use std::{
	fs::File,
	io::Write,
};

use glam::{
	Mat4,
	Vec3,
};

fn main () {
	let (document, buffers, _images) = gltf::import ("input.glb").unwrap ();
	let buffer = buffers.get (0).unwrap ();
	
	let mut vertexes = Vec::default ();
	let mut triangles = Vec::default ();
	let mut meshes = Vec::default ();
	let mut texts = String::default ();
	
	for node in document.nodes () {
		let mesh = match node.mesh () {
			None => continue,
			Some (x) => x,
		};
		
		let m = gltf_node_get_mat4 (&node);
		
		for prim in mesh.primitives () {
			assert_eq! (prim.mode (), gltf::mesh::Mode::Triangles);
			
			let indices = prim.indices ().unwrap ();
			let indices_view = indices.view ().unwrap ();
			let indices_offset = indices.offset () + indices_view.offset ();
			let indices_slice = &buffer [indices_offset..(indices_offset + indices.count () * 2)];
			
			let pos = prim.get (&gltf::Semantic::Positions).unwrap ();
			let pos_view = pos.view ().unwrap ();
			let pos_offset = pos.offset () + pos_view.offset ();
			let pos_slice = &buffer [pos_offset..(pos_offset + pos.count () * 4 * 3)];
			
			let first_vertex = vertexes.len ();
			
			let mesh = iqm::Mesh {
				name: u32::try_from (texts.len ()).unwrap (),
				material: 0,
				first_vertex: u32::try_from (first_vertex).unwrap (),
				num_vertexes: u32::try_from (indices_slice.len () / 2).unwrap (),
				// num_vertexes: u32::try_from (3).unwrap (),
				first_triangle: u32::try_from (triangles.len ()).unwrap (),
				num_triangles: u32::try_from (indices_slice.len () / 6).unwrap (),
				//num_triangles: u32::try_from (1).unwrap (),
			};
			texts.push_str ("\0");
			
			meshes.push (mesh);
			
			for chunk in indices_slice.chunks_exact (2 * 3) {
				let read_idx = |i: usize| u16::from_le_bytes ([chunk [i * 2 + 0], chunk [i * 2 + 1]]);
				
				let idxs = [
					read_idx (0),
					read_idx (1),
					read_idx (2),
				];
				
				let read_pos_coord = |i| f32::from_le_bytes ([
					pos_slice [i * 4 + 0],
					pos_slice [i * 4 + 1],
					pos_slice [i * 4 + 2],
					pos_slice [i * 4 + 3],
				]);
				
				let read_pos = move |i| {
					let i = usize::try_from (i).unwrap ();
					m.transform_point3 (Vec3::new (
						read_pos_coord (i * 3 + 0),
						read_pos_coord (i * 3 + 1),
						read_pos_coord (i * 3 + 2),
					))
				};
				
				let verts = [
					read_pos (idxs [0]),
					read_pos (idxs [2]),
					read_pos (idxs [1]),
				];
				
				let tri_start = u32::try_from (vertexes.len ()).unwrap ();
				triangles.push ([
					tri_start + 0,
					tri_start + 1,
					tri_start + 2,
				]);
				
				for v in verts {
					vertexes.push (v.to_array ());
				}
			}
		}
	}
	
	let vertexes = vertexes;
	let triangles = triangles;
	let meshes = meshes;
	let texts = texts;
	
	let num_vertexes = u32::try_from (vertexes.len ()).unwrap ();
	let num_triangles = u32::try_from (triangles.len ()).unwrap ();
	
	let num_text = texts.len ();
	let num_text = u32::try_from (num_text).unwrap ();
	
	let num_meshes = u32::try_from (meshes.len ()).unwrap ();
	let num_vertexarrays = 1u32;
	
	let header_len = 124u32;
	let ofs_meshes = header_len;
	let ofs_vertexarrays = ofs_meshes + num_meshes * 6 * 4;
	let ofs_triangles = ofs_vertexarrays + num_vertexarrays * 5 * 4 + num_vertexes * 3 * 4;
	let ofs_text = ofs_triangles + num_triangles * 3 * 4;
	
	let filesize = ofs_text + num_text;
	
	let mut f = File::create ("output.iqm").unwrap ();
	
	f.write_all (b"INTERQUAKEMODEL\0").unwrap ();
	
	f.write_all (&(2u32.to_le_bytes ())).unwrap ();
	
