KStarbound/src/main/kotlin/ru/dbotthepony/kstarbound/defs/JsonDriven.kt

package ru.dbotthepony.kstarbound.defs

import com.google.gson.JsonArray
import com.google.gson.JsonElement
import com.google.gson.JsonObject
import com.google.gson.TypeAdapter
import com.google.gson.reflect.TypeToken
import it.unimi.dsi.fastutil.objects.Object2ObjectOpenHashMap
import ru.dbotthepony.kommons.util.Either
import ru.dbotthepony.kstarbound.Starbound
import ru.dbotthepony.kstarbound.util.AssetPathStack
import ru.dbotthepony.kommons.gson.set
import java.util.function.Consumer
import java.util.function.Function
import java.util.function.Supplier
import kotlin.properties.ReadWriteProperty
import kotlin.reflect.KProperty
import kotlin.reflect.javaType

/**
 * Base class for instances which can be mutated by altering underlying JSON
 */
abstract class JsonDriven(val path: String) {
	private val delegates = ArrayList<Property<*>>()
	private val delegatesMap = Object2ObjectOpenHashMap<String, ArrayList<Property<*>>>()

	private val lazies = ArrayList<LazyData<*>>()
	private val namedLazies = Object2ObjectOpenHashMap<String, ArrayList<LazyData<*>>>()

	protected val properties = JsonObject()

	/**
	 * [JsonObject]s which define behavior of properties
	 */
	protected abstract fun defs(): Collection<JsonObject>

	protected open fun invalidate() {
		delegates.forEach { it.invalidate() }
		lazies.forEach { it.invalidate() }
	}

	protected open fun invalidate(name: String) {
		delegatesMap[name]?.forEach { it.invalidate() }
		namedLazies[name]?.forEach { it.invalidate() }
		lazies.forEach { it.invalidate() }
	}

	inner class LazyData<T>(names: Iterable<String> = listOf(), private val initializer: () -> T) : Lazy<T> {
		constructor(initializer: () -> T) : this(listOf(), initializer)

		init {
			for (name in names) {
				namedLazies.computeIfAbsent(name, Function { ArrayList() }).add(this)
			}
		}

		private var _value: Any? = mark

		override val value: T get() {
			var value = _value

			if (value !== mark) {
				return value as T
			}

			value = initializer.invoke()
			_value = value
			return value
		}

		override fun isInitialized(): Boolean {
			return _value !== mark
		}

		fun invalidate() {
			_value = mark
		}
	}

	inner class Property<T>(
		name: String? = null,
		val default: Either<Supplier<T>, JsonElement>? = null,
		private var adapter: TypeAdapter<T>? = null,
	) : Supplier<T>, Consumer<T>, ReadWriteProperty<Any?, T> {
		constructor(name: String, default: T, adapter: TypeAdapter<T>? = null) : this(name, Either.left(Supplier { default }), adapter)
		constructor(name: String, default: Supplier<T>, adapter: TypeAdapter<T>? = null) : this(name, Either.left(default), adapter)
		constructor(name: String, default: JsonElement, adapter: TypeAdapter<T>? = null) : this(name, Either.right(default), adapter)
		constructor(default: T, adapter: TypeAdapter<T>? = null) : this(null, Either.left(Supplier { default }), adapter)
		constructor(default: Supplier<T>, adapter: TypeAdapter<T>? = null) : this(null, Either.left(default), adapter)
		constructor(default: JsonElement, adapter: TypeAdapter<T>? = null) : this(null, Either.right(default), adapter)

		var name: String? = name
			private set(value) {
				if (field != null)
					throw IllegalStateException()

				field = value
				delegatesMap.computeIfAbsent(value, Function { ArrayList() }).add(this)
			}

		init {
			delegates.add(this)

			if (name != null)
				delegatesMap.computeIfAbsent(name, Function { ArrayList() }).add(this)
		}

		private var value: Supplier<T> = never as Supplier<T>

		private fun compute(): T {
			val value = dataValue(checkNotNull(name))

			if (value == null) {
				if (default == null) {
					throw NoSuchElementException("No json value present at '$name', and no default value was provided")
				} else if (default.isLeft) {
					return default.left().get()
				} else {
					AssetPathStack.block(path) {
						return adapter!!.fromJsonTree(default.right())
					}
				}
			} else {
				AssetPathStack.block(path) {
					return adapter!!.fromJsonTree(value)
				}
			}
		}

		fun invalidate() {
			value = Supplier {
				val new = compute()
				this.value = Supplier { new }
				new
			}
		}

		init {
			invalidate()
		}

		override fun get(): T {
			return value.get()
		}

		override fun accept(t: T) {
			AssetPathStack.block(path) {
				properties[checkNotNull(name)] = adapter!!.toJsonTree(t)
			}

			// value = Supplier { t }
			invalidate(name!!)
		}

		@OptIn(ExperimentalStdlibApi::class)
		override fun getValue(thisRef: Any?, property: KProperty<*>): T {
			if (adapter == null) {
				adapter = Starbound.gson.getAdapter(TypeToken.get(property.returnType.javaType)) as TypeAdapter<T>
			}

			if (name == null) {
				name = property.name
			}

			return value.get()
		}

		@OptIn(ExperimentalStdlibApi::class)
		override fun setValue(thisRef: Any?, property: KProperty<*>, value: T) {
			if (adapter == null) {
				adapter = Starbound.gson.getAdapter(TypeToken.get(property.returnType.javaType)) as TypeAdapter<T>
			}

			if (name == null) {
				name = property.name
			}

			return accept(value)
		}
	}

	fun dataValue(name: String, alwaysCopy: Boolean = false): JsonElement? {
		val defs = defs()
		var value: JsonElement?

		if (defs.isEmpty()) {
			value = properties[name]?.let { if (alwaysCopy) it.deepCopy() else it }
		} else {
			val itr = defs.iterator()
			var isCopy = false
			value = properties[name]

			while ((value == null || value is JsonObject) && itr.hasNext()) {
				val next = itr.next()[name]

				if (value is JsonObject) {
					if (next !is JsonObject) continue
					value = mergeNoCopy(if (isCopy) value else value.deepCopy(), next)
					isCopy = true
				} else {
					value = next
				}
			}
		}

		return value
	}

	fun hasDataValue(name: String): Boolean {
		if (properties[name] != null) return true
		return defs().any { it[name] != null }
	}

	companion object {
		private val mark = Any()
		private val never = Supplier { throw NoSuchElementException() }

		@JvmStatic
		fun mergeNoCopy(a: JsonObject, b: JsonObject): JsonObject {
			for ((k, v) in b.entrySet()) {
				val existing = a[k]

				if (existing is JsonObject && v is JsonObject) {
					a[k] = mergeNoCopy(existing, v)
				} else if (existing !is JsonObject) {
					a[k] = v.deepCopy()
				}
			}

			return a
		}
	}
}