/* This Source Code Form is subject to the terms of the Mozilla Public
 * License, v. 2.0. If a copy of the MPL was not distributed with this
 * file, You can obtain one at http://mozilla.org/MPL/2.0/. */

package org.mozilla.gecko.util;

import androidx.annotation.Nullable;
import org.mozilla.gecko.annotation.RobocopTarget;
import org.mozilla.gecko.annotation.WrapForJNI;
import org.mozilla.geckoview.GeckoResult;

/**
 * Callback interface for Gecko requests.
 *
 * <p>For each instance of EventCallback, exactly one of sendResponse, sendError, or sendCancel must
 * be called to prevent observer leaks. If more than one send* method is called, or if a single send
 * method is called multiple times, an {@link IllegalStateException} will be thrown.
 */
@RobocopTarget
@WrapForJNI(calledFrom = "gecko")
public interface EventCallback {
  /**
   * Sends a success response with the given data.
   *
   * @param response The response data to send to Gecko. Can be any of the types accepted by
   *     JSONObject#put(String, Object).
   */
  void sendSuccess(Object response);

  /**
   * Sends an error response with the given data.
   *
   * @param response The response data to send to Gecko. Can be any of the types accepted by
   *     JSONObject#put(String, Object).
   */
  void sendError(Object response);

  /**
   * Resolve this Event callback with the result from the {@link GeckoResult}.
   *
   * @param response the result that will be used for this callback.
   */
  default <T> void resolveTo(final @Nullable GeckoResult<T> response) {
    if (response == null) {
      sendSuccess(null);
      return;
    }
    response.accept(
        this::sendSuccess,
        throwable -> {
          // Don't propagate Errors, just crash
          if (!(throwable instanceof Exception)) {
            throw new GeckoResult.UncaughtException(throwable);
          }
          sendError(throwable.getMessage());
        });
  }
}