ValueHasher::getEquivalence() - Code Metrics - marcospassos/phpcommon-comparison - Measure and Improve Code Quality continuously with Scrutinizer

ValueHasher::getEquivalence() A
last analyzed 2017-09-09 14:35 UTC

↳ Parent: ValueHasher

Complexity

Conditions	4
Paths	4

Size

Total Lines	16
Code Lines	8

Duplication

Lines	0
Ratio	0 %

Code Coverage

Tests	8
CRAP Score	4

Importance

Changes

Metric	Value
dl	0
loc	16
c	0
b	0
f	0
ccs	8
cts	8
cp	1
rs	9.2
cc	4
eloc	8
nc	4
nop	1
crap	4

<?php

/**
 * This file is part of the phpcommon/comparison package.
 *
 * (c) Marcos Passos <[email protected]>
 *
 * For the full copyright and license information, please view the LICENSE file
 * that was distributed with this source code.
 */

namespace PhpCommon\Comparison\Hasher;

use InvalidArgumentException;
use PhpCommon\Comparison\Equatable;
use PhpCommon\Comparison\Equivalence;
use PhpCommon\Comparison\Hasher;
use PhpCommon\Comparison\Hashable;

/**
 * Provides an external means for producing hash codes and comparing values for
 * equality.
 *
 * This equivalence relation delegates the equality check and hashing
 * strategy to the methods {@link PhpCommon\Comparison\Equatable::equals()} and
 * {@link PhpCommon\Comparison\Hashable::getHash()}, whenever the handled
 * values are instances of `Equatable` and `Hashable` respectively.
 *
 * @author Marcos Passos <[email protected]>
 */
class ValueHasher extends IdentityHasher
{
    /**
     * Maps a class name to an equivalence relation.
     *
     * @var Equivalence[]
     */
    protected $equivalences = [];

    /**
     * Creates a new value based equivalence relation.
     *
     * @param array $equivalences The equivalence relation mapping, with class
     *                            names as keys and relations as value.
     */
    public function __construct(array $equivalences = [])
    {
        $this->equivalences = $equivalences;
    }

    /**
     * {@inheritdoc}
     *
     * Two instances are considered equals if they are of the same
     * and if every type-specific relation defined in one is equal to the
     * corresponding relation in the other.
     */
    public function equals(Equatable $other)
    {
        if ($this === $other) {
            return true;
        }

        if (!parent::equals($other)) {
            return false;
        }

        /** @var ValueHasher $other */
        $equivalences = $other->getEquivalences();

        if (count($this->equivalences) !== count($equivalences)) {
            return false;
        }

        foreach ($this->equivalences as $type => $equivalence) {
            if (!isset($equivalences[$type])) {
                return false;
            }

            if (!$equivalence->equals($equivalences[$type])) {
                return false;
            }
        }

        return true;
    }

    /**
     * Returns the type-specific equivalence relations.
     *
     * @return Equivalence[] The type-specific relations, with class names as
     *                       keys and relations as values.
     */
    public function getEquivalences()
    {
        return $this->equivalences;
    }

    /**
     * Returns an equivalence relation suitable for comparing objects of the
     * specified class, if any.
     *
     * When no relation is explicitly defined for the specified class, this
     * method traverses up the class hierarchy to find the nearest ancestor for
     * which a relation is specified. For example, a relation specified for the
     * class `Vehicle` is used to compare instances of its subclass `Car`, when
     * no relation is explicitly specified for it.
     *
     * @param string $className The fully qualified name of the class for which
     *                          the relation should be suitable for.
     *
     * @return Equivalence|boolean The relation suitable for comparing objects
     *                             of the specified class, or `null` no
     *                             suitable relation is found.
     */
    protected function getEquivalence($className)
    {
        if (empty($this->equivalences)) {
            return false;
        }

        if (isset($this->equivalences[$className])) {
            return $this->equivalences[$className];
        }

        if (($parent = get_parent_class($className)) !== false) {
            return $this->getEquivalence($parent);
        }

        return false;
    }

    /**
     * {@inheritdoc}
     */
    protected function equivalentArray(array $left, $right)
    {
        if (!is_array($right) || count($left) !== count($right)) {
            return false;
        }

        foreach ($left as $key => $value) {
            if (!$this->equivalentString($key, key($right))) {
                return false;
            }

            if (!$this->equivalent($value, current($right))) {
                return false;
            }

            next($right);
        }

        return true;
    }

    /**
     * {@inheritdoc}
     *
     * The values are considered equivalent if any of the following conditions
     * hold:
     *
     * 1. The reference value is an instance of {@link Equatable} and the
     *    expression `$left->equals($right)` is evaluated to `true`
     * 2. A specific equivalence relation is mapped to the type of the left-hand
     *    value and the expression `$relation->equivalent($left, $right)` is
     *    evaluated to `true`
     * 3. Both values refer to the same instance of the same class (in a
     *    particular namespace)
     */
    protected function equivalentObject($left, $right)
    {
        if ($left instanceof Equatable xor $right instanceof Equatable) {
            return false;
        }

        if ($left instanceof Equatable) {
            return $left->equals($right);
        }

