<?php

namespace Box\Spout\Reader\XLSX\Helper\SharedStringsCaching;

use Box\Spout\Reader\Exception\SharedStringNotFoundException;

/**
 * Class InMemoryStrategy
 *
 * This class implements the in-memory caching strategy for shared strings.
 * This strategy is used when the number of unique strings is low, compared to the memory available.
 *
 * @package Box\Spout\Reader\XLSX\Helper\SharedStringsCaching
 */
class InMemoryStrategy implements CachingStrategyInterface {

	/** @var \SplFixedArray Array used to cache the shared strings */
	protected $inMemoryCache;

	/** @var bool Whether the cache has been closed */
	protected $isCacheClosed;

	/**
	 * @param int $sharedStringsUniqueCount Number of unique shared strings
	 */
	public function __construct( $sharedStringsUniqueCount ) {
		$this->inMemoryCache = new \SplFixedArray( $sharedStringsUniqueCount );
		$this->isCacheClosed = false;
	}

	/**
	 * Adds the given string to the cache.
	 *
	 * @param string $sharedString The string to be added to the cache
	 * @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
	 * @return void
	 */
	public function addStringForIndex( $sharedString, $sharedStringIndex ) {
		if ( ! $this->isCacheClosed ) {
			$this->inMemoryCache->offsetSet( $sharedStringIndex, $sharedString );
		}
	}

	/**
	 * Closes the cache after the last shared string was added.
	 * This prevents any additional string from being added to the cache.
	 *
	 * @return void
	 */
	public function closeCache() {
		$this->isCacheClosed = true;
	}

	/**
	 * Returns the string located at the given index from the cache.
	 *
	 * @param int $sharedStringIndex Index of the shared string in the sharedStrings.xml file
	 * @return string The shared string at the given index
	 * @throws \Box\Spout\Reader\Exception\SharedStringNotFoundException If no shared string found for the given index
	 */
	public function getStringAtIndex( $sharedStringIndex ) {
		try {
			return $this->inMemoryCache->offsetGet( $sharedStringIndex );
		} catch ( \RuntimeException $e ) {
			throw new SharedStringNotFoundException( "Shared string not found for index: $sharedStringIndex" );
		}
	}

	/**
	 * Destroys the cache, freeing memory and removing any created artifacts
	 *
	 * @return void
	 */
	public function clearCache() {
		unset( $this->inMemoryCache );
		$this->isCacheClosed = false;
	}
}