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<?php

namespace Aws\Token;

use Aws;

use Aws\Api\DateTimeResult;

use Aws\CacheInterface;

use Aws\Exception\TokenException;

use GuzzleHttp\Promise;

/**

 * Token providers are functions that accept no arguments and return a

 * promise that is fulfilled with an {@see \Aws\Token\TokenInterface}

 * or rejected with an {@see \Aws\Exception\TokenException}.

 *

 * <code>

 * use Aws\Token\TokenProvider;

 * $provider = TokenProvider::defaultProvider();

 * // Returns a TokenInterface or throws.

 * $token = $provider()->wait();

 * </code>

 *

 * Token providers can be composed to create a token using conditional

 * logic that can create different tokens in different environments. You

 * can compose multiple providers into a single provider using

 * {@see Aws\Token\TokenProvider::chain}. This function accepts

 * providers as variadic arguments and returns a new function that will invoke

 * each provider until a token is successfully returned.

 */

class TokenProvider

{

    use ParsesIniTrait;

    const ENV_PROFILE = 'AWS_PROFILE';

    /**

     * Create a default token provider tha checks for cached a SSO token from

     * the CLI

     *

     * This provider is automatically wrapped in a memoize function that caches

     * previously provided tokens.

     *

     * @param array $config Optional array of token provider options.

     *

     * @return callable

     */

    public static function defaultProvider(array $config = [])

    {

        $cacheable = [

            'sso',

        ];

        $defaultChain = [];

        if (

            !isset($config['use_aws_shared_config_files'])

            || $config['use_aws_shared_config_files'] !== false

        ) {

            $profileName = getenv(self::ENV_PROFILE) ?: 'default';

            $defaultChain['sso'] = self::sso(

                $profileName,

                self::getHomeDir() . '/.aws/config',

                $config

            );

        }

        if (isset($config['token'])

            && $config['token'] instanceof CacheInterface

        ) {

            foreach ($cacheable as $provider) {

                if (isset($defaultChain[$provider])) {

                    $defaultChain[$provider] = self::cache(

                        $defaultChain[$provider],

                        $config['token'],

                        'aws_cached_' . $provider . '_token'

                    );

                }

            }

        }

        return self::memoize(

            call_user_func_array(

                [TokenProvider::class, 'chain'],

                array_values($defaultChain)

            )

        );

    }

    /**

     * Create a token provider function from a static token.

     *

     * @param TokenInterface $token

     *

     * @return callable

     */

    public static function fromToken(TokenInterface $token)

    {

        $promise = Promise\Create::promiseFor($token);

        return function () use ($promise) {

            return $promise;

        };

    }

    /**

     * Creates an aggregate token provider that invokes the provided

     * variadic providers one after the other until a provider returns

     * a token.

     *

     * @return callable

     */

    public static function chain()

    {

        $links = func_get_args();

        //Common use case for when aws_shared_config_files is false

        if (empty($links)) {

            return function () {

                return Promise\Create::promiseFor(false);

            };

        }

        return function () use ($links) {

            /** @var callable $parent */

            $parent = array_shift($links);

            $promise = $parent();

            while ($next = array_shift($links)) {

                $promise = $promise->otherwise($next);

            }

            return $promise;

        };

    }

    /**

     * Wraps a token provider and caches a previously provided token.

     * Ensures that cached tokens are refreshed when they expire.

     *

     * @param callable $provider Token provider function to wrap.

     * @return callable

     */

    public static function memoize(callable $provider)

    {

        return function () use ($provider) {

            static $result;

            static $isConstant;

            // Constant tokens will be returned constantly.

            if ($isConstant) {

                return $result;

            }

            // Create the initial promise that will be used as the cached value

            // until it expires.

            if (null === $result) {

                $result = $provider();

            }

            // Return a token that could expire and refresh when needed.

            return $result

                ->then(function (TokenInterface $token) use ($provider, &$isConstant, &$result) {

                    // Determine if the token is constant.

                    if (!$token->getExpiration()) {

                        $isConstant = true;

                        return $token;

                    }

                    if (!$token->isExpired()) {

                        return $token;

                    }

                    return $result = $provider();

                })

                ->otherwise(function($reason) use (&$result) {

                    // Cleanup rejected promise.

                    $result = null;

                    return Promise\Create::promiseFor(null);

                });

        };

    }

    /**

     * Wraps a token provider and saves provided token in an

     * instance of Aws\CacheInterface. Forwards calls when no token found

     * in cache and updates cache with the results.

     *

     * @param callable $provider Token provider function to wrap

     * @param CacheInterface $cache Cache to store the token

     * @param string|null $cacheKey (optional) Cache key to use

     *

     * @return callable

     */

    public static function cache(

        callable $provider,

        CacheInterface $cache,

        $cacheKey = null

    ) {

        $cacheKey = $cacheKey ?: 'aws_cached_token';

        return function () use ($provider, $cache, $cacheKey) {

            $found = $cache->get($cacheKey);

            if (is_array($found) && isset($found['token'])) {

                $foundToken = $found['token'];

                if ($foundToken instanceof TokenInterface) {

                    if (!$foundToken->isExpired()) {

                        return Promise\Create::promiseFor($foundToken);

                    }

                    if (isset($found['refreshMethod']) && is_callable($found['refreshMethod'])) {

                        return Promise\Create::promiseFor($found['refreshMethod']());

                    }

                }

            }

            return $provider()

                ->then(function (TokenInterface $token) use (

                    $cache,

                    $cacheKey

                ) {

                    $cache->set(

                        $cacheKey,

                        $token,

                        null === $token->getExpiration() ?

                    );

                    return $token;

                });

        };

    }

    /**

     * Gets profiles from the ~/.aws/config ini file

     */

    private static function loadDefaultProfiles() {

        $profiles = [];

        $configFile = self::getHomeDir() . '/.aws/config';

        if (file_exists($configFile)) {

            $configProfileData = \Aws\parse_ini_file($configFile, true, INI_SCANNER_RAW);

            foreach ($configProfileData as $name => $profile) {

                // standardize config profile names

                $name = str_replace('profile ', '', $name);

                if (!isset($profiles[$name])) {

                    $profiles[$name] = $profile;

                }

            }

        }

        return $profiles;

    }

    private static function reject($msg)

    {

        return new Promise\RejectedPromise(new TokenException($msg));

    }

    /**

     * Token provider that creates a token from cached sso credentials

     *

     * @param string $profileName the name of the ini profile name

     * @param string $filename the location of the ini file

     * @param array $config configuration options

     *

     * @return SsoTokenProvider

     * @see Aws\Token\SsoTokenProvider for $config details.

     */

    public static function sso($profileName, $filename, $config = [])

    {

        $ssoClient = isset($config['ssoClient']) ? $config['ssoClient'] : null;

        return new SsoTokenProvider($profileName, $filename, $ssoClient);

    }

}