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use na::*;
use ::Node;
use angle::*;
use ::Rect;

#[derive(Clone,Copy,Debug)]
pub enum CoordinateOrigin{
    TopLeft,
    BottomLeft,
    CenterUp,
    CenterDown,
}

impl CoordinateOrigin{
    pub fn upwards(&self) -> bool{
        match *self{
            CoordinateOrigin::BottomLeft | CoordinateOrigin::CenterUp => true,
            _ => false
        }
    }

    pub fn downwards(&self) -> bool{
        !self.upwards()
    }
}

#[derive(Clone,Copy,Debug)]
pub enum Projection{
    Perspective{viewport: Rect<i32>, fov: Deg<f32>, znear: f32, zfar: f32, coordinate_origin: CoordinateOrigin},
    Ortho{viewport: Rect<i32>, znear: f32, zfar: f32, coordinate_origin: CoordinateOrigin}
}

impl Projection{
    pub fn new_perspective(viewport: Rect<i32>, fov: Deg<f32>, coordinate_origin: CoordinateOrigin) -> Projection{
        //let view_w = viewport.width as f32;
        let view_h = viewport.height as f32;
        let eye_y = view_h / 2.0;
        let half_fov = fov * 0.5;
        let the_tan = half_fov.tan();
        let dist = eye_y / the_tan;

        let znear = dist / 10.0;
        let zfar  = dist * 10.0;

        Projection::Perspective{
            viewport: viewport,
            fov: fov.to_deg(),
            znear: znear,
            zfar: zfar,
            coordinate_origin: coordinate_origin
        }
    }

    pub fn new_ortho(viewport: Rect<i32>, coordinate_origin: CoordinateOrigin) -> Projection{
        Projection::Ortho{
            viewport: viewport,
            znear: -1.0,
            zfar: 1.0,
            coordinate_origin: coordinate_origin
        }
    }

    pub fn new_ortho_clipped(viewport: Rect<i32>, coordinate_origin: CoordinateOrigin, near: f32, far: f32) -> Projection{
        Projection::Ortho{
            viewport: viewport,
            znear: near,
            zfar: far,
            coordinate_origin: coordinate_origin
        }
    }

    pub fn into_parts(self) -> (Rect<i32>, Mat4, Mat4, CoordinateOrigin){
        match self{
            Projection::Perspective{viewport, fov, znear, zfar, coordinate_origin} => {
                let eye_x = (viewport.width - viewport.pos.x) as f32 / 2.0;
                let eye_y = (viewport.height - viewport.pos.y) as f32 / 2.0;
                let aspect_ratio = viewport.width as f32/viewport.height as f32;
                let half_fov = fov * 0.5;
                let the_tan = half_fov.tan();
                let fd = 1.0 / the_tan;
                let dist = eye_y * fd;

                let sx = fd / aspect_ratio as f32;
                let sy = match coordinate_origin{
                    CoordinateOrigin::TopLeft => -fd,
                    CoordinateOrigin::BottomLeft => fd,
                    CoordinateOrigin::CenterDown => -fd,
                    CoordinateOrigin::CenterUp => fd
                };
                let sz = (zfar + znear) / (zfar - znear);
                let tz = (2.0 * zfar * znear) / (zfar - znear);

                let projection =
                    Mat4::new(  sx, 0.0,  0.0,  0.0,
                               0.0,  sy,  0.0,  0.0,
                               0.0, 0.0,   sz,   tz,
                               0.0, 0.0, -1.0,  0.0);
                //let projection = PerspMat3::new(aspect_ratio, fov.to_rad().value(), znear, zfar).to_mat();

                let view = Node::new_look_at(pnt3(eye_x,eye_y,dist),pnt3(eye_x,eye_y,0.0),Vec3::y())
                    .inv_global_transformation();

                (viewport, projection, view, coordinate_origin)
            }

            Projection::Ortho{viewport, znear, zfar, coordinate_origin} => {
                let (left,right) = match coordinate_origin{
                    CoordinateOrigin::BottomLeft | CoordinateOrigin::TopLeft => (viewport.pos.x, viewport.pos.x + viewport.width),
                    CoordinateOrigin::CenterUp | CoordinateOrigin::CenterDown => (viewport.pos.x - viewport.width/2, viewport.pos.x + viewport.width/2)
                };
                let (top,bottom) = match coordinate_origin{
                    CoordinateOrigin::BottomLeft => (viewport.pos.y + viewport.height, viewport.pos.y),
                    CoordinateOrigin::TopLeft => (viewport.pos.y, viewport.pos.y + viewport.height),
                    CoordinateOrigin::CenterUp => (viewport.pos.y + viewport.height / 2, viewport.pos.y - viewport.height / 2),
                    CoordinateOrigin::CenterDown => (viewport.pos.y - viewport.height / 2, viewport.pos.y + viewport.height / 2),
                };
                let tx = -(right+left) as f32/(right-left) as f32;
                let ty = -(top+bottom) as f32/(top-bottom) as f32;
                let tz = -(zfar+znear) as f32/(zfar-znear) as f32;
                let projection =
                    Mat4::new(2.0/(right-left) as f32,  0.0,                     0.0,               tx,
                              0.0,                      2.0/(top-bottom) as f32, 0.0,               ty,
                              0.0,                      0.0,                    -2.0/(zfar-znear),  tz,
                              0.0,                      0.0,                     0.0,               one());

                (viewport, projection, one(), coordinate_origin)
            }
        }
    }

    pub fn viewport(&self) -> Rect<i32>{
        match self{
            &Projection::Perspective{viewport, ..} => {
                viewport
            }

            &Projection::Ortho{viewport, ..} => {
                viewport
            }
        }
    }

    pub fn origin(&self) -> CoordinateOrigin{
        match self{
            &Projection::Perspective{coordinate_origin, ..} => {
                coordinate_origin
            }

            &Projection::Ortho{coordinate_origin, ..} => {
                coordinate_origin
            }
        }
    }
}