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1<?php
2
3/**
4 * This program is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU General Public License
6 * as published by the Free Software Foundation; under version 2
7 * of the License (non-upgradable).
8 *
9 * This program is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
12 * GNU General Public License for more details.
13 *
14 * You should have received a copy of the GNU General Public License
15 * along with this program; if not, write to the Free Software
16 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
17 *
18 * Copyright (c) 2019 (original work) Open Assessment Technologies SA;
19 */
20
21namespace oat\generis\model\resource;
22
23use common_persistence_SqlPersistence;
24use core_kernel_classes_Class;
25use Countable;
26use Iterator;
27use common_persistence_sql_Filter as Filter;
28use oat\generis\model\OntologyAwareTrait;
29use oat\generis\model\OntologyRdf;
30use Zend\ServiceManager\ServiceLocatorAwareTrait;
31
32/**
33 * Collection for resources.
34 *
35 * @author Martijn Swinkels <martijn@taotesting.com>
36 */
37class ResourceCollection implements Iterator, Countable
38{
39    use ServiceLocatorAwareTrait;
40    use OntologyAwareTrait;
41
42    public const CACHE_SIZE = 100;
43
44    /**
45     * @var string[]
46     */
47    private $resources;
48
49    /**
50     * @var int
51     */
52    private $index = 0;
53
54    /**
55     * @var Filter
56     */
57    private $filter;
58
59    /**
60     * @var bool
61     */
62    private $endOfClass;
63
64    /**
65     * @var core_kernel_classes_Class
66     */
67    private $class;
68
69    /**
70     * @var int
71     */
72    private $cacheSize;
73
74    /**
75     * @var int
76     */
77    private $lastId = 0;
78
79    /**
80     * @var bool
81     */
82    private $classFilterSet = false;
83
84    /**
85     * @var int
86     */
87    private $limit;
88
89    /**
90     * ResourceCollection constructor.
91     *
92     * @param null|string|core_kernel_classes_Class $class
93     * @param int $cacheSize
94     */
95    public function __construct($class = null, $cacheSize = self::CACHE_SIZE)
96    {
97        if ($class !== null) {
98            $class = $this->getClass($class);
99        }
100        $this->class = $class;
101        $this->filter = new Filter();
102        $this->cacheSize = $cacheSize;
103    }
104
105    /**
106     * Load a collection of resources
107     *
108     * @return bool
109     */
110    protected function load()
111    {
112        if ($this->resources !== null) {
113            return $this->count() > 0;
114        }
115
116        $this->resources = null;
117        $this->index = 0;
118        $this->loadResources();
119
120        return $this->count() > 0;
121    }
122
123    /**
124     * Load resources from storage
125     */
126    private function loadResources()
127    {
128        if ($this->class !== null && $this->classFilterSet === false) {
129            $this->addClassFilter();
130        }
131
132        /** @var common_persistence_SqlPersistence $persistence */
133        $persistence = $this->getModel()->getPersistence();
134        $platform = $persistence->getPlatForm();
135        $query = $platform->getQueryBuilder()
136            ->select('*')
137            ->from('statements')
138            ->andWhere('id > ' . $this->lastId)
139            ->orderBy('id');
140
141        if ($this->cacheSize > 0) {
142            $query->setMaxResults($this->cacheSize);
143        }
144
145        $query = $this->filter->applyFilters($query);
146        $results = $query->execute();
147
148        if ($this->cacheSize > 0) {
149            $this->endOfClass = $results->rowCount() < $this->cacheSize;
150        }
151
152        foreach ($results->fetchAll() as $result) {
153            $this->resources[] = $result;
154            $this->lastId = $result['id'] > $this->lastId ? $result['id'] : $this->lastId;
155        }
156    }
157
158    /**
159     * Add a filter to filter the resources we should iterate over.
160     *
161     * @param string $column
162     * @param string $operator
163     * @param mixed $value
164     * @return ResourceCollection
165     */
166    public function addFilter($column, $operator, $value)
167    {
168        $this->filter->addFilter($column, $operator, $value);
169        return $this;
170    }
171
172    /**
173     * Add a type resource filter.
174     *
175     * @param string $type
176     * @return ResourceCollection
177     */
178    public function addTypeFilter($type)
179    {
180        $this->filter->eq('predicate', OntologyRdf::RDF_TYPE)
181                     ->eq('object', $type);
182        return $this;
183    }
184
185    /**
186     * @inheritdoc
187     */
188    public function count()
189    {
190        if (!is_array($this->resources) && !$this->resources instanceof Countable) {
191            return 0;
192        }
193
194        return count($this->resources);
195    }
196
197    /**
198     * @inheritdoc
199     */
200    public function current()
201    {
202        return $this->resources[$this->index];
203    }
204
205    /**
206     * @inheritdoc
207     */
208    public function next()
209    {
210        $this->index++;
211    }
212
213    /**
214     * @inheritdoc
215     */
216    public function key()
217    {
218        return $this->index;
219    }
220
221    /**
222     * @inheritdoc
223     */
224    public function valid()
225    {
226        if ($this->resources === null) {
227            return $this->load();
228        }
229
230        if ($this->endOfClass === false && !isset($this->resources[$this->index])) {
231            if ($this->isLimitReached()) {
232                $this->resources = null;
233                return false;
234            }
235            $this->resources = null;
236            return $this->load();
237        }
238
239        return isset($this->resources[$this->index]);
240    }
241
242    /**
243     * @inheritdoc
244     */
245    public function rewind()
246    {
247        $this->index = 0;
248    }
249
250    /**
251     * Activate a limitation of how many resources should be processed. This is different from cache size, since it
252     * limits the amount of items that are processed in e.g. a foreach loop without loading remaining resources.
253     */
254    public function useLimit()
255    {
256        $this->limit = $this->cacheSize;
257    }
258
259    /**
260     * Check if we reached the limit of the amount of items we should process.
261     *
262     * @return bool
263     */
264    private function isLimitReached()
265    {
266        return $this->limit !== null && $this->count() >= $this->limit;
267    }
268
269    /**
270     * Check if the end of the current class is reached (no more records available)
271     * @return bool
272     */
273    public function getEndReached()
274    {
275        return $this->endOfClass;
276    }
277
278    /**
279     * Adds a filter for a class
280     */
281    private function addClassFilter()
282    {
283        $this->addTypeFilter($this->class->getUri());
284        $this->classFilterSet = true;
285    }
286}