84 lines
2.4 KiB
PHP
84 lines
2.4 KiB
PHP
<?php
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namespace App\Services;
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use Illuminate\Support\Collection;
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use Illuminate\Support\Facades\Cache;
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use Lvl0\AnagramFinder\Core\Matcher;
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/**
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* Caches anagram lookups. A search scans the whole dictionary — 466k words —
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* and the result is fixed for a given (letters, minLength, dictionary), so it
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* only ever needs computing once.
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*/
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class AnagramSearch
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{
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private const DICTIONARY = __DIR__ . '/../../vendor/anagram-finder/core/assets/words.txt';
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public function find(string $anagram, int $minLength = 3): Collection
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{
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$key = $this->key($anagram, $minLength);
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// Cache a plain array: a serialised Collection comes back as
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// __PHP_Incomplete_Class through the database store.
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$words = Cache::rememberForever(
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$key,
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fn () => Matcher::findWords($this->normalise($anagram), $minLength)
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->values()
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->all(),
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);
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return new Collection($words);
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}
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/**
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* Entries live forever; the dictionary hash in the key is the invalidation
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* mechanism. Replacing words.txt makes every old key unreachable rather
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* than stale, so nothing has to be flushed by hand.
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*/
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private function key(string $anagram, int $minLength): string
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{
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return sprintf(
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'anagram:%s:%d:%s',
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$this->dictionaryHash(),
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$minLength,
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$this->normalise($anagram),
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);
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}
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/**
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* Sorted letters, so "eamstoxil" and "latoximse" share one entry — the same
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* bag of letters is the same query.
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*/
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private function normalise(string $anagram): string
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{
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$letters = str_split(strtolower($anagram));
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sort($letters);
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return implode('', $letters);
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}
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/**
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* Content-addressed, not mtime: the dictionary ships inside the image, so
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* its mtime changes on every rebuild even when the words do not.
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*
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* Hashing 4.6MB per request would undo the saving, so the hash is itself
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* cached under a key made of the cheap stat values that change whenever the
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* file is replaced.
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*/
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private function dictionaryHash(): string
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{
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$path = self::DICTIONARY;
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if (! is_file($path)) {
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return 'nodict';
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}
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$stat = filemtime($path) . ':' . filesize($path);
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return Cache::rememberForever(
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"anagram:dict:{$stat}",
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fn () => hash_file('xxh128', $path),
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);
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}
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}
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