v2: Updates

* Simplifies & beautifies everything
* Introduces a new Class system.
* Errors are defaulted to AWS's handler.
* New function names & more efficient handling.
* Should fix a majority of the errors.

Please read the README for more!

aws/Aws/AbstractConfigurationProvider.php

@@ -0,0 +1,157 @@
+<?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));
+    }
+}