MessageKit/Sources/Views/Cells/LocationMessageCell.swift

// MIT License
//
// Copyright (c) 2017-2019 MessageKit
//
// 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, EXPRESS OR
// IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
// FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. 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 MapKit
import UIKit

/// A subclass of `MessageContentCell` used to display location messages.
open class LocationMessageCell: MessageContentCell {
  // MARK: Open

  /// The activity indicator to be displayed while the map image is loading.
  open var activityIndicator = UIActivityIndicatorView(style: .medium)

  /// The image view holding the map image.
  open var imageView = UIImageView()

  open override func setupSubviews() {
    super.setupSubviews()
    imageView.contentMode = .scaleAspectFill
    messageContainerView.addSubview(imageView)
    messageContainerView.addSubview(activityIndicator)
    setupConstraints()
  }

  /// Responsible for setting up the constraints of the cell's subviews.
  open func setupConstraints() {
    imageView.fillSuperview()
    activityIndicator.centerInSuperview()
  }

  open override func prepareForReuse() {
    super.prepareForReuse()
    snapShotter?.cancel()
  }

  open override func configure(
    with message: MessageType,
    at indexPath: IndexPath,
    and messagesCollectionView: MessagesCollectionView)
  {
    super.configure(with: message, at: indexPath, and: messagesCollectionView)

    guard case .location(let locationItem) = message.kind else { fatalError("Configuring LocationMessageCell with wrong message kind") }
    guard CLLocationCoordinate2DIsValid(locationItem.location.coordinate) else {
      return
    }

    guard let displayDelegate = messagesCollectionView.messagesDisplayDelegate else {
      fatalError(MessageKitError.nilMessagesDisplayDelegate)
    }
    let options = displayDelegate.snapshotOptionsForLocation(message: message, at: indexPath, in: messagesCollectionView)
    let annotationView = displayDelegate.annotationViewForLocation(
      message: message,
      at: indexPath,
      in: messagesCollectionView)
    let animationBlock = displayDelegate.animationBlockForLocation(
      message: message,
      at: indexPath,
      in: messagesCollectionView)

    activityIndicator.startAnimating()

    let snapshotOptions = MKMapSnapshotter.Options()
    snapshotOptions.region = MKCoordinateRegion(center: locationItem.location.coordinate, span: options.span)
    snapshotOptions.showsBuildings = options.showsBuildings
    snapshotOptions.pointOfInterestFilter = options.showsPointsOfInterest ? .includingAll : .excludingAll

    let snapShotter = MKMapSnapshotter(options: snapshotOptions)
    self.snapShotter = snapShotter
    snapShotter.start { snapshot, error in
      defer {
        self.activityIndicator.stopAnimating()
      }
      guard let snapshot = snapshot, error == nil else {
        // show an error image?
        return
      }

      guard let annotationView = annotationView else {
        self.imageView.image = snapshot.image
        return
      }

      UIGraphicsBeginImageContextWithOptions(snapshotOptions.size, true, 0)

      snapshot.image.draw(at: .zero)

      var point = snapshot.point(for: locationItem.location.coordinate)
      // Move point to reflect annotation anchor
      point.x -= annotationView.bounds.size.width / 2
      point.y -= annotationView.bounds.size.height / 2
      point.x += annotationView.centerOffset.x
      point.y += annotationView.centerOffset.y

      annotationView.image?.draw(at: point)
      let composedImage = UIGraphicsGetImageFromCurrentImageContext()

      UIGraphicsEndImageContext()
      self.imageView.image = composedImage
      animationBlock?(self.imageView)
    }
  }

  // MARK: Private

  private weak var snapShotter: MKMapSnapshotter?
}