summaryrefslogtreecommitdiffstats
path: root/vendor/guzzlehttp/promises/src/Promise.php
blob: 3d118c718dd763f698beae5aecd74aa4854948a0 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
<?php

namespace GuzzleHttp\Promise;

/**
 * Promises/A+ implementation that avoids recursion when possible.
 *
 * @link https://promisesaplus.com/
 */
class Promise implements PromiseInterface
{
    private $state = self::PENDING;
    private $result;
    private $cancelFn;
    private $waitFn;
    private $waitList;
    private $handlers = [];

    /**
     * @param callable $waitFn   Fn that when invoked resolves the promise.
     * @param callable $cancelFn Fn that when invoked cancels the promise.
     */
    public function __construct(
        callable $waitFn = null,
        callable $cancelFn = null
    ) {
        $this->waitFn = $waitFn;
        $this->cancelFn = $cancelFn;
    }

    public function then(
        callable $onFulfilled = null,
        callable $onRejected = null
    ) {
        if ($this->state === self::PENDING) {
            $p = new Promise(null, [$this, 'cancel']);
            $this->handlers[] = [$p, $onFulfilled, $onRejected];
            $p->waitList = $this->waitList;
            $p->waitList[] = $this;
            return $p;
        }

        // Return a fulfilled promise and immediately invoke any callbacks.
        if ($this->state === self::FULFILLED) {
            $promise = Create::promiseFor($this->result);
            return $onFulfilled ? $promise->then($onFulfilled) : $promise;
        }

        // It's either cancelled or rejected, so return a rejected promise
        // and immediately invoke any callbacks.
        $rejection = Create::rejectionFor($this->result);
        return $onRejected ? $rejection->then(null, $onRejected) : $rejection;
    }

    public function otherwise(callable $onRejected)
    {
        return $this->then(null, $onRejected);
    }

    public function wait($unwrap = true)
    {
        $this->waitIfPending();

        if ($this->result instanceof PromiseInterface) {
            return $this->result->wait($unwrap);
        }
        if ($unwrap) {
            if ($this->state === self::FULFILLED) {
                return $this->result;
            }
            // It's rejected so "unwrap" and throw an exception.
            throw Create::exceptionFor($this->result);
        }
    }

    public function getState()
    {
        return $this->state;
    }

    public function cancel()
    {
        if ($this->state !== self::PENDING) {
            return;
        }

        $this->waitFn = $this->waitList = null;

        if ($this->cancelFn) {
            $fn = $this->cancelFn;
            $this->cancelFn = null;
            try {
                $fn();
            } catch (\Throwable $e) {
                $this->reject($e);
            } catch (\Exception $e) {
                $this->reject($e);
            }
        }

        // Reject the promise only if it wasn't rejected in a then callback.
        /** @psalm-suppress RedundantCondition */
        if ($this->state === self::PENDING) {
            $this->reject(new CancellationException('Promise has been cancelled'));
        }
    }

    public function resolve($value)
    {
        $this->settle(self::FULFILLED, $value);
    }

    public function reject($reason)
    {
        $this->settle(self::REJECTED, $reason);
    }

    private function settle($state, $value)
    {
        if ($this->state !== self::PENDING) {
            // Ignore calls with the same resolution.
            if ($state === $this->state && $value === $this->result) {
                return;
            }
            throw $this->state === $state
                ? new \LogicException("The promise is already {$state}.")
                : new \LogicException("Cannot change a {$this->state} promise to {$state}");
        }

        if ($value === $this) {
            throw new \LogicException('Cannot fulfill or reject a promise with itself');
        }

        // Clear out the state of the promise but stash the handlers.
        $this->state = $state;
        $this->result = $value;
        $handlers = $this->handlers;
        $this->handlers = null;
        $this->waitList = $this->waitFn = null;
        $this->cancelFn = null;

        if (!$handlers) {
            return;
        }

        // If the value was not a settled promise or a thenable, then resolve
        // it in the task queue using the correct ID.
        if (!is_object($value) || !method_exists($value, 'then')) {
            $id = $state === self::FULFILLED ? 1 : 2;
            // It's a success, so resolve the handlers in the queue.
            Utils::queue()->add(static function () use ($id, $value, $handlers) {
                foreach ($handlers as $handler) {
                    self::callHandler($id, $value, $handler);
                }
            });
        } elseif ($value instanceof Promise && Is::pending($value)) {
            // We can just merge our handlers onto the next promise.
            $value->handlers = array_merge($value->handlers, $handlers);
        } else {
            // Resolve the handlers when the forwarded promise is resolved.
            $value->then(
                static function ($value) use ($handlers) {
                    foreach ($handlers as $handler) {
                        self::callHandler(1, $value, $handler);
                    }
                },
                static function ($reason) use ($handlers) {
                    foreach ($handlers as $handler) {
                        self::callHandler(2, $reason, $handler);
                    }
                }
            );
        }
    }

    /**
     * Call a stack of handlers using a specific callback index and value.
     *
     * @param int   $index   1 (resolve) or 2 (reject).
     * @param mixed $value   Value to pass to the callback.
     * @param array $handler Array of handler data (promise and callbacks).
     */
    private static function callHandler($index, $value, array $handler)
    {
        /** @var PromiseInterface $promise */
        $promise = $handler[0];

        // The promise may have been cancelled or resolved before placing
        // this thunk in the queue.
        if (Is::settled($promise)) {
            return;
        }

        try {
            if (isset($handler[$index])) {
                /*
                 * If $f throws an exception, then $handler will be in the exception
                 * stack trace. Since $handler contains a reference to the callable
                 * itself we get a circular reference. We clear the $handler
                 * here to avoid that memory leak.
                 */
                $f = $handler[$index];
                unset($handler);
                $promise->resolve($f($value));
            } elseif ($index === 1) {
                // Forward resolution values as-is.
                $promise->resolve($value);
            } else {
                // Forward rejections down the chain.
                $promise->reject($value);
            }
        } catch (\Throwable $reason) {
            $promise->reject($reason);
        } catch (\Exception $reason) {
            $promise->reject($reason);
        }
    }

    private function waitIfPending()
    {
        if ($this->state !== self::PENDING) {
            return;
        } elseif ($this->waitFn) {
            $this->invokeWaitFn();
        } elseif ($this->waitList) {
            $this->invokeWaitList();
        } else {
            // If there's no wait function, then reject the promise.
            $this->reject('Cannot wait on a promise that has '
                . 'no internal wait function. You must provide a wait '
                . 'function when constructing the promise to be able to '
                . 'wait on a promise.');
        }

        Utils::queue()->run();

        /** @psalm-suppress RedundantCondition */
        if ($this->state === self::PENDING) {
            $this->reject('Invoking the wait callback did not resolve the promise');
        }
    }

    private function invokeWaitFn()
    {
        try {
            $wfn = $this->waitFn;
            $this->waitFn = null;
            $wfn(true);
        } catch (\Exception $reason) {
            if ($this->state === self::PENDING) {
                // The promise has not been resolved yet, so reject the promise
                // with the exception.
                $this->reject($reason);
            } else {
                // The promise was already resolved, so there's a problem in
                // the application.
                throw $reason;
            }
        }
    }

    private function invokeWaitList()
    {
        $waitList = $this->waitList;
        $this->waitList = null;

        foreach ($waitList as $result) {
            do {
                $result->waitIfPending();
                $result = $result->result;
            } while ($result instanceof Promise);

            if ($result instanceof PromiseInterface) {
                $result->wait(false);
            }
        }
    }
}