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<?phpnamespace Aws\Endpoint;
 
 use Aws\Exception\UnresolvedEndpointException;
 
 /**
 * Endpoint providers.
 *
 * An endpoint provider is a function that accepts a hash of endpoint options,
 * including but not limited to "service" and "region" key value pairs. The
 * endpoint provider function returns a hash of endpoint data, which MUST
 * include an "endpoint" key value pair that represents the resolved endpoint
 * or NULL if an endpoint cannot be determined.
 *
 * You can wrap your calls to an endpoint provider with the
 * {@see EndpointProvider::resolve} function to ensure that an endpoint hash is
 * created. If an endpoint hash is not created, then the resolve() function
 * will throw an {@see Aws\Exception\UnresolvedEndpointException}.
 *
 *     use Aws\Endpoint\EndpointProvider;
 *     $provider = EndpointProvider::defaultProvider();
 *     // Returns an array or NULL.
 *     $endpoint = $provider(['service' => 'ec2', 'region' => 'us-west-2']);
 *     // Returns an endpoint array or throws.
 *     $endpoint = EndpointProvider::resolve($provider, [
 *         'service' => 'ec2',
 *         'region'  => 'us-west-2'
 *     ]);
 *
 * You can compose multiple providers into a single provider using
 * {@see Aws\or_chain}. This function accepts providers as arguments and
 * returns a new function that will invoke each provider until a non-null value
 * is returned.
 *
 *     $a = function (array $args) {
 *         if ($args['region'] === 'my-test-region') {
 *             return ['endpoint' => 'http://localhost:123/api'];
 *         }
 *     };
 *     $b = EndpointProvider::defaultProvider();
 *     $c = \Aws\or_chain($a, $b);
 *     $config = ['service' => 'ec2', 'region' => 'my-test-region'];
 *     $res = $c($config);  // $a handles this.
 *     $config['region'] = 'us-west-2';
 *     $res = $c($config); // $b handles this.
 */
 class EndpointProvider
 {
 /**
 * Resolves and endpoint provider and ensures a non-null return value.
 *
 * @param callable $provider Provider function to invoke.
 * @param array    $args     Endpoint arguments to pass to the provider.
 *
 * @return array
 * @throws UnresolvedEndpointException
 */
 public static function resolve(callable $provider, array $args = [])
 {
 $result = $provider($args);
 if (is_array($result)) {
 return $result;
 }
 
 throw new UnresolvedEndpointException(
 'Unable to resolve an endpoint using the provider arguments: '
 . json_encode($args) . '. Note: you can provide an "endpoint" '
 . 'option to a client constructor to bypass invoking an endpoint '
 . 'provider.');
 }
 
 /**
 * Creates and returns the default SDK endpoint provider.
 *
 * @return callable
 */
 public static function defaultProvider()
 {
 $data = \Aws\load_compiled_json(__DIR__ . '/../data/endpoints.json');
 
 return new PatternEndpointProvider($data['endpoints']);
 }
 
 /**
 * Creates and returns an endpoint provider that uses patterns from an
 * array.
 *
 * @param array $patterns Endpoint patterns
 *
 * @return callable
 */
 public static function patterns(array $patterns)
 {
 return new PatternEndpointProvider($patterns);
 }
 }
 
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