custom_wda/WebDriverAgentLib/Utilities/FBW3CActionsSynthesizer.m

/**
 * Copyright (c) 2015-present, Facebook, Inc.
 * All rights reserved.
 *
 * This source code is licensed under the BSD-style license found in the
 * LICENSE file in the root directory of this source tree.
 */

#import "FBW3CActionsSynthesizer.h"

#import "FBErrorBuilder.h"
#import "FBElementCache.h"
#import "FBConfiguration.h"
#import "FBLogger.h"
#import "FBMacros.h"
#import "FBMathUtils.h"
#import "FBProtocolHelpers.h"
#import "FBW3CActionsHelpers.h"
#import "FBXCodeCompatibility.h"
#import "FBXCTestDaemonsProxy.h"
#import "FBXCElementSnapshotWrapper+Helpers.h"
#import "XCUIApplication+FBHelpers.h"
#import "XCUIDevice.h"
#import "XCUIElement+FBCaching.h"
#import "XCUIElement+FBIsVisible.h"
#import "XCUIElement+FBUtilities.h"
#import "XCUIElement.h"
#import "XCSynthesizedEventRecord.h"
#import "XCPointerEventPath.h"
#import "XCPointerEvent.h"


static NSString *const FB_KEY_TYPE = @"type";
static NSString *const FB_ACTION_TYPE_POINTER = @"pointer";
static NSString *const FB_ACTION_TYPE_KEY = @"key";
static NSString *const FB_ACTION_TYPE_NONE = @"none";

static NSString *const FB_PARAMETERS_KEY_POINTER_TYPE = @"pointerType";
static NSString *const FB_POINTER_TYPE_MOUSE = @"mouse";
static NSString *const FB_POINTER_TYPE_PEN = @"pen";
static NSString *const FB_POINTER_TYPE_TOUCH = @"touch";

static NSString *const FB_ACTION_ITEM_KEY_ORIGIN = @"origin";
static NSString *const FB_ORIGIN_TYPE_VIEWPORT = @"viewport";
static NSString *const FB_ORIGIN_TYPE_POINTER = @"pointer";

static NSString *const FB_ACTION_ITEM_KEY_TYPE = @"type";
static NSString *const FB_ACTION_ITEM_TYPE_POINTER_MOVE = @"pointerMove";
static NSString *const FB_ACTION_ITEM_TYPE_POINTER_DOWN = @"pointerDown";
static NSString *const FB_ACTION_ITEM_TYPE_POINTER_UP = @"pointerUp";
static NSString *const FB_ACTION_ITEM_TYPE_POINTER_CANCEL = @"pointerCancel";
static NSString *const FB_ACTION_ITEM_TYPE_PAUSE = @"pause";
static NSString *const FB_ACTION_ITEM_TYPE_KEY_UP = @"keyUp";
static NSString *const FB_ACTION_ITEM_TYPE_KEY_DOWN = @"keyDown";

static NSString *const FB_ACTION_ITEM_KEY_X = @"x";
static NSString *const FB_ACTION_ITEM_KEY_Y = @"y";
static NSString *const FB_ACTION_ITEM_KEY_BUTTON = @"button";
static NSString *const FB_ACTION_ITEM_KEY_PRESSURE = @"pressure";

static NSString *const FB_KEY_ID = @"id";
static NSString *const FB_KEY_PARAMETERS = @"parameters";
static NSString *const FB_KEY_ACTIONS = @"actions";


#if !TARGET_OS_TV
@interface FBW3CGestureItem : FBBaseGestureItem

@property (nullable, readonly, nonatomic) FBBaseGestureItem *previousItem;

@end

@interface FBPointerDownItem : FBW3CGestureItem
@property (nullable, readonly, nonatomic) NSNumber *pressure;
@end

@interface FBPointerMoveItem : FBW3CGestureItem

@end

@interface FBPointerUpItem : FBW3CGestureItem

@end

@interface FBPointerPauseItem : FBW3CGestureItem

@end


@interface FBW3CKeyItem : FBBaseActionItem

@property (nullable, readonly, nonatomic) FBW3CKeyItem *previousItem;

@end

@interface FBKeyUpItem : FBW3CKeyItem

@property (readonly, nonatomic) NSString *value;

@end

@interface FBKeyDownItem : FBW3CKeyItem

@property (readonly, nonatomic) NSString *value;

