class PhpParser

final class PhpParser {
    
    /**
     * Parse a class or function for use statements.
     *
     * @param ReflectionClass|ReflectionFunction $reflection
     *
     * @psalm-return array<string, string> a list with use statements in the form (Alias => FQN).
     */
    public function parseUseStatements($reflection) : array {
        if (method_exists($reflection, 'getUseStatements')) {
            return $reflection->getUseStatements();
        }
        $filename = $reflection->getFileName();
        if ($filename === false) {
            return [];
        }
        $content = $this->getFileContent($filename, $reflection->getStartLine());
        if ($content === null) {
            return [];
        }
        $namespace = preg_quote($reflection->getNamespaceName());
        $content = preg_replace('/^.*?(\\bnamespace\\s+' . $namespace . '\\s*[;{].*)$/s', '\\1', $content);
        $tokenizer = new TokenParser('<?php ' . $content);
        return $tokenizer->parseUseStatements($reflection->getNamespaceName());
    }
    
    /**
     * Gets the content of the file right up to the given line number.
     *
     * @param string $filename   The name of the file to load.
     * @param int    $lineNumber The number of lines to read from file.
     *
     * @return string|null The content of the file or null if the file does not exist.
     */
    private function getFileContent(string $filename, $lineNumber) {
        if (!is_file($filename)) {
            return null;
        }
        $content = '';
        $lineCnt = 0;
        $file = new SplFileObject($filename);
        while (!$file->eof()) {
            if ($lineCnt++ === $lineNumber) {
                break;
            }
            $content .= $file->fgets();
        }
        return $content;
    }

}