GhostDisplays/main/kotlin/net/hareworks/ghostdisplays/internal/controller/BaseDisplayController.kt

package net.hareworks.ghostdisplays.internal.controller

import java.util.HashSet
import java.util.UUID
import java.util.concurrent.CompletableFuture
import java.util.concurrent.ConcurrentHashMap
import java.util.concurrent.CopyOnWriteArrayList
import java.util.concurrent.atomic.AtomicBoolean
import net.hareworks.ghostdisplays.api.DisplayController
import net.hareworks.ghostdisplays.api.audience.AudiencePredicate
import net.hareworks.ghostdisplays.api.click.ClickPriority
import net.hareworks.ghostdisplays.api.click.ClickSurface
import net.hareworks.ghostdisplays.api.click.DisplayClickContext
import net.hareworks.ghostdisplays.api.click.DisplayClickHandler
import net.hareworks.ghostdisplays.api.click.HandlerRegistration
import org.bukkit.Bukkit
import org.bukkit.entity.Display
import org.bukkit.entity.Entity
import org.bukkit.entity.Interaction
import org.bukkit.entity.Player
import org.bukkit.event.player.PlayerInteractEntityEvent
import org.bukkit.plugin.java.JavaPlugin

internal class BaseDisplayController<T : Display>(
    private val plugin: JavaPlugin,
    override val display: T,
    override val interaction: Interaction?,
    private val registry: DisplayRegistry
) : DisplayController<T> {
    private val destroyed = AtomicBoolean(false)
    private val viewerCounts = ConcurrentHashMap<UUID, Int>()
    private val handlers = CopyOnWriteArrayList<HandlerEntry>()
    private val audiences = CopyOnWriteArrayList<AudienceBindingImpl>()

    override fun show(player: Player) {
        runSync {
            val uuid = player.uniqueId
            val newCount = viewerCounts.compute(uuid) { _, count -> (count ?: 0) + 1 } ?: 1
            if (newCount == 1) {
                player.showEntity(plugin, display)
                interaction?.let { player.showEntity(plugin, it) }
            }
        }
    }

    override fun hide(player: Player) {
        runSync {
            val uuid = player.uniqueId
            val current = viewerCounts[uuid] ?: return@runSync
            if (current <= 1) {
                viewerCounts.remove(uuid)
                player.hideEntity(plugin, display)
                interaction?.let { player.hideEntity(plugin, it) }
            } else {
                viewerCounts[uuid] = current - 1
            }
        }
    }

    override fun isViewing(playerId: UUID): Boolean = viewerCounts.containsKey(playerId)

    override fun viewerIds(): Set<UUID> = HashSet(viewerCounts.keys)

    override fun applyEntityUpdate(mutator: (T) -> Unit) {
        callSync {
            mutator(display)
            display.updateDisplay(false)
        }
    }

    override fun destroy() {
        if (!destroyed.compareAndSet(false, true)) return
        registry.unregister(this)
        val viewers = viewerIds().mapNotNull { Bukkit.getPlayer(it) }
        runSync {
            viewers.forEach {
                it.hideEntity(plugin, display)
                interaction?.let { interactionEntity -> it.hideEntity(plugin, interactionEntity) }
            }
            display.remove()
            interaction?.remove()
            viewerCounts.clear()
        }
        handlers.clear()
        audiences.forEach { it.clear() }
        audiences.clear()
    }

    override fun onClick(priority: ClickPriority, handler: DisplayClickHandler): HandlerRegistration {
        val entry = HandlerEntry(priority, handler)
        handlers += entry
        return HandlerRegistration {
            handlers.remove(entry)
        }
    }

    override fun addAudience(predicate: AudiencePredicate): HandlerRegistration {
        val binding = AudienceBindingImpl(predicate)
        audiences += binding
        refreshAudienceInternal(binding = binding)
        return HandlerRegistration { binding.unregister() }
    }

    private fun refreshAudienceInternal(target: Player? = null, binding: AudienceBindingImpl? = null) {
        runSync {
            val players = target?.let { listOf(it) } ?: Bukkit.getOnlinePlayers()
            val targets = binding?.let { listOf(it) } ?: audiences
            if (players.isEmpty() || targets.isEmpty()) return@runSync
            players.forEach { player ->
                targets.forEach { it.evaluate(player) }
            }
        }
    }

    override fun refreshAudience(target: Player?) {
        refreshAudienceInternal(target, null)
    }

    internal fun handleClick(event: PlayerInteractEntityEvent, clicked: Entity, surface: ClickSurface) {
        val sortedHandlers = handlers.sortedBy { it.priority.ordinal }
        if (sortedHandlers.isEmpty()) return
        val context = DisplayClickContext(
            player = event.player,
            hand = event.hand,
            clickedEntity = clicked,
            surface = surface,
            controller = this,
            event = event
        )
        sortedHandlers.forEach { entry ->
            entry.handler.handle(context)
            if (event.isCancelled) return
        }
    }

    internal fun handlePlayerQuit(player: Player) {
        val uuid = player.uniqueId
        viewerCounts.remove(uuid)
        audiences.forEach { it.forget(uuid) }
    }

    private fun runSync(action: () -> Unit) {
        if (Bukkit.isPrimaryThread()) {
            action()
        } else {
            Bukkit.getScheduler().runTask(plugin, action)
        }
    }

    private fun <R> callSync(action: () -> R): R {
        return if (Bukkit.isPrimaryThread()) {
            action()
        } else {
            val future = CompletableFuture<R>()
            Bukkit.getScheduler().runTask(plugin) { future.complete(action()) }
            future.join()
        }
    }

    private inner class AudienceBindingImpl(
        private val predicate: AudiencePredicate
    ) {
        private val activeViewers = ConcurrentHashMap.newKeySet<UUID>()

        fun evaluate(player: Player) {
            val uuid = player.uniqueId
            val matches = runCatching { predicate.test(player) }.getOrDefault(false)
            if (matches) {
                if (activeViewers.add(uuid)) {
                    show(player)
                }
            } else {
                if (activeViewers.remove(uuid)) {
                    hide(player)
                }
            }
        }

        fun forget(playerId: UUID) {
            activeViewers.remove(playerId)
        }

        fun unregister() {
            audiences.remove(this)
            val targets = activeViewers.toList()
            targets.mapNotNull { Bukkit.getPlayer(it) }.forEach { hide(it) }
            activeViewers.clear()
        }

        fun clear() {
            activeViewers.clear()
        }
    }

    private data class HandlerEntry(
        val priority: ClickPriority,
        val handler: DisplayClickHandler
    )
}