@end

@interface FBKeyPauseItem : FBW3CKeyItem

@property (readonly, nonatomic) double duration;

@end



@implementation FBW3CGestureItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBBaseGestureItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super init];
  if (self) {
    self.actionItem = actionItem;
    self.application = application;
    self.offset = offset;
    _previousItem = previousItem;
    NSNumber *durationObj = FBOptDuration(actionItem, @0, error);
    if (nil == durationObj) {
      return nil;
    }
    self.duration = durationObj.doubleValue;
    XCUICoordinate *position = [self positionWithError:error];
    if (nil == position) {
      return nil;
    }
    self.atPosition = position;
  }
  return self;
}

- (nullable XCUICoordinate *)positionWithError:(NSError **)error
{
  if (nil == self.previousItem) {
    NSString *errorDescription = [NSString stringWithFormat:@"The '%@' action item must be preceded by %@ item", self.actionItem, FB_ACTION_ITEM_TYPE_POINTER_MOVE];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:errorDescription] build];
    }
    return nil;
  }
  return self.previousItem.atPosition;
}

- (nullable XCUICoordinate *)hitpointWithElement:(nullable XCUIElement *)element
                                  positionOffset:(nullable NSValue *)positionOffset
                                           error:(NSError **)error
{
  if (nil == element || nil == positionOffset) {
    return [super hitpointWithElement:element positionOffset:positionOffset error:error];
  }

  // An offset relative to the element is defined
  if (CGRectIsEmpty(element.frame)) {
    [FBLogger log:self.application.fb_descriptionRepresentation];
    NSString *description = [NSString stringWithFormat:@"The element '%@' is not visible on the screen and thus is not interactable",
                             element.description];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  // W3C standard requires that relative element coordinates start at the center of the element's rectangle
  CGVector offset = CGVectorMake(positionOffset.CGPointValue.x, positionOffset.CGPointValue.y);
  // TODO: Shall we throw an exception if hitPoint is out of the element frame?
  return [[element coordinateWithNormalizedOffset:CGVectorMake(0.5, 0.5)] coordinateWithOffset:offset];
}

@end

@implementation FBPointerDownItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBW3CGestureItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super initWithActionItem:actionItem application:application previousItem:previousItem offset:offset error:error];
  if (self) {
    _pressure = [actionItem objectForKey:FB_ACTION_ITEM_KEY_PRESSURE];
  }
  return self;
}

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_POINTER_DOWN;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  if (nil != eventPath && currentItemIndex == 1) {
    FBW3CGestureItem *preceedingItem = [allItems objectAtIndex:currentItemIndex - 1];
    if ([preceedingItem isKindOfClass:FBPointerMoveItem.class]) {
      return @[];
    }
  }
  if (nil == self.pressure) {
    XCPointerEventPath *result = [[XCPointerEventPath alloc] initForTouchAtPoint:self.atPosition.screenPoint
                                                                          offset:FBMillisToSeconds(self.offset)];
    return @[result];
  }

  if (nil == eventPath) {
    NSString *description = [NSString stringWithFormat:@"'%@' action with pressure must be preceeded with at least one '%@' action without this option", self.class.actionName, self.class.actionName];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }
  if (![XCUIDevice sharedDevice].supportsPressureInteraction) {
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:@"This device does not support force press interactions"] build];
    }
    return nil;
  }
  [eventPath pressDownWithPressure:self.pressure.doubleValue
                          atOffset:FBMillisToSeconds(self.offset)];
  return @[];
}

@end

@implementation FBPointerMoveItem

- (nullable XCUICoordinate *)positionWithError:(NSError **)error
{
  static NSArray<NSString *> *supportedOriginTypes;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    supportedOriginTypes = @[FB_ORIGIN_TYPE_POINTER, FB_ORIGIN_TYPE_VIEWPORT];
  });
  id origin = [self.actionItem objectForKey:FB_ACTION_ITEM_KEY_ORIGIN] ?: FB_ORIGIN_TYPE_VIEWPORT;
  BOOL isOriginAnElement = [origin isKindOfClass:XCUIElement.class] && [(XCUIElement *)origin exists];
  if (!isOriginAnElement && ![supportedOriginTypes containsObject:origin]) {
    NSString *description = [NSString stringWithFormat:@"Unsupported %@ type '%@' is set for '%@' action item. Supported origin types: %@ or an element instance", FB_ACTION_ITEM_KEY_ORIGIN, origin, self.actionItem, supportedOriginTypes];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }
  
