<?php

abstract class Job {
	private $_jobid = 0;
	private $_source = "unknown";

	public function __construct($source = "unknown") {
		$this->_source = $source;
	}

	// Implement this function to actually do the job
	abstract public function run();

	// Place the current job onto the queue ready for processing.
	public function queue() {
        $class = get_called_class();
		$data = serialize($this);
		$db = DB::getInstance();

		$this->_jobid = $db->insert("job", [
			"class" => $class,
			"data" => $data,
			"queued" => time(),
			"source" => $this->_source,
			"status" => "Queued",
		]);

		return $this->_jobid;
	}

	public function getJobClass() {
        $class = get_called_class();
		return $class;
	}

	public function jobID() {
		return $this->_jobid;
	}

	public function setJobID($id) {
		$this->_jobid = $id;
	}

	// Set the current status message
	public function status($txt) {
		$db = DB::getInstance();
		$db->update("job", $this->_jobid, [
			"status" => $txt
		]);
	}

	// Mark the job as completed successfully
	public function finish() {
		$db = DB::getInstance();
		$db->update("job", $this->_jobid, [
			"finished" => time(),
		]);
	}

	// Mark the job as failed miserably
	public function fail() {
		$db = DB::getInstance();
		$db->update("job", $this->_jobid, [
			"failed" => time(),
		]);
	}

	// Restart the job.
	public function retry() {
		$db = DB::getInstance();
		$db->update("job", $this->_jobid, [
			"failed" => 0,
			"finished" => 0,
			"started" => 0,
			"status" => "Retrying"
		]);
	}

	// Restart the job and defer it to a later time.
	public function defer($when) {
		$db = DB::getInstance();
		$db->update("job", $this->_jobid, [
			"failed" => 0,
			"finished" => 0,
			"started" => 0,
			"queued" => $when,
			"status" => "Deferred until " . gmdate("Y-m-d\TH:i:s\Z", $when)
		]);
	}
		
	// Look for the next available job that optionally has 
	// the requested class. Mark it as started, deserialize
	// it, and return the job runner object.
	// Returns false if no job available.
	public static function consumeNextJob($class = null) {
		$db = DB::getInstance();

		$db->query("lock table job write");
		if ($class == null) {
			$q = $db->query("select * from job where started=0 and queued < unix_timestamp(now()) order by queued limit 1");
		} else {
			$q = $db->query("select * from job where started=0 and queued < unix_timestamp(now()) and class=:class order by queued limit 1", ["class" => $class]);
		}
		$r = $db->nextRecord($q);
		if (!$r) {
			$db->query("unlock tables");
			return false;
		} 

		$db->update("job", $r->id, [
			"started" => time()
		]);
		$db->query("unlock tables");

		$ob = unserialize($r->data);
		$ob->setJobID($r->id);
		return $ob;
	}
}