/*
 * 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.
 */

package im.vector.riotx.features.home.room.detail

import android.net.Uri
import android.text.TextUtils
import androidx.annotation.IdRes
import androidx.lifecycle.LiveData
import androidx.lifecycle.MutableLiveData
import com.airbnb.mvrx.FragmentViewModelContext
import com.airbnb.mvrx.MvRxViewModelFactory
import com.airbnb.mvrx.Success
import com.airbnb.mvrx.ViewModelContext
import com.jakewharton.rxrelay2.BehaviorRelay
import com.squareup.inject.assisted.Assisted
import com.squareup.inject.assisted.AssistedInject
import im.vector.matrix.android.api.MatrixCallback
import im.vector.matrix.android.api.session.Session
import im.vector.matrix.android.api.session.content.ContentAttachmentData
import im.vector.matrix.android.api.session.events.model.isImageMessage
import im.vector.matrix.android.api.session.events.model.isTextMessage
import im.vector.matrix.android.api.session.events.model.toModel
import im.vector.matrix.android.api.session.file.FileService
import im.vector.matrix.android.api.session.room.model.Membership
import im.vector.matrix.android.api.session.room.model.message.MessageContent
import im.vector.matrix.android.api.session.room.model.message.MessageType
import im.vector.matrix.android.api.session.room.model.message.getFileUrl
import im.vector.matrix.android.api.session.room.timeline.TimelineEvent
import im.vector.matrix.android.internal.crypto.attachments.toElementToDecrypt
import im.vector.matrix.android.internal.crypto.model.event.EncryptedEventContent
import im.vector.matrix.rx.rx
import im.vector.riotx.R
import im.vector.riotx.core.extensions.postLiveEvent
import im.vector.riotx.core.intent.getFilenameFromUri
import im.vector.riotx.core.platform.VectorViewModel
import im.vector.riotx.core.resources.UserPreferencesProvider
import im.vector.riotx.core.utils.LiveEvent
import im.vector.riotx.core.utils.subscribeLogError
import im.vector.riotx.features.command.CommandParser
import im.vector.riotx.features.command.ParsedCommand
import im.vector.riotx.features.home.room.detail.timeline.helper.TimelineDisplayableEvents
import io.reactivex.rxkotlin.subscribeBy
import org.commonmark.parser.Parser
import org.commonmark.renderer.html.HtmlRenderer
import timber.log.Timber
import java.io.File
import java.util.concurrent.TimeUnit


class RoomDetailViewModel @AssistedInject constructor(@Assisted initialState: RoomDetailViewState,
                                                      userPreferencesProvider: UserPreferencesProvider,
                                                      private val session: Session
) : VectorViewModel<RoomDetailViewState>(initialState) {

    private val room = session.getRoom(initialState.roomId)!!
    private val roomId = initialState.roomId
    private val eventId = initialState.eventId
    private val displayedEventsObservable = BehaviorRelay.create<RoomDetailActions.EventDisplayed>()
    private val allowedTypes = if (userPreferencesProvider.shouldShowHiddenEvents()) {
        TimelineDisplayableEvents.DEBUG_DISPLAYABLE_TYPES
    } else {
        TimelineDisplayableEvents.DISPLAYABLE_TYPES
    }
    private var timeline = room.createTimeline(eventId, allowedTypes)

    // Slot to keep a pending action during permission request
    var pendingAction: RoomDetailActions? = null

    @AssistedInject.Factory
    interface Factory {
        fun create(initialState: RoomDetailViewState): RoomDetailViewModel
    }

    companion object : MvRxViewModelFactory<RoomDetailViewModel, RoomDetailViewState> {

        const val PAGINATION_COUNT = 50

        @JvmStatic
        override fun create(viewModelContext: ViewModelContext, state: RoomDetailViewState): RoomDetailViewModel? {
            val fragment: RoomDetailFragment = (viewModelContext as FragmentViewModelContext).fragment()

            return fragment.roomDetailViewModelFactory.create(state)
        }
    }

    init {
        observeRoomSummary()
        observeEventDisplayedActions()
        observeInvitationState()
        room.rx().loadRoomMembersIfNeeded().subscribeLogError().disposeOnClear()
        timeline.start()
        setState { copy(timeline = this@RoomDetailViewModel.timeline) }
    }