  XCUIElement *element = isOriginAnElement ? (XCUIElement *)origin : nil;
  NSNumber *x = [self.actionItem objectForKey:FB_ACTION_ITEM_KEY_X];
  NSNumber *y = [self.actionItem objectForKey:FB_ACTION_ITEM_KEY_Y];
  if ((nil != x && nil == y) || (nil != y && nil == x) ||
      ([origin isKindOfClass:NSString.class] && [origin isEqualToString:FB_ORIGIN_TYPE_VIEWPORT] && (nil == x || nil == y))) {
    NSString *errorDescription = [NSString stringWithFormat:@"Both 'x' and 'y' options should be set for '%@' action item", self.actionItem];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:errorDescription] build];
    }
    return nil;
  }
  
  if (nil != element) {
    if (nil == x && nil == y) {
      return [self hitpointWithElement:element positionOffset:nil error:error];
    }
    return [self hitpointWithElement:element positionOffset:[NSValue valueWithCGPoint:CGPointMake(x.floatValue, y.floatValue)] error:error];
  }
  
  if ([origin isKindOfClass:NSString.class] && [origin isEqualToString:FB_ORIGIN_TYPE_VIEWPORT]) {
    return [self hitpointWithElement:nil positionOffset:[NSValue valueWithCGPoint:CGPointMake(x.floatValue, y.floatValue)] error:error];
  }
  
  // origin == FB_ORIGIN_TYPE_POINTER
  if (nil == self.previousItem) {
    NSString *errorDescription = [NSString stringWithFormat:@"There is no previous item for '%@' action item, however %@ is set to '%@'", self.actionItem, FB_ACTION_ITEM_KEY_ORIGIN, FB_ORIGIN_TYPE_POINTER];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:errorDescription] build];
    }
    return nil;
  }
  XCUICoordinate *recentPosition = self.previousItem.atPosition;
  CGVector offsetRelativeToRecentPosition = (nil == x && nil == y) ? CGVectorMake(0, 0) : CGVectorMake(x.floatValue, y.floatValue);
  return [recentPosition coordinateWithOffset:offsetRelativeToRecentPosition];
}

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_POINTER_MOVE;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  if (nil == eventPath) {
    return @[[[XCPointerEventPath alloc] initForTouchAtPoint:self.atPosition.screenPoint
                                                      offset:FBMillisToSeconds(self.offset + self.duration)]];
  }
  [eventPath moveToPoint:self.atPosition.screenPoint
                atOffset:FBMillisToSeconds(self.offset + self.duration)];
  return @[];
}

@end

@implementation FBPointerPauseItem

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_PAUSE;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  return @[];
}

@end

@implementation FBPointerUpItem

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_POINTER_UP;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  if (nil == eventPath) {
    NSString *description = [NSString stringWithFormat:@"Pointer Up must not be the first action in '%@'", self.actionItem];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  [eventPath liftUpAtOffset:FBMillisToSeconds(self.offset)];
  return @[];
}

@end

@implementation FBW3CKeyItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBW3CKeyItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super init];
  if (self) {
    self.actionItem = actionItem;
    self.application = application;
    self.offset = offset;
    _previousItem = previousItem;
  }
  return self;
}

@end


@implementation FBKeyUpItem : FBW3CKeyItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBW3CKeyItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super initWithActionItem:actionItem
                       application:application
                      previousItem:previousItem
                            offset:offset
                             error:error];
  if (self) {
    NSString *value = FBRequireValue(actionItem, error);
    if (nil == value) {
      return nil;
    }
    _value = value;
  }
  return self;
}

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_KEY_UP;
}

- (BOOL)hasDownPairInItems:(NSArray *)allItems
          currentItemIndex:(NSUInteger)currentItemIndex
{
  NSInteger balance = 1;
  for (NSInteger index = currentItemIndex - 1; index >= 0; index--) {
    FBW3CKeyItem *item = [allItems objectAtIndex:index];
    BOOL isKeyDown = [item isKindOfClass:FBKeyDownItem.class];
    BOOL isKeyUp = !isKeyDown && [item isKindOfClass:FBKeyUpItem.class];
    if (!isKeyUp && !isKeyDown) {
      break;
    }

