Minecraft/Forge NBT DSL

NBTUtil.kt

abstract class ItemNBTHolder(val stack: ItemStack, val compound: CompoundNBT) {
    protected fun byte(defaultValue: Byte) = SimpleNBTDelegate(defaultValue, CompoundNBT::getByte, CompoundNBT::putByte)
    protected fun short(defaultValue: Short) = SimpleNBTDelegate(defaultValue, CompoundNBT::getShort, CompoundNBT::putShort)
    protected fun int(defaultValue: Int) = SimpleNBTDelegate(defaultValue, CompoundNBT::getInt, CompoundNBT::putInt)
    protected fun long(defaultValue: Long) = SimpleNBTDelegate(defaultValue, CompoundNBT::getLong, CompoundNBT::putLong)
    protected fun float(defaultValue: Float) = SimpleNBTDelegate(defaultValue, CompoundNBT::getFloat, CompoundNBT::putFloat)
    protected fun double(defaultValue: Double) = SimpleNBTDelegate(defaultValue, CompoundNBT::getDouble, CompoundNBT::putDouble)
    protected fun string(defaultValue: String) = SimpleNBTDelegate(defaultValue, CompoundNBT::getString, CompoundNBT::putString)
    protected fun byteArray(defaultValue: ByteArray = ByteArray(0)) = SimpleNBTDelegate(defaultValue, CompoundNBT::getByteArray, CompoundNBT::putByteArray)
    protected fun intArray(defaultValue: IntArray = IntArray(0)) = SimpleNBTDelegate(defaultValue, CompoundNBT::getIntArray, CompoundNBT::putIntArray)
    protected fun longArray(defaultValue: LongArray = LongArray(0)) = SimpleNBTDelegate(defaultValue, CompoundNBT::getLongArray, CompoundNBT::putLongArray)
    protected fun boolean(defaultValue: Boolean) = SimpleNBTDelegate(defaultValue, CompoundNBT::getBoolean, CompoundNBT::putBoolean)

    protected fun uuid() = object : MutableNBTDelegate<UUID?>() {
        override fun getValue(stack: ItemStack, compound: CompoundNBT, tag: String): UUID? {
            return if (isTagExisting(stack, tag + "Most") && isTagExisting(stack, tag + "Least")) {
                compound.getUniqueId(tag)
            } else {
                null
            }
        }

        override fun setValue(stack: ItemStack, compound: CompoundNBT, tag: String, value: UUID?) {
            if (value != null) {
                compound.putUniqueId(tag, value)
            }
        }

    }

    protected fun <R : ItemNBTHolder> compound(nested: (ItemStack, CompoundNBT) -> R) = object : NBTDelegate<CompoundHelper<R>>() {
        override fun getValue(stack: ItemStack, compound: CompoundNBT, tag: String): CompoundHelper<R> {
            return if (isTagExisting(stack, tag)) {
                val newCompound = compound.getCompound(tag)
                CompoundHelper(nested(stack, compound.getCompound(tag)), { compound.put(tag, newCompound) })
            } else {
                val newCompound = CompoundNBT()
                CompoundHelper(nested(stack, newCompound), { compound.put(tag, newCompound) })
            }
        }
    }
}

class CompoundHelper<T : ItemNBTHolder>(private val holder: T, private val callback: () -> Unit) {
    operator fun <R> invoke(func: T.() -> R): R {
        val result = func(holder)
        callback()
        return result
    }
}

abstract class NBTDelegate<R> : ReadOnlyProperty<ItemNBTHolder, R> {
    protected fun isTagExisting(stack: ItemStack, tag: String) = !stack.isEmpty && stack.orCreateTag.contains(tag)

    abstract fun getValue(stack: ItemStack, compound: CompoundNBT, tag: String): R

    override fun getValue(thisRef: ItemNBTHolder, property: KProperty<*>) = getValue(thisRef.stack, thisRef.compound, property.name)
}

abstract class MutableNBTDelegate<R> : NBTDelegate<R>(), ReadWriteProperty<ItemNBTHolder, R> {
    abstract fun setValue(stack: ItemStack, compound: CompoundNBT, tag: String, value: R)

    override fun setValue(thisRef: ItemNBTHolder, property: KProperty<*>, value: R) = setValue(thisRef.stack, thisRef.compound, property.name, value)
}

class SimpleNBTDelegate<R : Any>(private val defaultValue: R, private val getter: CompoundNBT.(String) -> R, private val setter: CompoundNBT.(String, R) -> Unit) : MutableNBTDelegate<R>() {
    override fun getValue(stack: ItemStack, compound: CompoundNBT, tag: String): R {
        return if (isTagExisting(stack, tag)) {
            getter(compound, tag)
        } else {
            defaultValue
        }
    }

    override fun setValue(stack: ItemStack, compound: CompoundNBT, tag: String, value: R) {
        setter(compound, tag, value)
    }
}