package o1game.Server


// TODO: TLS/SSL / import javax.net.ssl.SSLServerSocketFactory

import java.lang.Thread.{currentThread, sleep}
import java.io.IOException
import java.net.{ServerSocket, Socket}
import o1game.constants.*
import o1game.Model.Adventure
import o1game.Model.Entity
import o1game.utils.stringToByteArray

import java.lang.System.currentTimeMillis
import scala.util.Try


/** `Server` exists to initialize a server for the game
  *  and run it with its method `startServer`.
  *
  * @param port the TCP port the server should listen on
  * @param maxClients the maximum number of clients that may be in the game
  *                   simultaneously.
  * @param timeLimit the time limit clients should have to execute their turns.
  * @param joinAfterStart whether new clients are accepted after the game has
  *                       been started
  */
class Server(
	port: Int,
	maxClients: Int,
	val timeLimit: Int,
	val joinAfterStart: Boolean
):

	private val socket = ServerSocket(port)
	private val clientGetter = ConnectionGetter(socket)
	private val clients: Clients = Clients(maxClients)
	private val buffer: Array[Byte] = Array.ofDim(1024)
	private var bufferIndex = 0
	private var adventure: Option[Adventure] = None
	private var previousTurn = 0.0

	/** Starts the server. Won't terminate under normal circumstances. */
	def startServer(): Unit =
		while true do
			this.serverStep()
			sleep(POLL_INTERVAL)

	private def serverStep(): Unit =
		this.clients.removeNonCompliant()
		if this.adventure.isEmpty || this.joinAfterStart then
			this.receiveNewClient()
		this.readFromAll()
		this.clients.foreach(_.interpretData())
		this.writeClientDataToClients()
		if this.canExecuteTurns then
			this.clients.inRandomOrder(_.act())
			this.writeClientDataToClients()
			this.clients.foreach(c =>
				this.writeToClient(this.turnStartInfo(c), c)
			)
			this.previousTurn = currentTimeMillis() / 1000
		if this.adventure.isDefined && this.joinAfterStart then
			this.clients.foreach( c => if c.isReadyForGameStart then
				this.adventure.foreach(a =>
					c.getName.foreach(n => a.addPlayer(n))
				)
				startGameForClient(c)
			)
		else if this.adventure.isEmpty && !this.clients.isEmpty && this.clients.forall(_.isReadyForGameStart) then
			this.adventure = Some(Adventure(this.clients.names))
			this.clients.foreach(startGameForClient(_))
			this.previousTurn = currentTimeMillis() / 1000

	/** Helper function to start the game for the specified client c.
	  * MAY ONLY BE USED IF `this.adventure` is Some!
	  * Apparently guard clauses are bad because they use return or something,
	  * but assertions should be fine, as long as they enforce the function
	  * contract?
	  */
	private def startGameForClient(c: Client): Unit =
		assert(this.adventure.isDefined)
		c.gameStart()
		val name = c.getName

		val entity: Option[Entity] = name match
			case Some(n) => this.adventure match
				case Some(a) => a.getPlayer(n)
				case None => None
			case None => None
		entity.foreach(c.giveEntity(_))

		this.writeToClient(
			s"$timeLimit\r\n${this.turnStartInfo(c)}", c
		)


	/** Helper function to determine if the next turn can be taken */
	private def canExecuteTurns: Boolean =
		val requirement1 = this.adventure.isDefined
		val requirement2 = !this.clients.isEmpty // nice! you can just return
		                                         // to the game after everyone
		                                         // left and everything is just
		                                         // as before!
		val allPlayersReady = this.clients.forall(_.isReadyToAct)
		val requirement3 = (allPlayersReady
			|| currentTimeMillis() / 1000 >= previousTurn + timeLimit)
		requirement1 && requirement2 && requirement3


	/** Receives a new client and stores it in `clients`.
	  *
	  * @return describes if a client was added
	  */
	private def receiveNewClient(): Boolean =
		this.clientGetter.newClient() match
			case Some(c) =>
				clients.addClient(Client(c))
				true
			case None =>
				false

	private def turnStartInfo(client: Client): String =
		val clientArea = client.entity.map(_.location)
		val areaDesc = clientArea
			.map(_.description)
			.getOrElse("You are floating in the middle of a soothing void.")
		val directions = clientArea
			.map(_.getNeighborNames.mkString(LIST_SEPARATOR))
			.getOrElse("")
		val items = clientArea
			.map(_.getItemNames.mkString(LIST_SEPARATOR))
			.getOrElse("")
		val entities = client.entity.map(c =>
			c.location
				.getEntityNames
				.filter(c.name != _)
				.mkString(LIST_SEPARATOR)
		).getOrElse("")
		s"$TURN_INDICATOR\r\n$areaDesc\r\n$directions\r\n$items\r\n$entities\r\n"

	/** Sends `message` to all clients
	  *
	  * @param message the message to send
	  */
	private def writeToAll(message: String): Unit =
		this.clients.mapAndRemove(c =>
			val output = c.socket.getOutputStream
			output.write(message.toVector.map(_.toByte).toArray)
			output.flush()
		)

	private def writeToClient(message: String, client: Client): Unit =
		try {
			val output = client.socket.getOutputStream
			output.write(message.toVector.map(_.toByte).toArray)
			output.flush()
		} catch {
			case e: IOException => client.failedProtocol()
		}

	/** Sends every client's `dataToThisClient` to the client */
	private def writeClientDataToClients(): Unit =
		this.clients.mapAndRemove(c =>
			val output = c.socket.getOutputStream
			val data = c.dataToThisClient()
			output.write(data.toVector.map(_.toByte).toArray)
			output.flush()
		)

	/** Reads data sent by clients and stores it in the `Client`s of `clients` */
	private def readFromAll(): Unit =
		clients.mapAndRemove(c =>
			val input = c.socket.getInputStream
			while input.available() != 0 do
				val bytesRead = input.read(buffer)
				if bytesRead != -1 then
					c.receiveData(buffer.take(bytesRead).toVector)
		)

end Server