ona/demos/inputs.zig

const gfx = @import("gfx");

const hid = @import("hid");

const ona = @import("ona");

const std = @import("std");

const Spawned = struct {
	visual: struct {
		color: gfx.Color,
		position: gfx.Vector2,
		rotation: f32,
	},

	lifetime_seconds: f32,
};

const Visuals = struct {
	spawned: ona.stack.Parallel(Spawned) = .{},
	random: std.Random.Xoroshiro128,
	mouse_position: @Vector(2, f32) = @splat(0),
};

fn cleanup(visuals: ona.Write(Visuals)) !void {
	visuals.state.spawned.deinit();
}

fn load(visuals: ona.Write(Visuals)) !void {
	const initial_spawn_capacity = 1024;

	try visuals.state.spawned.grow(initial_spawn_capacity);
}

pub const main = ona.App.game
	.with_module(gfx)
	.with_module(hid)
	.with_state(Visuals{.random = std.Random.Xoroshiro128.init(47342563891212)})
	.with_system(.load, ona.system_fn(load), .{.label = "load visuals"})
	.with_system(.update, ona.system_fn(update), .{.label = "spawn visuals"})
	.with_system(.render, ona.system_fn(render), .{.label = "render visuals"})
	.with_system(.exit, ona.system_fn(cleanup), .{.label = "clean up visuals"}).build();

fn update(visuals: ona.Write(Visuals), events: ona.Receive(hid.Event), display: ona.Read(gfx.Display)) !void {
	update_spawned(&visuals.state.spawned);

	const random = visuals.state.random.random();
	const width: f32 = @floatFromInt(display.state.width);
	const height: f32 = @floatFromInt(display.state.height);

	for (events.messages()) |event| {
		switch (event) {
			.key_down => {
				try visuals.state.spawned.push_grow(.{
					.lifetime_seconds = 2.5 + (5 * random.float(f32)),

					.visual = .{
						.color = .{random.float(f32), random.float(f32), random.float(f32), random.float(f32)},
						.position = .{width * random.float(f32), height},
						.rotation = std.math.pi * random.float(f32),
					},
				});
			},

			.mouse_down => {
				try visuals.state.spawned.push_grow(.{
					.lifetime_seconds = 2.5 + (5 * random.float(f32)),

					.visual = .{
						.color = .{random.float(f32), random.float(f32), random.float(f32), random.float(f32)},
						.position = visuals.state.mouse_position,
						.rotation = std.math.pi * random.float(f32),
					},
				});
			},

			.mouse_motion => |motion| {
				visuals.state.mouse_position = motion.absolute_position;
			},

			else => {}
		}
	}
}

fn update_spawned(spawned: *ona.stack.Parallel(Spawned)) void {
	const float_speed = 6;

	for (spawned.values.slice(.visual)) |*visual| {
		visual.position -= .{0, float_speed};
	}

	{
		var range = spawned.len();
		var index: usize = 0;

		while (index < range) : (index += 1) {
			const lifetime_seconds = spawned.values.get(.lifetime_seconds, index).?;

			lifetime_seconds.* -= 1.0 / 60.0;

			if (lifetime_seconds.* <= 0) {
				range -= 1;

				std.mem.swap(f32, lifetime_seconds, spawned.values.get(.lifetime_seconds, range).?);
			}
		}

		std.debug.assert(spawned.pop_many(spawned.len() - range));
	}
}

fn render(visuals: ona.Write(Visuals), commands: gfx.Commands(.foreground)) !void {
	for (visuals.state.spawned.values.slice(.visual)) |visual| {
		try commands.draw_texture(.{
			.anchor = @splat(0.5),
			.position = visual.position,
			.tint = visual.color,
			.size = @as(gfx.Vector2, @splat(64)),
		});
	}
}