    fun process(action: RoomDetailActions) {
        when (action) {
            is RoomDetailActions.SendMessage            -> handleSendMessage(action)
            is RoomDetailActions.SendMedia              -> handleSendMedia(action)
            is RoomDetailActions.EventDisplayed         -> handleEventDisplayed(action)
            is RoomDetailActions.LoadMore               -> handleLoadMore(action)
            is RoomDetailActions.SendReaction           -> handleSendReaction(action)
            is RoomDetailActions.AcceptInvite           -> handleAcceptInvite()
            is RoomDetailActions.RejectInvite           -> handleRejectInvite()
            is RoomDetailActions.RedactAction           -> handleRedactEvent(action)
            is RoomDetailActions.UndoReaction           -> handleUndoReact(action)
            is RoomDetailActions.UpdateQuickReactAction -> handleUpdateQuickReaction(action)
            is RoomDetailActions.EnterEditMode          -> handleEditAction(action)
            is RoomDetailActions.EnterQuoteMode         -> handleQuoteAction(action)
            is RoomDetailActions.EnterReplyMode         -> handleReplyAction(action)
            is RoomDetailActions.DownloadFile           -> handleDownloadFile(action)
            is RoomDetailActions.NavigateToEvent        -> handleNavigateToEvent(action)
            is RoomDetailActions.ResendMessage          -> handleResendEvent(action)
            is RoomDetailActions.RemoveFailedEcho       -> handleRemove(action)
            is RoomDetailActions.ClearSendQueue         -> handleClearSendQueue()
            is RoomDetailActions.ResendAll              -> handleResendAll()
            else                                        -> Timber.e("Unhandled Action: $action")
        }
    }

    private fun enterEditMode(event: TimelineEvent) {
        setState {
            copy(
                    sendMode = SendMode.EDIT(event)
            )
        }
    }

    fun resetSendMode() {
        setState {
            copy(
                    sendMode = SendMode.REGULAR
            )
        }
    }

    private val _nonBlockingPopAlert = MutableLiveData<LiveEvent<Pair<Int, List<Any>>>>()
    val nonBlockingPopAlert: LiveData<LiveEvent<Pair<Int, List<Any>>>>
        get() = _nonBlockingPopAlert


    private val _sendMessageResultLiveData = MutableLiveData<LiveEvent<SendMessageResult>>()
    val sendMessageResultLiveData: LiveData<LiveEvent<SendMessageResult>>
        get() = _sendMessageResultLiveData

    private val _navigateToEvent = MutableLiveData<LiveEvent<String>>()
    val navigateToEvent: LiveData<LiveEvent<String>>
        get() = _navigateToEvent

    private val _downloadedFileEvent = MutableLiveData<LiveEvent<DownloadFileState>>()
    val downloadedFileEvent: LiveData<LiveEvent<DownloadFileState>>
        get() = _downloadedFileEvent


    fun isMenuItemVisible(@IdRes itemId: Int): Boolean {
        if (itemId == R.id.clear_message_queue) {
            //For now always disable, woker cancellation is not working properly
            return false//timeline.pendingEventCount() > 0
        }
        if (itemId == R.id.resend_all) {
            return timeline.failedToDeliverEventCount() > 0
        }
        if (itemId == R.id.clear_all) {
            return timeline.failedToDeliverEventCount() > 0
        }
        return false
    }

    // PRIVATE METHODS *****************************************************************************

    private fun handleSendMessage(action: RoomDetailActions.SendMessage) {
        withState { state ->
            when (state.sendMode) {
                SendMode.REGULAR  -> {
                    val slashCommandResult = CommandParser.parseSplashCommand(action.text)

