Complex classes like Calendar often do a lot of different things. To break such a class down, we need to identify a cohesive component within that class. A common approach to find such a component is to look for fields/methods that share the same prefixes, or suffixes. You can also have a look at the cohesion graph to spot any un-connected, or weakly-connected components.
Once you have determined the fields that belong together, you can apply the Extract Class refactoring. If the component makes sense as a sub-class, Extract Subclass is also a candidate, and is often faster.
While breaking up the class, it is a good idea to analyze how other classes use Calendar, and based on these observations, apply Extract Interface, too.
| 1 | <?php  | 
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| 19 | final class Calendar implements CalendarInterface, JsonLdSerializableInterface, SerializableInterface  | 
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| 20 | { | 
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| 21 | /**  | 
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| 22 | * @var CalendarType  | 
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| 23 | */  | 
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| 24 | protected $type;  | 
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| 25 | |||
| 26 | /**  | 
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| 27 | * @var DateTimeInterface  | 
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| 28 | */  | 
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| 29 | protected $startDate;  | 
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| 30 | |||
| 31 | /**  | 
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| 32 | * @var DateTimeInterface  | 
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| 33 | */  | 
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| 34 | protected $endDate;  | 
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| 35 | |||
| 36 | /**  | 
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| 37 | * @var Timestamp[]  | 
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| 38 | */  | 
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| 39 | protected $timestamps = [];  | 
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| 40 | |||
| 41 | /**  | 
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| 42 | * @var OpeningHour[]  | 
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| 43 | */  | 
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| 44 | protected $openingHours = [];  | 
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| 45 | |||
| 46 | /**  | 
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| 47 | * @param CalendarType $type  | 
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| 48 | * @param DateTimeInterface|null $startDate  | 
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| 49 | * @param DateTimeInterface|null $endDate  | 
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| 50 | * @param Timestamp[] $timestamps  | 
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| 51 | * @param OpeningHour[] $openingHours  | 
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| 52 | */  | 
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| 53 | public function __construct(  | 
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| 54 | CalendarType $type,  | 
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| 55 | ?DateTimeInterface $startDate = null,  | 
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| 56 | ?DateTimeInterface $endDate = null,  | 
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| 57 | array $timestamps = [],  | 
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| 58 | array $openingHours = []  | 
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| 59 |     ) { | 
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| 60 |         if (empty($timestamps) && ($type->is(CalendarType::SINGLE()) || $type->is(CalendarType::MULTIPLE()))) { | 
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| 61 |             throw new \UnexpectedValueException('A single or multiple calendar should have timestamps.'); | 
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| 62 | }  | 
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| 63 | |||
| 64 |         if (($startDate === null || $endDate === null) && $type->is(CalendarType::PERIODIC())) { | 
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| 65 |             throw new \UnexpectedValueException('A period should have a start- and end-date.'); | 
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| 66 | }  | 
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| 67 | |||
| 68 |         foreach ($timestamps as $timestamp) { | 
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| 69 |             if (!is_a($timestamp, Timestamp::class)) { | 
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| 70 |                 throw new \InvalidArgumentException('Timestamps should have type TimeStamp.'); | 
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| 71 | }  | 
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| 72 | }  | 
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| 73 | |||
| 74 |         foreach ($openingHours as $openingHour) { | 
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| 75 |             if (!is_a($openingHour, OpeningHour::class)) { | 
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| 76 |                 throw new \InvalidArgumentException('OpeningHours should have type OpeningHour.'); | 
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| 77 | }  | 
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| 78 | }  | 
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| 79 | |||
| 80 | $this->type = $type->toNative();  | 
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| 81 | $this->startDate = $startDate;  | 
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| 82 | $this->endDate = $endDate;  | 
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| 83 | $this->openingHours = $openingHours;  | 
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| 84 | |||
| 85 |         usort($timestamps, function (Timestamp $timestamp, Timestamp $otherTimestamp) { | 
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| 86 | return $timestamp->getStartDate() <=> $otherTimestamp->getStartDate();  | 
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| 87 | });  | 
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| 88 | |||
| 89 | $this->timestamps = $timestamps;  | 
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| 90 | |||
| 91 | }  | 
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| 92 | |||
| 93 | public function getType(): CalendarType  | 
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| 94 |     { | 
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| 95 | return CalendarType::fromNative($this->type);  | 
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| 96 | }  | 
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| 97 | |||
| 98 | public function serialize(): array  | 
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| 99 |     { | 
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| 100 | $serializedTimestamps = array_map(  | 
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| 101 |             function (Timestamp $timestamp) { | 
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| 102 | return $timestamp->serialize();  | 
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| 103 | },  | 
