MessageKit/Sources/Layout/MessageSizeCalculator.swift

/*
 MIT License

 Copyright (c) 2017-2018 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

open class MessageSizeCalculator: CellSizeCalculator {

    public init(layout: MessagesCollectionViewFlowLayout? = nil) {
        super.init()
        
        self.layout = layout
    }

    public var incomingAvatarSize = CGSize(width: 30, height: 30)
    public var outgoingAvatarSize = CGSize(width: 30, height: 30)

    public var incomingAvatarPosition = AvatarPosition(vertical: .cellBottom)
    public var outgoingAvatarPosition = AvatarPosition(vertical: .cellBottom)

    public var incomingMessagePadding = UIEdgeInsets(top: 0, left: 4, bottom: 0, right: 30)
    public var outgoingMessagePadding = UIEdgeInsets(top: 0, left: 30, bottom: 0, right: 4)

    public var incomingCellTopLabelAlignment = LabelAlignment(textAlignment: .center, textInsets: .zero)
    public var outgoingCellTopLabelAlignment = LabelAlignment(textAlignment: .center, textInsets: .zero)

    public var incomingMessageTopLabelAlignment = LabelAlignment(textAlignment: .left, textInsets: UIEdgeInsets(left: 42))
    public var outgoingMessageTopLabelAlignment = LabelAlignment(textAlignment: .right, textInsets: UIEdgeInsets(right: 42))

    public var incomingMessageBottomLabelAlignment = LabelAlignment(textAlignment: .left, textInsets: UIEdgeInsets(left: 42))
    public var outgoingMessageBottomLabelAlignment = LabelAlignment(textAlignment: .right, textInsets: UIEdgeInsets(right: 42))

    open override func configure(attributes: UICollectionViewLayoutAttributes) {
        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.avatarSize = avatarSize(for: message)
        attributes.avatarPosition = avatarPosition(for: message)

        attributes.messageContainerPadding = messageContainerPadding(for: message)
        attributes.messageContainerSize = messageContainerSize(for: message)
        attributes.cellTopLabelSize = cellTopLabelSize(for: message, at: indexPath)
        attributes.messageTopLabelSize = messageTopLabelSize(for: message, at: indexPath)
        attributes.messageTopLabelAlignment = messageTopLabelAlignment(for: message)

        attributes.messageBottomLabelAlignment = messageBottomLabelAlignment(for: message)
        attributes.messageBottomLabelSize = messageBottomLabelSize(for: message, at: indexPath)

        attributes.accessoryViewSize = accessoryViewSize(for: message)
        attributes.accessoryViewPadding = accessoryViewPadding(for: message)
    }

    open override func sizeForItem(at indexPath: IndexPath) -> CGSize {
        let dataSource = messagesLayout.messagesDataSource
        let message = dataSource.messageForItem(at: indexPath, in: messagesLayout.messagesCollectionView)
        let itemHeight = cellContentHeight(for: message, at: indexPath)
        return CGSize(width: messagesLayout.itemWidth, height: itemHeight)
    }

    open func cellContentHeight(for message: MessageType, at indexPath: IndexPath) -> CGFloat {

        let messageContainerHeight = messageContainerSize(for: message).height
        let messageBottomLabelHeight = messageBottomLabelSize(for: message, at: indexPath).height
        let cellTopLabelHeight = cellTopLabelSize(for: message, at: indexPath).height
        let messageTopLabelHeight = messageTopLabelSize(for: message, at: indexPath).height
        let messageVerticalPadding = messageContainerPadding(for: message).vertical
        let avatarHeight = avatarSize(for: message).height
        let avatarVerticalPosition = avatarPosition(for: message).vertical

        switch avatarVerticalPosition {
        case .messageCenter:
            let totalLabelHeight: CGFloat = cellTopLabelHeight + messageTopLabelHeight
                + messageContainerHeight + messageVerticalPadding + messageBottomLabelHeight
            return max(avatarHeight, totalLabelHeight)
        case .messageBottom:
            var cellHeight: CGFloat = 0
            cellHeight += messageBottomLabelHeight
            let labelsHeight = messageContainerHeight + messageVerticalPadding + cellTopLabelHeight + messageTopLabelHeight
            cellHeight += max(labelsHeight, avatarHeight)
            return cellHeight
        case .messageTop:
            var cellHeight: CGFloat = 0
            cellHeight += cellTopLabelHeight
            cellHeight += messageTopLabelHeight
            let labelsHeight = messageContainerHeight + messageVerticalPadding + messageBottomLabelHeight
            cellHeight += max(labelsHeight, avatarHeight)
            return cellHeight
        case .messageLabelTop:
            var cellHeight: CGFloat = 0
            cellHeight += cellTopLabelHeight
            let messageLabelsHeight = messageContainerHeight + messageBottomLabelHeight + messageVerticalPadding + messageTopLabelHeight
            cellHeight += max(messageLabelsHeight, avatarHeight)
            return cellHeight
        case .cellTop, .cellBottom:
            let totalLabelHeight: CGFloat = cellTopLabelHeight + messageTopLabelHeight
                + messageContainerHeight + messageVerticalPadding + messageBottomLabelHeight
            return max(avatarHeight, totalLabelHeight)
        }
    }

