use core_types::gpoll::{Extent, GPoll, GraphError, Interrupt};
use core_types::list::List;
use core_types::{Color, ExtractVarArgs};
use core_types::{Ctx, ExtractIndex, ExtractIndices, ExtractPosition};
use glam::DVec2;
use graphic_types::vector_types::Gradient;
use graphic_types::{Graphic, Vector};
use raster_types::{CPU, Raster};

/// The mapped row riding as vararg 0, in the production single-item shape.
fn vararg_list<T: 'static>(ctx: &impl ExtractVarArgs) -> Option<&List<T>> {
	let arg = ctx.vararg(0).ok()?;
	(arg as &dyn std::any::Any).downcast_ref::<List<T>>()
}

/// Lanes of a leveled vararg source: one per item, none without a row,
/// matching the legacy empty-list return.
fn vararg_lanes<T: 'static>(ctx: &impl ExtractVarArgs, level: u8) -> GPoll<Extent> {
	match level {
		0 => GPoll::Final(Extent::Exactly(vararg_list::<T>(ctx).map_or(0, List::len))),
		_ => GPoll::Final(Extent::Exactly(1)),
	}
}

fn vararg_element<T: Clone + 'static>(ctx: &(impl ExtractVarArgs + ExtractIndex)) -> Result<T, Interrupt> {
	vararg_list::<T>(ctx)
		.and_then(|list| list.element(ctx.index() as usize))
		.cloned()
		.ok_or_else(|| GraphError::new("vararg row addressed past its items").into())
}

// The vararg readers: the mapped row's items as the lanes of a level, elements
// only, one node per element type since a reader names its type.
macro_rules! vararg_readers {
	($($node:ident / $extent:ident / $node_type:ident: $element:ty;)*) => {
		$(
			#[node_macro::node(category("Context"), path(graphene_core::vector), extent_raw($extent))]
			pub fn $node(ctx: impl Ctx + ExtractVarArgs + ExtractIndex, _primary: ()) -> Result<IList<$element>, Interrupt> {
				vararg_element(ctx)
			}

			fn $extent<C: Ctx + ExtractVarArgs, N>(_: &$node_type<N>, ctx: &C, level: u8) -> GPoll<Extent> {
				vararg_lanes::<$element>(ctx, level)
			}
		)*
	};
}

vararg_readers! {
	read_graphic / read_graphic_extent / ReadGraphicNode: Graphic<'static>;
	read_vector / read_vector_extent / ReadVectorNode: Vector;
	read_raster / read_raster_extent / ReadRasterNode: Raster<CPU>;
	read_color / read_color_extent / ReadColorNode: Color;
	read_gradient / read_gradient_extent / ReadGradientNode: Gradient;
	read_string / read_string_extent / ReadStringNode: String;
	read_number / read_number_extent / ReadNumberNode: f64;
}

#[node_macro::node(category("Context"), path(core_types::vector))]
fn read_position(
	ctx: impl Ctx + ExtractPosition,
	_primary: (),
	/// The number of nested loops to traverse outwards (from the innermost loop) to get the position from. The most upstream loop is level 0, and downstream loops add levels.
	///
	/// In programming terms: inside the double loop `i { j { ... } }`, *Loop Level* 0 = `j` and 1 = `i`. After inserting a third loop `k { ... }`, inside it, levels would be 0 = `k`, 1 = `j`, and 2 = `i`.
	loop_level: u32,
) -> DVec2 {
	ctx.try_position().and_then(|mut iter| iter.nth(loop_level as usize).or_else(|| iter.last())).unwrap_or(DVec2::ZERO)
}

// TODO: Return u32, u64, or usize instead of f64 after #1621 is resolved and has allowed us to implement automatic type conversion in the node graph for nodes with generic type inputs.
// TODO: (Currently automatic type conversion only works for concrete types, via the Graphene preprocessor and not the full Graphene type system.)
/// Produces the index of the current iteration of a loop by reading from the evaluation context, which is supplied by downstream nodes such as *Repeat*.
///
/// Nested loops can enable 2D or higher-dimensional iteration by using the *Loop Level* parameter to read the index from outer levels of loops.
#[node_macro::node(category("Context"), path(core_types::vector))]
fn read_index(
	// `loop_level` is a runtime input, so no level is statically known and the
	// whole chain has to survive nullification.
	ctx: impl Ctx + ExtractIndices,
	_primary: (),
	/// The number of nested loops to traverse outwards (from the innermost loop) to get the index from. The most upstream loop is level 0, and downstream loops add levels.
	///
	/// In programming terms: inside the double loop `i { j { ... } }`, *Loop Level* 0 = `j` and 1 = `i`. After inserting a third loop `k { ... }`, inside it, levels would be 0 = `k`, 1 = `j`, and 2 = `i`.
	loop_level: u32,
) -> f64 {
	// The chain's innermost entry is the consuming input's own lane from the
	// decompose-and-promote split; the loops the reader counts sit above it.
	ctx.try_index().and_then(|mut iter| iter.nth(loop_level as usize + 1)).unwrap_or(0) as f64
}