extern crate gfx;
extern crate gfx_device_gl;
extern crate nalgebra as na;
extern crate num_traits;
extern crate openvr as vr;
extern crate openvr_sys;

pub use self::vr::Eye;
pub use self::vr::common::Size;
pub use self::vr::tracking::{TrackedDeviceClass, TrackedDevicePoses};

use self::gfx::{tex, Factory, Typed};
use self::gfx_device_gl::Resources as GLResources;
use self::na::Inverse;
use self::num_traits::identities::Zero;
use self::num_traits::identities::One;
use self::openvr_sys::{VREvent_Controller_t, VREvent_t};

pub struct VR {
  system: vr::IVRSystem,
  compositor: vr::IVRCompositor,
  gfx_handles: gfx::handle::Manager<GLResources>,
}

#[derive(Debug)]
pub enum Event {
  Touch { dev_idx: u32, controller: VREvent_Controller_t },
  Press { dev_idx: u32, controller: VREvent_Controller_t },
  Unpress { dev_idx: u32, controller: VREvent_Controller_t },
  Untouch { dev_idx: u32, controller: VREvent_Controller_t },
  Other(VREvent_t),
}

impl VR {
  pub fn new() -> Result<VR, vr::Error<openvr_sys::EVRInitError>> {
    Ok(VR {
      system: try!(vr::init()),
      compositor: try!(vr::compositor()),
      gfx_handles: gfx::handle::Manager::new(),
    })
  }

  pub fn poses(&mut self) -> vr::tracking::TrackedDevicePoses {
    self.gfx_handles.clear();
    self.compositor.wait_get_poses()
  }

  pub fn submit<T>(&mut self, eye: Eye, tex: &gfx::handle::Texture<GLResources, T>) {
    let tex_id = match self.gfx_handles.ref_texture(tex.raw()) {
      &gfx_device_gl::NewTexture::Surface(id) => id,
      _ => panic!("Not a surface")
    };
    self.compositor.submit(eye,
                           tex_id as usize,
                           vr::common::TextureBounds::new((0.0, 1.0), (0.0, 1.0)));
  }

  pub fn recommended_render_target_size(&self) -> Size {
    self.system.recommended_render_target_size()
  }

  pub fn projection_matrix(self: &Self, eye: Eye, near: f32, far: f32) -> na::Matrix4<f32> {
    self.system.projection_matrix(eye, near, far).as_matrix4()
  }

  pub fn head_to_eye_transform(self: &Self, eye: Eye) -> na::Matrix4<f32> {
    let mut mat = self.system.eye_to_head_transform(eye).as_matrix4();
    assert!(mat.inverse_mut(), "inverse eye matrix");
    mat
  }

  pub fn poll_next_event(&mut self) -> Option<Event> {
    use self::openvr_sys::EVREventType as EvType;
    unsafe {
      let system = * { self.system.0 as *mut openvr_sys::VR_IVRSystem_FnTable };
      let mut event: openvr_sys::VREvent_t = ::std::mem::zeroed();

      if system.PollNextEvent.unwrap()(&mut event,
                                       ::std::mem::size_of::<openvr_sys::VREvent_t>() as u32
      ) == 0 {
        return None;
      }

      let dev_idx = event.trackedDeviceIndex;
      Some(match ::std::mem::transmute(event.eventType) {
        EvType::EVREventType_VREvent_ButtonTouch =>
          Event::Touch { dev_idx: dev_idx as u32, controller: *event.data.controller() },
        EvType::EVREventType_VREvent_ButtonPress =>
          Event::Press { dev_idx: dev_idx as u32, controller: *event.data.controller() },
        EvType::EVREventType_VREvent_ButtonUnpress =>
          Event::Unpress { dev_idx: dev_idx as u32, controller: *event.data.controller() },
        EvType::EVREventType_VREvent_ButtonUntouch =>
          Event::Untouch { dev_idx: dev_idx as u32, controller: *event.data.controller() },
        _ => Event::Other(event),
      })
    }
  }

  pub fn get_controller_state(&self, index: u32) -> Option<openvr_sys::VRControllerState_t> {
    unsafe {
      let system = * { self.system.0 as *const openvr_sys::VR_IVRSystem_FnTable };
      let mut state: openvr_sys::VRControllerState_t = ::std::mem::zeroed();

      match system.GetControllerState.unwrap()(
          index,
          &mut state,
      ) {
        0 => None,
        _ => Some(state)
      }
    }
  }
}

impl Drop for VR {
  fn drop(&mut self) {
    vr::shutdown()
  }
}

pub trait AsMatrix4<N> {
  fn as_matrix4(self) -> na::Matrix4<N>;
}
impl<N: Copy + Zero + One> AsMatrix4<N> for [[N; 4]; 3] {
  #[inline]
  fn as_matrix4(self) -> na::Matrix4<N> {
    na::Matrix4::new(self[0][0], self[0][1], self[0][2], self[0][3],
                     self[1][0], self[1][1], self[1][2], self[1][3],
                     self[2][0], self[2][1], self[2][2], self[2][3],
                     N::zero(),  N::zero(),  N::zero(),  N::one())
  }
}
impl<N: Copy> AsMatrix4<N> for [[N; 4]; 4] {
  #[inline]
  fn as_matrix4(self) -> na::Matrix4<N> {
    na::Matrix4::new(self[0][0], self[0][1], self[0][2], self[0][3],
                     self[1][0], self[1][1], self[1][2], self[1][3],
                     self[2][0], self[2][1], self[2][2], self[2][3],
                     self[3][0], self[3][1], self[3][2], self[3][3])
  }
}

pub struct EyeBuffer<T, D>
  where T: gfx::format::RenderFormat + gfx::format::TextureFormat,
        D: gfx::format::DepthFormat + gfx::format::TextureFormat {

  pub tex: gfx::handle::Texture<GLResources, T::Surface>,
  pub target: gfx::handle::RenderTargetView<GLResources, T>,
  pub depth: gfx::handle::DepthStencilView<GLResources, D>,
}

pub fn create_eyebuffer<T, D>(factory: &mut gfx_device_gl::Factory,
                              size: Size)
                              -> Result<EyeBuffer<T, D>, gfx::CombinedError>
  where T: gfx::format::RenderFormat + gfx::format::TextureFormat,
        D: gfx::format::DepthFormat + gfx::format::TextureFormat {
  let tex = try!(factory.create_texture(
      tex::Kind::D2(size.width as tex::Size, size.height as tex::Size, tex::AaMode::Single),
      1, // levels
      gfx::RENDER_TARGET, // bind
      gfx::Usage::GpuOnly, // Usage
      Some(<T::Channel as gfx::format::ChannelTyped>::get_channel_type()))); // hint: format::ChannelType?
  let tgt = try!(factory.view_texture_as_render_target(&tex, 0, None));
  let depth = try!(factory.create_depth_stencil_view_only(size.width as tex::Size,
                                                          size.height as tex::Size));
  Ok(EyeBuffer { tex: tex, target: tgt, depth: depth })
}