    NSString *value = [item performSelector:@selector(value)];
    if (isKeyDown && [value isEqualToString:self.value]) {
      balance--;
    }
    if (isKeyUp && [value isEqualToString:self.value]) {
      balance++;
    }
  }
  return 0 == balance;
}

- (NSString *)collectTextWithItems:(NSArray *)allItems
                  currentItemIndex:(NSUInteger)currentItemIndex
{
  NSMutableArray *result = [NSMutableArray array];
  for (NSInteger index = currentItemIndex; index >= 0; index--) {
    FBW3CKeyItem *item = [allItems objectAtIndex:index];
    BOOL isKeyDown = [item isKindOfClass:FBKeyDownItem.class];
    BOOL isKeyUp = !isKeyDown && [item isKindOfClass:FBKeyUpItem.class];
    if (!isKeyUp && !isKeyDown) {
      break;
    }

    NSString *value = [item performSelector:@selector(value)];
    if (isKeyUp) {
      [result addObject:FBMapIfSpecialCharacter(value)];
    }
  }
  return [result.reverseObjectEnumerator.allObjects componentsJoinedByString:@""];
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  if (![self hasDownPairInItems:allItems currentItemIndex:currentItemIndex]) {
    NSString *description = [NSString stringWithFormat:@"Key Up action '%@' is not balanced with a preceding Key Down one in '%@'", self.value, self.actionItem];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  BOOL isLastKeyUpInGroup = currentItemIndex == allItems.count - 1
    || [[allItems objectAtIndex:currentItemIndex + 1] isKindOfClass:FBKeyPauseItem.class];
  if (!isLastKeyUpInGroup) {
    return @[];
  }

  NSString *text = [self collectTextWithItems:allItems currentItemIndex:currentItemIndex];
  NSTimeInterval offset = FBMillisToSeconds(self.offset);
  XCPointerEventPath *resultPath = [[XCPointerEventPath alloc] initForTextInput];
  [resultPath typeText:text
              atOffset:offset
           typingSpeed:FBConfiguration.maxTypingFrequency
          shouldRedact:YES];
  return @[resultPath];
}

@end

@implementation FBKeyDownItem : FBW3CKeyItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBW3CKeyItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super initWithActionItem:actionItem
                       application:application
                      previousItem:previousItem
                            offset:offset
                             error:error];
  if (self) {
    NSString *value = FBRequireValue(actionItem, error);
    if (nil == value) {
      return nil;
    }
    _value = value;
  }
  return self;
}

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_KEY_DOWN;
}

- (BOOL)hasUpPairInItems:(NSArray *)allItems
        currentItemIndex:(NSUInteger)currentItemIndex
{
  NSInteger balance = 1;
  for (NSUInteger index = currentItemIndex + 1; index < allItems.count; index++) {
    FBW3CKeyItem *item = [allItems objectAtIndex:index];
    BOOL isKeyDown = [item isKindOfClass:FBKeyDownItem.class];
    BOOL isKeyUp = !isKeyDown && [item isKindOfClass:FBKeyUpItem.class];
    if (!isKeyUp && !isKeyDown) {
      break;
    }

    NSString *value = [item performSelector:@selector(value)];
    if (isKeyUp && [value isEqualToString:self.value]) {
      balance--;
    }
    if (isKeyDown && [value isEqualToString:self.value]) {
      balance++;
    }
  }
  return 0 == balance;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  if (![self hasUpPairInItems:allItems currentItemIndex:currentItemIndex]) {
    NSString *description = [NSString stringWithFormat:@"Key Down action '%@' must have a closing Key Up successor in '%@'", self.value, self.actionItem];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  return @[];
}

@end

@implementation FBKeyPauseItem

- (nullable instancetype)initWithActionItem:(NSDictionary<NSString *, id> *)actionItem
                                application:(XCUIApplication *)application
                               previousItem:(nullable FBW3CKeyItem *)previousItem
                                     offset:(double)offset
                                      error:(NSError **)error
{
  self = [super initWithActionItem:actionItem
                       application:application
                      previousItem:previousItem
                            offset:offset
                             error:error];
  if (self) {
    NSNumber *duration = FBOptDuration(actionItem, nil, error);
    if (nil == duration) {
      return nil;
    }
    _duration = [duration doubleValue];
  }
  return self;
}

+ (NSString *)actionName
{
  return FB_ACTION_ITEM_TYPE_PAUSE;
}

- (NSArray<XCPointerEventPath *> *)addToEventPath:(XCPointerEventPath *)eventPath
                                         allItems:(NSArray *)allItems
                                 currentItemIndex:(NSUInteger)currentItemIndex
                                            error:(NSError **)error
{
  return @[];
}