                    when (slashCommandResult) {
                        is ParsedCommand.ErrorNotACommand         -> {
                            // Send the text message to the room
                            room.sendTextMessage(action.text, autoMarkdown = action.autoMarkdown)
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.MessageSent)
                        }
                        is ParsedCommand.ErrorSyntax              -> {
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandError(slashCommandResult.command))
                        }
                        is ParsedCommand.ErrorEmptySlashCommand   -> {
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandUnknown("/"))
                        }
                        is ParsedCommand.ErrorUnknownSlashCommand -> {
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandUnknown(slashCommandResult.slashCommand))
                        }
                        is ParsedCommand.Invite                   -> {
                            handleInviteSlashCommand(slashCommandResult)
                        }
                        is ParsedCommand.SetUserPowerLevel        -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.ClearScalarToken         -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.SetMarkdown              -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.UnbanUser                -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.BanUser                  -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.KickUser                 -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.JoinRoom                 -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.PartRoom                 -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                        is ParsedCommand.SendEmote                -> {
                            room.sendTextMessage(slashCommandResult.message, msgType = MessageType.MSGTYPE_EMOTE)
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandHandled)
                        }
                        is ParsedCommand.ChangeTopic              -> {
                            handleChangeTopicSlashCommand(slashCommandResult)
                        }
                        is ParsedCommand.ChangeDisplayName        -> {
                            // TODO
                            _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandNotImplemented)
                        }
                    }
                }
                is SendMode.EDIT  -> {

                    //is original event a reply?
                    val inReplyTo = state.sendMode.timelineEvent.root.getClearContent().toModel<MessageContent>()?.relatesTo?.inReplyTo?.eventId
                            ?: state.sendMode.timelineEvent.root.content.toModel<EncryptedEventContent>()?.relatesTo?.inReplyTo?.eventId
                    if (inReplyTo != null) {
                        //TODO check if same content?
                        room.getTimeLineEvent(inReplyTo)?.let {
                            room.editReply(state.sendMode.timelineEvent, it, action.text)
                        }
                    } else {
                        val messageContent: MessageContent? =
                                state.sendMode.timelineEvent.annotations?.editSummary?.aggregatedContent.toModel()
                                ?: state.sendMode.timelineEvent.root.getClearContent().toModel()
                        val existingBody = messageContent?.body ?: ""
                        if (existingBody != action.text) {
                            room.editTextMessage(state.sendMode.timelineEvent.root.eventId
                                                 ?: "", messageContent?.type
                                                        ?: MessageType.MSGTYPE_TEXT, action.text, action.autoMarkdown)
                        } else {
                            Timber.w("Same message content, do not send edition")
                        }
                    }
                    setState {
                        copy(
                                sendMode = SendMode.REGULAR
                        )
                    }
                    _sendMessageResultLiveData.postLiveEvent(SendMessageResult.MessageSent)
                }
                is SendMode.QUOTE -> {
                    val messageContent: MessageContent? =
                            state.sendMode.timelineEvent.annotations?.editSummary?.aggregatedContent.toModel()
                            ?: state.sendMode.timelineEvent.root.getClearContent().toModel()
                    val textMsg = messageContent?.body

                    val finalText = legacyRiotQuoteText(textMsg, action.text)

                    //TODO Refactor this, just temporary for quotes
                    val parser = Parser.builder().build()
                    val document = parser.parse(finalText)
                    val renderer = HtmlRenderer.builder().build()
                    val htmlText = renderer.render(document)
                    if (TextUtils.equals(finalText, htmlText)) {
                        room.sendTextMessage(finalText)
                    } else {
                        room.sendFormattedTextMessage(finalText, htmlText)
                    }
                    setState {
                        copy(
                                sendMode = SendMode.REGULAR
                        )
                    }
                    _sendMessageResultLiveData.postLiveEvent(SendMessageResult.MessageSent)
                }
                is SendMode.REPLY -> {
                    state.sendMode.timelineEvent.let {
                        room.replyToMessage(it, action.text, action.autoMarkdown)
                        setState {
                            copy(
                                    sendMode = SendMode.REGULAR
                            )
                        }
                        _sendMessageResultLiveData.postLiveEvent(SendMessageResult.MessageSent)
                    }

