MessageKit/Sources/Layout/LinkPreviewMessageSizeCalculator.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 Foundation
import UIKit

// MARK: - LinkPreviewMessageSizeCalculator

open class LinkPreviewMessageSizeCalculator: TextMessageSizeCalculator {
  // MARK: Lifecycle

  public override init(layout: MessagesCollectionViewFlowLayout?) {
    let titleFont = UIFont.systemFont(ofSize: 13, weight: .semibold)
    let titleFontMetrics = UIFontMetrics(forTextStyle: .footnote)
    self.titleFont = titleFontMetrics.scaledFont(for: titleFont)

    let domainFont = UIFont.systemFont(ofSize: 12, weight: .semibold)
    let domainFontMetrics = UIFontMetrics(forTextStyle: .caption1)
    self.domainFont = domainFontMetrics.scaledFont(for: domainFont)

    super.init(layout: layout)
  }

  // MARK: Open

  open override func messageContainerMaxWidth(for message: MessageType, at indexPath: IndexPath) -> CGFloat {
    switch message.kind {
    case .linkPreview:
      let maxWidth = super.messageContainerMaxWidth(for: message, at: indexPath)
      return max(maxWidth, (layout?.collectionView?.bounds.width ?? 0) * 0.75)
    default:
      return super.messageContainerMaxWidth(for: message, at: indexPath)
    }
  }

  open override func messageContainerSize(for message: MessageType, at indexPath: IndexPath) -> CGSize {
    guard case MessageKind.linkPreview(let linkItem) = message.kind else {
      fatalError("messageContainerSize received unhandled MessageDataType: \(message.kind)")
    }

    var containerSize = super.messageContainerSize(for: message, at: indexPath)
    containerSize.width = max(containerSize.width, messageContainerMaxWidth(for: message, at: indexPath))

    let labelInsets: UIEdgeInsets = messageLabelInsets(for: message)

    let minHeight = containerSize.height + LinkPreviewMessageSizeCalculator.imageViewSize
    let previewMaxWidth = containerSize
      .width -
      (
        LinkPreviewMessageSizeCalculator.imageViewSize + LinkPreviewMessageSizeCalculator.imageViewMargin + labelInsets
          .horizontal)

    calculateContainerSize(
      with: NSAttributedString(string: linkItem.title ?? "", attributes: [.font: titleFont]),
      containerSize: &containerSize,
      maxWidth: previewMaxWidth)

    calculateContainerSize(
      with: NSAttributedString(string: linkItem.teaser, attributes: [.font: teaserFont]),
      containerSize: &containerSize,
      maxWidth: previewMaxWidth)

    calculateContainerSize(
      with: NSAttributedString(string: linkItem.url.host ?? "", attributes: [.font: domainFont]),
      containerSize: &containerSize,
      maxWidth: previewMaxWidth)

    containerSize.height = max(minHeight, containerSize.height) + labelInsets.vertical

    return containerSize
  }

  open override func configure(attributes: UICollectionViewLayoutAttributes) {
    super.configure(attributes: attributes)
    guard let attributes = attributes as? MessagesCollectionViewLayoutAttributes else { return }
    attributes.linkPreviewFonts = LinkPreviewFonts(titleFont: titleFont, teaserFont: teaserFont, domainFont: domainFont)
  }

  // MARK: Public

  public var titleFont: UIFont
  public var teaserFont: UIFont = .preferredFont(forTextStyle: .caption2)
  public var domainFont: UIFont

  // MARK: Internal

  static let imageViewSize: CGFloat = 60
  static let imageViewMargin: CGFloat = 8
}

extension LinkPreviewMessageSizeCalculator {
  private func calculateContainerSize(
    with attributedString: NSAttributedString,
    containerSize: inout CGSize,
    maxWidth: CGFloat)
  {
    guard !attributedString.string.isEmpty else { return }
    let size = labelSize(for: attributedString, considering: maxWidth)
    containerSize.height += size.height
  }
}