@end


@interface FBW3CGestureItemsChain : FBBaseActionItemsChain

@end

@implementation FBW3CGestureItemsChain

- (void)addItem:(FBBaseActionItem *)item
{
  self.durationOffset += ((FBBaseGestureItem *)item).duration;
  [self.items addObject:item];
}

@end


@interface FBW3CKeyItemsChain : FBBaseActionItemsChain

@end

@implementation FBW3CKeyItemsChain

- (void)addItem:(FBBaseActionItem *)item
{
  if ([item isKindOfClass:FBKeyPauseItem.class]) {
    self.durationOffset += ((FBKeyPauseItem *)item).duration;
  }
  [self.items addObject:item];
}

@end


@implementation FBW3CActionsSynthesizer

- (NSArray<NSDictionary<NSString *, id> *> *)preprocessedActionItemsWith:(NSArray<NSDictionary<NSString *, id> *> *)actionItems
{
  NSMutableArray<NSDictionary<NSString *, id> *> *result = [NSMutableArray array];
  BOOL shouldCancelNextItem = NO;
  for (NSDictionary<NSString *, id> *actionItem in [actionItems reverseObjectEnumerator]) {
    if (shouldCancelNextItem) {
      shouldCancelNextItem = NO;
      continue;
    }
    NSString *actionItemType = [actionItem objectForKey:FB_ACTION_ITEM_KEY_TYPE];
    if (actionItemType != nil && [actionItemType isEqualToString:FB_ACTION_ITEM_TYPE_POINTER_CANCEL]) {
      shouldCancelNextItem = YES;
      continue;
    }
    
    if (nil == self.elementCache) {
      [result addObject:actionItem];
      continue;
    }
    id origin = [actionItem objectForKey:FB_ACTION_ITEM_KEY_ORIGIN];
    if (nil == origin || [@[FB_ORIGIN_TYPE_POINTER, FB_ORIGIN_TYPE_VIEWPORT] containsObject:origin]) {
      [result addObject:actionItem];
      continue;
    }
    // Selenium Python client passes 'origin' element in the following format:
    //
    // if isinstance(origin, WebElement):
    //    action["origin"] = {"element-6066-11e4-a52e-4f735466cecf": origin.id}
    if ([origin isKindOfClass:NSDictionary.class]) {
      id element = FBExtractElement(origin);
      if (nil != element) {
        origin = element;
      }
    }

    XCUIElement *instance;
    if ([origin isKindOfClass:XCUIElement.class]) {
      instance = origin;
    } else if ([origin isKindOfClass:NSString.class]) {
      instance = [self.elementCache elementForUUID:(NSString *)origin checkStaleness:YES];
    } else {
      [result addObject:actionItem];
      continue;
    }
    NSMutableDictionary<NSString *, id> *processedItem = actionItem.mutableCopy;
    [processedItem setObject:instance forKey:FB_ACTION_ITEM_KEY_ORIGIN];
    [result addObject:processedItem.copy];
  }
  return [[result reverseObjectEnumerator] allObjects];
}

- (nullable NSArray<XCPointerEventPath *> *)eventPathsWithKeyAction:(NSDictionary<NSString *, id> *)actionDescription forActionId:(NSString *)actionId error:(NSError **)error
{
  static NSDictionary<NSString *, Class> *keyItemsMapping;
  static NSArray<NSString *> *supportedActionItemTypes;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    NSMutableDictionary<NSString *, Class> *itemsMapping = [NSMutableDictionary dictionary];
    for (Class cls in @[FBKeyDownItem.class,
                        FBKeyPauseItem.class,
                        FBKeyUpItem.class]) {
      [itemsMapping setObject:cls forKey:[cls actionName]];
    }
    keyItemsMapping = itemsMapping.copy;
    supportedActionItemTypes = @[FB_ACTION_ITEM_TYPE_PAUSE,
                                 FB_ACTION_ITEM_TYPE_KEY_UP,
                                 FB_ACTION_ITEM_TYPE_KEY_DOWN];
  });

