      return False;

    pg_query($this->pg_src_con, "BEGIN;");
    $ret = $this->unregister();

    if( $ret ) {
      $ret = $this->drop_queue();
    }
    pg_query($this->pg_src_con, "COMMIT;");

    $this->disconnect();
    return $ret;
  }

  /**
* Consumer check: check the queue exists and the consumer is
* registered.
*/
  protected function check() {
    if( $this->connect() === False )
      return False;

    $ret = $this->queue_exists();

    if( $ret ) {
      $ret = $this->is_registered();
    }
    $this->disconnect();

    return $ret;
  }

  /**
* check_unregister returns True when we can unregister without
* loosing data.
*
* This now means there's some other consumer registered.
* TODO: check for trigger absence when only 1 consumer is registered (us).
*/
  protected function check_unregister() {
    $consumers = $this->get_consumers();

    if( $consumers === False ) {
      $this->log->error("Couldn't get consumer list for %s", $this->qname);
      return False;
    }

    if ( count($consumers) > 1 ) {
      $this->log->notice("Some other consumers are registered, ".
"unregistering %s.", $this->cname);
      return True;
    }
    else {
      // We are the only one consumer
      $this->log->warning("This %s consumer is the only one registered, ".
"use --force to unregister it.", $this->cname);
      return False;
    }
    return False;
  }

  /**
* unregister without bothering.
*/
  protected function force_unregister() {
    return $this->unregister();
  }

  /**
* TODO.
* drop triggers on the provider
*/
  protected function drop_trigger() {
    return False;
  }

  /**
* TODO.
*
* keep data job is to go find non consumed events in the pgq queue
* and insert them again in the main table.
*/
  protected function keep_data() {
    if( $this->drop_trigger() ) {
      return False;
    }
    return False;
  }

  /**
* Connects to the conw & conp connection strings.
*/
  public function connect($force = False) {
    if( $this->connected && ! $force ) {
      $this->log->notice("connect called when connected is True");
      return True;
    }

    if( $this->src_constr != "" ) {
      $this->log->verbose("Opening pg_src connexion '%s'.", $this->src_constr);
      $this->pg_src_con = pg_connect($this->src_constr);

      if( $this->pg_src_con === False ) {
$this->log->error("Could not open pg_src connection '%s'.",
$this->src_constr);
// $this->stop();
return False;
      }
    }
    else {
      $this->log->error("Connexion string is empty, please fix.");
      return False;
    }

    $this->connected = True;
    return True;
  }

  /**
* Disconnect from databases
*/
  public function disconnect() {
    if( ! $this->connected ) {
      $this->log->notice("disconnect called when $this->connected is False");
      return;
    }

    if( $this->pg_src_con != null && $this->pg_src_con !== False ) {
      $this->log->verbose("Closing pg_src connection '%s'.",
$this->src_constr);
      pg_close($this->pg_src_con);
      $this->pg_src_con = null;
    }
    $this->connected = False;
  }

  /**
* ROLLBACK ongoing transactions on src & dst connections
*/
  protected function rollback() {
    if( $this->pg_src_con != null && $this->pg_src_con !== False ) {
      $this->log->notice("ROLLBACK pg_src connection '%s'.",
$this->src_constr);
      pg_query($this->pg_src_con, "ROLLBACK;");
    }
  }

  /**
* This hook is called when a PHP error at level
* E_USER_ERROR or E_ERROR is raised.
*
* Those errors are not considered fatal: abort current batch
* processing, but don't have the PGQConsumer daemon quit.
*/
  protected function php_error_hook() {
    $this->rollback();
  }


  protected function create_queue() {
    return PGQ::create_queue($this->log, $this->pg_src_con, $this->qname);
  }

  protected function drop_queue() {
    return PGQ::drop_queue($this->log, $this->pg_src_con, $this->qname);
  }

  protected function queue_exists() {
    return PGQ::queue_exists($this->log, $this->pg_src_con, $this->qname);
  }

  protected function register() {
    return PGQ::register($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function unregister() {
    return PGQ::unregister($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function is_registered() {
    return PGQ::is_registered($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function get_consumer_info() {
    return PGQ::get_consumer_info($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  public function get_consumers() {
    return PGQ::get_consumers($this->log, $this->pg_src_con, $this->qname);
  }

  protected function next_batch() {
    return PGQ::next_batch($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function finish_batch($batch_id) {
    return PGQ::finish_batch($this->log, $this->pg_src_con, $batch_id);
  }

  protected function get_batch_events($batch_id) {
    return PGQ::get_batch_events($this->log, $this->pg_src_con, $batch_id);
  }

  protected function event_failed($batch_id, $event) {
    return PGQ::event_failed($this->log, $this->pg_src_con, $batch_id, $event);
  }

  protected function event_retry($batch_id, $event) {
    return PGQ::event_retry($this->log, $this->pg_src_con, $batch_id, $event);
  }

  protected function maint_retry_events() {
    return PGQ::maint_retry_events($this->log, $this->pg_src_con);
  }

  protected function failed_event_list() {
    return PGQ::failed_event_list($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function failed_event_delete_all() {
    return PGQ::failed_event_delete_all($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function failed_event_delete($event_id) {
    return PGQ::failed_event_delete($this->log, $this->pg_src_con,
$this->qname, $this->cname, $event_id);
  }

  protected function failed_event_retry_all() {
    return PGQ::failed_event_retry_all($this->log, $this->pg_src_con,
$this->qname, $this->cname);
  }

  protected function failed_event_retry($event_id) {
    return PGQ::failed_event_retry($this->log, $this->pg_src_con,
$this->qname, $this->cname, $event_id);
  }
}
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