	// filesize
	f.write_all (&(filesize.to_le_bytes ())).unwrap ();
	
	// flags
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_text, ofs_text
	f.write_all (&(num_text.to_le_bytes ())).unwrap ();
	f.write_all (&(ofs_text.to_le_bytes ())).unwrap ();
	
	// num_meshes, ofs_meshes
	f.write_all (&(num_meshes.to_le_bytes ())).unwrap ();
	f.write_all (&(ofs_meshes.to_le_bytes ())).unwrap ();
	
	// num_vertexarrays, num_vertexes, ofs_vertexarrays
	f.write_all (&(num_vertexarrays.to_le_bytes ())).unwrap ();
	f.write_all (&(num_vertexes.to_le_bytes ())).unwrap ();
	f.write_all (&(ofs_vertexarrays.to_le_bytes ())).unwrap ();
	
	// num_triangles, ofs_triangles, ofs_adjacency
	f.write_all (&(num_triangles.to_le_bytes ())).unwrap ();
	f.write_all (&(ofs_triangles.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_joints, ofs_joints
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_poses, ofs_poses
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_anims, ofs_anims
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_frames, num_framechannels, ofs_frames, ofs_bounds
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_comment, ofs_comment
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// num_extensions, ofs_extensions
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// Meshes
	
	for mesh in meshes {
		f.write_all (&(mesh.name.to_le_bytes ())).unwrap ();
		f.write_all (&(mesh.material.to_le_bytes ())).unwrap ();
		f.write_all (&(mesh.first_vertex.to_le_bytes ())).unwrap ();
		f.write_all (&(mesh.num_vertexes.to_le_bytes ())).unwrap ();
		f.write_all (&(mesh.first_triangle.to_le_bytes ())).unwrap ();
		f.write_all (&(mesh.num_triangles.to_le_bytes ())).unwrap ();
	}
	
	// Vertex arrays
	
	// type
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// flags
	f.write_all (&(0u32.to_le_bytes ())).unwrap ();
	
	// format
	f.write_all (&(7u32.to_le_bytes ())).unwrap ();
	
	// size
	f.write_all (&(3u32.to_le_bytes ())).unwrap ();
	
	// offset
	f.write_all (&((ofs_vertexarrays + 5 * 4 * 1).to_le_bytes ())).unwrap ();
	
	// Vertexes
	
	for t in vertexes {
		for x in t {
			f.write_all (&(f32::to_le_bytes (x))).unwrap ();
		}
	}
	
	// Triangles
	
	for t in triangles {
		for x in t {
			f.write_all (&(u32::to_le_bytes (x))).unwrap ();
		}
	}
	
	// Text
	f.write_all (texts.as_bytes ()).unwrap ();
}

fn gltf_node_get_mat4 (node: &gltf::Node) -> Mat4 {
	Mat4::from_cols_array_2d (&node.transform ().matrix ())
}

/// IQM structures as written to disk

mod iqm {
	pub struct Mesh {
		pub name: u32,
		pub material: u32,
		pub first_vertex: u32,
		pub num_vertexes: u32,
		pub first_triangle: u32,
		pub num_triangles: u32,
	}
	
	struct VertexArray {
		r#type: u32,
		flags: u32,
		format: u32,
		size: u32,
		offset: u32,
	}
	
	struct Triangle {
		vertex: [u32; 3],
	}
	
	struct Vertex {
		position: [f32; 3],
	}
}