  NSArray<NSDictionary<NSString *, id> *> *actionItems = [actionDescription objectForKey:FB_KEY_ACTIONS];
  if (nil == actionItems || 0 == actionItems.count) {
   NSString *description = [NSString stringWithFormat:@"It is mandatory to have at least one item defined for each action. Action with id '%@' contains none", actionId];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  FBW3CKeyItemsChain *chain = [[FBW3CKeyItemsChain alloc] init];
  NSArray<NSDictionary<NSString *, id> *> *processedItems = [self preprocessedActionItemsWith:actionItems];
  for (NSDictionary<NSString *, id> *actionItem in processedItems) {
    id actionItemType = [actionItem objectForKey:FB_ACTION_ITEM_KEY_TYPE];
    if (![actionItemType isKindOfClass:NSString.class]) {
      NSString *description = [NSString stringWithFormat:@"The %@ property is mandatory to set for '%@' action item", FB_ACTION_ITEM_KEY_TYPE, actionItem];
      if (error) {
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }

    Class keyItemClass = [keyItemsMapping objectForKey:actionItemType];
    if (nil == keyItemClass) {
      NSString *description = [NSString stringWithFormat:@"'%@' action item type '%@' is not supported. Only the following action item types are supported: %@", actionId, actionItemType, supportedActionItemTypes];
      if (error) {
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }

    FBW3CKeyItem *keyItem = [[keyItemClass alloc] initWithActionItem:actionItem
                                                         application:self.application
                                                        previousItem:[chain.items lastObject]
                                                              offset:chain.durationOffset
                                                               error:error];
    if (nil == keyItem) {
      return nil;
    }

    [chain addItem:keyItem];
  }

  return [chain asEventPathsWithError:error];
}

- (nullable NSArray<XCPointerEventPath *> *)eventPathsWithGestureAction:(NSDictionary<NSString *, id> *)actionDescription forActionId:(NSString *)actionId error:(NSError **)error
{
  static NSDictionary<NSString *, Class> *gestureItemsMapping;
  static NSArray<NSString *> *supportedActionItemTypes;
  static dispatch_once_t onceToken;
  dispatch_once(&onceToken, ^{
    NSMutableDictionary<NSString *, Class> *itemsMapping = [NSMutableDictionary dictionary];
    for (Class cls in @[FBPointerDownItem.class,
                        FBPointerMoveItem.class,
                        FBPointerPauseItem.class,
                        FBPointerUpItem.class]) {
      [itemsMapping setObject:cls forKey:[cls actionName]];
    }
    gestureItemsMapping = itemsMapping.copy;
    supportedActionItemTypes = @[FB_ACTION_ITEM_TYPE_PAUSE,
                                 FB_ACTION_ITEM_TYPE_POINTER_UP,
                                 FB_ACTION_ITEM_TYPE_POINTER_DOWN,
                                 FB_ACTION_ITEM_TYPE_POINTER_MOVE];
  });

  id parameters = [actionDescription objectForKey:FB_KEY_PARAMETERS];
  id pointerType = FB_POINTER_TYPE_MOUSE;
  if ([parameters isKindOfClass:NSDictionary.class]) {
    pointerType = [parameters objectForKey:FB_PARAMETERS_KEY_POINTER_TYPE] ?: FB_POINTER_TYPE_MOUSE;
  }
  if (![pointerType isKindOfClass:NSString.class] || ![pointerType isEqualToString:FB_POINTER_TYPE_TOUCH]) {
    NSString *description = [NSString stringWithFormat:@"Only pointer type '%@' is supported. '%@' is given instead for action with id '%@'", FB_POINTER_TYPE_TOUCH, pointerType, actionId];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  NSArray<NSDictionary<NSString *, id> *> *actionItems = [actionDescription objectForKey:FB_KEY_ACTIONS];
  if (nil == actionItems || 0 == actionItems.count) {
    NSString *description = [NSString stringWithFormat:@"It is mandatory to have at least one gesture item defined for each action. Action with id '%@' contains none", actionId];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  FBW3CGestureItemsChain *chain = [[FBW3CGestureItemsChain alloc] init];
  NSArray<NSDictionary<NSString *, id> *> *processedItems = [self preprocessedActionItemsWith:actionItems];
  for (NSDictionary<NSString *, id> *actionItem in processedItems) {
    id actionItemType = [actionItem objectForKey:FB_ACTION_ITEM_KEY_TYPE];
    if (![actionItemType isKindOfClass:NSString.class]) {
      NSString *description = [NSString stringWithFormat:@"The %@ property is mandatory to set for '%@' action item", FB_ACTION_ITEM_KEY_TYPE, actionItem];
      if (error) {
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }

    Class gestureItemClass = [gestureItemsMapping objectForKey:actionItemType];
    if (nil == gestureItemClass) {
      NSString *description = [NSString stringWithFormat:@"'%@' action item type '%@' is not supported. Only the following action item types are supported: %@", actionId, actionItemType, supportedActionItemTypes];
      if (error) {
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }

    FBW3CGestureItem *gestureItem = [[gestureItemClass alloc] initWithActionItem:actionItem application:self.application previousItem:[chain.items lastObject] offset:chain.durationOffset error:error];
    if (nil == gestureItem) {
      return nil;
    }

    [chain addItem:gestureItem];
  }

  return [chain asEventPathsWithError:error];
}

- (nullable NSArray<XCPointerEventPath *> *)eventPathsWithActionDescription:(NSDictionary<NSString *, id> *)actionDescription forActionId:(NSString *)actionId error:(NSError **)error
{
  id actionType = [actionDescription objectForKey:FB_KEY_TYPE];
  if (![actionType isKindOfClass:NSString.class] ||
      !([actionType isEqualToString:FB_ACTION_TYPE_POINTER]
        || ([XCPointerEvent.class fb_areKeyEventsSupported] && [actionType isEqualToString:FB_ACTION_TYPE_KEY]))) {
    NSString *description = [NSString stringWithFormat:@"Only actions of '%@' types are supported. '%@' is given instead for action with id '%@'", @[FB_ACTION_TYPE_POINTER, FB_ACTION_TYPE_KEY], actionType, actionId];
    if (error) {
      *error = [[FBErrorBuilder.builder withDescription:description] build];
    }
    return nil;
  }

  if ([actionType isEqualToString:FB_ACTION_TYPE_POINTER]) {
    return [self eventPathsWithGestureAction:actionDescription forActionId:actionId error:error];
  }

  return [self eventPathsWithKeyAction:actionDescription forActionId:actionId error:error];
}

- (nullable XCSynthesizedEventRecord *)synthesizeWithError:(NSError **)error
{
  XCSynthesizedEventRecord *eventRecord = [[XCSynthesizedEventRecord alloc]
                                           initWithName:@"W3C Touch Action"
                                           interfaceOrientation:self.application.interfaceOrientation];
  NSMutableDictionary<NSString *, NSDictionary<NSString *, id> *> *actionsMapping = [NSMutableDictionary new];
  NSMutableArray<NSString *> *actionIds = [NSMutableArray new];
  for (NSDictionary<NSString *, id> *action in self.actions) {
    id actionId = [action objectForKey:FB_KEY_ID];
    if (![actionId isKindOfClass:NSString.class] || 0 == [actionId length]) {
      if (error) {
        NSString *description = [NSString stringWithFormat:@"The mandatory action %@ field is missing or empty for '%@'", FB_KEY_ID, action];
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }
    if (nil != [actionsMapping objectForKey:actionId]) {
      if (error) {
        NSString *description = [NSString stringWithFormat:@"Action %@ '%@' is not unique for '%@'", FB_KEY_ID, actionId, action];
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }    
    NSArray<NSDictionary<NSString *, id> *> *actionItems = [action objectForKey:FB_KEY_ACTIONS];
    if (nil == actionItems) {
     NSString *description = [NSString stringWithFormat:@"It is mandatory to have at least one item defined for each action. Action with id '%@' contains none", actionId];
      if (error) {
        *error = [[FBErrorBuilder.builder withDescription:description] build];
      }
      return nil;
    }
    if (0 == actionItems.count) {
      [FBLogger logFmt:@"Action items in the action id '%@' had an empty array. Skipping the action.", actionId];
      continue;
    }

    [actionIds addObject:actionId];
    [actionsMapping setObject:action forKey:actionId];
  }
  for (NSString *actionId in actionIds.copy) {
    NSDictionary<NSString *, id> *actionDescription = [actionsMapping objectForKey:actionId];
    NSArray<XCPointerEventPath *> *eventPaths = [self eventPathsWithActionDescription:actionDescription forActionId:actionId error:error];
    if (nil == eventPaths) {
      return nil;
    }
    for (XCPointerEventPath *eventPath in eventPaths) {
      [eventRecord addPointerEventPath:eventPath];
    }
  }
  return eventRecord;
}

@end
#endif