                }
            }
        }
        // Handle slash command

    }

    private fun legacyRiotQuoteText(quotedText: String?, myText: String): String {
        val messageParagraphs = quotedText?.split("\n\n".toRegex())?.dropLastWhile { it.isEmpty() }?.toTypedArray()
        var quotedTextMsg = StringBuilder()
        if (messageParagraphs != null) {
            for (i in messageParagraphs.indices) {
                if (messageParagraphs[i].trim({ it <= ' ' }) != "") {
                    quotedTextMsg.append("> ").append(messageParagraphs[i])
                }

                if (i + 1 != messageParagraphs.size) {
                    quotedTextMsg.append("\n\n")
                }
            }
        }
        val finalText = "$quotedTextMsg\n\n$myText"
        return finalText
    }

    private fun handleChangeTopicSlashCommand(changeTopic: ParsedCommand.ChangeTopic) {
        _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandHandled)

        room.updateTopic(changeTopic.topic, object : MatrixCallback<Unit> {
            override fun onSuccess(data: Unit) {
                _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandResultOk)
            }

            override fun onFailure(failure: Throwable) {
                _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandResultError(failure))
            }
        })
    }

    private fun handleInviteSlashCommand(invite: ParsedCommand.Invite) {
        _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandHandled)

        room.invite(invite.userId, object : MatrixCallback<Unit> {
            override fun onSuccess(data: Unit) {
                _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandResultOk)
            }

            override fun onFailure(failure: Throwable) {
                _sendMessageResultLiveData.postLiveEvent(SendMessageResult.SlashCommandResultError(failure))
            }
        })
    }


    private fun handleSendReaction(action: RoomDetailActions.SendReaction) {
        room.sendReaction(action.reaction, action.targetEventId)
    }

    private fun handleRedactEvent(action: RoomDetailActions.RedactAction) {
        val event = room.getTimeLineEvent(action.targetEventId) ?: return
        room.redactEvent(event.root, action.reason)
    }

    private fun handleUndoReact(action: RoomDetailActions.UndoReaction) {
        room.undoReaction(action.key, action.targetEventId, session.myUserId)
    }


    private fun handleUpdateQuickReaction(action: RoomDetailActions.UpdateQuickReactAction) {
        if (action.add) {
            room.sendReaction(action.selectedReaction, action.targetEventId)
        } else {
            room.undoReaction(action.selectedReaction, action.targetEventId, session.myUserId)
        }
    }

    private fun handleSendMedia(action: RoomDetailActions.SendMedia) {
        val attachments = action.mediaFiles.map {
            val nameWithExtension = getFilenameFromUri(null, Uri.parse(it.path))

            ContentAttachmentData(
                    size = it.size,
                    duration = it.duration,
                    date = it.date,
                    height = it.height,
                    width = it.width,
                    name = nameWithExtension ?: it.name,
                    path = it.path,
                    mimeType = it.mimeType,
                    type = ContentAttachmentData.Type.values()[it.mediaType]
            )
        }
        room.sendMedias(attachments)
    }

    private fun handleEventDisplayed(action: RoomDetailActions.EventDisplayed) {
        if (action.event.root.sendState.isSent()) { //ignore pending/local events
            displayedEventsObservable.accept(action)
        }
        //We need to update this with the related m.replace also (to move read receipt)
        action.event.annotations?.editSummary?.sourceEvents?.forEach {
            room.getTimeLineEvent(it)?.let { event ->
                displayedEventsObservable.accept(RoomDetailActions.EventDisplayed(event))
            }
        }
    }

    private fun handleLoadMore(action: RoomDetailActions.LoadMore) {
        timeline.paginate(action.direction, PAGINATION_COUNT)
    }

    private fun handleRejectInvite() {
        room.leave(object : MatrixCallback<Unit> {})
    }

    private fun handleAcceptInvite() {
        room.join(object : MatrixCallback<Unit> {})
    }

    private fun handleEditAction(action: RoomDetailActions.EnterEditMode) {
        room.getTimeLineEvent(action.eventId)?.let {
            enterEditMode(it)
        }
    }

    private fun handleQuoteAction(action: RoomDetailActions.EnterQuoteMode) {
        room.getTimeLineEvent(action.eventId)?.let {
            setState {
                copy(
                        sendMode = SendMode.QUOTE(it)
                )
            }
        }
    }

    private fun handleReplyAction(action: RoomDetailActions.EnterReplyMode) {
        room.getTimeLineEvent(action.eventId)?.let {
            setState {
                copy(
                        sendMode = SendMode.REPLY(it)
                )
            }
        }
    }

    data class DownloadFileState(
            val mimeType: String,
            val file: File?,
            val throwable: Throwable?
    )

