KtIrc/src/main/kotlin/com/dmdirc/ktirc/IrcClientImpl.kt

package com.dmdirc.ktirc

import com.dmdirc.ktirc.events.*
import com.dmdirc.ktirc.events.handlers.eventHandlers
import com.dmdirc.ktirc.events.mutators.eventMutators
import com.dmdirc.ktirc.io.LineBufferedSocket
import com.dmdirc.ktirc.io.LineBufferedSocketImpl
import com.dmdirc.ktirc.io.MessageHandler
import com.dmdirc.ktirc.io.MessageParser
import com.dmdirc.ktirc.messages.*
import com.dmdirc.ktirc.messages.processors.messageProcessors
import com.dmdirc.ktirc.model.*
import com.dmdirc.ktirc.util.RemoveIn
import com.dmdirc.ktirc.util.currentTimeProvider
import com.dmdirc.ktirc.util.generateLabel
import com.dmdirc.ktirc.util.logger
import kotlinx.coroutines.*
import kotlinx.coroutines.channels.Channel
import kotlinx.coroutines.channels.map
import kotlinx.coroutines.sync.Mutex
import java.net.Inet6Address
import java.net.InetAddress
import java.time.Duration
import java.util.logging.Level

/**
 * Concrete implementation of an [IrcClient].
 */
internal class IrcClientImpl(private val config: IrcClientConfig) : ExperimentalIrcClient, CoroutineScope {

    private val log by logger()

    @ExperimentalCoroutinesApi
    override val coroutineContext = GlobalScope.newCoroutineContext(Dispatchers.IO)

    @ExperimentalCoroutinesApi
    internal var socketFactory: (CoroutineScope, String, String, Int, Boolean) -> LineBufferedSocket = ::LineBufferedSocketImpl
    internal var resolver: (String) -> Collection<ResolveResult> = { host ->
        InetAddress.getAllByName(host).map { ResolveResult(it.hostAddress, it is Inet6Address) }
    }

    internal var asyncTimeout = Duration.ofSeconds(20)

    override var behaviour = config.behaviour

    override val serverState = ServerState(config.profile.nickname, config.server.host, config.sasl)
    override val channelState = ChannelStateMap { caseMapping }
    override val localUser = User(config.profile.nickname)
    override val userState = UserState { caseMapping }.apply { this += localUser }

    private val messageHandler = MessageHandler(messageProcessors, eventMutators, eventHandlers)
    private val messageBuilder = MessageBuilder()

    private val parser = MessageParser()
    private var socket: LineBufferedSocket? = null

    private val connecting = Mutex(false)

    @Deprecated("Use structured send instead", ReplaceWith("send(command, arguments)"))
    @RemoveIn("2.0.0")
    override fun send(message: String) {
        socket?.sendChannel?.offer(message.toByteArray()) ?: log.warning { "No send channel for message: $message" }
    }

    override fun send(tags: Map<MessageTag, String>, command: String, vararg arguments: String) {
        maybeEchoMessage(command, arguments)
        socket?.sendChannel?.offer(messageBuilder.build(tags, command, arguments))
                ?: log.warning { "No send channel for command: $command" }
    }

    override fun sendAsync(tags: Map<MessageTag, String>, command: String, arguments: Array<String>, matcher: (IrcEvent) -> Boolean) = async {
        val label = generateLabel(this@IrcClientImpl)
        val channel = Channel<IrcEvent>(1)

        if (serverState.asyncResponseState.supportsLabeledResponses) {
            serverState.asyncResponseState.pendingResponses[label] = channel to { event -> event.metadata.label == label }
            send(tags + (MessageTag.Label to label), command, *arguments)
        } else {
            serverState.asyncResponseState.pendingResponses[label] = channel to matcher
            send(tags, command, *arguments)
        }

        withTimeoutOrNull(asyncTimeout.toMillis()) {
            channel.receive()
        }.also { serverState.asyncResponseState.pendingResponses.remove(label) }
    }

    override fun connect() {
        check(connecting.tryLock()) { "IrcClient is already connected to a server" }

        val ip: String
        try {
            ip = resolve(config.server.host)
        } catch (ex: Exception) {
            log.log(Level.SEVERE, ex) { "Error resolving ${config.server.host}" }
            emitEvent(ServerConnectionError(EventMetadata(currentTimeProvider()), ConnectionError.UnresolvableAddress, ex.localizedMessage))
            reset()
            return
        }

        @Suppress("EXPERIMENTAL_API_USAGE")
        with(socketFactory(this, config.server.host, ip, config.server.port, config.server.useTls)) {
            socket = this

            emitEvent(ServerConnecting(EventMetadata(currentTimeProvider())))

            launch {
                try {
                    connect()
                    emitEvent(ServerConnected(EventMetadata(currentTimeProvider())))
                    sendCapabilityList()
                    sendPasswordIfPresent()
                    sendNickChange(config.profile.nickname)
                    sendUser(config.profile.username, config.profile.realName)
                    messageHandler.processMessages(this@IrcClientImpl, receiveChannel.map { parser.parse(it) })
                } catch (ex: Exception) {
                    log.log(Level.SEVERE, ex) { "Error connecting to ${config.server.host}:${config.server.port}" }
                    emitEvent(ServerConnectionError(EventMetadata(currentTimeProvider()), ex.toConnectionError(), ex.localizedMessage))
                }

                reset()
                emitEvent(ServerDisconnected(EventMetadata(currentTimeProvider())))
            }
        }
    }

    override fun disconnect() {
        runBlocking {
            socket?.disconnect()
            connecting.lock()
            connecting.unlock()
        }
    }

    override fun onEvent(handler: (IrcEvent) -> Unit) = messageHandler.addEmitter(handler)

    private fun emitEvent(event: IrcEvent) = messageHandler.handleEvent(this, event)
    private fun sendPasswordIfPresent() = config.server.password?.let(this::sendPassword)

    private fun maybeEchoMessage(command: String, arguments: Array<out String>) {
        // TODO: Is this the best place to do it? It'd be nicer to actually build the message and
        //       reflect the raw line back through all the processors etc.
        if (command == "PRIVMSG" && behaviour.alwaysEchoMessages && !serverState.capabilities.enabledCapabilities.contains(Capability.EchoMessages)) {
            emitEvent(MessageReceived(
                    EventMetadata(currentTimeProvider()),
                    localUser,
                    arguments[0],
                    arguments[1]
            ))
        }
    }

    private fun resolve(host: String): String {
        val hosts = resolver(host)
        val preferredHosts = hosts.filter { it.isV6 == behaviour.preferIPv6 }
        return if (preferredHosts.isNotEmpty()) {
            preferredHosts.random().ip
        } else {
            hosts.random().ip
        }
    }

    internal fun reset() {
        serverState.reset()
        channelState.clear()
        userState.reset()
        localUser.reset(config.profile.nickname)
        userState += localUser
        socket = null
        connecting.tryLock()
        connecting.unlock()
    }

}

internal data class ResolveResult(val ip: String, val isV6: Boolean)