import OrderedCollections
import Maths


public struct Model<T: Vertex>: Resource
{
	public let meshes: [Mesh<T>]
}

public struct Mesh<T: Vertex>: Resource
{
	public typealias Index = UInt16

	public struct SubMesh
	{
		public let start, length: Int
		public let material: Int  //hack

		public init(start: Int, length: Int, material: Int = -1)
		{
			self.start = start
			self.length = length
			self.material = material
		}
	}

	public let vertices: [T]
	public let indices: [Index]
	public let subMeshes: OrderedDictionary<String, SubMesh>
	public let materials: [Material]  // hack
}

public extension Mesh
{
	static var empty: Self { Self(vertices: .init(), indices: .init(), subMeshes: .init(), materials: .init()) }

	init(vertices: [T], indices: [Index])
	{
		self.init(
			vertices: vertices,
			indices: indices,
			subMeshes: .init(),
			materials: .init())
	}

	init(vertices: [T], indices: [Index], subMeshes: OrderedDictionary<String, SubMesh>)
	{
		self.init(
			vertices: vertices,
			indices: indices,
			subMeshes: subMeshes,
			materials: .init())
	}
}


public protocol Vertex: Equatable {}

public struct VertexPositionNormalTexcoord: Vertex
{
	public let position: Vec3f
	public let normal: Vec3f
	public let texCoord: Vec2f

	public init(position: Vec3f, normal: Vec3f, texCoord: Vec2f)
	{
		self.position = position
		self.normal = normal
		self.texCoord = texCoord
	}
}

public struct VertexPositionNormalColourTexcoord: Vertex
{
	public let position: Vec3f
	public let normal: Vec3f
	public let colour: Colour
	public let texCoord: Vec2f

	public init(position: Vec3f, colour: Colour, normal: Vec3f, texCoord: Vec2f)
	{
		self.position = position
		self.colour = colour
		self.normal = normal
		self.texCoord = texCoord
	}
}