cobblemon-survival-pack/mod/src/main/kotlin/dev/cobblesurvival/progress/CobblebaseGate.kt

package dev.cobblesurvival.progress

import com.cobblemon.mod.common.entity.pokemon.PokemonEntity
import dev.cobblesurvival.CobbleSurvival
import net.neoforged.fml.ModList
import java.lang.reflect.InvocationHandler
import java.lang.reflect.InvocationTargetException
import java.lang.reflect.Method
import java.lang.reflect.Proxy

/**
 * Puts [Gates] in front of Cobblebase's skills, by reflection (Cobblebase is not a compile dependency): every skill
 * executor in Cobblebase's `ExecutorRegistry` is replaced by a proxy that runs it only when the pastured Pokémon passes
 * that skill's soft gate (level or held material); otherwise its owner is told what it needs. Cobblebase looks the executor up on every tick, so the proxies take effect at once. One
 * executor can serve several skills (all the finders), so the check is per skill, not per executor.
 */
object CobblebaseGate {
    private const val CORE = "notlown.cobblebase.core"

    val installed: Boolean get() = ModList.get().isLoaded("cobblebase")

    internal val executorType by lazy { Class.forName("$CORE.SkillExecutor") }
    internal val skillEntry by lazy { Class.forName("$CORE.SkillEntry") }
    private val executors by lazy { Class.forName("$CORE.ExecutorRegistry").let { it to it.getField("INSTANCE").get(null) } }
    private val skillRegistry by lazy { Class.forName("$CORE.SkillRegistry").let { it to it.getField("INSTANCE").get(null) } }
    internal val skillDef by lazy { Class.forName("$CORE.SkillDef") }
    private val skillId by lazy { skillDef.getMethod("getId") }

    /** Skill id → its definition (Cobblebase's SkillDef). */
    @Suppress("UNCHECKED_CAST")
    fun skills(): Map<String, Any> {
        val (type, instance) = skillRegistry
        val all = type.getMethod("getAll").invoke(instance) as Map<String, Any>
        return all.values.associateBy { skillId.invoke(it) as String }
    }

    fun skillName(id: String): String? = skills()[id]?.let { skillDef.getMethod("getName").invoke(it) as String }

    fun executor(name: String): Any? {
        val (type, instance) = executors
        return type.getMethod("get", String::class.java).invoke(instance, name)
    }

    /** The executor names the skills use (several skills can share one). */
    fun executorNames(): Set<String> = skills().values.map { skillDef.getMethod("getExecutor").invoke(it) as String }.toSortedSet()

    fun install() {
        if (!installed) return
        val (type, instance) = executors
        val register = type.getMethod("register", String::class.java, executorType)
        var wrapped = 0
        for (name in executorNames()) {
            val original = executor(name) ?: continue
            if (isGated(original)) continue
            register.invoke(instance, name, wrap(original))
            wrapped++
        }
        CobbleSurvival.LOGGER.info("Progression gates in front of {} Cobblebase skill executors", wrapped)
    }

    fun isGated(executor: Any): Boolean =
        Proxy.isProxyClass(executor.javaClass) && Proxy.getInvocationHandler(executor) is Gate

    /** [original] behind the gates: `tick(level, pos, pokemonEntity, skillDef, skillEntry)` only runs if allowed. */
    fun wrap(original: Any): Any = Proxy.newProxyInstance(executorType.classLoader, arrayOf(executorType), Gate(original))

    private class Gate(private val original: Any) : InvocationHandler {
        override fun invoke(proxy: Any, method: Method, args: Array<out Any?>?): Any? {
            if (method.name == "tick" && args != null && args.size == 5) {
                val entity = args[2] as PokemonEntity
                val skill = skillId.invoke(args[3]) as String
                if (!Gates.skillOpen(entity.pokemon, skill)) {
                    Gates.noticeIdle(entity, skill)
                    return null
                }
            }
            return try {
                method.invoke(original, *(args ?: emptyArray()))
            } catch (e: InvocationTargetException) {
                throw e.targetException
            }
        }
    }
}