package lyra:api;

interface ecs {
    record entity-id {
        id: u64,
    }

    record entity {
        id: entity-id,
        generation: u64,
    }

    record wasm-type-id {
        // represents a u128, can be converted into that with mem::transmute
        inner: tuple<u64, u64>,
    }

    record component-info {
        host-name: option<string>,
        /// The size of the component in memory.
        size: u64,
        /// The alignment of the component in memory.
        alignment: u64,
        /// The type id of the component.
        ///
        /// This must be unique between component types since its used to identify the components
        /// in spawning and querying.
        type-id: wasm-type-id,
    }

    resource ecs-dynamic-view {
        constructor(wrld: borrow<ecs-world>, component-infos: list<component-info>);

        /// Get the bytes of the next row in the view.
        /// 
        /// A row contains multiple component serialized as bytes. The buffer is tighly packed.
        next: func() -> option<tuple<entity, list<u8>>>;
    }

    /// An resource that can be "downcasted" to a specific type.
    /// 
    /// You can use `T.from-ecs-resource` to "downcast" the type
    resource ecs-resource {

    }

    variant world-resource-result {
        none,
        wasm-resource(ecs-resource),
        bytes(list<u8>),
    }

    resource ecs-world {
        constructor();

        /// Spawn an entity.
        ///
        /// Parameters:
        /// * `components`: A tightly packed byte buffer containing the components to spawn
        /// with the entity. This expects the components in the same order of `component-infos`.
        /// * `component-infos`: A list of `component-infos` uses to identify the components
        /// and specify the layouts of them.
        spawn: func(components: list<u8>, component-infos: list<component-info>) -> entity;

        /// Insert components into an existing entity.
        /// 
        /// Parameters:
        /// * `en`: The entity to insert into.
        /// * `components`: A tightly packed byte buffer containing the components to spawn
        /// with the entity. This expects the components in the same order of `component-infos`.
        /// * `component-infos`: A list of `component-infos` uses to identify the components
        /// and specify the layouts of them.
        insert: func(en: entity, components: list<u8>, component-infos: list<component-info>);

        /// Query for a list of entities and their components.
        ///
        /// Parameters:
        /// * `component-infos`: The `component-info`'s of the components that you are querying.
        ///
        /// Returns: an iterator that returns the byte buffers of each row.
        view: func(component-infos: list<component-info>) -> ecs-dynamic-view;

        /// Query for components from a single entity.
        ///
        /// Parameters:
        /// * `en`: The entity to query components from.
        /// * `component-infos`: The `component-info`'s of the components that you are querying.
        ///
        /// Returns: A row of components serialized as bytes. The buffer is tighly packed.
        view-one: func(en: entity, component-infos: list<component-info>) -> option<list<u8>>;

        get-resource: func(type-id: wasm-type-id) -> world-resource-result;

        //with_system: func(stage: string, component-infos: list<component-info>, system: func(components: list<u8>));
    }
}