#[macro_use]
extern crate iota;

use std::convert::TryInto;
use std::io::Cursor;

use byteorder::{LittleEndian, ReadBytesExt};

pub mod names;
pub mod zero_copy;

pub use crate::names::consts;
pub use crate::names::types;
pub use zero_copy::Error;
use zero_copy::usize_from;

#[derive (Debug, Default)]
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,
}

#[derive (Debug, Default)]
pub struct Header {
	pub fields: [u32; 27],
}

#[derive (Debug, Default)]
pub struct VertexArray {
	va_type: u32,
	va_flags: u32,
	va_format: u32,
	va_size: u32,
	va_offset: u32,
}

#[derive (Debug)]
pub struct Model <'data> {
	zc: zero_copy::Model <'data>,
	
	pub header: Header,
	text: Vec <u8>,
	pub meshes: Vec <Mesh>,
	vertexarrays: Vec <VertexArray>,
}

impl Header {
	pub fn from_zc (zc: &zero_copy::Model) -> Header {
		let mut header = Header::default ();
		
		for (i, value) in zc.header_fields ().enumerate () {
			header.fields [i] = value;
		}
		
		header
	}
}

impl Mesh {
	pub fn from_zc (zc: &zero_copy::Mesh) -> Mesh {
		use crate::names::consts::*;
		
		Mesh {
			name: zc.field (MESH_NAME),
			material: zc.field (MESH_MATERIAL),
			first_vertex: zc.field (MESH_FIRST_VERTEX),
			num_vertexes: zc.field (MESH_NUM_VERTEXES),
			first_triangle: zc.field (MESH_FIRST_TRIANGLE),
			num_triangles: zc.field (MESH_NUM_TRIANGLES),
		}
	}
}

impl VertexArray {
	pub fn from_slice (input: &[u8]) -> Result <VertexArray, Error> {
		let mut va = VertexArray::default ();
		
		let mut rdr = Cursor::new (input);
		
		for field in [
			&mut va.va_type,
			&mut va.va_flags,
			&mut va.va_format,
			&mut va.va_size,
			&mut va.va_offset,
		].iter_mut () {
			**field = rdr.read_u32::<LittleEndian> ().map_err (|_| Error::ParseVertexArrayFailed)?;
		}
		
		Ok (va)
	}
	
	pub fn from_zc (zc: &zero_copy::VertexArray) -> VertexArray {
		use crate::names::consts::*;
		
		VertexArray {
			va_type: zc.field (VA_TYPE),
			va_flags: zc.field (VA_FLAGS),
			va_format: zc.field (VA_FORMAT),
			va_size: zc.field (VA_SIZE),
			va_offset: zc.field (VA_OFFSET),
		}
	}
}

impl <'a> Model <'a> {
	pub fn from_slice (data: &'a [u8]) -> Result <Model <'a>, Error> {
		let zc = zero_copy::Model::get_root (data)?;
		
		let header = Header::from_zc (&zc);
		
		let text = {
			let offset = usize_from (zc.header_field (consts::OFS_TEXT));
			let num = usize_from (zc.header_field (consts::NUM_TEXT));
			Vec::from (&data [offset..offset + num])
		};
		
		let meshes = zc.meshes ().map (|zc_mesh| {
			Mesh::from_zc (&zc_mesh)
		}).collect ();
		
		let vertexarrays = zc.vertexarrays ().map (|zc_va| {
			VertexArray::from_zc (&zc_va)
		}).collect ();
		
		Ok (Model {
			zc,
			
			header,
			text,
			meshes,
			vertexarrays,
		})
	}
	
	pub fn get_vertex_slice (&self, idx: usize) -> &[u8] {
		self.zc.vertexarray (idx).get_vertex_slice ()
	}
	
	pub fn get_index_slice (&self, mesh_index: usize) -> &[u8] {
		let mesh = &self.meshes [mesh_index];
		let bytes_per_u32 = 4;
		let indexes_per_tri = 3;
		let stride = bytes_per_u32 * indexes_per_tri;
		
		let offset: usize = (self.header.fields [consts::OFS_TRIANGLES] + stride * mesh.first_triangle).try_into ().unwrap ();
		
		let num_bytes: usize = (stride * mesh.num_triangles).try_into ().unwrap ();
		
