cobblemon-survival-pack/mod/src/main/kotlin/dev/cobblesurvival/zone/ZoneHazards.kt

package dev.cobblesurvival.zone

import com.google.gson.Gson
import com.google.gson.JsonElement
import dev.cobblesurvival.CobbleSurvival
import net.minecraft.ChatFormatting
import net.minecraft.core.Holder
import net.minecraft.core.registries.BuiltInRegistries
import net.minecraft.core.registries.Registries
import net.minecraft.network.chat.Component
import net.minecraft.resources.ResourceLocation
import net.minecraft.server.level.ServerPlayer
import net.minecraft.server.packs.resources.ResourceManager
import net.minecraft.server.packs.resources.SimpleJsonResourceReloadListener
import net.minecraft.tags.TagKey
import net.minecraft.util.profiling.ProfilerFiller
import net.minecraft.world.effect.MobEffect
import net.minecraft.world.effect.MobEffectInstance
import net.minecraft.world.entity.EquipmentSlot
import net.minecraft.world.item.Item
import net.neoforged.neoforge.common.NeoForge
import net.neoforged.neoforge.event.AddReloadListenerEvent
import net.neoforged.neoforge.event.tick.ServerTickEvent
import java.util.UUID

/**
 * Zone hazards that Cold Sweat doesn't cover (roadmap Phase 3: "a poison swamp ... as area effects"): while a player
 * is in the zone and wears nothing from the protection tag, they keep getting the effect. Potions, milk and golden
 * apples still work against it. Definitions: `data/cobblesurvival/zone_hazards/<name>.json`.
 */
object ZoneHazards : SimpleJsonResourceReloadListener(Gson(), "zone_hazards") {
    private const val CHECK_TICKS = 10

    class Hazard(
        val zone: String,
        val effect: Holder<MobEffect>,
        val amplifier: Int,
        val durationTicks: Int,
        val everyTicks: Int,
        val protection: TagKey<Item>,
        val warning: String?,
    )

    var hazards: List<Hazard> = emptyList()
        private set
    private val warned = HashMap<UUID, String>()

    fun register() {
        NeoForge.EVENT_BUS.addListener<AddReloadListenerEvent> { it.addListener(this) }
        NeoForge.EVENT_BUS.addListener(::onServerTick)
    }

    override fun apply(files: Map<ResourceLocation, JsonElement>, resources: ResourceManager, profiler: ProfilerFiller) {
        hazards = files.mapNotNull { (id, element) ->
            val json = element.asJsonObject
            val effectId = ResourceLocation.parse(json.get("effect").asString)
            val effect = BuiltInRegistries.MOB_EFFECT.getHolder(effectId).orElse(null)
            if (effect == null) {
                CobbleSurvival.LOGGER.error("Zone hazard {}: unknown effect {}", id, effectId)
                return@mapNotNull null
            }
            Hazard(
                zone = json.get("zone").asString,
                effect = effect,
                amplifier = json.get("amplifier")?.asInt ?: 0,
                durationTicks = json.get("duration_ticks").asInt,
                everyTicks = json.get("every_ticks").asInt,
                protection = TagKey.create(Registries.ITEM, ResourceLocation.parse(json.get("protection").asString)),
                warning = json.get("warning")?.asString,
            )
        }
        CobbleSurvival.LOGGER.info("Loaded {} zone hazards", hazards.size)
    }

    private fun onServerTick(event: ServerTickEvent.Post) {
        if (hazards.isEmpty()) return
        if (event.server.tickCount % CHECK_TICKS != 0) return
        for (player in event.server.playerList.players) {
            if (player.isCreative || player.isSpectator) continue
            val zone = Zones.at(player.serverLevel(), player.blockPosition())?.id
            if (zone == null || hazards.none { it.zone == zone }) {
                warned.remove(player.uuid)
                continue
            }
            for (hazard in hazards) {
                if (hazard.zone != zone || isProtected(player, hazard)) continue
                // At once on entering the zone (Adrian, 2026-11-09), then renewed every every_ticks.
                val current = player.getEffect(hazard.effect)
                if (current != null && current.duration > hazard.durationTicks - hazard.everyTicks) continue
                player.addEffect(MobEffectInstance(hazard.effect, hazard.durationTicks, hazard.amplifier))
                if (hazard.warning != null && warned[player.uuid] != zone) {
                    warned[player.uuid] = zone
                    player.displayClientMessage(Component.translatable(hazard.warning).withStyle(ChatFormatting.DARK_GREEN), true)
                }
            }
        }
    }

    fun isProtected(player: ServerPlayer, hazard: Hazard) =
        listOf(EquipmentSlot.HEAD, EquipmentSlot.CHEST, EquipmentSlot.LEGS, EquipmentSlot.FEET)
            .any { player.getItemBySlot(it).`is`(hazard.protection) }
}