    private fun handleDownloadFile(action: RoomDetailActions.DownloadFile) {
        session.downloadFile(
                FileService.DownloadMode.TO_EXPORT,
                action.eventId,
                action.messageFileContent.getFileName(),
                action.messageFileContent.getFileUrl(),
                action.messageFileContent.encryptedFileInfo?.toElementToDecrypt(),
                object : MatrixCallback<File> {
                    override fun onSuccess(data: File) {
                        _downloadedFileEvent.postLiveEvent(DownloadFileState(
                                action.messageFileContent.getMimeType(),
                                data,
                                null
                        ))
                    }

                    override fun onFailure(failure: Throwable) {
                        _downloadedFileEvent.postLiveEvent(DownloadFileState(
                                action.messageFileContent.getMimeType(),
                                null,
                                failure
                        ))
                    }
                })

    }


    private fun handleNavigateToEvent(action: RoomDetailActions.NavigateToEvent) {
        val targetEventId = action.eventId

        if (action.position != null) {
            // Event is already in RAM
            withState {
                if (it.eventId == targetEventId) {
                    // ensure another click on the same permalink will also do a scroll
                    setState {
                        copy(
                                eventId = null
                        )
                    }
                }

                setState {
                    copy(
                            eventId = targetEventId
                    )
                }
            }

            _navigateToEvent.postLiveEvent(targetEventId)
        } else {
            // change timeline
            timeline.dispose()
            timeline = room.createTimeline(targetEventId, allowedTypes)
            timeline.start()

            withState {
                if (it.eventId == targetEventId) {
                    // ensure another click on the same permalink will also do a scroll
                    setState {
                        copy(
                                eventId = null
                        )
                    }
                }

                setState {
                    copy(
                            eventId = targetEventId,
                            timeline = this@RoomDetailViewModel.timeline
                    )
                }
            }

            _navigateToEvent.postLiveEvent(targetEventId)
        }
    }

    private fun handleResendEvent(action: RoomDetailActions.ResendMessage) {
        val targetEventId = action.eventId
        room.getTimeLineEvent(targetEventId)?.let {
            //State must be UNDELIVERED or Failed
            if (!it.root.sendState.hasFailed()) {
                Timber.e("Cannot resend message, it is not failed, Cancel first")
                return
            }
            if (it.root.isTextMessage()) {
                room.resendTextMessage(it)
            } else if (it.root.isImageMessage()) {
                room.resendMediaMessage(it)
            } else {
                //TODO
            }
        }

    }

    private fun handleRemove(action: RoomDetailActions.RemoveFailedEcho) {
        val targetEventId = action.eventId
        room.getTimeLineEvent(targetEventId)?.let {
            //State must be UNDELIVERED or Failed
            if (!it.root.sendState.hasFailed()) {
                Timber.e("Cannot resend message, it is not failed, Cancel first")
                return
            }
            room.deleteFailedEcho(it)
        }
    }

    private fun handleClearSendQueue() {
        room.clearSendingQueue()
    }

    private fun handleResendAll() {
        room.resendAllFailedMessages()
    }


    private fun observeEventDisplayedActions() {
        // We are buffering scroll events for one second
        // and keep the most recent one to set the read receipt on.
        displayedEventsObservable
                .buffer(1, TimeUnit.SECONDS)
                .filter { it.isNotEmpty() }
                .subscribeBy(onNext = { actions ->
                    val mostRecentEvent = actions.maxBy { it.event.displayIndex }
                    mostRecentEvent?.event?.root?.eventId?.let { eventId ->
                        room.setReadReceipt(eventId, callback = object : MatrixCallback<Unit> {})
                    }
                })
                .disposeOnClear()
    }

    private fun observeRoomSummary() {
        room.rx().liveRoomSummary()
                .execute { async ->
                    copy(
                            asyncRoomSummary = async,
                            isEncrypted = room.isEncrypted()
                    )
                }
    }

    private fun observeInvitationState() {
        asyncSubscribe(RoomDetailViewState::asyncRoomSummary) { summary ->
            if (summary.membership == Membership.INVITE) {
                summary.latestEvent?.root?.senderId?.let { senderId ->
                    session.getUser(senderId)
                }?.also {
                    setState { copy(asyncInviter = Success(it)) }
                }
            }
        }
    }

    override fun onCleared() {
        timeline.dispose()
        super.onCleared()
    }

}