		&self.zc.data [offset..offset + num_bytes]
	}
	
	pub fn get_all_indexes (&self) -> &[u8] {
		let bytes_per_u32 = 4;
		let indexes_per_tri = 3;
		let stride = bytes_per_u32 * indexes_per_tri;
		
		let offset: usize = self.header.fields [consts::OFS_TRIANGLES].try_into ().unwrap ();
		
		let num_bytes: usize = (stride * self.header.fields [consts::NUM_TRIANGLES]).try_into ().unwrap ();
		
		&self.zc.data [offset..offset + num_bytes]
	}
	
	// I don't think IQM makes any guarantees about UTF-8
	// so I will only say that the slice has no NULs
	
	pub fn get_mesh_name (&self, index: usize) -> &[u8] {
		let mesh = &self.meshes [index];
		
		let ofs: usize = (self.header.fields [consts::OFS_TEXT] + mesh.name).try_into ().unwrap ();
		
		// There should be an easy way to do this with CString?
		let mut nul_index = None;
		for (j, c) in self.zc.data [ofs..].iter ().enumerate () {
			if *c == 0 {
				nul_index = Some (j);
				break;
			}
		}
		let nul_index = nul_index.unwrap ();
		
		&self.zc.data [ofs..ofs + nul_index]
	}
}

#[cfg (test)]
mod borrow_test {
	struct Model <'data> {
		data: &'data [u8],
	}
	
	struct VertexArray <'model: 'data, 'data> {
		model: &'model Model <'data>,
	}
	
	impl <'data> Model <'data> {
		pub fn va (&self) -> VertexArray {
			VertexArray {
				model: self,
			}
		}
		
		pub fn slice (&'data self) -> &'data [u8] {
			let va = self.va ();
			va.slice ()
		}
	}
	
	impl <'model: 'data, 'data> VertexArray <'model, 'data> {
		pub fn slice (&self) -> &'data [u8] {
			self.model.data
		}
	}
	
	#[test]
	fn nothing () {
		let data = [1, 1, 2, 3, 5, 8];
		
		let model = Model {
			data: &data,
		};
		
		let va = model.va ();
		
		let slice = model.va ().slice ();
		let slice = model.slice ();
	}
}

#[cfg (test)]
mod test {
	use std::path::Path;
	
	fn load_file <P: AsRef <Path>> (filename: P) -> Vec <u8> {
		use std::convert::TryInto;
		use std::fs::File;
		use std::io::Read;
		
		
		let mut f = File::open (filename).unwrap ();
		let mut data = vec! [0u8; f.metadata ().unwrap ().len ().try_into ().unwrap ()];
		f.read_exact (&mut data).unwrap ();
		data
	}
	
	#[test]
	pub fn load_models () {
		use super::*;
		
		let airplane_bytes = load_file ("airplane.iqm");
		let arrow_bytes = load_file ("arrow.iqm");
		let truk_bytes = load_file ("truk.iqm");
		
		let airplane = Model::from_slice (&airplane_bytes).unwrap ();
		let arrow = Model::from_slice (&arrow_bytes).unwrap ();
		let truk = Model::from_slice (&truk_bytes).unwrap ();
		
		use crate::names::consts::*;
		
		assert_eq! (airplane.header.fields [NUM_VERTEXES], 304);
		assert_eq! (airplane.header.fields [NUM_TRIANGLES], 156);
		assert_eq! (airplane.meshes.len (), 1);
		assert_eq! (airplane.vertexarrays.len (), 4);
		
		assert_eq! (arrow.header.fields [NUM_VERTEXES], 109);
		assert_eq! (arrow.header.fields [NUM_TRIANGLES], 117);
		assert_eq! (arrow.meshes.len (), 1);
		assert_eq! (arrow.vertexarrays.len (), 4);
		
		assert_eq! (truk.header.fields [NUM_VERTEXES], 256);
		assert_eq! (truk.header.fields [NUM_TRIANGLES], 180);
		assert_eq! (truk.meshes.len (), 5);
		assert_eq! (truk.vertexarrays.len (), 4);
	}
	
	#[test]
	pub fn load_zero_copy () {
		use crate::zero_copy::*;
		
		let airplane_bytes = load_file ("airplane.iqm");
		let arrow_bytes = load_file ("arrow.iqm");
		let truk_bytes = load_file ("truk.iqm");
		
		let airplane = Model::get_root (&airplane_bytes);
		let arrow = Model::get_root (&arrow_bytes);
		let truk = Model::get_root (&truk_bytes);
	}
}