<?php
// DbStatementCache.php
// Created: 2023-07-21
// Updated: 2024-08-03

namespace Index\Data;

/**
 * Container to avoid having many prepared instances of the same query.
 */
class DbStatementCache {
    /** @var array<string, IDbStatement> */
    private array $stmts = [];

    /**
     * @param IDbConnection $dbConn Connection to use with this cache.
     */
    public function __construct(
        private IDbConnection $dbConn
    ) {}

    private static function hash(string $query): string {
        return hash('xxh3', $query, true);
    }

    /**
     * Gets a cached or creates a new IDbStatement instance.
     *
     * @param string $query SQL query.
     * @return IDbStatement Statement representing the query.
     */
    public function get(string $query): IDbStatement {
        $hash = self::hash($query);

        if(array_key_exists($hash, $this->stmts)) {
            $stmt = $this->stmts[$hash];
            $stmt->reset();
            return $stmt;
        }

        return $this->stmts[$hash] = $this->dbConn->prepare($query);
    }

    /**
     * Removes a cached statement from the cache.
     *
     * @param string $query SQL query of the statement to remove from the cache.
     */
    public function remove(string $query): void {
        unset($this->stmts[self::hash($query)]);
    }

    /**
     * Closes all statement instances and resets the cache.
     */
    public function clear(): void {
        foreach($this->stmts as $stmt)
            $stmt->close();
        $this->stmts = [];
    }
}