        $equivalence = $this->getEquivalence(get_class($left));

        if ($equivalence !== false) {
            return $equivalence->equivalent($left, $right);
        }

        if (is_object($right)) {
            $equivalence = $this->getEquivalence(get_class($right));

            if ($equivalence !== false) {
                return $equivalence->equivalent($right, $left);
            }
        }

        return parent::equivalentObject($left, $right);
    }

    /**
     * {@inheritdoc}
     *
     * The resulting hash code is guaranteed to be _consistent_ with the
     * {@link equivalentObject()} method, which means that for any references
     * `$x` and `$y`, if `equivalentObject($x, $y)`, then
     * `hashObject($x) === hashObject($y)`.
     *
     * The hash code is computed as follows:
     *
     * 1. If the specified object is an instance of {@link Hashable}, delegates
     *    the hashing strategy to the object being hashed.
     * 2. If a specific equivalence relation of type {@link Hasher} is mapped
     *    to the type of the given object, then uses the method
     *    {@link PhpCommon\Comparison\Hasher::hash()} as the hashing function
     * 3. If none of the previous rules apply, uses the method
     *    {@link PhpCommon\Comparison\Hasher\IdentityHasher::hashObject()} as
     *    the hash function
     *
     * @see hashObject()
     * @see PhpCommon\Comparison\Hashable::getHash()
     */
    protected function hashObject($value)
    {
        if ($value instanceof Hashable) {
            return self::HASH_OBJECT + $value->getHash();
        } elseif ($value instanceof Equatable) {
            throw new InvalidArgumentException(sprintf(
                'Any object implementing %s interface must also implement %s ' .
                'interface, otherwise the resulting hash code cannot be ' .
                'guaranteed by %s to be distributable across equivalences.',
                Equatable::class,
                Hashable::class,
                static::class
            ));
        }

        $equivalence = $this->getEquivalence(get_class($value));

        if ($equivalence instanceof Hasher) {
            return self::HASH_OBJECT + $equivalence->hash($value);
        }