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| 104 | $this->timestamps  | 
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| 105 | );  | 
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| 106 | |||
| 107 | $serializedOpeningHours = array_map(  | 
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| 108 |             function (OpeningHour $openingHour) { | 
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| 109 | return $openingHour->serialize();  | 
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| 110 | },  | 
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| 111 | $this->openingHours  | 
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| 112 | );  | 
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| 113 | |||
| 114 | $calendar = [  | 
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| 115 | 'type' => $this->type,  | 
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| 116 | ];  | 
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| 117 | |||
| 118 | empty($this->startDate) ?: $calendar['startDate'] = $this->startDate->format(DateTime::ATOM);  | 
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| 119 | empty($this->endDate) ?: $calendar['endDate'] = $this->endDate->format(DateTime::ATOM);  | 
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| 120 | empty($serializedTimestamps) ?: $calendar['timestamps'] = $serializedTimestamps;  | 
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| 121 | empty($serializedOpeningHours) ?: $calendar['openingHours'] = $serializedOpeningHours;  | 
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| 122 | |||
| 123 | return $calendar;  | 
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| 124 | }  | 
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| 125 | |||
| 126 | public static function deserialize(array $data): Calendar  | 
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| 127 |     { | 
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| 128 | $calendarType = CalendarType::fromNative($data['type']);  | 
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| 129 | |||
| 130 | // Backwards compatibility for serialized single or multiple calendar types that are missing timestamps but do  | 
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| 131 | // have a start and end date.  | 
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| 132 | $defaultTimeStamps = [];  | 
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| 133 |         if ($calendarType->sameValueAs(CalendarType::SINGLE()) || $calendarType->sameValueAs(CalendarType::MULTIPLE())) { | 
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| 134 | $defaultTimeStampStartDate = !empty($data['startDate']) ? self::deserializeDateTime($data['startDate']) : null;  | 
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| 135 | $defaultTimeStampEndDate = !empty($data['endDate']) ? self::deserializeDateTime($data['endDate']) : $defaultTimeStampStartDate;  | 
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| 136 | $defaultTimeStamp = $defaultTimeStampStartDate && $defaultTimeStampEndDate ? new Timestamp($defaultTimeStampStartDate, $defaultTimeStampEndDate) : null;  | 
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| 137 | $defaultTimeStamps = $defaultTimeStamp ? [$defaultTimeStamp] : [];  | 
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| 138 | }  | 
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| 139 | |||
| 140 | return new self(  | 
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| 141 | $calendarType,  | 
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| 142 | !empty($data['startDate']) ? self::deserializeDateTime($data['startDate']) : null,  | 
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| 143 | !empty($data['endDate']) ? self::deserializeDateTime($data['endDate']) : null,  | 
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| 144 | !empty($data['timestamps']) ? array_map(  | 
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| 145 |                 function ($timestamp) { | 
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| 146 | return Timestamp::deserialize($timestamp);  | 
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| 147 | },  | 
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| 148 | $data['timestamps']  | 
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| 149 | ) : $defaultTimeStamps,  | 
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| 150 | !empty($data['openingHours']) ? array_map(  | 
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| 151 |                 function ($openingHour) { | 
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| 152 | return OpeningHour::deserialize($openingHour);  | 
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| 153 | },  | 
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| 154 | $data['openingHours']  | 
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| 155 | ) : []  | 
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| 156 | );  | 
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| 157 | }  | 
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| 158 | |||
| 159 | /**  | 
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| 160 | * This deserialization function takes into account old data that might be missing a timezone.  | 
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| 161 | * It will fall back to creating a DateTime object and assume Brussels.  | 
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| 162 | * If this still fails an error will be thrown.  | 
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| 163 | */  | 
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| 164 | private static function deserializeDateTime(string $dateTimeData): DateTime  | 
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| 178 | |||
| 179 | public function getStartDate(): ?DateTimeInterface  | 
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| 180 |     { | 
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| 181 | $timestamps = $this->getTimestamps();  | 
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| 182 | |||
| 196 | |||
| 197 | public function getEndDate(): ?DateTimeInterface  | 
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| 214 | |||
| 215 | /**  | 
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| 216 | * @return array|OpeningHour[]  | 
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| 217 | */  | 
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| 218 | public function getOpeningHours(): array  | 
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| 222 | |||
| 223 | /**  | 
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| 224 | * @return array|Timestamp[]  | 
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| 225 | */  | 
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| 226 | public function getTimestamps(): array  | 
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| 230 | |||
| 231 | public function getEventStatusType(): EventStatusType  | 
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| 257 | |||
| 258 | public function toJsonLd(): array  | 
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| 293 | |||
| 294 | public function sameAs(Calendar $otherCalendar): bool  | 
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| 298 | |||
| 299 | public static function fromUdb3ModelCalendar(Udb3ModelCalendar $calendar): Calendar  | 
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| 333 | }  | 
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| 334 |