UIViewController+Snippets.swift

// Snippets UIViewController+Snippets.swift
//
// Copyright © 2015, 2016, Roy Ratcliffe, Pioneering Software, United Kingdom
//
// Permission is hereby granted, free of charge, to any person obtaining a copy
// of this software and associated documentation files (the “Software”), to deal
// in the Software without restriction, including without limitation the rights
// to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
// copies of the Software, and to permit persons to whom the Software is
// furnished to do so, subject to the following conditions:
//
//  The above copyright notice and this permission notice shall be included in
//  all copies or substantial portions of the Software.
//
// THE SOFTWARE IS PROVIDED “AS IS,” WITHOUT WARRANTY OF ANY KIND, EITHER
// EXPRESSED OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NON-INFRINGEMENT. IN NO
// EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES
// OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE,
// ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER
// DEALINGS IN THE SOFTWARE.
//
//------------------------------------------------------------------------------

import UIKit

extension UIViewController {

  /// Displays the given content within this container.
  ///
  /// - parameter content: Content view controller to display within this
  ///     container's content hierarchy.
  ///
  /// - parameter frameForView: Optional capture describing how to set up the
  ///     new content's frame. If not given, the content's frame remains
  ///     unchanged, and therefore assumes that layout constraints will
  ///     determine the view's position and size within the new container. The
  ///     capture's argument takes this container's view and answers the new
  ///     content's frame within that view.
  ///
  /// Adds the other view controller's view to this container's view
  /// hierarchy. Automatically removes the content from any other container
  /// before adding it to this container, invoking
  /// `willMoveToParentViewController` on the content view controller.
  ///
  /// View controllers, amongst other things, can operate as containers for
  /// other content controllers; they have a self-referencing
  /// container-content relationship. Content controllers become children
  /// belonging to a parent container. Content views join the container's view
  /// hierarchy.
  public func display(content: UIViewController,
                      frameForView: ((UIView) -> CGRect)? = nil) {
    addChildViewController(content)
    if let frameForView = frameForView {
      content.view.frame = frameForView(view)
    }
    view.addSubview(content.view)
    content.didMove(toParentViewController: self)
  }

  public func hide(content: UIViewController) {
    content.willMove(toParentViewController: nil)
    content.view.removeFromSuperview()
    content.removeFromParentViewController()
  }

  /// Cycles from an existing content view controller to another new content
  /// view controller. Handles the will- and did-move-to-parent messages for
  /// both the incoming and outgoing view controllers. Removes the existing
  /// content view controller from the parent view controller when animation
  /// finishes.
  public func cycle(from content: UIViewController,
                    // swiftlint:disable:previous function_parameter_count
                    to newContent: UIViewController,
                    duration: TimeInterval,
                    options: UIViewAnimationOptions,
                    newContentStartFrame: CGRect?,
                    contentEndFrame: CGRect?) {
    content.willMove(toParentViewController: nil)
    addChildViewController(newContent)
    if let frame = newContentStartFrame {
      newContent.view.frame = frame
    }
    transition(from: content,
               to: newContent,
               duration: duration,
               options: options,
               animations: {
      newContent.view.frame = content.view.frame
      if let frame = contentEndFrame {
        content.view.frame = frame
      }
    }) { finished in
      content.removeFromParentViewController()
      newContent.didMove(toParentViewController: self)
    }
  }

  /// Cycles, hides or displays content controllers based on the existence of
  /// the controllers: cycles if both the incoming and outgoing controllers
  /// exist; hides if only the outgoing controller exists; or displays if only
  /// the incoming controller exists.
  public func cycle(from content: UIViewController?,
                    // swiftlint:disable:previous function_parameter_count
                    to newContent: UIViewController?,
                    duration: TimeInterval,
                    options: UIViewAnimationOptions,
                    newContentStartFrame: CGRect?,
                    contentEndFrame: CGRect?) {
    if let content = content {
      if let newContent = newContent {
        cycle(from: content,
              to: newContent,
              duration: duration,
              options: options,
              newContentStartFrame: newContentStartFrame,
              contentEndFrame: contentEndFrame)
      } else {
        hide(content: content)
      }
    } else {
      if let newContent = newContent {
        display(content: newContent)
      }
    }
  }

  /// Supports view controller transitions. Allows concatenating of multiple
  /// animations and completion blocks.
  public struct Transition {

    public typealias Animations = () -> Void

    public typealias Completion = (Bool) -> Void

    public let controller: UIViewController

    public var options: UIViewAnimationOptions = []

    public var animations: Animations?

    public var completion: Completion?

    public init(controller: UIViewController, completion: Completion? = nil) {
      self.controller = controller
      self.completion = completion
    }

    /// Adds an animation block.
    /// - parameter animations: Block to add to animations.
    public mutating func addAnimations(_ animations: @escaping Animations) {
      if let currentAnimations = self.animations {
        self.animations = {
          currentAnimations()
          animations()
        }
      } else {
        self.animations = animations
      }
    }

    /// Adds a completion block.
    /// - parameter completion: Block to add to chain of completion blocks.
    public mutating func addCompletion(_ completion: @escaping Completion) {
      if let currentCompletion = self.completion {
        self.completion = { (finished) in
          currentCompletion(finished)
          completion(finished)
        }
      } else {
        self.completion = completion
      }
    }

    /// Displays the given content within this container.
    ///
    /// Adds the other view controller's (content) view to this container's view
    /// hierarchy. Automatically removes the content from any other container
    /// before adding it to this container, invoking
    /// `willMoveToParentViewController` on the content view controller.
    ///
    /// - parameter content: Content view controller to display within this
    ///   container's content hierarchy.
    public func display(content: UIViewController) {
      controller.addChildViewController(content)
      controller.view.addSubview(content.view)
      content.didMove(toParentViewController: controller)
    }

    /// Hides the given content.
    public func hide(content: UIViewController) {
      content.willMove(toParentViewController: nil)
      content.view.removeFromSuperview()
      content.removeFromParentViewController()
    }

    /// Cycles from an existing content view controller to another new content
    /// view controller. Handles the will- and did-move-to-parent messages for
    /// both the incoming and outgoing view controllers. Removes the existing
    /// content view controller from the parent view controller when animation
    /// finishes.
    ///
    /// - parameter from: Outgoing content view controller.
    /// - parameter to: New incoming content view controller.
    /// - parameter duration: Total duration of animations in seconds.
    public func cycle(from: UIViewController, to: UIViewController, duration: TimeInterval) {
      from.willMove(toParentViewController: nil)
      controller.addChildViewController(to)
      controller.transition(from: from, to: to, duration: duration, options: options, animations: animations) { (finished) in
        from.removeFromParentViewController()
        to.didMove(toParentViewController: self.controller)
        self.completion?(finished)
      }
    }

    /// Cycles, hides or displays content controllers based on the existence of
    /// the controllers: cycles if both the incoming and outgoing controllers
    /// exist; hides if only the outgoing controller exists; or displays if only
    /// the incoming controller exists.
    ///
    /// - parameter from: Outgoing content view controller, optional.
    /// - parameter to: New incoming content view controller, optional.
    /// - parameter duration: Total duration of animations in seconds. Only used
    ///   when cycling from and to content controllers.
    public func cycle(from: UIViewController?, to: UIViewController?, duration: TimeInterval) {
      if let from = from {
        if let to = to {
          cycle(from: from, to: to, duration: duration)
        } else {
          hide(content: from)
        }
      } else {
        if let to = to {
          display(content: to)
        }
      }
    }

  }

}