    // MARK: - Avatar

    public func avatarPosition(for message: MessageType) -> AvatarPosition {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        var position = isFromCurrentSender ? outgoingAvatarPosition : incomingAvatarPosition

        switch position.horizontal {
        case .cellTrailing, .cellLeading:
            break
        case .natural:
            position.horizontal = isFromCurrentSender ? .cellTrailing : .cellLeading
        }
        return position
    }

    public func avatarSize(for message: MessageType) -> CGSize {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        return isFromCurrentSender ? outgoingAvatarSize : incomingAvatarSize
    }

    // MARK: - Top cell Label

    public func cellTopLabelSize(for message: MessageType, at indexPath: IndexPath) -> CGSize {
        let layoutDelegate = messagesLayout.messagesLayoutDelegate
        let collectionView = messagesLayout.messagesCollectionView
        let height = layoutDelegate.cellTopLabelHeight(for: message, at: indexPath, in: collectionView)
        return CGSize(width: messagesLayout.itemWidth, height: height)
    }

    public func cellTopLabelAlignment(for message: MessageType) -> LabelAlignment {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        return isFromCurrentSender ? outgoingCellTopLabelAlignment : incomingCellTopLabelAlignment
    }
    
    // MARK: - Top message Label
    
    public func messageTopLabelSize(for message: MessageType, at indexPath: IndexPath) -> CGSize {
        let layoutDelegate = messagesLayout.messagesLayoutDelegate
        let collectionView = messagesLayout.messagesCollectionView
        let height = layoutDelegate.messageTopLabelHeight(for: message, at: indexPath, in: collectionView)
        return CGSize(width: messagesLayout.itemWidth, height: height)
    }
    
    public func messageTopLabelAlignment(for message: MessageType) -> LabelAlignment {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        return isFromCurrentSender ? outgoingMessageTopLabelAlignment : incomingMessageTopLabelAlignment
    }

    // MARK: - Bottom Label

    public func messageBottomLabelSize(for message: MessageType, at indexPath: IndexPath) -> CGSize {
        let layoutDelegate = messagesLayout.messagesLayoutDelegate
        let collectionView = messagesLayout.messagesCollectionView
        let height = layoutDelegate.messageBottomLabelHeight(for: message, at: indexPath, in: collectionView)
        return CGSize(width: messagesLayout.itemWidth, height: height)
    }

    public func messageBottomLabelAlignment(for message: MessageType) -> LabelAlignment {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        return isFromCurrentSender ? outgoingMessageBottomLabelAlignment : incomingMessageBottomLabelAlignment
    }

    // MARK: - Accessory View

    public func accessoryViewSize(for message: MessageType) -> CGSize {
        let layoutDelegate = messagesLayout.messagesLayoutDelegate
        let collectionView = messagesLayout.messagesCollectionView
        return layoutDelegate.accessoryViewSize(for: message, in: collectionView)
    }

    public func accessoryViewPadding(for message: MessageType) -> UIEdgeInsets {
        let layoutDelegate = messagesLayout.messagesLayoutDelegate
        let collectionView = messagesLayout.messagesCollectionView
        return layoutDelegate.accessoryViewPadding(for: message, in: collectionView)
    }

    // MARK: - MessageContainer

    public func messageContainerPadding(for message: MessageType) -> UIEdgeInsets {
        let dataSource = messagesLayout.messagesDataSource
        let isFromCurrentSender = dataSource.isFromCurrentSender(message: message)
        return isFromCurrentSender ? outgoingMessagePadding : incomingMessagePadding
    }

    open func messageContainerSize(for message: MessageType) -> CGSize {
        // Returns .zero by default
        return .zero
    }

    open func messageContainerMaxWidth(for message: MessageType) -> CGFloat {
        let avatarWidth = avatarSize(for: message).width
        let messagePadding = messageContainerPadding(for: message)
        let accessoryWidth = accessoryViewSize(for: message).width
        let accessoryPadding = accessoryViewPadding(for: message)
        return messagesLayout.itemWidth - avatarWidth - messagePadding.horizontal - accessoryWidth - accessoryPadding.horizontal
    }

    // MARK: - Helpers

    public var messagesLayout: MessagesCollectionViewFlowLayout {
        guard let layout = layout as? MessagesCollectionViewFlowLayout else {
            fatalError("Layout object is missing or is not a MessagesCollectionViewFlowLayout")
        }
        return layout
    }

    internal func labelSize(for attributedText: NSAttributedString, considering maxWidth: CGFloat) -> CGSize {
        let constraintBox = CGSize(width: maxWidth, height: .greatestFiniteMagnitude)
        let rect = attributedText.boundingRect(with: constraintBox, options: [.usesLineFragmentOrigin, .usesFontLeading], context: nil).integral

        return rect.size
    }
}

fileprivate extension UIEdgeInsets {
    init(top: CGFloat = 0, bottom: CGFloat = 0, left: CGFloat = 0, right: CGFloat = 0) {
        self.init(top: top, left: left, bottom: bottom, right: right)
    }
}