<?php
namespace Aws;
use GuzzleHttp\Promise;
/**
* A configuration provider is a function that returns a promise that is
* fulfilled with a configuration object. This class provides base functionality
* usable by specific configuration provider implementations
*/
abstract class AbstractConfigurationProvider
{
const ENV_PROFILE = 'AWS_PROFILE';
const ENV_CONFIG_FILE = 'AWS_CONFIG_FILE';
public static $cacheKey;
protected static $interfaceClass;
protected static $exceptionClass;
/**
* Wraps a config provider and saves provided configuration in an
* instance of Aws\CacheInterface. Forwards calls when no config found
* in cache and updates cache with the results.
*
* @param callable $provider Configuration provider function to wrap
* @param CacheInterface $cache Cache to store configuration
* @param string|null $cacheKey (optional) Cache key to use
*
* @return callable
*/
public static function cache(
callable $provider,
CacheInterface $cache,
$cacheKey = null
) {
$cacheKey = $cacheKey ?: static::$cacheKey;
return function () use ($provider, $cache, $cacheKey) {
$found = $cache->get($cacheKey);
if ($found instanceof static::$interfaceClass) {
return Promise\promise_for($found);
}
return $provider()
->then(function ($config) use (
$cache,
$cacheKey
) {
$cache->set($cacheKey, $config);
return $config;
});
};
}
/**
* Creates an aggregate configuration provider that invokes the provided
* variadic providers one after the other until a provider returns
* configuration.
*
* @return callable
*/
public static function chain()
{
$links = func_get_args();
if (empty($links)) {
throw new \InvalidArgumentException('No providers in chain');
}
return function () use ($links) {
/** @var callable $parent */
$parent = array_shift($links);
$promise = $parent();
while ($next = array_shift($links)) {
$promise = $promise->otherwise($next);
}
return $promise;
};
}
/**
* Gets the environment's HOME directory if available.
*
* @return null|string
*/
protected static function getHomeDir()
{
// On Linux/Unix-like systems, use the HOME environment variable
if ($homeDir = getenv('HOME')) {
return $homeDir;
}
// Get the HOMEDRIVE and HOMEPATH values for Windows hosts
$homeDrive = getenv('HOMEDRIVE');
$homePath = getenv('HOMEPATH');
return ($homeDrive && $homePath) ? $homeDrive . $homePath : null;
}
/**
* Gets default config file location from environment, falling back to aws
* default location
*
* @return string
*/
protected static function getDefaultConfigFilename()
{
if ($filename = getenv(self::ENV_CONFIG_FILE)) {
return $filename;
}
return self::getHomeDir() . '/.aws/config';
}
/**
* Wraps a config provider and caches previously provided configuration.
*
* @param callable $provider Config provider function to wrap.
*
* @return callable
*/
public static function memoize(callable $provider)
{
return function () use ($provider) {
static $result;
static $isConstant;
// Constant config will be returned constantly.
if ($isConstant) {
return $result;
}
// Create the initial promise that will be used as the cached value
if (null === $result) {
$result = $provider();
}
// Return config and set flag that provider is already set
return $result
->then(function ($config) use (&$isConstant) {
$isConstant = true;
return $config;
});
};
}
/**
* Reject promise with standardized exception.
*
* @param $msg
* @return Promise\RejectedPromise
*/
protected static function reject($msg)
{
$exceptionClass = static::$exceptionClass;
return new Promise\RejectedPromise(new $exceptionClass($msg));
}
}