element-ios/Riot/Categories/UIViewController.swift

/*
 Copyright 2019 New Vector Ltd
 
 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at
 
 http://www.apache.org/licenses/LICENSE-2.0
 
 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

import UIKit

extension UIViewController {
    
    private enum UIViewControllerConstants {
        static let fabButtonSize = CGSize(width: 78, height: 78)
        static let fabButtonTrailingMargin: CGFloat = 0
        static let fabButtonBottomMargin: CGFloat = 9
    }
    
    /// Remove back bar button title when pushing a view controller.
    /// This method should be called on the previous controller in UINavigationController stack.
    @objc func vc_removeBackTitle() {
        self.navigationItem.backButtonDisplayMode = .minimal
    }

    /// Add a child view controller matching current view controller view.
    ///
    /// - Parameter viewController: The child view controller to add.
    func vc_addChildViewController(viewController: UIViewController) {
        self.vc_addChildViewController(viewController: viewController, onView: self.view)
    }
    
    
    /// Add a child view controller on current view controller.
    ///
    /// - Parameters:
    ///   - viewController: The child view controller to add.
    ///   - view: The view on which to add the child view controller view.
    ///   - animated: true to add a fade in animation
    func vc_addChildViewController(viewController: UIViewController, onView view: UIView, animated: Bool = false) {
        self.addChild(viewController)
        
        viewController.view.frame = view.bounds
        if animated {
            viewController.view.alpha = 0
        }
        view.vc_addSubViewMatchingParent(viewController.view)
        if animated {
            UIView.animate(withDuration: 0.2) {
                viewController.view.alpha = 1
            }
        }
        viewController.didMove(toParent: self)
    }
    
    
    /// Remove a child view controller from current view controller.
    ///
    /// - Parameters:
    ///     - viewController: The child view controller to remove.
    ///     - animated: true to add a fade out animation
    func vc_removeChildViewController(viewController: UIViewController, animated: Bool = false) {
        viewController.willMove(toParent: nil)
        if animated {
            UIView.animate(withDuration: 0.2) {
                viewController.view.alpha = 0
            } completion: { finished in
                viewController.view.removeFromSuperview()
                viewController.view.alpha = 1
            }
        } else {
            viewController.view.removeFromSuperview()
        }
        viewController.removeFromParent()
    }
    
    
    /// Remove current view controller from parent.
    ///
    /// - Parameter animated: true to add a fade out animation
    func vc_removeFromParent(animated: Bool = false) {
        self.vc_removeChildViewController(viewController: self, animated: animated)
    }
    
    /// Adds a floating action button to the bottom-right of the page.
    /// - Parameters:
    ///   - image: Image to be showed in fab
    ///   - target: target of the button
    ///   - action: action of the button
    /// - Returns: The FAB view
    @discardableResult
    @objc func vc_addFAB(withImage image: UIImage,
                         target: Any?,
                         action: Selector?) -> UIImageView {
        
        let fabImageView = UIImageView(image: image)
        fabImageView.translatesAutoresizingMaskIntoConstraints = false
        fabImageView.backgroundColor = .clear
        fabImageView.contentMode = .center
        fabImageView.layer.shadowOpacity = 0.3
        fabImageView.layer.shadowOffset = CGSize(width: 0, height: 3)
        fabImageView.isUserInteractionEnabled = true
        
        self.view.addSubview(fabImageView)
        
        fabImageView.widthAnchor.constraint(equalToConstant: UIViewControllerConstants.fabButtonSize.width).isActive = true
        fabImageView.heightAnchor.constraint(equalToConstant: UIViewControllerConstants.fabButtonSize.height).isActive = true
        fabImageView.trailingAnchor.constraint(equalTo: self.view.safeAreaLayoutGuide.trailingAnchor,
                                               constant: UIViewControllerConstants.fabButtonTrailingMargin).isActive = true
        self.view.safeAreaLayoutGuide.bottomAnchor.constraint(equalTo: fabImageView.bottomAnchor,
                                                              constant: UIViewControllerConstants.fabButtonBottomMargin).isActive = true
        
        let tapGestureRecognizer = UITapGestureRecognizer(target: target, action: action)
        tapGestureRecognizer.numberOfTouchesRequired = 1
        tapGestureRecognizer.numberOfTapsRequired = 1
        fabImageView.addGestureRecognizer(tapGestureRecognizer)
        
        return fabImageView
    }
    
    /// Defines the large title display mode for the view controller
    /// - Parameters:
    ///   - largeTitleDisplayMode: large title display mode
    @objc func vc_setLargeTitleDisplayMode(_ largeTitleDisplayMode: UINavigationItem.LargeTitleDisplayMode) {
        switch largeTitleDisplayMode {
        case .automatic:
              guard let navigationController = navigationController else { break }
            if let index = navigationController.children.firstIndex(of: self) {
                vc_setLargeTitleDisplayMode(index == 0 ? .always : .never)
            } else {
                vc_setLargeTitleDisplayMode(.always)
            }
        case .always, .never:
            navigationItem.largeTitleDisplayMode = largeTitleDisplayMode
            // Even when .never, needs to be true otherwise animation will be broken on iOS11, 12, 13
            navigationController?.navigationBar.prefersLargeTitles = true
        @unknown default:
            MXLog.failure("[UIViewController] setLargeTitleDisplayMode: Missing handler", context: largeTitleDisplayMode)
        }
    }

    /// Set leftBarButtonItem with split view display mode button if there is no leftBarButtonItem defined and splitViewController exists.
    /// To be Used when view controller is displayed as detail controller in split view.
    func vc_setupDisplayModeLeftBarButtonItemIfNeeded() {
        guard let splitViewController = self.splitViewController, self.navigationItem.leftBarButtonItem == nil else {
            return
        }
        
        // If there is no leftBarButtonItem defined,
        // set split view display mode button as left bar button item
        self.navigationItem.leftBarButtonItem = splitViewController.displayModeButtonItem
    }

    /// Set the view controller to be displayed in fullscreen modal presentation style on any iOS version.
    ///
    /// - Parameters:
    ///   - isFullScreen: whether view controller should be displayed full screen
    /// - Returns: the view controller
    @discardableResult
    func vc_setModalFullScreen(_ isFullScreen: Bool) -> UIViewController {
        if #available(iOS 13.0, *) {
            self.modalPresentationStyle = isFullScreen ? .fullScreen : .automatic
        }

        return self
    }
}