package ru.dbotthepony.kstarbound.defs

import com.google.gson.Gson
import com.google.gson.TypeAdapter
import com.google.gson.TypeAdapterFactory
import com.google.gson.reflect.TypeToken
import com.google.gson.stream.JsonReader
import com.google.gson.stream.JsonToken
import com.google.gson.stream.JsonWriter
import it.unimi.dsi.fastutil.objects.ObjectOpenHashSet
import ru.dbotthepony.kstarbound.util.AssetPathStack
import java.io.Reader
import java.lang.reflect.ParameterizedType
import java.util.*
import java.util.concurrent.ConcurrentHashMap

/**
 * Данный [AssetReferenceFactory] реализует возможности чтения данных по "ссылке" на файл.
 *
 * Созданный [TypeAdapter] имеет встроенный кеш.
 */
class AssetReferenceFactory(val remapper: AssetPathStack, val reader: (String) -> Reader?) : TypeAdapterFactory {
	override fun <T : Any?> create(gson: Gson, type: TypeToken<T>): TypeAdapter<T>? {
		if (type.rawType == AssetReference::class.java) {
			val param = type.type as? ParameterizedType ?: return null

			return object : TypeAdapter<AssetReference<Any>>() {
				private val cache = ConcurrentHashMap<String, Any>()
				private val adapter = gson.getAdapter(TypeToken.get(param.actualTypeArguments[0])) as TypeAdapter<Any>
				private val strings = gson.getAdapter(String::class.java)
				private val missing = Collections.synchronizedSet(ObjectOpenHashSet<String>())

				override fun write(out: JsonWriter, value: AssetReference<Any>?) {
					if (value == null)
						out.nullValue()
					else
						out.value(value.fullPath)
				}

				override fun read(`in`: JsonReader): AssetReference<Any>? {
					if (`in`.peek() == JsonToken.NULL) {
						return null
					} else if (`in`.peek() == JsonToken.STRING) {
						val path = strings.read(`in`)!!
						val fullPath = remapper.remap(path)
						val get = cache[fullPath]

						if (get != null)
							return AssetReference(path, fullPath, get)

						if (fullPath in missing)
							return null

						val reader = reader.invoke(fullPath)

						if (reader == null) {
							missing.add(fullPath)
							return AssetReference(path, fullPath, null)
						}

						val value = remapper(fullPath) {
							adapter.read(JsonReader(reader).also {
								it.isLenient = true
							}) ?: return AssetReference(path, fullPath, null)
						}

						cache[fullPath] = value
						return AssetReference(path, fullPath, value)
					} else {
						val value = adapter.read(`in`) ?: return null
						return AssetReference(null, null, value)
					}
				}
			} as TypeAdapter<T>
		}

		return null
	}
}

data class AssetReference<V>(val path: String?, val fullPath: String?, val value: V?)