ELSeekableVideoPlayerView.m

//
//  ELSeekableVideoPlayerView.m
//  CKSiS
//
//  Created by Milan Vít on 13.03.17.
//  Copyright (c) 2017 EYELEVEL. All rights reserved.
//

#import <Masonry/Masonry.h>
#import "ELSeekableVideoPlayerView.h"

@interface ELSeekableVideoPlayerView ()
@property (strong, nonatomic) UIPanGestureRecognizer *panGestureRecognizer;
@property (assign, nonatomic) CMTime currentTime;
@property (assign, nonatomic) CMTime chaseTime;
@property (assign, nonatomic) BOOL seekInProgress;
@end

@implementation ELSeekableVideoPlayerView
#pragma mark - NSObject
- (void)awakeFromNib {
	[super awakeFromNib];

	self.panGestureRecognizer = [[UIPanGestureRecognizer alloc] initWithTarget:self action:@selector(panVideo:)];

	[self addGestureRecognizer:self.panGestureRecognizer];
}

#pragma mark - IBAction
- (IBAction)panVideo:(UIPanGestureRecognizer *)sender {
	switch (sender.state) {
		case UIGestureRecognizerStateBegan:
			self.player.rate = 0;
			self.currentTime = self.player.currentTime;

			break;
		case UIGestureRecognizerStateChanged: {
			CGPoint translation = [sender translationInView:self];
			float horizontalTranslation = translation.x;
			float durationInSeconds = (float) CMTimeGetSeconds(self.player.currentItem.asset.duration);
			float translationLimit = self.bounds.size.width;

			if (horizontalTranslation > translationLimit) {
				horizontalTranslation = translationLimit;
			}

			if (horizontalTranslation < -translationLimit) {
				horizontalTranslation = -translationLimit;
			}

			float timeToSeekTo = [self normalize:horizontalTranslation minDelta:-translationLimit maxDelta:translationLimit minDuration:-durationInSeconds maxDuration:durationInSeconds];

			if (CMTIME_IS_VALID(self.currentTime)) {
				float seconds = self.currentTime.value / self.currentTime.timescale;
				float finalTime = MAX(0, seconds + timeToSeekTo);

				[self seekSmoothlyToTime:CMTimeMakeWithSeconds(finalTime, self.player.currentTime.timescale)];
			} else {
				[self seekSmoothlyToTime:CMTimeMakeWithSeconds(timeToSeekTo, self.player.currentTime.timescale)];
			}

			break;
		}
		default:
			break;
	}
}

- (void)seekSmoothlyToTime:(CMTime)newTime {
	if (CMTIME_COMPARE_INLINE(newTime, !=, self.chaseTime)) {
		self.chaseTime = newTime;

		if (!self.seekInProgress) {
			[self trySeekToChaseTime];
		}
	}
}

- (void)trySeekToChaseTime {
	if (self.player.currentItem.status == AVPlayerStatusReadyToPlay) {
		[self actuallySeekToChaseTime];
	}
}

- (void)actuallySeekToChaseTime {
	self.seekInProgress = YES;
	CMTime seekTimeInProgress = self.chaseTime;

	[self.player seekToTime:seekTimeInProgress toleranceBefore:kCMTimeZero toleranceAfter:kCMTimeZero completionHandler:^(BOOL finished) {
		if (CMTIME_COMPARE_INLINE(seekTimeInProgress, ==, self.chaseTime)) {
			self.seekInProgress = NO;
		} else {
			[self trySeekToChaseTime];
		}
	}];
}

- (float)normalize:(float)delta minDelta:(float)minDelta maxDelta:(float)maxDelta minDuration:(float)minDuration maxDuration:(float)maxDuration {
	return ((delta - minDelta) * (maxDuration - minDuration) / (maxDelta - minDelta) + minDuration);
}
@end