const std = @import("std");

pub fn Matrix(comptime n: usize, comptime Element: type) type {
	return [n]@Vector(n, Element);
}

pub const ProjectionMatrix = Matrix(4, f32);

pub const Rect = struct {
	left: f32,
	top: f32,
	right: f32,
	bottom: f32,
};

pub fn cross(v1: anytype, v2: anytype) @typeInfo(@TypeOf(v1, v2)).Vector.child {
	const multipled = v1 * v2;
	const vector_info = @typeInfo(@TypeOf(v1)).Vector;
	var result = multipled[0];
	comptime var index = @as(usize, 1);

	inline while (index < vector_info.len) : (index += 1) {
		result -= multipled[index];
	}

	return result;
}

pub fn distance(v1: anytype, v2: anytype) @typeInfo(@TypeOf(v1, v2)).Vector.child {
	return length(v1 - v2);
}

pub fn dot(v1: anytype, v2: anytype) @typeInfo(@TypeOf(v1, v2)).Vector.child {
	const multipled = v1 * v2;
	const vector_info = @typeInfo(@TypeOf(v1)).Vector;
	var result = multipled[0];
	comptime var index = @as(usize, 1);

	inline while (index < vector_info.len) : (index += 1) {
		result += multipled[index];
	}

	return result;
}

pub fn length(v: anytype) @typeInfo(@TypeOf(v)).Vector.child {
	return @sqrt(length_squared(v));
}

pub fn length_squared(v: anytype) @typeInfo(@TypeOf(v)).Vector.child {
	return dot(v, v);
}

pub fn normal(v: anytype) @TypeOf(v) {
	const ls = length_squared(v);
	const Vector = @TypeOf(v);

	if (ls > std.math.floatEps(@typeInfo(Vector).Vector.child)) {
		return v / @as(Vector, @splat(@sqrt(ls)));
	}

	return v;
}

pub fn orthographic_projection(near: f32, far: f32, viewport: Rect) Matrix(4, f32) {
	const width = viewport.right - viewport.left;
	const height = viewport.bottom - viewport.top;

	return .{
		.{2 / width, 0, 0, 0},
		.{0, 2 / height, 0, 0},
		.{0, 0, 1 / (far - near), 0},
		.{-((viewport.left + viewport.right) / width), -((viewport.top + viewport.bottom) / height), near / (near - far), 1},
	};
}