MessageKit/Sources/Layout/TextMessageSizeCalculator.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

open class TextMessageSizeCalculator: MessageSizeCalculator {
  // MARK: Open

  open override func messageContainerMaxWidth(for message: MessageType, at indexPath: IndexPath) -> CGFloat {
    let maxWidth = super.messageContainerMaxWidth(for: message, at: indexPath)
    let textInsets = messageLabelInsets(for: message)
    return maxWidth - textInsets.horizontal
  }

  open override func messageContainerSize(for message: MessageType, at indexPath: IndexPath) -> CGSize {
    let maxWidth = messageContainerMaxWidth(for: message, at: indexPath)

    var messageContainerSize: CGSize
    let attributedText: NSAttributedString

    let textMessageKind = message.kind.textMessageKind
    switch textMessageKind {
    case .attributedText(let text):
      attributedText = text
    case .text(let text), .emoji(let text):
      attributedText = NSAttributedString(string: text, attributes: [.font: messageLabelFont])
    default:
      fatalError("messageContainerSize received unhandled MessageDataType: \(message.kind)")
    }

    messageContainerSize = labelSize(for: attributedText, considering: maxWidth)

    let messageInsets = messageLabelInsets(for: message)
    messageContainerSize.width += messageInsets.horizontal
    messageContainerSize.height += messageInsets.vertical

    return messageContainerSize
  }

  open override func configure(attributes: UICollectionViewLayoutAttributes) {
    super.configure(attributes: attributes)
    guard let attributes = attributes as? MessagesCollectionViewLayoutAttributes else { return }

    let dataSource = messagesLayout.messagesDataSource
    let indexPath = attributes.indexPath
    let message = dataSource.messageForItem(at: indexPath, in: messagesLayout.messagesCollectionView)

    attributes.messageLabelInsets = messageLabelInsets(for: message)
    attributes.messageLabelFont = messageLabelFont

    switch message.kind {
    case .attributedText(let text):
      guard !text.string.isEmpty else { return }
      guard let font = text.attribute(.font, at: 0, effectiveRange: nil) as? UIFont else { return }
      attributes.messageLabelFont = font
    default:
      break
    }
  }

  // MARK: Public

  public var incomingMessageLabelInsets = UIEdgeInsets(top: 7, left: 18, bottom: 7, right: 14)
  public var outgoingMessageLabelInsets = UIEdgeInsets(top: 7, left: 14, bottom: 7, right: 18)

  public var messageLabelFont = UIFont.preferredFont(forTextStyle: .body)

  // MARK: Internal

  internal func messageLabelInsets(for message: MessageType) -> UIEdgeInsets {
    let dataSource = messagesLayout.messagesDataSource
    let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
    return isFromCurrentSender ? outgoingMessageLabelInsets : incomingMessageLabelInsets
  }
}