KtIrc/src/main/kotlin/com/dmdirc/ktirc/events/ChannelStateHandler.kt

package com.dmdirc.ktirc.events

import com.dmdirc.ktirc.IrcClient
import com.dmdirc.ktirc.model.ChannelState
import com.dmdirc.ktirc.model.ChannelUser
import com.dmdirc.ktirc.util.logger

internal class ChannelStateHandler : EventHandler {

    private val log by logger()

    override fun processEvent(client: IrcClient, event: IrcEvent): List<IrcEvent> {
        when (event) {
            is ChannelJoined -> handleJoin(client, event)
            is ChannelParted -> handlePart(client, event)
            is ChannelNamesReceived -> handleNamesReceived(client, event)
            is ChannelNamesFinished -> handleNamesFinished(client, event)
            is ChannelUserKicked -> handleKick(client, event)
            is ModeChanged -> handleModeChanged(client, event)
            is UserQuit -> return handleQuit(client, event)
        }
        return emptyList()
    }

    private fun handleJoin(client: IrcClient, event: ChannelJoined) {
        if (client.isLocalUser(event.user)) {
            log.info { "Joined new channel: ${event.channel}" }
            client.channelState += ChannelState(event.channel) { client.caseMapping }
        }

        client.channelState[event.channel]?.let { it.users += ChannelUser(event.user.nickname) }
    }

    private fun handlePart(client: IrcClient, event: ChannelParted) {
        if (client.isLocalUser(event.user)) {
            log.info { "Left channel: ${event.channel}" }
            client.channelState -= event.channel
        } else {
            client.channelState[event.channel]?.let {
                it.users -= event.user.nickname
            }
        }
    }

    private fun handleKick(client: IrcClient, event: ChannelUserKicked) {
        if (client.isLocalUser(event.victim)) {
            log.info { "Kicked from channel: ${event.channel}" }
            client.channelState -= event.channel
        } else {
            client.channelState[event.channel]?.let {
                it.users -= event.victim
            }
        }
    }

    private fun handleNamesReceived(client: IrcClient, event: ChannelNamesReceived) {
        val channel = client.channelState[event.channel] ?: return

        if (!channel.receivingUserList) {
            log.finer { "Started receiving names list for ${channel.name}" }
            channel.users.clear()
            channel.receivingUserList = true
        }

        event.toModesAndUsers(client).forEach { (modes, user) ->
            channel.users += ChannelUser(user.nickname, modes)
        }
    }

    private fun handleNamesFinished(client: IrcClient, event: ChannelNamesFinished) {
        client.channelState[event.channel]?.let {
            it.receivingUserList = false
            log.finest { "Finished receiving names in ${event.channel}. Users: ${it.users.toList()}" }
        }
    }

    private fun handleModeChanged(client: IrcClient, event: ModeChanged) {
        val chan = client.channelState[event.target] ?: return
        if (event.discovered) {
            chan.modesDiscovered = true
            chan.modes.clear()
        }

        var adding = true
        var argumentOffset = 0
        for (char in event.modes) {
            when (char) {
                '+' -> adding = true
                '-' -> adding = false
                else -> argumentOffset += adjustMode(client, chan, char, event.arguments, argumentOffset, adding)
            }
        }
    }

    private fun adjustMode(client: IrcClient, chan: ChannelState, mode: Char, arguments: Array<String>, argumentOffset: Int, adding: Boolean): Int {
        return if (client.serverState.isChannelUserMode(mode)) {
            adjustUserMode(client, chan, mode, adding, arguments[argumentOffset])
            1
        } else {
            val type = client.serverState.channelModeType(mode)
            val takesParam = if (adding) type.needsParameterToSet else type.needsParameterToUnset
            val param = if (takesParam) arguments[argumentOffset] else ""
            if (adding) {
                chan.modes[mode] = param
            } else {
                chan.modes.remove(mode)
            }
            if (takesParam) 1 else 0
        }
    }

    private fun adjustUserMode(client: IrcClient, chan: ChannelState, mode: Char, adding: Boolean, user: String) {
        chan.users[user]?.let { channelUser ->
            // Filter from the master list of mode prefixes so that ordering is consistent
            channelUser.modes = client.serverState.channelModePrefixes.modes.filter {
                if (adding) {
                    it == mode || it in channelUser.modes
                } else {
                    it != mode && it in channelUser.modes
                }
            }
        }
    }

    private fun handleQuit(client: IrcClient, event: UserQuit) = sequence {
        client.channelState.forEach {
            if (it.users.contains(event.user.nickname)) {
                it.users -= event.user.nickname
                yield(ChannelQuit(event.time, event.user, it.name, event.reason))
            }
        }
    }.toList()

}