bundesmessenger-ios/Riot/Modules/Room/ContextualMenu/ReactionsMenu/ReactionsMenuViewModel.swift

/*
 Copyright 2019 New Vector Ltd

 Licensed under the Apache License, Version 2.0 (the "License");
 you may not use this file except in compliance with the License.
 You may obtain a copy of the License at

 http://www.apache.org/licenses/LICENSE-2.0

 Unless required by applicable law or agreed to in writing, software
 distributed under the License is distributed on an "AS IS" BASIS,
 WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 See the License for the specific language governing permissions and
 limitations under the License.
 */

import UIKit

final class ReactionsMenuViewModel: ReactionsMenuViewModelType {

    // MARK: - Properties

    // MARK: Private
    private let session: MXSession              // TODO: To remove. Only required for reactUsingHack()
    private let aggregations: MXAggregations
    private let roomId: String
    private let eventId: String

    // MARK: Public

    private(set) var isAgreeButtonSelected: Bool = false
    private(set) var isDisagreeButtonSelected: Bool = false
    private(set) var isLikeButtonSelected: Bool = false
    private(set) var isDislikeButtonSelected: Bool = false

    weak var viewDelegate: ReactionsMenuViewModelDelegate?
    weak var coordinatorDelegate: ReactionsMenuViewModelCoordinatorDelegate?

    // MARK: - Setup

    init(aggregations: MXAggregations, roomId: String, eventId: String, session: MXSession) {
        self.aggregations = aggregations
        self.roomId = roomId
        self.eventId = eventId
        self.session = session

        self.loadData()
        self.listenToDataUpdate()
    }

    // MARK: - Public

    func process(viewAction: ReactionsMenuViewAction) {
        var reaction: ReactionsMenuReaction?
        var newState: Bool?

        switch viewAction {
        case .toggleReaction(let menuReaction):
            reaction = menuReaction

            switch menuReaction {
            case .agree:
                newState = !self.isAgreeButtonSelected
            case .disagree:
                newState = !self.isDisagreeButtonSelected
            case .like:
                newState = !self.isLikeButtonSelected
            case .dislike:
                newState = !self.isDislikeButtonSelected
            }
        }

        guard let theReaction = reaction, let theNewState = newState else {
            return
        }

        self.react(withReaction: theReaction, selected: theNewState)
    }

    // MARK: - Private

    private func resetData() {
        self.isAgreeButtonSelected = false
        self.isDisagreeButtonSelected = false
        self.isLikeButtonSelected = false
        self.isDislikeButtonSelected = false
    }

    private func loadData() {
        guard let reactionCounts = self.aggregations.aggregatedReactions(onEvent: self.eventId, inRoom: self.roomId)?.reactions else {
            return
        }

        self.resetData()
        reactionCounts.forEach { (reactionCount) in
            if reactionCount.myUserHasReacted {
                if let reaction = ReactionsMenuReaction(rawValue: reactionCount.reaction) {
                    switch reaction {
                    case .agree:
                        self.isAgreeButtonSelected = true
                    case .disagree:
                        self.isDisagreeButtonSelected = true
                    case .like:
                        self.isLikeButtonSelected = true
                    case .dislike:
                        self.isDislikeButtonSelected = true
                    }
                }
            }
        }

        self.viewDelegate?.reactionsMenuViewModelDidUpdate(self)
    }

    private func listenToDataUpdate() {
        self.aggregations.listenToReactionCountUpdate(inRoom: self.roomId) { [weak self] (changes) in

            guard let sself = self else {
                return
            }

            if changes[sself.eventId] != nil {
                sself.loadData()
            }
        }
    }

    private func react(withReaction reaction: ReactionsMenuReaction, selected: Bool) {
        if selected {
            self.aggregations.sendReaction(reaction.rawValue, toEvent: self.eventId, inRoom: self.roomId, success: {[weak self] _ in

                guard let sself = self else {
                    return
                }

                sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionComplete: reaction.rawValue, isAddReaction: true)

            }, failure: {[weak self] (error) in
                print("[ReactionsMenuViewModel] react: Error: \(error)")

                guard let sself = self else {
                    return
                }

                // The server does not support support reaction yet
                // Use a fallback mechanism
                // TODO: To remove once the feature has landed on matrix.org homeserver
                if let mxError = MXError(nsError: error) {
                    if mxError.errcode == kMXErrCodeStringUnrecognized {
                        sself.reactUsingHack(withReaction: reaction)
                        return
                    }
                }

                sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionFailedWithError: error, reaction: reaction.rawValue, isAddReaction: true)
            })
        } else {

            self.aggregations.unReact(onReaction: reaction.rawValue, toEvent: self.eventId, inRoom: self.roomId, success: {[weak self] in

                guard let sself = self else {
                    return
                }

                sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionComplete: reaction.rawValue, isAddReaction: false)

                }, failure: {[weak self] (error) in
                    print("[ReactionsMenuViewModel] react: Error: \(error)")

                    guard let sself = self else {
                        return
                    }

                    sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionFailedWithError: error, reaction: reaction.rawValue, isAddReaction: false)
            })
        }

        self.coordinatorDelegate?.reactionsMenuViewModel(self, didSendReaction: reaction.rawValue, isAddReaction: !selected)

        if selected {
            self.ensure3StateButtons(withReaction: reaction)
        }
    }

    // We can like, dislike, be indifferent but we cannot like & dislike at the same time
    private func ensure3StateButtons(withReaction reaction: ReactionsMenuReaction) {
        var unreaction: ReactionsMenuReaction?

        switch reaction {
        case .agree:
            if isDisagreeButtonSelected {
                unreaction = .disagree
            }
        case .disagree:
            if isAgreeButtonSelected {
                unreaction = .agree
            }
        case .like:
            if isDislikeButtonSelected {
                unreaction = .dislike
            }
        case .dislike:
            if isLikeButtonSelected {
                unreaction = .like
            }
        }

        if let unreaction = unreaction {
            self.react(withReaction: unreaction, selected: false)
        }
    }

    /// reactUsingHack directly sends a `m.reaction` room message instead of using the `/send_relation` api.
    ///
    /// TODO: To remove once the feature has landed on matrix.org homeserver
    ///
    /// - Parameter reaction: the reaction
    private func reactUsingHack(withReaction reaction: ReactionsMenuReaction) {
        guard let room = self.session.room(withRoomId: self.roomId) else {
            print("[ReactionsMenuViewModel] reactUsingHack: Error: Unknown room: \(self.roomId)")
            return
        }

        print("[ReactionsMenuViewModel] reactUsingHack")

        let reactionContent = [
            "m.relates_to": [
                "rel_type": "m.annotation",
                "event_id": self.eventId,
                "key": reaction.rawValue]
        ]

        var nilEvent: MXEvent?
        room.sendEvent(.reaction, content: reactionContent, localEcho: &nilEvent, completion: { [weak self] ( completion) in
            guard let sself = self else {
                return
            }
            switch completion {
            case .success:
                print("[ReactionsMenuViewModel] reactUsingHack: Success")
                sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionComplete: reaction.rawValue, isAddReaction: true)

            case.failure(let error):
                print("[ReactionsMenuViewModel] reactUsingHack: Error: \(error)")
                sself.coordinatorDelegate?.reactionsMenuViewModel(sself, didReactionFailedWithError: error, reaction: reaction.rawValue, isAddReaction: true)
            }
        })
    }
}