MessageKit/Sources/Protocols/MessagesDataSource.swift

// MIT License
//
// Copyright (c) 2017-2019 MessageKit
//
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// SOFTWARE.

import UIKit

// MARK: - MessagesDataSource

/// An object that adopts the `MessagesDataSource` protocol is responsible for providing
/// the data required by a `MessagesCollectionView`.
@MainActor
public protocol MessagesDataSource: AnyObject {
  /// The `SenderType` of new messages in the `MessagesCollectionView`.
  var currentSender: SenderType { get }

  /// A helper method to determine if a given message is from the current `SenderType`.
  ///
  /// - Parameters:
  ///   - message: The message to check if it was sent by the current `SenderType`.
  ///
  /// - Note:
  ///   The default implementation of this method checks for equality between
  ///   the message's `SenderType` and the current `SenderType`.
  func isFromCurrentSender(message: MessageType) -> Bool

  /// The message to be used for a `MessageCollectionViewCell` at the given `IndexPath`.
  ///
  /// - Parameters:
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which the message will be displayed.
  func messageForItem(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageType

  /// The number of sections to be displayed in the `MessagesCollectionView`.
  ///
  /// - Parameters:
  ///   - messagesCollectionView: The `MessagesCollectionView` in which the messages will be displayed.
  func numberOfSections(in messagesCollectionView: MessagesCollectionView) -> Int

  /// The number of cells to be displayed in the `MessagesCollectionView`.
  ///
  /// - Parameters:
  ///   - section: The number of the section in which the cells will be displayed.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which the messages will be displayed.
  /// - Note:
  ///   The default implementation of this method returns 1. Putting each message in its own section.
  func numberOfItems(inSection section: Int, in messagesCollectionView: MessagesCollectionView) -> Int

  /// The attributed text to be used for cell's top label.
  ///
  /// - Parameters:
  ///   - message: The `MessageType` that will be displayed by this cell.
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// The default value returned by this method is `nil`.
  func cellTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?

  /// The attributed text to be used for cell's bottom label.
  ///
  /// - Parameters:
  ///   - message: The `MessageType` that will be displayed by this cell.
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// The default value returned by this method is `nil`.
  func cellBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?

  /// The attributed text to be used for message bubble's top label.
  ///
  /// - Parameters:
  ///   - message: The `MessageType` that will be displayed by this cell.
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// The default value returned by this method is `nil`.
  func messageTopLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?

  /// The attributed text to be used for cell's bottom label.
  ///
  /// - Parameters:
  ///   - message: The `MessageType` that will be displayed by this cell.
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// The default value returned by this method is `nil`.
  func messageBottomLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?

  /// The attributed text to be used for cell's timestamp label.
  /// The timestamp label is shown when showMessageTimestampOnSwipeLeft is enabled by swiping left over the chat controller.
  ///
  /// - Parameters:
  ///   - message: The `MessageType` that will be displayed by this cell.
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// The default value returned by this method is `nil`.
  func messageTimestampLabelAttributedText(for message: MessageType, at indexPath: IndexPath) -> NSAttributedString?

  /// Text collectionView cell for message with `text`, `attributedText`, `emoji` message types.
  ///
  /// - Parameters:
  ///   - message: The `text`, `attributedText`, `emoji` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will return nil by default. You must override this method only if you want your own cell.
  func textCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell?

  /// Photo or Video collectionView cell for message with `photo`, `video` message types.
  ///
  /// - Parameters:
  ///   - message: The `photo`, `video` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will return nil by default. You must override this method only if you want your own cell.
  func photoCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell?

  /// Location collectionView cell for message with `location` message type.
  ///
  /// - Parameters:
  ///   - message: The `location` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will return nil by default. You must override this method only if you want your own cell.
  func locationCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell?

  /// Audio collectionView cell for message with `audio` message type.
  ///
  /// - Parameters:
  ///   - message: The `audio` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will return nil by default. You must override this method only if you want your own cell.
  func audioCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell?

  /// Contact collectionView cell for message with `contact` message type.
  ///
  /// - Parameters:
  ///   - message: The `contact` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will return nil by default. You must override this method only if you want your own cell.
  func contactCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell?

  /// Custom collectionView cell for message with `custom` message type.
  ///
  /// - Parameters:
  ///   - message: The `custom` message type
  ///   - indexPath: The `IndexPath` of the cell.
  ///   - messagesCollectionView: The `MessagesCollectionView` in which this cell will be displayed.
  ///
  /// - Note:
  ///   This method will call fatalError() on default. You must override this method if you are using MessageKind.custom messages.
  func customCell(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell

  /// Typing indicator cell used when the indicator is set to be shown
  ///
  /// - Parameters:
  ///   - indexPath: The index path to dequeue the cell at
  ///   - messagesCollectionView: The `MessagesCollectionView` the cell is to be rendered in
  /// - Returns: A `UICollectionViewCell` that indicates a user is typing
  func typingIndicator(at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UICollectionViewCell
}

extension MessagesDataSource {
  public func isFromCurrentSender(message: MessageType) -> Bool {
    message.sender.senderId == currentSender.senderId
  }

  public func numberOfItems(inSection _: Int, in _: MessagesCollectionView) -> Int {
    1
  }

  public func cellTopLabelAttributedText(for _: MessageType, at _: IndexPath) -> NSAttributedString? {
    nil
  }

  public func cellBottomLabelAttributedText(for _: MessageType, at _: IndexPath) -> NSAttributedString? {
    nil
  }

  public func messageTopLabelAttributedText(for _: MessageType, at _: IndexPath) -> NSAttributedString? {
    nil
  }

  public func messageBottomLabelAttributedText(for _: MessageType, at _: IndexPath) -> NSAttributedString? {
    nil
  }

  public func messageTimestampLabelAttributedText(for message: MessageType, at _: IndexPath) -> NSAttributedString? {
    let sentDate = message.sentDate
    let sentDateString = MessageKitDateFormatter.shared.string(from: sentDate)
    let timeLabelFont: UIFont = .boldSystemFont(ofSize: 10)
    let timeLabelColor: UIColor
    timeLabelColor = .systemGray
    return NSAttributedString(
      string: sentDateString,
      attributes: [NSAttributedString.Key.font: timeLabelFont, NSAttributedString.Key.foregroundColor: timeLabelColor])
  }

  public func textCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell? {
    nil
  }

  public func photoCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell? {
    nil
  }

  public func locationCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell? {
    nil
  }

  public func audioCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell? {
    nil
  }

  public func contactCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell? {
    nil
  }

  public func customCell(for _: MessageType, at _: IndexPath, in _: MessagesCollectionView) -> UICollectionViewCell {
    fatalError(MessageKitError.customDataUnresolvedCell)
  }

  public func typingIndicator(
    at indexPath: IndexPath,
    in messagesCollectionView: MessagesCollectionView)
    -> UICollectionViewCell
  {
    messagesCollectionView.dequeueReusableCell(TypingIndicatorCell.self, for: indexPath)
  }
}