About CRecipePredicate

What is CRecipePredicate?

CRecipePredicate is a functional interface for inserting inspections that target the recipe as a whole, rather than individual item slots, into a CRecipe. While CMatterPredicate inspects the item in each individual slot, CRecipePredicate can reference the entire input item arrangement, player information, recipe information, and more all at once.

fun interface CRecipePredicate {
    fun test(ctx: Context): Boolean
}

It is held as a list in the CRecipe.predicates field. The recipe is considered a match only when all predicates in the list return true.

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Context

The context passed to the test function has the following fields:

Field	Type	Description
input	CraftView	The input state of the crafting UI (item arrangement, result slot)
crafterID	UUID	The UUID of the player who performed the craft
recipe	CRecipe	The recipe being inspected
relation	MappedRelation	The mapping between recipe coordinates and input slot coordinates (generated after CMatter inspections pass)
asyncContext	AsyncContext?	Context for async execution; null during synchronous execution (available from 5.0.20 onwards)

Because execution may occur on an asynchronous thread, it is recommended to check for interrupts via asyncContext?.isInterrupted(). Also, because access to BukkitAPI worlds and entities is not permitted on asynchronous threads, it is recommended to check the execution context with ctx.isAsync().

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Implementation examples

Allow crafting only for specific players

val onlyAdminPredicate = CRecipePredicate { ctx ->
    val player = Bukkit.getPlayer(ctx.crafterID) ?: return@CRecipePredicate false
    player.isOp
}

val recipe = CRecipeImpl(
    name = "admin-only-recipe",
    items = mapOf(CoordinateComponent(0, 0) to CMatterImpl.of(Material.DIAMOND)),
    results = listOf(ResultSupplier.timesSingle(ItemStack.of(Material.NETHERITE_INGOT))),
    type = CRecipe.Type.SHAPED,
    predicates = listOf(onlyAdminPredicate)
)

Referencing an external file or database (with async consideration)

val externalCheckPredicate = CRecipePredicate { ctx ->
    // Check for interrupts when called from an async thread
    if (ctx.asyncContext?.isInterrupted() == true) {
        return@CRecipePredicate false
    }

    // BukkitAPI access is not permitted on async threads
    // Example of querying the database using UUID
    val hasPermission: Boolean = MyDatabase.hasPermission(ctx.crafterID, "special-recipe")
    hasPermission
}

Using the total number of matched items as a condition

You can use relation to reference the mapping between recipe coordinates and input coordinates.

val multipleItemsPredicate = CRecipePredicate { ctx ->
    // Check whether all input items have the same stack size
    val inputItems = ctx.input.materials.values
    val firstAmount = inputItems.firstOrNull()?.amount ?: return@CRecipePredicate true
    inputItems.all { it.amount == firstAmount }
}

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When to use CRecipePredicate vs CMatterPredicate

	CMatterPredicate	CRecipePredicate
Inspection scope	A single item in an individual slot	The entire recipe and all input items
Available information	The placed item, coordinates, recipe	The full CraftView, player UUID, recipe, MappedRelation
Use cases	Per-item checks such as item type, enchantments, potions	Player permissions, logic spanning the entire input arrangement, external data lookups

Note

CRecipePredicate is executed after all CMatterPredicate checks have passed. Therefore, CRecipePredicate.Context.relation holds a finalised coordinate mapping generated from the item arrangement that passed the CMatter inspections.