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diff --git a/lib/public/Http/Client/IPromise.php b/lib/public/Http/Client/IPromise.php
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+<?php
+
+declare(strict_types=1);
+/**
+ * SPDX-FileCopyrightText: 2023 Nextcloud GmbH and Nextcloud contributors
+ * SPDX-License-Identifier: AGPL-3.0-or-later
+ */
+namespace OCP\Http\Client;
+
+use Exception;
+use LogicException;
+
+/**
+ * A wrapper around Guzzle's PromiseInterface
+ * @see \GuzzleHttp\Promise\PromiseInterface
+ * @since 28.0.0
+ */
+interface IPromise {
+	/**
+	 * @since 28.0.0
+	 */
+	public const STATE_PENDING = 'pending';
+	/**
+	 * @since 28.0.0
+	 */
+	public const STATE_FULFILLED = 'fulfilled';
+	/**
+	 * @since 28.0.0
+	 */
+	public const STATE_REJECTED = 'rejected';
+
+	/**
+	 * Appends fulfillment and rejection handlers to the promise, and returns
+	 * a new promise resolving to the return value of the called handler.
+	 *
+	 * @param ?callable(IResponse): void $onFulfilled Invoked when the promise fulfills. Gets an \OCP\Http\Client\IResponse passed in as argument
+	 * @param ?callable(Exception): void $onRejected Invoked when the promise is rejected. Gets an \Exception passed in as argument
+	 *
+	 * @return IPromise
+	 * @since 28.0.0
+	 */
+	public function then(
+		?callable $onFulfilled = null,
+		?callable $onRejected = null,
+	): IPromise;
+
+	/**
+	 * Get the state of the promise ("pending", "rejected", or "fulfilled").
+	 *
+	 * The three states can be checked against the constants defined:
+	 * STATE_PENDING, STATE_FULFILLED, and STATE_REJECTED.
+	 *
+	 * @return self::STATE_*
+	 * @since 28.0.0
+	 */
+	public function getState(): string;
+
+	/**
+	 * Cancels the promise if possible.
+	 *
+	 * @link https://github.com/promises-aplus/cancellation-spec/issues/7
+	 * @since 28.0.0
+	 */
+	public function cancel(): void;
+
+	/**
+	 * Waits until the promise completes if possible.
+	 *
+	 * Pass $unwrap as true to unwrap the result of the promise, either
+	 * returning the resolved value or throwing the rejected exception.
+	 *
+	 * If the promise cannot be waited on, then the promise will be rejected.
+	 *
+	 * @param bool $unwrap
+	 *
+	 * @return mixed
+	 *
+	 * @throws LogicException if the promise has no wait function or if the
+	 *                        promise does not settle after waiting.
+	 * @since 28.0.0
+	 */
+	public function wait(bool $unwrap = true): mixed;
+}