MessageKit/Sources/MessagesDisplayDelegate.swift

/*
 MIT License
 
 Copyright (c) 2017 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

public protocol MessagesDisplayDelegate: class {
    
    func textColor(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor

    func messageStyle(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageStyle
    
    func backgroundColor(for message: MessageType, at  indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor
    
    func messageHeaderView(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageHeaderView?

    func shouldDisplayHeader(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> Bool
    
    func messageFooterView(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageFooterView?

}

public extension MessagesDisplayDelegate {
    
    func textColor(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor {
        guard let dataSource = messagesCollectionView.messagesDataSource else { return .darkText }
        return dataSource.isFromCurrentSender(message: message) ? .white : .darkText
    }
    
    func messageStyle(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageStyle {
        return .bubble
    }

    func backgroundColor(for message: MessageType, at  indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> UIColor {
        guard let dataSource = messagesCollectionView.messagesDataSource else { return .white }
        return dataSource.isFromCurrentSender(message: message) ? .outgoingGreen : .incomingGray
    }
    
    func messageHeaderView(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageHeaderView? {
        let header = messagesCollectionView.dequeueMessageHeaderView(withReuseIdentifier: "MessageDateHeaderView", for: indexPath) as? MessageDateHeaderView
        header?.dateLabel.text = MessageKitDateFormatter.shared.string(from: message.sentDate)
        return header
    }

    func shouldDisplayHeader(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> Bool {
        guard let dataSource = messagesCollectionView.messagesDataSource else { return false }
        if indexPath.section == 0 { return false }
        let previousSection = indexPath.section - 1
        let previousIndexPath = IndexPath(item: 0, section: previousSection)
        let previousMessage = dataSource.messageForItem(at: previousIndexPath, in: messagesCollectionView)
        let timeIntervalSinceLastMessage = message.sentDate.timeIntervalSince(previousMessage.sentDate)
        return timeIntervalSinceLastMessage >= messagesCollectionView.showsDateHeaderAfterTimeInterval
    }

    func messageFooterView(for message: MessageType, at indexPath: IndexPath, in messagesCollectionView: MessagesCollectionView) -> MessageFooterView? {
        return nil
    }

}