//! Grapics data types

use {
    anyhow::{Error, Result},
    fna3d::Color,
    std::mem,
};

use super::embedded;

/// GPU texture disposed automatically
#[derive(Debug, Clone)]
pub struct Texture2dDrop {
    device: fna3d::Device,
    pub raw: *mut fna3d::Texture,
    pub w: u32,
    pub h: u32,
}

impl Drop for Texture2dDrop {
    fn drop(&mut self) {
        self.device.add_dispose_texture(self.raw);
    }
}

impl Texture2dDrop {
    /// For use with `include_bytes!`
    pub fn from_encoded_bytes(device: &fna3d::Device, bytes: &[u8]) -> Self {
        let (ptr, len, [w, h]) = fna3d::img::from_encoded_bytes(bytes);

        if ptr == std::ptr::null_mut() {
            panic!("Unable to read the encoded bytes as an image!");
        }

        let pixels: &[u8] = unsafe { std::slice::from_raw_parts(ptr, len as usize) };
        let tex = Self::from_decoded_bytes(device, w, h, pixels);

        // free the CPU texture
        fna3d::img::free(ptr);

        tex
    }

    pub fn from_decoded_bytes(device: &fna3d::Device, w: u32, h: u32, pixels: &[u8]) -> Self {
        let raw = device.create_texture_2d(fna3d::SurfaceFormat::Color, w, h, 1, false);
        device.set_texture_data_2d(raw, 0, 0, w, h, 0, pixels);

        Self {
            device: device.clone(),
            raw,
            w,
            h,
        }
    }
}

// use std::{ops::Deref, rc::Rc};
//
// pub struct TextureData2d {
//     inner: Rc<Texture2dDrop>,
// }
//
// impl Deref for TextureData2d {
//     type Target = Texture2dDrop;
//
//     fn deref(&self) -> &Self::Target {
//         &self.inner
//     }
// }

/// The vertex data
///
/// `#[repr(C)]` is required.
#[derive(Debug, Clone)]
#[repr(C)]
pub struct Vertex {
    /// Destination position in pixels
    ///
    /// We don't need the z coordinate but the shader (`SpriteEffect.fxb`) requires it.
    ///
    /// TODO: really? setup 2D only vertices
    pub dst: [f32; 3],
    /// Color of the vertex
    pub color: Color,
    /// Texture coordinates in normalized range [0, 1] (or wraps if it's out of the range)
    pub uv: [f32; 2],
}

impl Default for Vertex {
    fn default() -> Self {
        Self {
            dst: [0.0, 0.0, 0.0],
            color: Color::rgba(255, 255, 255, 255),
            uv: [0.0, 0.0],
        }
    }
}

impl Vertex {
    pub fn new(dst: [f32; 3], uv: [f32; 2], color: Color) -> Self {
        Self { dst, uv, color }
    }

    /// Vertex attribute elements
    const ELEMS: &'static [fna3d::VertexElement; 3] = &[
        // offsets are in bytes
        fna3d::VertexElement {
            offset: 0,
            vertexElementFormat: fna3d::VertexElementFormat::Vector3 as u32,
            vertexElementUsage: fna3d::VertexElementUsage::Position as u32,
            usageIndex: 0,
        },
        fna3d::VertexElement {
            offset: 12,
            vertexElementFormat: fna3d::VertexElementFormat::Color as u32,
            vertexElementUsage: fna3d::VertexElementUsage::Color as u32,
            usageIndex: 0,
        },
        fna3d::VertexElement {
            offset: 16,
            vertexElementFormat: fna3d::VertexElementFormat::Vector2 as u32,
            vertexElementUsage: fna3d::VertexElementUsage::TextureCoordinate as u32,
            usageIndex: 0,
        },
    ];

    /// Set of vertex element formats
    ///
    /// We _could_ make a derive macro that implements this constant.. but it requires **some**
    /// effort to learn procedual macros in Rust!
    pub const DECLARATION: fna3d::VertexDeclaration = fna3d::VertexDeclaration {
        // byte length of the vertex
        vertexStride: mem::size_of::<Vertex>() as i32,
        elementCount: 3,
        elements: Self::ELEMS as *const _ as *mut _,
    };
}

/// `SpriteEffect`, one of "Effects" in XNA
///
/// It's a combination of vertex/fragment shaders. I hear that it's not a good abstraction though.
///
/// Disposed automatically.
#[derive(Debug)]
pub struct Shader2d {
    device: fna3d::Device,
    effect: *mut fna3d::Effect,
    effect_data: *mut fna3d::mojo::Effect,
}

impl Drop for Shader2d {
    fn drop(&mut self) {
        // frees both `effect` and `effect_data`
        self.device.add_dispose_effect(self.effect);
    }
}

impl Shader2d {
    /// Create SpriteEffect from FNA3D device and the screen size
    pub fn new(device: &fna3d::Device, w: u32, h: u32) -> Result<Self> {
        // create the `SpriteEffect` shader
        let (effect, effect_data) =
            fna3d::mojo::from_bytes(&device, embedded::SHADER).map_err(Error::msg)?;

        Self::set_mat(effect_data, w as f32, h as f32)?;

        Ok(Self {
            device: device.clone(),
            effect,
            effect_data,
        })
    }

    /// Set the matrix parameter of the SpriteEffect shader to orthographic projection matrix
    fn set_mat(
        data: *mut fna3d::mojo::Effect,
        w: f32,
        h: f32,
    ) -> std::result::Result<(), std::ffi::NulError> {
        let mat = fna3d::mojo::orthographic_off_center(0.0, w as f32, h as f32, 0.0, 1.0, 0.0);
        // the name is hardcoded to the original shader source file (`SpriteEffect.fx`)
        let name = "MatrixTransform";
        unsafe {
            let name = std::ffi::CString::new(name)?;
            if !fna3d::mojo::set_param(data, &name, &mat) {
                eprintln!("Failed to set MatrixTransform shader paramter. Probablly we're not using `SpriteEffect.fxb`");
            }
        };

        Ok(())
    }

    // pub fn on_update_viewport_size(&mut self, w: f32, h: f32) {
    //     Self::set_mat(self.effect_data, w, h);
    // }

    pub fn apply_to_device(&self) {
        let pass = 0;
        self.device
            .apply_effect(self.effect, pass, &fna3d::utils::no_change_effect());
    }
}