        return parent::hashObject($value);
    }
}


1		<?php
2
3		/**
4		* This file is part of the phpcommon/comparison package.
5		*
6		* (c) Marcos Passos <[email protected]>
7		*
8		* For the full copyright and license information, please view the LICENSE file
9		* that was distributed with this source code.
10		*/
11
12		namespace PhpCommon\Comparison\Hasher;
13
14		use InvalidArgumentException;
15		use PhpCommon\Comparison\Equatable;
16		use PhpCommon\Comparison\Equivalence;
17		use PhpCommon\Comparison\Hasher;
18		use PhpCommon\Comparison\Hashable;
19
20		/**
21		* Provides an external means for producing hash codes and comparing values for
22		* equality.
23		*
24		* This equivalence relation delegates the equality check and hashing
25		* strategy to the methods {@link PhpCommon\Comparison\Equatable::equals()} and
26		* {@link PhpCommon\Comparison\Hashable::getHash()}, whenever the handled
27		* values are instances of `Equatable` and `Hashable` respectively.
28		*
29		* @author Marcos Passos <[email protected]>
30		*/
31		class ValueHasher extends IdentityHasher
32		{
33		/**
34		* Maps a class name to an equivalence relation.
35		*
36		* @var Equivalence[]
37		*/
38		protected $equivalences = [];
39
40		/**
41		* Creates a new value based equivalence relation.
42		*
43		* @param array $equivalences The equivalence relation mapping, with class
44		* names as keys and relations as value.
45		*/
46	156	public function __construct(array $equivalences = [])
47		{
48	156	$this->equivalences = $equivalences;
49	156	}
50
51		/**
52		* {@inheritdoc}
53		*
54		* Two instances are considered equals if they are of the same
55		* and if every type-specific relation defined in one is equal to the
56		* corresponding relation in the other.
57		*/
58	20	public function equals(Equatable $other)
59		{
60	20	if ($this === $other) {
61	4	return true;
62		}
63
64	16	if (!parent::equals($other)) {
65	2	return false;
66		}
67
68		/** @var ValueHasher $other */
69	14	$equivalences = $other->getEquivalences();
70
71	14	if (count($this->equivalences) !== count($equivalences)) {
72	2	return false;
73		}
74
75	12	foreach ($this->equivalences as $type => $equivalence) {
76	8	if (!isset($equivalences[$type])) {
77	2	return false;
78		}
79
80	6	if (!$equivalence->equals($equivalences[$type])) {
81	2	return false;
82		}
83	8	}
84
85	8	return true;
86		}
87
88		/**
89		* Returns the type-specific equivalence relations.
90		*
91		* @return Equivalence[] The type-specific relations, with class names as
92		* keys and relations as values.
93		*/
94	14	public function getEquivalences()
95		{
96	14	return $this->equivalences;
97		}
98
99		/**
100		* Returns an equivalence relation suitable for comparing objects of the
101		* specified class, if any.
102		*
103		* When no relation is explicitly defined for the specified class, this
104		* method traverses up the class hierarchy to find the nearest ancestor for
105		* which a relation is specified. For example, a relation specified for the
106		* class `Vehicle` is used to compare instances of its subclass `Car`, when
107		* no relation is explicitly specified for it.
108		*
109		* @param string $className The fully qualified name of the class for which
110		* the relation should be suitable for.
111		*
112		* @return Equivalence\|boolean The relation suitable for comparing objects
113		* of the specified class, or `null` no
114		* suitable relation is found.
115		*/
116	34	protected function getEquivalence($className)
117		{
118	34	if (empty($this->equivalences)) {
119	28	return false;
120		}
121
122	6	if (isset($this->equivalences[$className])) {
123	6	return $this->equivalences[$className];
124		}
125
126	6	if (($parent = get_parent_class($className)) !== false) {
127	4	return $this->getEquivalence($parent);
128		}
129
130	2	return false;
131		}
132
133		/**
134		* {@inheritdoc}
135		*/
136	72	protected function equivalentArray(array $left, $right)
137		{
138	72	if (!is_array($right) \|\| count($left) !== count($right)) {
139	8	return false;
140		}
141
142	64	foreach ($left as $key => $value) {
143	54	if (!$this->equivalentString($key, key($right))) {
144	4	return false;
145		}
146
147	50	if (!$this->equivalent($value, current($right))) {
148	28	return false;
149		}
150
151	26	next($right);
152	36	}
153
154	32	return true;
155		}
156
157		/**
158		* {@inheritdoc}
159		*
160		* The values are considered equivalent if any of the following conditions
161		* hold:
162		*
163		* 1. The reference value is an instance of {@link Equatable} and the
164		* expression `$left->equals($right)` is evaluated to `true`
165		* 2. A specific equivalence relation is mapped to the type of the left-hand
166		* value and the expression `$relation->equivalent($left, $right)` is
167		* evaluated to `true`
168		* 3. Both values refer to the same instance of the same class (in a
169		* particular namespace)
170		*/
171	62	protected function equivalentObject($left, $right)
172		{
173	62	if ($left instanceof Equatable xor $right instanceof Equatable) {
174	6	return false;
175		}
176
177	56	if ($left instanceof Equatable) {
178	24	return $left->equals($right);
179		}
180
181	32	$equivalence = $this->getEquivalence(get_class($left));
182
183	32	if ($equivalence !== false) {
184	4	return $equivalence->equivalent($left, $right);
185		}
186
187	30	if (is_object($right)) {
188	26	$equivalence = $this->getEquivalence(get_class($right));
189
190	26	if ($equivalence !== false) {
191	2	return $equivalence->equivalent($right, $left);
192		}
193	24	}
194
195	28	return parent::equivalentObject($left, $right);
196		}
197
198		/**
199		* {@inheritdoc}
200		*
201		* The resulting hash code is guaranteed to be _consistent_ with the
202		* {@link equivalentObject()} method, which means that for any references
203		* `$x` and `$y`, if `equivalentObject($x, $y)`, then
204		* `hashObject($x) === hashObject($y)`.
205		*
206		* The hash code is computed as follows:
207		*
208		* 1. If the specified object is an instance of {@link Hashable}, delegates
209		* the hashing strategy to the object being hashed.
210		* 2. If a specific equivalence relation of type {@link Hasher} is mapped
211		* to the type of the given object, then uses the method
212		* {@link PhpCommon\Comparison\Hasher::hash()} as the hashing function
213		* 3. If none of the previous rules apply, uses the method
214		* {@link PhpCommon\Comparison\Hasher\IdentityHasher::hashObject()} as
215		* the hash function
216		*
217		* @see hashObject()
218		* @see PhpCommon\Comparison\Hashable::getHash()
219		*/
220	14	protected function hashObject($value)
221		{
222	14	if ($value instanceof Hashable) {
223	6	return self::HASH_OBJECT + $value->getHash();
224	8	} elseif ($value instanceof Equatable) {
225	2	throw new InvalidArgumentException(sprintf(
226		'Any object implementing %s interface must also implement %s ' .
227	2	'interface, otherwise the resulting hash code cannot be ' .
228	2	'guaranteed by %s to be distributable across equivalences.',
229	2	Equatable::class,
230	2	Hashable::class,
231	2	static::class
232	2	));
233		}
234
235	6	$equivalence = $this->getEquivalence(get_class($value));
236
237	6	if ($equivalence instanceof Hasher) {
238	2	return self::HASH_OBJECT + $equivalence->hash($value);
239		}
240
241	4	return parent::hashObject($value);
242		}
243		}
244

marcospassos / phpcommon-comparison

ValueHasher::getEquivalence() A last analyzed 2017-09-09 14:35 UTC

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ValueHasher::getEquivalence() A
last analyzed 2017-09-09 14:35 UTC