1<?php
2namespace Aws;
3
4use GuzzleHttp\Promise;
5
6/**
7 * A configuration provider is a function that returns a promise that is
8 * fulfilled with a configuration object. This class provides base functionality
9 * usable by specific configuration provider implementations
10 */
11abstract class AbstractConfigurationProvider
12{
13    const ENV_PROFILE = 'AWS_PROFILE';
14    const ENV_CONFIG_FILE = 'AWS_CONFIG_FILE';
15
16    public static $cacheKey;
17
18    protected static $interfaceClass;
19    protected static $exceptionClass;
20
21    /**
22     * Wraps a config provider and saves provided configuration in an
23     * instance of Aws\CacheInterface. Forwards calls when no config found
24     * in cache and updates cache with the results.
25     *
26     * @param callable $provider Configuration provider function to wrap
27     * @param CacheInterface $cache Cache to store configuration
28     * @param string|null $cacheKey (optional) Cache key to use
29     *
30     * @return callable
31     */
32    public static function cache(
33        callable $provider,
34        CacheInterface $cache,
35        $cacheKey = null
36    ) {
37        $cacheKey = $cacheKey ?: static::$cacheKey;
38
39        return function () use ($provider, $cache, $cacheKey) {
40            $found = $cache->get($cacheKey);
41            if ($found instanceof static::$interfaceClass) {
42                return Promise\promise_for($found);
43            }
44
45            return $provider()
46                ->then(function ($config) use (
47                    $cache,
48                    $cacheKey
49                ) {
50                    $cache->set($cacheKey, $config);
51                    return $config;
52                });
53        };
54    }
55
56    /**
57     * Creates an aggregate configuration provider that invokes the provided
58     * variadic providers one after the other until a provider returns
59     * configuration.
60     *
61     * @return callable
62     */
63    public static function chain()
64    {
65        $links = func_get_args();
66        if (empty($links)) {
67            throw new \InvalidArgumentException('No providers in chain');
68        }
69
70        return function () use ($links) {
71            /** @var callable $parent */
72            $parent = array_shift($links);
73            $promise = $parent();
74            while ($next = array_shift($links)) {
75                $promise = $promise->otherwise($next);
76            }
77            return $promise;
78        };
79    }
80
81    /**
82     * Gets the environment's HOME directory if available.
83     *
84     * @return null|string
85     */
86    protected static function getHomeDir()
87    {
88        // On Linux/Unix-like systems, use the HOME environment variable
89        if ($homeDir = getenv('HOME')) {
90            return $homeDir;
91        }
92
93        // Get the HOMEDRIVE and HOMEPATH values for Windows hosts
94        $homeDrive = getenv('HOMEDRIVE');
95        $homePath = getenv('HOMEPATH');
96
97        return ($homeDrive && $homePath) ? $homeDrive . $homePath : null;
98    }
99
100    /**
101     * Gets default config file location from environment, falling back to aws
102     * default location
103     *
104     * @return string
105     */
106    protected static function getDefaultConfigFilename()
107    {
108        if ($filename = getenv(self::ENV_CONFIG_FILE)) {
109            return $filename;
110        }
111        return self::getHomeDir() . '/.aws/config';
112    }
113
114    /**
115     * Wraps a config provider and caches previously provided configuration.
116     *
117     * @param callable $provider Config provider function to wrap.
118     *
119     * @return callable
120     */
121    public static function memoize(callable $provider)
122    {
123        return function () use ($provider) {
124            static $result;
125            static $isConstant;
126
127            // Constant config will be returned constantly.
128            if ($isConstant) {
129                return $result;
130            }
131
132            // Create the initial promise that will be used as the cached value
133            if (null === $result) {
134                $result = $provider();
135            }
136
137            // Return config and set flag that provider is already set
138            return $result
139                ->then(function ($config) use (&$isConstant) {
140                    $isConstant = true;
141                    return $config;
142                });
143        };
144    }
145
146    /**
147     * Reject promise with standardized exception.
148     *
149     * @param $msg
150     * @return Promise\RejectedPromise
151     */
152    protected static function reject($msg)
153    {
154        $exceptionClass = static::$exceptionClass;
155        return new Promise\RejectedPromise(new $exceptionClass($msg));
156    }
157}
158