/*
 * Copyright (c) Meta Platforms, Inc. and affiliates.
 *
 * This source code is licensed under the MIT license found in the
 * LICENSE file in the root directory of this source tree.
 */

package com.facebook.react.uimanager.events;

import androidx.annotation.Nullable;
import com.facebook.infer.annotation.Nullsafe;
import com.facebook.react.bridge.WritableMap;
import com.facebook.react.common.SystemClock;

/**
 * A UI event that can be dispatched to JS.
 *
 * <p>For dispatching events {@code getEventData} should be used. Once event object is passed to the
 * EventDispatched it should no longer be used as EventDispatcher may decide to recycle that object
 * (by calling {@link #dispose}).
 *
 * <p>If you need advanced customizations and overriding only {@code getEventData} doesn't work for
 * you, you must override both {@code dispatch} and {@code dispatchModern}. Both of these will be
 * deleted in the distant future and it is highly recommended to use only {@code getEventData}.
 *
 * <p>Old, pre-Fabric Events only used viewTag as the identifier, but Fabric needs surfaceId as well
 * as viewTag. You may use {@code UIManagerHelper.getSurfaceId} on a Fabric-managed View to get the
 * surfaceId. Fabric will work without surfaceId - making {@code Event} backwards-compatible - but
 * Events without SurfaceId are slightly slower to propagate.
 */
@Nullsafe(Nullsafe.Mode.LOCAL)
public abstract class Event<T extends Event> {

  private static int sUniqueID = 0;

  private boolean mInitialized;
  private int mSurfaceId;
  private int mViewTag;
  private long mTimestampMs;
  private int mUniqueID = sUniqueID++;
  private @Nullable EventAnimationDriverMatchSpec mEventAnimationDriverMatchSpec;

  protected Event() {}

  @Deprecated
  protected Event(int viewTag) {
    init(viewTag);
  }

  protected Event(int surfaceId, int viewTag) {
    init(surfaceId, viewTag);
  }

  @Deprecated
  protected void init(int viewTag) {
    init(-1, viewTag);
  }

  protected void init(int surfaceId, int viewTag) {
    init(surfaceId, viewTag, SystemClock.uptimeMillis());
  }

  /**
   * This method needs to be called before event is sent to event dispatcher. Event timestamps can
   * optionally be dated/backdated to a custom time: for example, touch events should be dated with
   * the system event time.
   */
  protected void init(int surfaceId, int viewTag, long timestampMs) {
    mSurfaceId = surfaceId;
    mViewTag = viewTag;
    mTimestampMs = timestampMs;
    mInitialized = true;
  }

  /**
   * @return the view id for the view that generated this event
   */
  public final int getViewTag() {
    return mViewTag;
  }

  /**
   * @return the surfaceId for the view that generated this event
   */
  public final int getSurfaceId() {
    return mSurfaceId;
  }

  /**
   * @return the time at which the event happened in the {@link android.os.SystemClock#uptimeMillis}
   *     base.
   */
  public final long getTimestampMs() {
    return mTimestampMs;
  }

  /**
   * @return false if this Event can *never* be coalesced
   */
  public boolean canCoalesce() {
    return true;
  }

  /**
   * Given two events, coalesce them into a single event that will be sent to JS instead of two
   * separate events. By default, just chooses the one the is more recent, or {@code this} if
   * timestamps are the same.
   *
   * <p>Two events will only ever try to be coalesced if they have the same event name, view id, and
   * coalescing key.
   */
  public T coalesce(T otherEvent) {
    return (T) (getTimestampMs() >= otherEvent.getTimestampMs() ? this : otherEvent);
  }

  /**
   * @return a key used to determine which other events of this type this event can be coalesced
   *     with. For example, touch move events should only be coalesced within a single gesture so a
   *     coalescing key there would be the unique gesture id.
   */
  public short getCoalescingKey() {
    return 0;
  }

  /**
   * @return The unique id of this event.
   */
  public int getUniqueID() {
    return mUniqueID;
  }

  /**
   * Called when the EventDispatcher is done with an event, either because it was dispatched or
   * because it was coalesced with another Event.
   */
  public void onDispose() {}

  /*package*/ boolean isInitialized() {
    return mInitialized;
  }

  /*package*/ final void dispose() {
    mInitialized = false;
    onDispose();
  }

  /**
   * @return the name of this event as registered in JS
   */
  public abstract String getEventName();

  public EventAnimationDriverMatchSpec getEventAnimationDriverMatchSpec() {
    if (mEventAnimationDriverMatchSpec == null) {
      mEventAnimationDriverMatchSpec =
          new EventAnimationDriverMatchSpec() {
            @Override
            public boolean match(int viewTag, String eventName) {
              return viewTag == getViewTag() && eventName.equals(getEventName());
            }
            ;
          };
    }
    return mEventAnimationDriverMatchSpec;
  }

  /**
   * Dispatch this event to JS using the given event emitter. Compatible with old and new renderer.
   * Instead of using this or dispatchModern, it is recommended that you simply override
   * `getEventData`.
   */
  @Deprecated
  public void dispatch(RCTEventEmitter rctEventEmitter) {
    rctEventEmitter.receiveEvent(getViewTag(), getEventName(), getEventData());
  }

  /** Can be overridden by classes when no custom logic for dispatching is needed. */
  @Nullable
  protected WritableMap getEventData() {
    return null;
  }

  @EventCategoryDef
  protected int getEventCategory() {
    return EventCategoryDef.UNSPECIFIED;
  }

  protected boolean experimental_isSynchronous() {
    return false;
  }

  /**
   * Dispatch this event to JS using a V2 EventEmitter. If surfaceId is not -1 and `getEventData` is
   * non-null, this will use the RCTModernEventEmitter API. Otherwise, it falls back to the
   * old-style dispatch function. For Event classes that need to do something different, this method
   * can always be overridden entirely, but it is not recommended.
   *
   * <p>This method additionally allows C++ to coalesce events and detect continuous ones for
   * concurrent mode (Fabric only).
   *
   * @see #dispatch
   */
  public void dispatchModern(RCTModernEventEmitter rctEventEmitter) {
    if (getSurfaceId() != -1) {
      rctEventEmitter.receiveEvent(
          getSurfaceId(),
          getViewTag(),
          getEventName(),
          canCoalesce(),
          getCoalescingKey(),
          getEventData(),
          getEventCategory());
    } else {
      dispatch(rctEventEmitter);
    }
  }

  public interface EventAnimationDriverMatchSpec {
    boolean match(int viewTag, String eventName);
  }
}