class Versions

class Versions {
    
    /**
     * @var string[]
     * @deprecated use Versions::CHANNELS
     */
    public static $channels = self::CHANNELS;
    public const CHANNELS = [
        'stable',
        'preview',
        'snapshot',
        '1',
        '2',
        '2.2',
    ];
    
    /** @var HttpDownloader */
    private $httpDownloader;
    
    /** @var Config */
    private $config;
    
    /** @var string */
    private $channel;
    
    /** @var array<string, array<int, array{path: string, version: string, min-php: int, eol?: true}>>|null */
    private $versionsData = null;
    public function __construct(Config $config, HttpDownloader $httpDownloader) {
        $this->httpDownloader = $httpDownloader;
        $this->config = $config;
    }
    public function getChannel() : string {
        if ($this->channel) {
            return $this->channel;
        }
        $channelFile = $this->config
            ->get('home') . '/update-channel';
        if (file_exists($channelFile)) {
            $channel = trim(file_get_contents($channelFile));
            if (in_array($channel, [
                'stable',
                'preview',
                'snapshot',
                '2.2',
            ], true)) {
                return $this->channel = $channel;
            }
        }
        return $this->channel = 'stable';
    }
    public function setChannel(string $channel, ?IOInterface $io = null) : void {
        if (!in_array($channel, self::CHANNELS, true)) {
            throw new \InvalidArgumentException('Invalid channel ' . $channel . ', must be one of: ' . implode(', ', self::CHANNELS));
        }
        $channelFile = $this->config
            ->get('home') . '/update-channel';
        $this->channel = $channel;
        // rewrite '2' and '1' channels to stable for future self-updates, but LTS ones like '2.2' remain pinned
        $storedChannel = Preg::isMatch('{^\\d+$}D', $channel) ? 'stable' : $channel;
        $previouslyStored = file_exists($channelFile) ? trim((string) file_get_contents($channelFile)) : null;
        file_put_contents($channelFile, $storedChannel . PHP_EOL);
        if ($io !== null && $previouslyStored !== $storedChannel) {
            $io->writeError('Storing "<info>' . $storedChannel . '</info>" as default update channel for the next self-update run.');
        }
    }
    
    /**
     * @return array{path: string, version: string, min-php: int, eol?: true}
     */
    public function getLatest(?string $channel = null) : array {
        $versions = $this->getVersionsData();
        foreach ($versions[$channel ?: $this->getChannel()] as $version) {
            if ($version['min-php'] <= \PHP_VERSION_ID) {
                return $version;
            }
        }
        throw new \UnexpectedValueException('There is no version of Composer available for your PHP version (' . PHP_VERSION . ')');
    }
    
    /**
     * @return array<string, array<int, array{path: string, version: string, min-php: int, eol?: true}>>
     */
    private function getVersionsData() : array {
        if (null === $this->versionsData) {
            if ($this->config
                ->get('disable-tls') === true) {
                $protocol = 'http';
            }
            else {
                $protocol = 'https';
            }
            $this->versionsData = $this->httpDownloader
                ->get($protocol . '://getcomposer.org/versions')
                ->decodeJson();
        }
        return $this->versionsData;
    }

}